Sample records for u-mo alloy based
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NASA Astrophysics Data System (ADS)
Allenou, J.; Tougait, O.; Pasturel, M.; Iltis, X.; Charollais, F.; Anselmet, M. C.; Lemoine, P.
2011-09-01
Si addition to Al is considered as a promising route to reduce (U,Mo)-Al interaction kinetics, due to its accumulation in the interaction layer, yielding the formation of silicide phases. The (U,Mo) alloy microstructure, and especially its homogenization state, could play a role on this accumulation process. The addition of a third element in γ(U,Mo) could also influence diffusion mechanisms of Al and Si. These two parameters were studied by means of diffusion couple experiments by joining γU based alloys with Al and (Al,Si) alloy. Chemical elements X added into γ(U,Mo) were thoroughly chosen on the following criteria: (i) the potential solubility of the alloying element into the γ(U,Mo) matrix, (ii) its capability to form the ternary aluminides based on the CeCr 2Al 20 and Ho 6Mo 4Al 43 - types, and (iii) the feasibility to control the microstructure of the alloys. On this basis, a test matrix is defined. It concerns γ(U80,Mo15,X5) alloys (in at.%) with X = Y, Cu, Zr, Ti or Cr. These alloys were homogenized and coupled with Al or (Al,Si) alloy. Results evidenced, first, the importance of the state of homogenization of the γ(U,Mo) binary alloy on interaction processes with (Al,Si) alloy, and the benefit on the diffusion of Si through the interaction layer, as observed on the elementary concentration profiles, when the third element X has some solubility into γ(U,Mo) alloy.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Devaraj, Arun; Jana, Saumyadeep; McInnis, Colleen A.
During eutectoid transformation of U-10Mo alloy, uniform metastable γ UMo phase is expected to transform to a mixture of α-U and γ’-U 2Mo phase. The presence of transformation products in final U-10Mo fuel, especially the α phase is considered detrimental for fuel irradiation performance, so it is critical to accurately evaluate the extent of transformation in the final U-10Mo alloy. This phase transformation can cause a volume change that induces a density change in final alloy. To understand this density and volume change, we developed a theoretical model to calculate the volume expansion and resultant density change of U-10Mo alloymore » as a function of the extent of eutectoid transformation. Based on the theoretically calculated density change for 0 to 100% transformation, we conclude that an experimental density measurement system will be challenging to employ to reliably detect and quantify the extent of transformation. Subsequently, to assess the ability of various methods to detect the transformation in U-10Mo, we annealed U-10Mo alloy samples at 500°C for various times to achieve in low, medium, and high extent of transformation. After the heat treatment at 500°C, the samples were metallographically polished and subjected to optical microscopy and x-ray diffraction (XRD) methods. Based on our assessment, optical microscopy and image processing can be used to determine the transformed area fraction, which can then be correlated with the α phase volume fraction measured by XRD analysis. XRD analysis of U-10Mo aged at 500°C detected only α phase and no γ’ was detected. To further validate the XRD results, atom probe tomography (APT) was used to understand the composition of transformed regions in U-10Mo alloys aged at 500°C for 10 hours. Based on the APT results, the lamellar transformation product was found to comprise α phase with close to 0 at% Mo and γ phase with 28–32 at% Mo, and the Mo concentration was highest at the α/γ interface.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
K. Huang; C. Kammerer; D. D. Keiser, Jr.
2014-04-01
U-Mo alloys are being developed as low enrichment monolithic fuel under the Reduced Enrichment for Research and Test Reactor (RERTR) Program. Diffusional interactions between the U-Mo fuel alloy and Al-alloy cladding within the monolithic fuel plate construct necessitate incorporation of a barrier layer. Fundamentally, a diffusion barrier candidate must have good thermal conductivity, high melting point, minimal metallurgical interaction, and good irradiation performance. Refractory metals, Zr, Mo, and Nb are considered based on their physical properties, and the diffusion behavior must be carefully examined first with U-Mo fuel alloy. Solid-to-solid U-10wt.%Mo vs. Mo, Zr, or Nb diffusion couples were assembledmore » and annealed at 600, 700, 800, 900 and 1000 degrees C for various times. The interdiffusion microstructures and chemical composition were examined via scanning electron microscopy and electron probe microanalysis, respectively. For all three systems, the growth rate of interdiffusion zone were calculated at 1000, 900 and 800 degrees C under the assumption of parabolic growth, and calculated for lower temperature of 700, 600 and 500 degrees C according to Arrhenius relationship. The growth rate was determined to be about 10 3 times slower for Zr, 10 5 times slower for Mo and 10 6 times slower for Nb, than the growth rates reported for the interaction between the U-Mo fuel alloy and pure Al or Al-Si cladding alloys. Zr, however was selected as the barrier metal due to a concern for thermo- mechanical behavior of UMo/Nb interface observed from diffusion couples, and for ductile-to-brittle transition of Mo near room temperature.« less
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First-principles study of the surface properties of U-Mo system
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mei, Zhi-Gang; Liang, Linyun; Yacout, Abdellatif M.
U-Mo alloys are promising fuels for future high-performance research reactors with low enriched uranium. Surface properties, such as surface energy, are important inputs for mesoscale simulations (e.g., phase field method) of fission gas bubble behaviors in irradiated nuclear fuels. The lack of surface energies of U-Mo alloys prevents an accurate modeling of the morphology of gas bubbles and gas bubble-induced fuel swelling. To this end, we study the surface properties of U-Mo system, including bcc Mo, alpha-U, gamma-U, and gamma U-Mo alloys. All surfaces up to a maximum Miller index of three and two are calculated for cubic Mo andmore » gamma-U and non-cubic alpha-U, respectively. The equilibrium crystal shapes of bcc Mo, alpha-U and gamma-U are constructed using the calculated surface energies. The dominant surface orientations and the area fraction of each facet are determined from the constructed equilibrium crystal shape. The disordered gamma U-Mo alloys are simulated using the Special Quasirandom Structure method. The (1 1 0) and (1 0 0) surface energies of gamma U-7Mo and U-10Mo alloys are predicted to lie between those of gamma-U and bcc Mo, following a linear combination of the two constituents' surface energies. To better compare with future measurements of surface energies, the area fraction weighted surface energies of alpha-U, gamma-U and gamma U-7Mo and U-10Mo alloys are also predicted. (C) 2017 Published by Elsevier B.V.« less
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Grain growth in U–7Mo alloy: A combined first-principles and phase field study
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mei, Zhi-Gang; Liang, Linyun; Kim, Yeon Soo
2016-05-01
Grain size is an important factor in controlling the swelling behavior in irradiated U-Mo dispersion fuels. Increasing the grain size in UeMo fuel particles by heat treatment is believed to delay the fuel swelling at high fission density. In this work, a multiscale simulation approach combining first-principles calculation and phase field modeling is used to investigate the grain growth behavior in U-7Mo alloy. The density functional theory based first-principles calculations were used to predict the material properties of U-7Mo alloy. The obtained grain boundary energies were then adopted as an input parameter for mesoscale phase field simulations. The effects ofmore » annealing temperature, annealing time and initial grain structures of fuel particles on the grain growth in U-7Mo alloy were examined. The predicted grain growth rate compares well with the empirical correlation derived from experiments. (C) 2016 Elsevier B.V. All rights reserved.« less
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NASA Astrophysics Data System (ADS)
Wang, Xiaowo; Xu, Zhijie; Soulami, Ayoub; Hu, Xiaohua; Lavender, Curt; Joshi, Vineet
2017-12-01
Low-enriched uranium alloyed with 10 wt.% molybdenum (U-10Mo) has been identified as a promising alternative to high-enriched uranium. Manufacturing U-10Mo alloy involves multiple complex thermomechanical processes that pose challenges for computational modeling. This paper describes the application of integrated computational materials engineering (ICME) concepts to integrate three individual modeling components, viz. homogenization, microstructure-based finite element method for hot rolling, and carbide particle distribution, to simulate the early-stage processes of U-10Mo alloy manufacture. The resulting integrated model enables information to be passed between different model components and leads to improved understanding of the evolution of the microstructure. This ICME approach is then used to predict the variation in the thickness of the Zircaloy-2 barrier as a function of the degree of homogenization and to analyze the carbide distribution, which can affect the recrystallization, hardness, and fracture properties of U-10Mo in subsequent processes.
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Micro-structural study and Rietveld analysis of fast reactor fuels: U-Mo fuels
NASA Astrophysics Data System (ADS)
Chakraborty, S.; Choudhuri, G.; Banerjee, J.; Agarwal, Renu; Khan, K. B.; Kumar, Arun
2015-12-01
U-Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U-Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U-Mo alloys as fast reactor fuel.
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Effect of Silicon in U-10Mo Alloy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kautz, Elizabeth J.; Devaraj, Arun; Kovarik, Libor
2017-08-31
This document details a method for evaluating the effect of silicon impurity content on U-10Mo alloys. Silicon concentration in U-10Mo alloys has been shown to impact the following: volume fraction of precipitate phases, effective density of the final alloy, and 235-U enrichment in the gamma-UMo matrix. This report presents a model for calculating these quantities as a function of Silicon concentration, which along with fuel foil characterization data, will serve as a reference for quality control of the U-10Mo final alloy Si content. Additionally, detailed characterization using scanning electron microscope imaging, transmission electron microscope diffraction, and atom probe tomography showedmore » that Silicon impurities present in U-10Mo alloys form a Si-rich precipitate phase.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Devaraj, Arun; Prabhakaran, Ramprashad; Joshi, Vineet V.
2016-04-12
The purpose of this document is to provide a theoretical framework for (1) estimating uranium carbide (UC) volume fraction in a final alloy of uranium with 10 weight percent molybdenum (U-10Mo) as a function of final alloy carbon concentration, and (2) estimating effective 235U enrichment in the U-10Mo matrix after accounting for loss of 235U in forming UC. This report will also serve as a theoretical baseline for effective density of as-cast low-enriched U-10Mo alloy. Therefore, this report will serve as the baseline for quality control of final alloy carbon content
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NASA Astrophysics Data System (ADS)
Park, Y.; Eriksson, N.; Newell, R.; Keiser, D. D.; Sohn, Y. H.
2016-11-01
Eutectoid decomposition of γ-phase (cI2) into α-phase (oC4) and γ‧-phase (tI6) during the hot isostatic pressing (HIP) of the U-10 wt% Mo (U10Mo) alloy was investigated using monolithic fuel plate samples consisting of U10Mo fuel alloy, Zr diffusion barrier and AA6061 cladding. The decomposition of the γ-phase was observed because the HIP process is carried out near the eutectoid temperature, 555 °C. Initially, a cellular structure, consisting of γ‧-phase surrounded by α-phase, developed from the destabilization of the γ-phase. The cellular structure further developed into an alternating lamellar structure of α- and γ‧-phases. Using scanning electron microscopy and transmission electron microscopy, qualitative and quantitative microstructural analyses were carried out to identify the phase constituents, and elucidate the microstructural development based on time-temperature-transformation diagram of the U10Mo alloy. The destabilization of γ -phase into α- and γ‧-phases would be minimized when HIP process was carried out with rapid ramping/cooling rate and dwell temperature higher than 560 °C.
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NASA Astrophysics Data System (ADS)
Burkes, Douglas E.; Casella, Andrew M.; Buck, Edgar C.; Casella, Amanda J.; Edwards, Matthew K.; MacFarlan, Paul J.; Pool, Karl N.; Smith, Frances N.; Steen, Franciska H.
2014-07-01
The uranium-molybdenum (U-Mo) alloy in a monolithic form has been proposed as one fuel design capable of converting some of the world's highest power research reactors from the use of high enriched uranium to low enriched uranium. One aspect of the fuel development and qualification process is to demonstrate appropriate understanding of the thermal-conductivity behavior of the fuel system as a function of temperature and expected irradiation conditions. The purpose of this paper is to verify functionality of equipment installed in hot cells for eventual measurements on irradiated uranium-molybdenum (U-Mo) monolithic fuel specimens, refine procedures to operate the equipment, and validate models to extract the desired thermal properties. The results presented here demonstrate the adequacy of the equipment, procedures, and models that have been developed for this purpose based on measurements conducted on surrogate depleted uranium-molybdenum (DU-Mo) alloy samples containing a Zr diffusion barrier and clad in aluminum alloy 6061 (AA6061). The results are in excellent agreement with thermal property data reported in the literature for similar U-Mo alloys as a function of temperature.
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Role of Si on the Diffusional Interactions Between U-Mo and Al-Si Alloys at 823 K (550 °C)
NASA Astrophysics Data System (ADS)
Perez, Emmanuel; Sohn, Yong-Ho; Keiser, Dennis D.
2013-01-01
U-Mo dispersions in Al-alloy matrix and monolithic fuels encased in Al-alloy are under development to fulfill the requirements for research and test reactors to use low-enriched molybdenum stabilized uranium alloy fuels. Significant interaction takes place between the U-Mo fuel and Al during manufacturing and in-reactor irradiation. The interaction products are Al-rich phases with physical and thermal characteristics that adversely affect fuel performance and result in premature failure. Detailed analysis of the interdiffusion and microstructural development of this system was carried through diffusion couples consisting of U-7 wt pct Mo, U-10 wt pct Mo and U-12 wt pct Mo in contact with pure Al, Al-2 wt pct Si, and Al-5 wt pct Si, annealed at 823 K (550 °C) for 1, 5 and 20 hours. Scanning electron microscopy and transmission electron microscopy were employed for the analysis. Diffusion couples consisting of U-Mo in contact with pure Al contained UAl3, UAl4, U6Mo4Al43, and UMo2Al20 phases. Additions of Si to the Al significantly reduced the thickness of the interdiffusion zone. The interdiffusion zones developed Al- and Si-enriched regions, whose locations and size depended on the Si and Mo concentrations in the terminal alloys. In these couples, the (U,Mo)(Al,Si)3 phase was observed throughout the interdiffusion zone, and the U6Mo4Al43 and UMo2Al20 phases were observed only where the Si concentrations were low.
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Cubic γ-phase U-Mo alloys synthesized by splat-cooling
NASA Astrophysics Data System (ADS)
Kim-Ngan, Nhu-T. H.; Tkach, I.; Mašková, S.; Havela, L.; Warren, A.; Scott, T.
2013-09-01
U-Mo alloys are the most promising materials fulfilling the requirements of using low enriched uranium (LEU) fuel in research reactors. From a fundamental standpoint, it is of interest to determine the basic thermodynamic properties of the cubic γ-phase U-Mo alloys. We focus our attention on the use of Mo doping together with ultrafast cooling (with high cooling rates ⩾106 K s-1), which helps to maintain the cubic γ-phase in U-Mo system to low temperatures and on determination of the low-temperature properties of these γ-U alloys. Using a splat cooling method it has been possible to maintain some fraction of the high-temperature γ-phase at room temperature in pure uranium. U-13 at.% Mo splat clearly exhibits the pure γ-phase structure. All the splats become superconducting with Tc in the range from 1.24 K (pure U splat) to 2.11 K (U-15 at.% Mo). The γ-phase in U-Mo alloys undergoes eutectoid decomposition to form equilibrium phases of orthorhombic α-uranium and tetragonal γ‧-phase upon annealing at 500 °C, while annealing at 800 °C has stabilized the initial γ phase. The α-U easily absorbs a large amount of hydrogen (UH3 hydride), while the cubic bcc phase does not absorb any detectable amount of hydrogen at pressures below 1 bar and at room temperature. At 80 bar, the U-15 at.% Mo splat becomes powder consisting of elongated particles of 1-2 mm, revealing amorphous state.
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NASA Astrophysics Data System (ADS)
Huang, Ke; Keiser, Dennis D.; Sohn, Yongho
2013-02-01
U-Mo alloys are being developed as low enrichment uranium fuels under the Reduced Enrichment for Research and Test Reactor (RERTR) Program. In order to understand the fundamental diffusion behavior of this system, solid-to-solid pure U vs Mo diffusion couples were assembled and annealed at 923 K, 973 K, 1073 K, 1173 K, and 1273 K (650 °C, 700 °C, 800 °C, 900 °C, and 1000 °C) for various times. The interdiffusion microstructures and concentration profiles were examined via scanning electron microscopy and electron probe microanalysis, respectively. As the Mo concentration increased from 2 to 26 at. pct, the interdiffusion coefficient decreased, while the activation energy increased. A Kirkendall marker plane was clearly identified in each diffusion couple and utilized to determine intrinsic diffusion coefficients. Uranium intrinsically diffused 5-10 times faster than Mo. Molar excess Gibbs free energy of U-Mo alloy was applied to calculate the thermodynamic factor using ideal, regular, and subregular solution models. Based on the intrinsic diffusion coefficients and thermodynamic factors, Manning's formalism was used to calculate the tracer diffusion coefficients, atomic mobilities, and vacancy wind parameters of U and Mo at the marker composition. The tracer diffusion coefficients and atomic mobilities of U were about five times larger than those of Mo, and the vacancy wind effect increased the intrinsic flux of U by approximately 30 pct.
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NASA Astrophysics Data System (ADS)
Johns, Jesse M.; Burkes, Douglas
2017-07-01
In this work, a multilayered perceptron (MLP) network is used to develop predictive isothermal time-temperature-transformation (TTT) models covering a range of U-Mo binary and ternary alloys. The selected ternary alloys for model development are U-Mo-Ru, U-Mo-Nb, U-Mo-Zr, U-Mo-Cr, and U-Mo-Re. These model's ability to predict 'novel' U-Mo alloys is shown quite well despite the discrepancies between literature sources for similar alloys which likely arise from different thermal-mechanical processing conditions. These models are developed with the primary purpose of informing experimental decisions. Additional experimental insight is necessary in order to reduce the number of experiments required to isolate ideal alloys. These models allow test planners to evaluate areas of experimental interest; once initial tests are conducted, the model can be updated and further improve follow-on testing decisions. The model also improves analysis capabilities by reducing the number of data points necessary from any particular test. For example, if one or two isotherms are measured during a test, the model can construct the rest of the TTT curve over a wide range of temperature and time. This modeling capability reduces the cost of experiments while also improving the value of the results from the tests. The reduced costs could result in improved material characterization and therefore improved fundamental understanding of TTT dynamics. As additional understanding of phenomena driving TTTs is acquired, this type of MLP model can be used to populate unknowns (such as material impurity and other thermal mechanical properties) from past literature sources.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Johns, Jesse M.; Burkes, Douglas
In this work, a multilayered perceptron (MLP) network is used to develop predictive isothermal time-temperature-transformation (TTT) models covering a range of U-Mo binary and ternary alloys. The selected ternary alloys for model development are U-Mo-Ru, U-Mo-Nb, U-Mo-Zr, U-Mo-Cr, and U-Mo-Re. These model’s ability to predict 'novel' U-Mo alloys is shown quite well despite the discrepancies between literature sources for similar alloys which likely arise from different thermal-mechanical processing conditions. These models are developed with the primary purpose of informing experimental decisions. Additional experimental insight is necessary in order to reduce the number of experiments required to isolate ideal alloys. Thesemore » models allow test planners to evaluate areas of experimental interest; once initial tests are conducted, the model can be updated and further improve follow-on testing decisions. The model also improves analysis capabilities by reducing the number of data points necessary from any particular test. For example, if one or two isotherms are measured during a test, the model can construct the rest of the TTT curve over a wide range of temperature and time. This modeling capability reduces the cost of experiments while also improving the value of the results from the tests. The reduced costs could result in improved material characterization and therefore improved fundamental understanding of TTT dynamics. As additional understanding of phenomena driving TTTs is acquired, this type of MLP model can be used to populate unknowns (such as material impurity and other thermal mechanical properties) from past literature sources.« less
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Modeling the Homogenization Kinetics of As-Cast U-10wt% Mo alloys
DOE Office of Scientific and Technical Information (OSTI.GOV)
Xu, Zhijie; Joshi, Vineet; Hu, Shenyang Y.
2016-01-15
Low-enriched U-22at% Mo (U-10Mo) alloy has been considered as an alternative material to replace the highly enriched fuels in research reactors. For the U-10Mo to work effectively and replace the existing fuel material, a thorough understanding of the microstructure development from as-cast to the final formed structure is required. The as-cast microstructure typically resembles an inhomogeneous microstructure with regions containing molybdenum-rich and -lean regions, which may affect the processing and possibly the in-reactor performance. This as-cast structure must be homogenized by thermal treatment to produce a uniform Mo distribution. The development of a modeling capability will improve the understanding ofmore » the effect of initial microstructures on the Mo homogenization kinetics. In the current work, we investigated the effect of as-cast microstructure on the homogenization kinetics. The kinetics of the homogenization was modeled based on a rigorous algorithm that relates the line scan data of Mo concentration to the gray scale in energy dispersive spectroscopy images, which was used to generate a reconstructed Mo concentration map. The map was then used as realistic microstructure input for physics-based homogenization models, where the entire homogenization kinetics can be simulated and validated against the available experiment data at different homogenization times and temperatures.« less
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Effects of heat treatment on U-Mo fuel foils with a zirconium diffusion barrier
NASA Astrophysics Data System (ADS)
Jue, Jan-Fong; Trowbridge, Tammy L.; Breckenridge, Cynthia R.; Moore, Glenn A.; Meyer, Mitchell K.; Keiser, Dennis D.
2015-05-01
A monolith fuel design based on U-Mo alloy has been selected as the fuel type for conversion of the United States' high performance research reactors (HPRRs) from highly enriched uranium (HEU) to low-enriched uranium (LEU). In this fuel design, a thin layer of zirconium is used to eliminate the direct interaction between the U-Mo fuel meat and the aluminum-alloy cladding during irradiation. The co-rolling process used to bond the Zr barrier layer to the U-Mo foil during fabrication alters the microstructure of both the U-10Mo fuel meat and the U-Mo/Zr interface. This work studied the effects of post-rolling annealing treatment on the microstructure of the co-rolled U-Mo fuel meat and the U-Mo/Zr interaction layer. Microscopic characterization shows that the grain size of U-Mo fuel meat increases with the annealing temperature, as expected. The grain sizes were ∼9, ∼13, and ∼20 μm for annealing temperature of 650, 750, and 850 °C, respectively. No abnormal grain growth was observed. The U-Mo/Zr interaction-layer thickness increased with the annealing temperature with an Arrhenius constant for growth of 184 kJ/mole, consistent with a previous diffusion-couple study. The interaction layer thickness was 3.2 ± 0.5 μm, 11.1 ± 2.1 μm, 27.1 ± 0.9 μm for annealing temperature of 650, 750, to 850 °C, respectively. The homogeneity of Mo improves with post rolling annealing temperature and with U-Mo coupon homogenization. The phases in the Zr/U-Mo interaction layer produced by co-rolling, however, differ from those reported in the previous diffusion couple studies.
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Interdiffusion and reactions between U-Mo and Zr at 650 °C as a function of time
NASA Astrophysics Data System (ADS)
Park, Y.; Keiser, D. D.; Sohn, Y. H.
2015-01-01
Development of monolithic U-Mo alloy fuel (typically U-10 wt.%Mo) for the Reduced Enrichment for Research and Test Reactors (RERTR) program entails a use of Zr diffusion barrier to eliminate the interdiffusion-reactions between the fuel alloy and Al-alloy cladding. The application of Zr barrier to the U-Mo fuel system requires a co-rolling process that utilizes a soaking temperature of 650 °C, which represents the highest temperature the fuel system is exposed to during both fuel manufacturing and reactor application. Therefore, in this study, development of phase constituents, microstructure and diffusion kinetics of U-10 wt.%Mo and Zr was examined using solid-to-solid diffusion couples annealed at 650 °C for 240, 480 and 720 h. Phase constituents and microstructural development were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Concentration profiles were mapped as diffusion paths on the isothermal ternary phase diagram. Within the diffusion zone, single-phase layers of β-Zr and β-U were observed along with a discontinuous layer of Mo2Zr between the β-Zr and β-U layers. In the vicinity of Mo2Zr phase, islands of α-Zr phases were also found. In addition, acicular α-Zr and U6Zr3Mo phases were observed within the γ-U(Mo) terminal alloy. Growth rate of the interdiffusion-reaction zone was determined to be 7.75 (± 5.84) × 10-16 m2/s at 650 °C, however with an assumption of a certain incubation period.
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Irradiation testing of high density uranium alloy dispersion fuels
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hayes, S.L.; Trybus, C.L.; Meyer, M.K.
1997-10-01
Two irradiation test vehicles have been designed, fabricated, and inserted into the Advanced Test Reactor in Idaho. Irradiation of these experiments began in August 1997. These irradiation tests were designed to obtain irradiation performance information on a variety of potential new, high-density dispersion fuels. Each of the two irradiation vehicles contains 32 microplates. Each microplate is aluminum clad, having an aluminum matrix phase and containing one of the following compositions as the fuel phase: U-10Mo, U-8Mo, U-6Mo, U-4Mo, U-9Nb-3Zr, U-6Nb-4Zr, U-5Nb-3Zr, U-6Mo-1Pt, U-6Mo-0.6Ru, U-10Mo-0.05Sn, U{sub 2}Mo, or U{sub 3}Si{sub 2}. These experiments will be discharged at peak fuel burnups ofmore » 40% and 80%. Of particular interest is the fission gas retention/swelling characteristics of these new fuel alloys. This paper presents the design of the irradiation vehicles and the irradiation conditions.« less
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Irradiated microstructure of U-10Mo monolithic fuel plate at very high fission density
NASA Astrophysics Data System (ADS)
Gan, J.; Miller, B. D.; Keiser, D. D.; Jue, J. F.; Madden, J. W.; Robinson, A. B.; Ozaltun, H.; Moore, G.; Meyer, M. K.
2017-08-01
Monolithic U-10Mo alloy fuel plates with Al-6061 cladding are being developed for use in research and test reactors as low enrichment fuel (<20% U-235 enrichment) as a result of its high uranium loading capacity compared to that of U-7Mo dispersion fuel. These fuel plates contain a Zr diffusion barrier between the U-10Mo fuel and Al-6061 cladding that suppresses the interaction between the U-Mo fuel foil and Al alloy cladding that is known to be problematic under irradiation. Different methods have been employed to fabricate monolithic fuel plates, including hot-rolling with no cold-rolling. L1P09T is a hot-rolled fuel plate irradiated to high fission density in the RERTR-9B experiment. This paper discusses the TEM characterization results for this U-10Mo/Zr/Al6061 monolithic fuel plate (∼59% U-235 enrichment) irradiated in Advanced Test Reactor at Idaho National Laboratory with an unprecedented high local fission density of 9.8E+21 fissions/cm3. The calculated fuel foil centerline temperature at the beginning of life and the end of life is 141 and 194 °C, respectively. TEM lamellas were prepared using focus ion beam lift-out technique. The estimated U-Mo fuel swelling, based on the fuel foil thickness change from SEM, is approximately 76%. Large bubbles (>1 μm) are distributed evenly in U-Mo and interlink of these bubbles is evident. The average size of subdivided grains at this fission density appears similar to that at 5.2E+21 fissions/cm3. The measured average Mo and Zr content in the fuel matrix is ∼30 at% and ∼7 at%, respectively, in general agreement with the calculated Mo and Zr from fission density.
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Irradiated microstructure of U-10Mo monolithic fuel plate at very high fission density
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gan, J.; Miller, B. D.; Keiser, D. D.
Monolithic U-10Mo alloy fuel plates with Al-6061 cladding are being developed for use in research and test reactors as low enrichment fuel (< 20% U-235 enrichment) as a result of its high uranium loading capacity compared to that of U-7Mo dispersion fuel. These fuel plates contain a Zr diffusion barrier between the U-10Mo fuel and Al-6061 cladding that suppresses the interaction between the U-Mo fuel foil and Al alloy cladding that is known to be problematic under irradiation. This paper discusses the TEM results of the U-10Mo/Zr/Al6061 monolithic fuel plate (Plate ID: L1P09T, ~ 59% U-235 enrichment) irradiated in Advancedmore » Test Reactor at Idaho National Laboratory as part of RERTR-9B irradiation campaign with an unprecedented high local fission density of 9.8E+21 fissions/cm3. The calculated fuel foil centerline temperature at the beginning of life and the end of life is 141 and 194 C, respectively. A total of 5 TEM lamellas were prepared using focus ion beam lift-out technique. The estimated U-Mo fuel swelling, based on the fuel foil thickness change from SEM, is approximately 76%. Large bubbles (> 1 µm) are distributed evenly in U-Mo and interlink of these bubbles is evident. The average size of subdivided grains at this fission density appears similar to that at 5.2E+21 fissions/cm3. The measured average Mo and Zr content in the fuel matrix is ~ 30 at% and ~ 7 at%, respectively, in general agreement with the calculated Mo and Zr from fission density.« less
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Grain boundary engineering to control the discontinuous precipitation in multicomponent U10Mo alloy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Devaraj, Arun; Kovarik, Libor; Kautz, Elizabeth
Grain boundaries in metallic alloys often play a crucial role, not only in determining the mechanical properties or thermal stability of alloys, but also in dictating the phase transformation kinetics during thermomechanical processing. We demonstrate that locally stabilized structure and compositional segregation at grain boundaries—“grain boundary complexions”—in a complex multicomponent alloy can be modified to influence the kinetics of cellular transformation during subsequent thermomechanical processing. Using aberration-corrected scanning transmission electron microscopy and atom probe tomography analysis of a metallic nuclear fuel highly relevant to worldwide nuclear non-proliferation efforts —uranium-10 wt% molybdenum (U-10Mo) alloy, new evidence for the existence of grainmore » boundary complexion is provided. We then modified the concentration of impurities dissolved in Υ-UMo grain interiors and/or segregated to Υ-UMo grain boundaries by changing the homogenization treatment, and these effects were used used to retard the kinetics of cellular transformation during subsequent sub-eutectoid annealing in this U-10-Mo alloy during sub-eutectoid annealing. Thus, this work provided insights on tailoring the final microstructure of the U-10Mo alloy, which can potentially improve the irradiation performance of this important class of alloy fuels.« less
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An Innovative Accident Tolerant LWR Fuel Rod Design Based on Uranium-Molybdenum Metal Alloy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Montgomery, Robert O.; Bennett, Wendy D.; Henager, Charles H.
2016-09-12
The US Department of Energy is developing a uranium-molybdenum metal alloy Enhanced Accident Tolerant Fuel concept for Light Water Reactor applications that provides improved fuel performance during normal operation, anticipated operational occurrences, and postulated accidents. The high initial uranium atom density, the high thermal conductivity, and a low heat capacity permit a U-Mo-based fuel assembly to meet important design and safety requirements. These attributes also result in a fuel design that can satisfy increased fuel utilization demands and allow for improved accident tolerance in LWRs. This paper summarizes the results obtained from the on-going activities to; 1) evaluate the impactmore » of the U-10wt%Mo thermal properties on operational and accident safety margins, 2) produce a triple extrusion of stainless steel cladding/niobium liner/U-10Mo fuel rod specimen and 3) test the high temperature water corrosion of rodlet samples containing a drilled hole in the cladding. Characterization of the cladding and liner thickness uniformity, microstructural features of the U-Mo gamma phase, and the metallurgical bond between the component materials will be presented. The results from corrosion testing will be discussed which yield insights into the resistance to attack by water ingress during high temperature water exposure for the triple extruded samples containing a drilled hole. These preliminary evaluations find that the U-10Mo fuel design concept has many beneficial features that can meet or improve conventional LWR fuel performance requirements under normal operation, AOOs, and postulated accidents. The viability of a deployable U-Mo fuel design hinges on demonstrating that fabrication processes and alloying additions can produce acceptable irradiation stability during normal operation and accident conditions and controlled metal-water reaction rates in the unlikely event of a cladding perforation. In the area of enhanced accident tolerance, a key objective is to establish that the lower stored energy of the U-Mo fuel design can provide the emergency core cooling systems the opportunity to maintain the reactor core in a coolable geometry following an accident.« less
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The irradiation behavior of atomized U-Mo alloy fuels at high temperature
NASA Astrophysics Data System (ADS)
Park, Jong-Man; Kim, Ki-Hwan; Kim, Chang-Kyu; Meyer, M. K.; Hofman, G. L.; Strain, R. V.
2001-04-01
Post-irradiation examinations of atomized U-10Mo, U-6Mo, and U-6Mo-1.7Os dispersion fuels from the RERTR-3 experiment irradiated in the Advanced Test Reactor (ATR) were carried out in order to investigate the fuel behavior of high uranium loading (8 gU/cc) at a high temperature (higher than 200°C). It was observed after about 40 at% BU that the U-Mo alloy fuels at a high temperature showed similar irradiation bubble morphologies compared to those at a lower temperature found in the RERTR-1 irradiation result, but there was a thick reaction layer with the aluminum matrix which was found to be greatly affected by the irradiation temperature and to a lesser degree by the fuel composition. In addition, the chemical analysis for the irradiated U-Mo fuels using the Electron Probe Micro Analysis (EPMA) method were conducted to investigate the compositional changes during the formation of the reaction product.
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Temperature dependent elastic properties of γ-phase U – 8 wt% Mo
Steiner, M. A.; Garlea, E.; Creasy, J.; ...
2017-12-28
Polycrystalline elastic moduli and stiffness tensor components of γ-phase U – 8 wt% Mo have been determined by resonant ultrasound spectroscopy in the temperature range of 25-650°C. The ambient temperature elastic properties are compared to results measured via other experimental methods and show reasonable agreement, though there is considerable variation of these properties within the literature at both the U – 8 wt% Mo composition and as a function of Mo concentration. The Young’s modulus of U – 8 wt% Mo measured in this study decreases steadily with temperature at a rate that is slower than trends previously observed atmore » similar Mo concentrations, though the difference is not statistically significant. This first measurement of the temperature dependent elastic stiffness tensor of a polycrystalline U-Mo alloy clarifies that the behavior of the Young’s modulus is due to a strongly weakening C 11 polycrystalline stiffness tensor component, along with milder decreases in C 12 and C 44. The unique partially auxetic properties recently predicted for singlecrystalline U-Mo are discussed in regard to their possible impact on the polycrystalline behavior of the alloy.« less
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Temperature dependent elastic properties of γ-phase U – 8 wt% Mo
DOE Office of Scientific and Technical Information (OSTI.GOV)
Steiner, M. A.; Garlea, E.; Creasy, J.
Polycrystalline elastic moduli and stiffness tensor components of γ-phase U – 8 wt% Mo have been determined by resonant ultrasound spectroscopy in the temperature range of 25-650°C. The ambient temperature elastic properties are compared to results measured via other experimental methods and show reasonable agreement, though there is considerable variation of these properties within the literature at both the U – 8 wt% Mo composition and as a function of Mo concentration. The Young’s modulus of U – 8 wt% Mo measured in this study decreases steadily with temperature at a rate that is slower than trends previously observed atmore » similar Mo concentrations, though the difference is not statistically significant. This first measurement of the temperature dependent elastic stiffness tensor of a polycrystalline U-Mo alloy clarifies that the behavior of the Young’s modulus is due to a strongly weakening C 11 polycrystalline stiffness tensor component, along with milder decreases in C 12 and C 44. The unique partially auxetic properties recently predicted for singlecrystalline U-Mo are discussed in regard to their possible impact on the polycrystalline behavior of the alloy.« less
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Thermal transport and thermopower of bcc U-Mo splat-cooled alloys
NASA Astrophysics Data System (ADS)
Falkowski, M.; Buturlim, V.; Paukov, M.; Havela, L.
2018-05-01
In order to characterize the electron and thermal transport properties in splat-cooled U-T alloys (T is transition metal), we measured the thermopower S and thermal conductivity κ of selected splat-cooled U-Mo alloys with 0, 11, 12.5, 15 and 17 at % Mo concentrations, as a function of temperature. Additionally, we compare our data with the results of S(T) and κ(T) for pure α-U bulk material. Moreover, what particularly motivated us for undertaking above mentioned investigation was the opportunity for prove the functionality of the TTO (Thermal Transport Option) insert of PPMS apparatus for such form of samples. Working with rapidly solidified materials in the form of splats, i.e. foils of typical thickness ∼ 0.2 mm, or even less, we need to test first whether the TTO output can be taken as reliable for the sample geometry, being far from typical bulk bar-shaped samples.
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Mesoscale model for fission-induced recrystallization in U-7Mo alloy
Liang, Linyun; Mei, Zhi -Gang; Kim, Yeon Soo; ...
2016-08-09
A mesoscale model is developed by integrating the rate theory and phase-field models and is used to study the fission-induced recrystallization in U-7Mo alloy. The rate theory model is used to predict the dislocation density and the recrystallization nuclei density due to irradiation. The predicted fission rate and temperature dependences of the dislocation density are in good agreement with experimental measurements. This information is used as input for the multiphase phase-field model to investigate the fission-induced recrystallization kinetics. The simulated recrystallization volume fraction and bubble induced swelling agree well with experimental data. The effects of the fission rate, initial grainmore » size, and grain morphology on the recrystallization kinetics are discussed based on an analysis of recrystallization growth rate using the modified Avrami equation. Here, we conclude that the initial microstructure of the U-Mo fuels, especially the grain size, can be used to effectively control the rate of fission-induced recrystallization and therefore swelling.« less
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Report on the Synchrotron Characterization of U-Mo and U-Zr Alloys and the Modeling Results
DOE Office of Scientific and Technical Information (OSTI.GOV)
Okuniewski, Maria A.; Ganapathy, Varsha; Hamilton, Brenden
2016-09-01
ABSTRACT Uranium-molybdenum (U-Mo) and uranium-zirconium (U-Zr) are two promising fuel candidates for nuclear transmutation reactors which burn long-lived minor actinides and fission products within fast spectrum reactors. The objectives of this research are centered on understanding the early stages of fuel performance through the examination of the irradiation induced microstructural changes in U-Zr and U-Mo alloys subjected to low neutron fluences. Specimens that were analyzed include those that were previously irradiated in the Advanced Test Reactor at INL. This most recent work has focused on a sub-set of the irradiated specimens, specifically U-Zr and U-Mo alloys that were irradiated tomore » 0.01 dpa at temperatures ranging from (150-800oC). These specimens were analyzed with two types of synchrotron techniques, including X-ray absorption fine structure and X-ray diffraction. These techniques provide non-destructive microstructural analysis, including phase identification and quantitation, lattice parameters, crystallite sizes, as well as bonding, structure, and chemistry. Preliminary research has shown changes in the phase fractions, crystallite sizes, and lattice parameters as a function of irradiation and temperature. Future data analyses will continue to explore these microstructural changes.« less
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TEM Characterization of High Burn-up Microstructure of U-7Mo Alloy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jian Gan; Brandon Miller; Dennis Keiser
2014-04-01
As an essential part of global nuclear non-proliferation effort, the RERTR program is developing low enriched U-Mo fuels (< 20% U-235) for use in research and test reactors that currently employ highly enriched uranium fuels. One type of fuel being developed is a dispersion fuel plate comprised of U-7Mo particles dispersed in Al alloy matrix. Recent TEM characterizations of the ATR irradiated U-7Mo dispersion fuel plates include the samples with a local fission densities of 4.5, 5.2, 5.6 and 6.3 E+21 fissions/cm3 and irradiation temperatures of 101-136?C. The development of the irradiated microstructure of the U-7Mo fuel particles consists ofmore » fission gas bubble superlattice, large gas bubbles, solid fission product precipitates and their association to the large gas bubbles, grain subdivision to tens or hundreds of nanometer size, collapse of bubble superlattice, and amorphisation. This presentation will describe the observed microstructures specifically focusing on the U-7Mo fuel particles. The impact of the observed microstructure on the fuel performance and the comparison of the relevant features with that of the high burn-up UO2 fuels will be discussed.« less
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U-10Mo Sample Preparation and Examination using Optical and Scanning Electron Microscopy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Prabhakaran, Ramprashad; Joshi, Vineet V.; Rhodes, Mark A.
2016-10-01
The purpose of this document is to provide guidelines to prepare specimens of uranium alloyed with 10 weight percent molybdenum (U-10Mo) for optical metallography and scanning electron microscopy. This document also provides instructions to set up an optical microscope and a scanning electron microscope to analyze U-10Mo specimens and to obtain the required information.
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U-10Mo Sample Preparation and Examination using Optical and Scanning Electron Microscopy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Prabhakaran, Ramprashad; Joshi, Vineet V.; Rhodes, Mark A.
2016-03-30
The purpose of this document is to provide guidelines to prepare specimens of uranium alloyed with 10 weight percent molybdenum (U-10Mo) for optical metallography and scanning electron microscopy. This document also provides instructions to set up an optical microscope and a scanning electron microscope to analyze U-10Mo specimens and to obtain the required information.
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Irradiation performance of U-Mo monolithic fuel
Meyer, M. K.; Gan, J.; Jue, J. F.; ...
2014-04-01
High-performance research reactors require fuel that operates at high specific power to high fission density, but at relatively low temperatures. Research reactor fuels are designed for efficient heat rejection, and are composed of assemblies of thin-plates clad in aluminum alloy. The development of low-enriched fuels to replace high-enriched fuels for these reactors requires a substantially increased uranium density in the fuel to offset the decrease in enrichment. Very few fuel phases have been identified that have the required combination of very-high uranium density and stable fuel behavior at high burnup. U-Mo alloys represent the best known tradeoff in these properties.more » Testing of aluminum matrix U-Mo aluminum matrix dispersion fuel revealed a pattern of breakaway swelling behavior at intermediate burnup, related to the formation of a molybdenum stabilized high aluminum intermetallic phase that forms during irradiation. In the case of monolithic fuel, this issue was addressed by eliminating, as much as possible, the interfacial area between U-Mo and aluminum. Based on scoping irradiation test data, a fuel plate system composed of solid U-10Mo fuel meat, a zirconium diffusion barrier, and Al6061 cladding was selected for development. Developmental testing of this fuel system indicates that it meets core criteria for fuel qualification, including stable and predictable swelling behavior, mechanical integrity to high burnup, and geometric stability. In addition, the fuel exhibits robust behavior during power-cooling mismatch events under irradiation at high power.« less
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NASA Astrophysics Data System (ADS)
Perez, E.; Keiser, D. D.; Sohn, Y. H.
2016-08-01
The U.S. Material Management and Minimization Reactor Conversion Program is developing low enrichment fuel systems encased in Al-alloy for use in research and test reactors. Monolithic fuel plates have local regions where the Usbnd Mo fuel plate may come into contact with the Al-alloy 6061 (AA6061) cladding. This results in the development of interdiffusion zones with complex microstructures with multiple phases. In this study, the microstructural development of diffusion couples, Usbnd 7 wt%Mo, Usbnd 10 wt%Mo, and Usbnd 12 wt%Mo vs. AA6061, annealed at 600 °C for 24 h and at 550 °C for 1, 5, and 20 h, were analyzed by scanning electron microscopy with x-ray energy dispersive spectroscopy. The microstructural development and kinetics were compared to diffusion couples Usbnd Mo vs. high purity Al and binary Alsbnd Si alloys. The diffusion couples developed complex interaction regions where phase development was influenced by the alloying additions of the AA6061.
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Stability Study of the RERTR Fuel Microstructure
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jian Gan; Dennis Keiser; Brandon Miller
2014-04-01
The irradiation stability of the interaction phases at the interface of fuel and Al alloy matrix as well as the stability of the fission gas bubble superlattice is believed to be very important to the U-Mo fuel performance. In this paper the recent result from TEM characterization of Kr ion irradiated U-10Mo-5Zr alloy will be discussed. The focus will be on the phase stability of Mo2-Zr, a dominated second phase developed at the interface of U-10Mo and the Zr barrier in a monolithic fuel plate from fuel fabrication. The Kr ion irradiations were conducted at a temperature of 200 degreesmore » C to an ion fluence of 2.0E+16 ions/cm2. To investigate the thermal stability of the fission gas bubble superlattice, a key microstructural feature in both irradiated dispersion U-7Mo fuel and monolithic U-10Mo fuel, a FIB-TEM sample of the irradiated U-10Mo fuel (3.53E+21 fission/cm3) was used for a TEM in-situ heating experiment. The preliminary result showed extraordinary thermal stability of the fission gas bubble superlattice. The implication of the TEM observation from these two experiments on the fuel microstructural evolution under irradiation will be discussed.« less
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NASA Astrophysics Data System (ADS)
Starikov, S. V.; Kolotova, L. N.; Kuksin, A. Yu.; Smirnova, D. E.; Tseplyaev, V. I.
2018-02-01
We studied structure and thermodynamic properties of cubic and tetragonal phases of pure uranium and U-Mo alloys using atomistic simulations: molecular dynamics and density functional theory. The main attention was paid to the metastable γ0 -phase that is formed in U-Mo alloys at low temperature. Structure of γ0 -phase is similar to body-centered tetragonal (bct) lattice with displacement of a central atom in the basic cell along [ 001 ] direction. Such displacements have opposite orientations for part of the neighbouring basic cells. In this case, such ordering of the displacements can be designated as antiferro-displacement. Formation of such complex structure may be interpreted through forming of short U-U bonds. At heating, the tetragonal structure transforms into cubic γs -phase, still showing ordering of central atom displacements. With rise in temperature, γs -phase transforms to γ-phase with a quasi body-centered cubic (q-bcc) lattice. The local positions of uranium atoms in γ-phase correspond to γs -phase, however, orientations of the central atom displacements become disordered. Transition from γ0 to γ can be considered as antiferro-to paraelastic transition of order-disorder type. This approach to the structure description of uranium alloy allows to explain a number of unusual features found in the experiments: anisotropy of lattice at low temperature; remarkably high self-diffusion mobility in γ-phase; decreasing of electrical resistivity at heating for some alloys. In addition, important part of this work is the development of new interatomic potential for U-Mo system made with taking into account details of studied structures.
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NASA Technical Reports Server (NTRS)
Yun, Hee Mann; Titran, Robert H.
1993-01-01
The tensile strain rate sensitivity and the stress-rupture strength of Mo-base and W-base alloy wires, 380 microns in diameter, were determined over the temperature range from 1200 K to 1600 K. Three molybdenum alloy wires; Mo + 1.1w/o hafnium carbide (MoHfC), Mo + 25w/o W + 1.1w/o hafnium carbide (MoHfC+25W) and Mo + 45w/o W + 1.1w/o hafnium carbide (MoHfC+45W), and a W + 0.4w/o hafnium carbide (WHfC) tungsten alloy wire were evaluated. The tensile strength of all wires studied was found to have a positive strain rate sensitivity. The strain rate dependency increased with increasing temperature and is associated with grain broadening of the initial fibrous structures. The hafnium carbide dispersed W-base and Mo-base alloys have superior tensile and stress-rupture properties than those without HfC. On a density compensated basis the MoHfC wires exhibit superior tensile and stress-rupture strengths to the WHfC wires up to approximately 1400 K. Addition of tungsten in the Mo-alloy wires was found to increase the long-term stress rupture strength at temperatures above 1400 K. Theoretical calculations indicate that the strength and ductility advantage of the HfC dispersed alloy wires is due to the resistance to recrystallization imparted by the dispersoid.
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Microstructure Characterization of RERTR Fuel
DOE Office of Scientific and Technical Information (OSTI.GOV)
J. Gan; B. D. Miller; D. D. Keiser
2008-09-01
A variety of phases have the potential to develop in the irradiated fuels for the reduced enrichment research test reactor (RERTR) program. To study the radiation stability of these potential phases, three depleted uranium alloys were cast. The phases of interest were identified including U(Si,Al)3, (U,Mo)(Si,Al)3, UMo2Al20, UAl4, and U6Mo4Al43. These alloys were irradiated with 2.6 MeV protons at 200ºC up to 3.0 dpa. The microstructure is characterized using SEM and TEM. Microstructural characterization for an archive dispersion fuel plate (U-7Mo fuel particles in Al-2%Si cladding) was also carried out. TEM sample preparation for the irradiated dispersion fuel has beenmore » developed.« less
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Grain boundary engineering to control the discontinuous precipitation in multicomponent U10Mo alloy
Devaraj, Arun; Kovarik, Libor; Kautz, Elizabeth; ...
2018-03-30
Here, we demonstrate here that locally stabilized structure and compositional segregation at grain boundaries in a complex multicomponent alloy can be modified using high temperature homogenization treatment to influence the kinetics of phase transformations initiating from grain boundaries during subsequent low temperature annealing. Using aberration-corrected scanning transmission electron microscopy and atom probe tomography of a model multicomponent metallic alloy —uranium-10 wt% molybdenum (U-10Mo) a nuclear fuel, that is highly relevant to worldwide nuclear non-proliferation efforts, we demonstrate the ability to change the structure and compositional segregation at grain boundary, which then controls the subsequent discontinuous precipitation kinetics during sub-eutectoid annealing.more » A change in grain boundary from one characterized by segregation of Mo and impurities at grain boundary to a phase boundary with a distinct U 2MoSi 2C wetting phase precipitates introducing Ni and Al rich interphase complexions caused a pronounced reduction in area fraction of subsequent discontinuous precipitation. The broader implication of this work is in highlighting the role of grain boundary structure and composition in metallic alloys on dictating the fate of grain boundary initiated phase transformations like discontinuous precipitation or cellular transformation. This work highlights a new pathway to tune the grain boundary structure and composition to tailor the final microstructure of multicomponent metallic alloys.« less
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Grain boundary engineering to control the discontinuous precipitation in multicomponent U10Mo alloy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Devaraj, Arun; Kovarik, Libor; Kautz, Elizabeth
Here, we demonstrate here that locally stabilized structure and compositional segregation at grain boundaries in a complex multicomponent alloy can be modified using high temperature homogenization treatment to influence the kinetics of phase transformations initiating from grain boundaries during subsequent low temperature annealing. Using aberration-corrected scanning transmission electron microscopy and atom probe tomography of a model multicomponent metallic alloy —uranium-10 wt% molybdenum (U-10Mo) a nuclear fuel, that is highly relevant to worldwide nuclear non-proliferation efforts, we demonstrate the ability to change the structure and compositional segregation at grain boundary, which then controls the subsequent discontinuous precipitation kinetics during sub-eutectoid annealing.more » A change in grain boundary from one characterized by segregation of Mo and impurities at grain boundary to a phase boundary with a distinct U 2MoSi 2C wetting phase precipitates introducing Ni and Al rich interphase complexions caused a pronounced reduction in area fraction of subsequent discontinuous precipitation. The broader implication of this work is in highlighting the role of grain boundary structure and composition in metallic alloys on dictating the fate of grain boundary initiated phase transformations like discontinuous precipitation or cellular transformation. This work highlights a new pathway to tune the grain boundary structure and composition to tailor the final microstructure of multicomponent metallic alloys.« less
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Perez, E.; Keiser, D. D.; Sohn, Y. H.
2016-05-10
The U.S. Material Management and Minimization Reactor Conversion Program is developing low enrichment fuel systems encased in Al-alloy for use in research and test reactors. Monolithic fuel plates have local regions where the Usingle bondMo fuel plate may come into contact with the Al-alloy 6061 (AA6061) cladding. This results in the development of interdiffusion zones with complex microstructures with multiple phases. In this study, the microstructural development of diffusion couples, U–7 wt%Mo, U–10 wt%Mo, and U–12 wt%Mo vs. AA6061, annealed at 600 °C for 24 h and at 550 °C for 1, 5, and 20 h, were analyzed by scanningmore » electron microscopy with x-ray energy dispersive spectroscopy. The microstructural development and kinetics were compared to diffusion couples U–Mo vs. high purity Al and binary Al–Si alloys. As a result, the diffusion couples developed complex interaction regions where phase development was influenced by the alloying additions of the AA6061.« less
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Microstructure of RERTR DU-alloys irradiated with krypton ions up to 100 dpa
NASA Astrophysics Data System (ADS)
Gan, J.; Keiser, D. D., Jr.; Miller, B. D.; Wachs, D. M.; Allen, T. R.; Kirk, M.; Rest, J.
2011-04-01
The radiation stability of the interaction product formed at the fuel-matrix interface of research reactor dispersion fuels, under fission-product bombardment, has a strong impact on fuel performance. Three depleted uranium alloys were cast that consisted of the following five phases to be investigated: U(Si, Al) 3, (U, Mo)(Si, Al) 3, UMo 2Al 20, U 6Mo 4Al 43, and UAl 4. Irradiation of transmission electron microscopy (TEM) disc samples with 500-keV Kr ions at 200 °C to doses up to ˜100 displacements per atom (dpa) were conducted using a 300-keV electron microscope equipped with an ion accelerator. TEM results show that the U(Si, Al) 3 and UAl 4 phases remain crystalline at 100 dpa without forming voids. The (U, Mo)(Si, Al) 3 and UMo 2Al 20 phases become amorphous at 1 and ˜2 dpa, respectively, and show no evidence of voids at 100 dpa. The U 6Mo 4Al 43 phase goes to amorphous at less than 1 dpa and reveals high density voids at 100 dpa.
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Characterization of High Damping Fe-Cr-Mo and Fe-Cr-Al Alloys for Naval Ships Application.
1988-03-01
austenitic , and martensitic. The high damping Fe-Cr-based alloys are closely related to ferritic stainless steels . Ferritic stainless steel consists of an Fe...cm reveme it Prectiaq #no ’uenf r oy o.o(a tflrowf U S9GO..P Damping; Ship Silencing; Ferritic Stainless Steels ; Ti-Ni 7 LhV I,. Cintunue on roere .r...decreased. E. METALLURGY OF THE IRON-CHROMIUM ALLOY SYSTEM 1. Physical Properties Stainless steels are divided into three main classes: ferritic
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Low-temperature irradiation behavior of uranium-molybdenum alloy dispersion fuel
NASA Astrophysics Data System (ADS)
Meyer, M. K.; Hofman, G. L.; Hayes, S. L.; Clark, C. R.; Wiencek, T. C.; Snelgrove, J. L.; Strain, R. V.; Kim, K.-H.
2002-08-01
Irradiation tests have been conducted to evaluate the performance of a series of high-density uranium-molybdenum (U-Mo) alloy, aluminum matrix dispersion fuels. Fuel plates incorporating alloys with molybdenum content in the range of 4-10 wt% were tested. Two irradiation test vehicles were used to irradiate low-enrichment fuels to approximately 40 and 70 at.% 235U burnup in the advanced test reactor at fuel temperatures of approximately 65 °C. The fuel particles used to fabricate dispersion specimens for most of the test were produced by generating filings from a cast rod. In general, fuels with molybdenum contents of 6 wt% or more showed stable in-reactor fission gas behavior, exhibiting a distribution of small, stable gas bubbles. Fuel particle swelling was moderate and decreased with increasing alloy content. Fuel particles with a molybdenum content of 4 wt% performed poorly, exhibiting extensive fuel-matrix interaction and the growth of relatively large fission gas bubbles. Fuel particles with 4 or 6 wt% molybdenum reacted more rapidly with the aluminum matrix than those with higher-alloy content. Fuel particles produced by an atomization process were also included in the test to determine the effect of fuel particle morphology and microstructure on fuel performance for the U-10Mo composition. Both of the U-10Mo fuel particle types exhibited good irradiation performance, but showed visible differences in fission gas bubble nucleation and growth behavior.
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NASA Astrophysics Data System (ADS)
Rest, J.; Hofman, G. L.; Kim, Yeon Soo
2009-04-01
An analytical model for the nucleation and growth of intra and intergranular fission-gas bubbles is used to characterize fission-gas bubble development in low-enriched U-Mo alloy fuel irradiated in the advanced test reactor in Idaho as part of the Reduced Enrichment for Research and Test Reactor (RERTR) program. Fuel burnup was limited to less than ˜7.8 at.% U in order to capture the fuel-swelling stage prior to irradiation-induced recrystallization. The model couples the calculation of the time evolution of the average intergranular bubble radius and number density to the calculation of the intergranular bubble-size distribution based on differential growth rate and sputtering coalescence processes. Recent results on TEM analysis of intragranular bubbles in U-Mo were used to set the irradiation-induced diffusivity and re-solution rate in the bubble-swelling model. Using these values, good agreement was obtained for intergranular bubble distribution compared against measured post-irradiation examination (PIE) data using grain-boundary diffusion enhancement factors of 15-125, depending on the Mo concentration. This range of enhancement factors is consistent with values obtained in the literature.
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Cross section TEM characterization of high-energy-Xe-irradiated U-Mo
Ye, B.; Jamison, L.; Miao, Y.; ...
2017-03-09
U-Mo alloys irradiated with 84 MeV Xe ions to various doses were characterized with transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) techniques. The TEM thin foils were prepared perpendicular to the irradiated surface to allow a direct observation of the entire region modified by ions. Furthermore, depth-selective microstructural information was revealed. Varied irradiation-induced phenomena such as gas bubble formation, phase reversal, and recrystallization were observed at different ion penetration depths in U-Mo.
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IRRADIATION PERFORMANCE OF U-Mo MONOLITHIC FUEL
DOE Office of Scientific and Technical Information (OSTI.GOV)
M.K. Meyer; J. Gan; J.-F. Jue
2014-04-01
High-performance research reactors require fuel that operates at high specific power to high fission density, but at relatively low temperatures. Research reactor fuels are designed for efficient heat rejection, and are composed of assemblies of thin-plates clad in aluminum alloy. The development of low-enriched fuels to replace high-enriched fuels for these reactors requires a substantially increased uranium density in the fuel to offset the decrease in enrichment. Very few fuel phases have been identified that have the required combination of very-high uranium density and stable fuel behavior at high burnup. UMo alloys represent the best known tradeoff in these properties.more » Testing of aluminum matrix U-Mo aluminum matrix dispersion fuel revealed a pattern of breakaway swelling behavior at intermediate burnup, related to the formation of a molybdenum stabilized high aluminum intermetallic phase that forms during irradiation. In the case of monolithic fuel, this issue was addressed by eliminating, as much as possible, the interfacial area between U-Mo and aluminum. Based on scoping irradiation test data, a fuel plate system composed of solid U-10Mo fuel meat, a zirconium diffusion barrier, and Al6061 cladding was selected for development. Developmental testing of this fuel system indicates that it meets core criteria for fuel qualification, including stable and predictable swelling behavior, mechanical integrity to high burnup, and geometric stability. In addition, the fuel exhibits robust behavior during power-cooling mismatch events under irradiation at high power.« less
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4-d magnetism: Electronic structure and magnetism of some Mo-based alloys
NASA Astrophysics Data System (ADS)
Liu, Yong; Bose, S. K.; Kudrnovský, J.
2017-02-01
We report results of a first-principles density-functional study of alloys of the 4 d -element Mo with group IV elements Si, Ge and Sn in zinc blende (ZB) and rock salt (RS) structures. The study was motivated by a similar study of ours based on the 4 d -element Tc, which showed the presence of half-metallic states with integer magnetic moment (1μB) per formula unit in TcX (X=C, Si, Ge) alloys. The calculated Curie temperatures for the ferromagnetic (FM) phases were low, around or less than 300 K. Searching for the possibility of 4 d -based alloys with higher Curie temperatures we have carried out the study involving the elements Mo, Ru and Rh. Among these the most promising case appears to be that involving the element Mo. Among the MoX (X=Si, Ge, Sn) alloys in ZB and RS structures, both MoGe and MoSn in ZB structures are found to possess an integer magnetic moment of 2μB per formula unit. ZB MoSn can be classified as a marginal/weak half-metal or a spin gapless semiconductor, while ZB MoGe would be best described as a gapless magnetic semiconductor. The calculated Curie temperatures are in the range 300-700 K. Considering the theoretical uncertainty in the band gaps due not only to the treatment of exchange and correlation effects, but density functional theory itself, these classifications may change somewhat, but both merit investigation from the viewpoint of potential spintronic application. Based on their higher Curie temperatures, Mo-based alloys would serve such purpose better than the previously reported Tc-based ones.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
None
The current PWR plant and core parameters are listed. Resign requirements are briefly summarized for a radiation monitoring system, a fuel handling water system, a coolant purification system, an electrical power distribution system, and component shielding. Results of studies on thermal bowing and stressing of UO/sub 2/ are reported. A graph is presented of reactor power vs. reactor flow for various hot channel conditions. Development of U-- Mo and U-Nb alloys has been stopped because of the recent selection of UO/sub 2/ fuel material for the PWR core and blanket. The fabrication characteristics of UO/sub 2/ powders are being studied.more » Seamless Zircaloy-2 tubing has been tested to determine elastic limits, bursting pressures, and corrosion resistance. Fabrication techniques and tests for corrosion and defects in Zircaloy-clad U-Mo and UO/sub 2/ fuel rods are described. The preparation of UO/sub 2/ by various methods is being studied to determine which method produces a material most suitable for PWR fuel elements. The stability of UO/sub 2/ compacts in high temperature water and steam is being determined. Surface area and density measurements have been performed on samples of UO/sub 2/ powder prepared by various methods. Revelopment work on U-- Mo and U--Nb alloys has included studies of the effect on corrosion behavior of additions to the test water, additions to the alloys, homogenization of the alloys, annealing times, cladding, and fabrication techniques. Data are presented on relaxation in spring materials after exposure to a corrosive environment. Results are reported from loop and autoclave tests on fission product and crud deposition. Results of irradiation and corrosion testing of clad and unclad U--Mo and U-Nh alloys are described. The UO/sub 2/ irradiation program has included studies of dimensional changes, release of fission gases, and activity in the water surrounding the samples. A review of the methods of calculating reactor physics parameters has been completed, and the established procedures have been applied to determination of PWR reference design parameters. Critical experiments and primary loop shielding analyses are described. (D.E.B.)« less
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McGeary, R.K.; Justusson, W.M.
1960-02-23
A reactor fuel element comprising a gamma-phase alloy consisting of 11 to 16 wt.% of molyhdenum and the balance uranium, annealed between 350 and 525 deg C and quenched to preserve the gamma phase, is reported.
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NASA Astrophysics Data System (ADS)
Keiser, Dennis D.; Jue, Jan-Fong; Miller, Brandon D.; Gan, Jian; Robinson, Adam B.; Medvedev, Pavel G.; Madden, James W.; Moore, Glenn A.
2016-06-01
Low-enriched (U-235 <20 pct) U-Mo dispersion fuel is being developed for use in research and test reactors. In most cases, fuel plates with Al or Al-Si alloy matrices have been tested in the Advanced Test Reactor to support this development. In addition, fuel plates with Mg as the matrix have also been tested. The benefit of using Mg as the matrix is that it potentially will not chemically interact with the U-Mo fuel particles during fabrication or irradiation, whereas with Al and Al-Si alloys such interactions will occur. Fuel plate R9R010 is a Mg matrix fuel plate that was aggressively irradiated in ATR. This fuel plate was irradiated as part of the RERTR-8 experiment at high temperature, high fission rate, and high power, up to high fission density. This paper describes the results of the scanning electron microscopy (SEM) analysis of an irradiated fuel plate using polished samples and those produced with a focused ion beam. A follow-up paper will discuss the results of transmission electron microscopy (TEM) analysis. Using SEM, it was observed that even at very aggressive irradiation conditions, negligible chemical interaction occurred between the irradiated U-7Mo fuel particles and Mg matrix; no interconnection of fission gas bubbles from fuel particle to fuel particle was observed; the interconnected fission gas bubbles that were observed in the irradiated U-7Mo particles resulted in some transport of solid fission products to the U-7Mo/Mg interface; the presence of microstructural pathways in some U-9.1 Mo particles that could allow for transport of fission gases did not result in the apparent presence of large porosity at the U-7Mo/Mg interface; and, the Mg-Al interaction layers that were present at the Mg matrix/Al 6061 cladding interface exhibited good radiation stability, i.e. no large pores.
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Interim Report on Mixing During the Casting of LEU-10Mo Plates in the Triple Plate Molds
DOE Office of Scientific and Technical Information (OSTI.GOV)
Aikin, Jr., Robert M.
LEU-10%Mo castings are commonly produced by down blending unalloyed HEU with a DU-12.7%Mo master-alloy. This work uses process modeling to provide insight into the mixing of the unalloyed uranium and U-Mo master alloy during melting and mold filling of a triple plate casting. Two different sets of situations are considered: (1) mixing during mold filling from a compositionally stratified crucible and (2) convective mixing of a compositionally stratified crucible during mold heating. The mold filling simulations are performed on the original Y-12 triple plate mold and the horizontal triple plate mold.
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Fabrication of a Mo based high temperature TZM alloy by non-consumable arc melting technique
DOE Office of Scientific and Technical Information (OSTI.GOV)
Chakraborty, S.P.; Krishnamurthy, N., E-mail: spc@barc.gov.in
High temperature structural materials are in great demand for power, chemical and nuclear industries which can perform beyond 1000 °C as super alloys usually fail. In this regard, Mo based TZM alloy is capable of retaining strength up to 1500 °C with excellent corrosion compatibility against molten alkali metals. Hence, currently this alloy is considered an important candidate material for high temperature compact nuclear and fusion reactors. Due to reactive nature of Mo and having high melting point, manufacturing this alloy by conventional process is unsuitable. Powder metallurgy technique has limited success due to restriction in quantity and purity. Thismore » paper deals with fabrication of TZM alloy by nonconsumable tungsten arc melting technique. Initially a ternary master alloy of Mo-Ti-Zr was prepared which subsequently by dilution method, was converted into TZM alloy gradually by external addition of Mo and C in various proportions. A number of melting trials were conducted to optimize the process parameters like current, voltage and time to achieve desired alloy composition. The alloy was characterized with respect to composition, elemental distribution profile, microstructure, hardness profile and phase analysis. Well consolidated alloy button was obtained having desired composition, negligible material loss and having microstructure as comparable to standard TZM alloy. (author)« less
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Rahman, T.; Ebert, W. L.; Indacochea, J. E.
2018-02-28
Alloys were made by alloying 5, 10, 15, 17.5, and 20 wt % Mo with Type 316L stainless steel. Sigma phases containing 21–29 wt % Mo formed along the austenite grain boundaries with the addition of 5 wt % Mo and increased with additions up to 15 wt % Mo, but they decreased with further additions. Laves phases containing 33–40 wt % Mo co-precipitated at additions of 10 wt % Mo which increased with further Mo increases. The corrosion resistance, assessed by potentiodynamic polarisation in a 10 mM NaCl solution adjusted to pH 4, increased relative to Type 316L formore » alloys made with 5 and 10 wt % added Mo, but decreased with further additions due to preferential corrosion of the Laves phase. The alloy made with 10 wt % added Mo had the highest corrosion resistance due primarily to the high Mo content of the austenite.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Rahman, T.; Ebert, W. L.; Indacochea, J. E.
Alloys were made by alloying 5, 10, 15, 17.5, and 20 wt % Mo with Type 316L stainless steel. Sigma phases containing 21–29 wt % Mo formed along the austenite grain boundaries with the addition of 5 wt % Mo and increased with additions up to 15 wt % Mo, but they decreased with further additions. Laves phases containing 33–40 wt % Mo co-precipitated at additions of 10 wt % Mo which increased with further Mo increases. The corrosion resistance, assessed by potentiodynamic polarisation in a 10 mM NaCl solution adjusted to pH 4, increased relative to Type 316L formore » alloys made with 5 and 10 wt % added Mo, but decreased with further additions due to preferential corrosion of the Laves phase. The alloy made with 10 wt % added Mo had the highest corrosion resistance due primarily to the high Mo content of the austenite.« less
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Postirradiation analysis of the latest high uranium density miniplate test: RERTR 8.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hofman, G. L.; Kim, Y. S.; Rest, J.
2008-01-01
Results of destructive examination of fuel miniplates irradiated in the RERTR-8 test are discussed. Metallographic features of dispersion fuel containing fuel particles of U-7wt%Mo with 1wt% Ti or 2wt% Zr are analyzed. It is hypothesized that Zr, either as alloy addition or fission product, may have a destabilizing effect on fission gas behavior. The purpose of miniplate test RERTR-8 was to obtain irradiation performance data on monolithic fuel plates fabricated by friction bonding (FB) and isostatic hot pressing (HIP), as well as dispersion fuel plates that contain U-7Mo fuel particles alloyed with small amounts of Zr or Ti (see Fig.more » 1). The results of the monolithic plates destructively examined to date were presented at the 2007 RERTR meeting in Prague. This paper presents the first results on the dispersion plates with Ti and Zr additions to U-7Mo. The effect of Ti and Zr additions to U-7wt%Mo on the extent of fuel-aluminum interdiffusion, although measureable, is small in absolute terms because of the overwhelming effect of the 5% Si addition to the Al matrix. Ti additions to the U-7wt%Mo have no discernable effect on swelling behavior of the fuel. However, there are indications that the addition of Zr may have a destabilizing effect on fission gas behavior at high burnup.« less
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Re Effects on Phase Stability and Mechanical Properties of MoSS+Mo3Si+Mo5SiB2 alloys
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, Ying; Bei, Hongbin; George, Easo P
2013-01-01
Because of their high melting points and good oxidation resistance Mo-Si-B alloys are of interest as potential ultrahigh-temperature structural materials. But their major drawbacks are poor ductility and fracture toughness at room temperature. Since alloying with Re has been suggested as a possible solution, we investigate here the effects of Re additions on the microstructure and mechanical properties of a ternary alloy with the composition Mo-12.5Si-8.5B (at.%). This alloy has a three-phase microstructure consisting of Mo solid-solution (MoSS), Mo3Si, and Mo5SiB2 and our results show that up to 8.4 at.% Re can be added to it without changing its microstructuremore » or forming any brittle phase at 1600 C. Three-point bend tests using chevron-notched specimens showed that Re did not improve fracture toughness of the three-phase alloy. Nanoindentation performed on the MoSS phase in the three-phase alloy showed that Re increases Young s modulus, but does not lower hardness as in some Mo solid solution alloys. Based on our thermodynamic calculations and microstructural analyses, the lack of a Re softening effect is attributed to the increased Si levels in the Re-containing MoSS phase since Si is known to increase its hardness. This lack of softening is possibly why there is no Re-induced improvement in fracture toughness.« less
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NASA Technical Reports Server (NTRS)
Barrett, Charles A.
1987-01-01
Cobalt levels were systematically varied in the Ni-base turbine alloys U-700 (cast), U-700m (PM/HIP), Waspaloy, Mar-M-247, In-738, Nimonic-115, U-720, and SX-R-150. the cobalt levels ranged from 0 wt pct to the nominal commercial content in each alloy. the alloys were tested in cyclic oxidation in static air at 1000, 1100 and 1150 C for 500, 200, and 100 hr, respectively. An oxidation attack parameter, Ka, derived from the specific weight change versus time data was used to evaluate the oxidation behavior of the alloys along with X-ray diffraction analysis of the surface oxides. The alloys tend to form either Cr2O3/chromite spinel or Al2O3/aluminate spinel depending on the Cr/Al ratio in the alloys. Alloys with a ratio of 3.5 or higher tend to favor the Cr oxides while those under 3.0 form mostly Al oxides. In general the Al2O3/aluminate spinel forming alloys have the better oxidation resistance. Increased cobalt content lowers the scaling resistance of the higher Cr allys while a 5.0 wt pct Co content is optimum for the Al controlling alloys. The refractory metals, particularly Ta, appear beneficial to both types of oxides, perhaps due to the formation of the omnipresent trirutile Ni(Ta, Cb, Mo, W)2O6. Both scales break down as increasing amounts of NiO are formed.
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Prediction of U-Mo dispersion nuclear fuels with Al-Si alloy using artificial neural network
DOE Office of Scientific and Technical Information (OSTI.GOV)
Susmikanti, Mike, E-mail: mike@batan.go.id; Sulistyo, Jos, E-mail: soj@batan.go.id
2014-09-30
Dispersion nuclear fuels, consisting of U-Mo particles dispersed in an Al-Si matrix, are being developed as fuel for research reactors. The equilibrium relationship for a mixture component can be expressed in the phase diagram. It is important to analyze whether a mixture component is in equilibrium phase or another phase. The purpose of this research it is needed to built the model of the phase diagram, so the mixture component is in the stable or melting condition. Artificial neural network (ANN) is a modeling tool for processes involving multivariable non-linear relationships. The objective of the present work is to developmore » code based on artificial neural network models of system equilibrium relationship of U-Mo in Al-Si matrix. This model can be used for prediction of type of resulting mixture, and whether the point is on the equilibrium phase or in another phase region. The equilibrium model data for prediction and modeling generated from experimentally data. The artificial neural network with resilient backpropagation method was chosen to predict the dispersion of nuclear fuels U-Mo in Al-Si matrix. This developed code was built with some function in MATLAB. For simulations using ANN, the Levenberg-Marquardt method was also used for optimization. The artificial neural network is able to predict the equilibrium phase or in the phase region. The develop code based on artificial neural network models was built, for analyze equilibrium relationship of U-Mo in Al-Si matrix.« less
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NASA Astrophysics Data System (ADS)
Keiser, Dennis D.; Jue, Jan-Fong; Gan, Jian; Miller, Brandon D.; Robinson, Adam B.; Madden, James W.; Ross Finlay, M.; Moore, Glenn; Medvedev, Pavel; Meyer, Mitch
2017-05-01
The Material Management and Minimization (M3) Reactor Conversion Program, in the past called the Reduced Enrichment for Research and Test Reactor (RERTR) Program, is developing low-enriched uranium (LEU) fuels for application in research and test reactors. U-Mo alloy dispersion fuel is one type being developed. Blister testing has been performed on different fuel plate samples to determine the margin to failure for fuel plates irradiated to different fission densities. Microstructural characterization was performed using scanning electron microscopy and transmission electron microscopy on a sample taken from a U-7Mo/AA4043 matrix dispersion fuel plate irradiated in the RERTR-6 experiment that was blister-tested up to a final temperature of 500 °C. The results indicated that two types of grain/cell boundaries were observed in the U-7Mo fuel particles, one with a relatively low Mo content and fission gas bubbles and a second type enriched in Si, due to interdiffusion from the Si-containing matrix, with little evidence of fission gas bubbles. With respect to the behavior of the major fission gas Xe, a significant amount of the Xe was still observed within the U-7Mo fuel particle, along with microns into the AA4043 matrix. For the fuel/matrix interaction layers that form during fabrication and then grow during irradiation, they change from the as-irradiated amorphous structure to one that is crystalline after blister testing. In the AA4043 matrix, the original Si-rich precipitates, which are typically observed in as-irradiated U-Mo dispersion fuel, get consumed due to interdiffusion with the U-7Mo fuel particles during the blister test. Finally, the fission gas bubbles that were originally around 3 nm in diameter and resided on a fission gas superlattice (FGS) in the intragranular regions of as-irradiated U-7Mo fuel grew in size (up to ∼20 nm diameter) during blister testing and, in many areas, are no longer organized as a superlattice.
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Interaction Between U-Mo Alloys and Alloys Al-Be
NASA Astrophysics Data System (ADS)
Nikitin, S. N.; Tarasov, B. A.; Shornikov, D. P.
The main objective of the work is the experimental determination of the effect of doping on the kinetics of the interaction of beryllium, aluminum and uranium-molybdenum alloy dispersed in the nuclear fuel. It is shown that an increase in the content of Be in Al leads to a linear decrease in the rate of interaction of the alloy with uranium-molybdenum alloy. Besides AlBe-alloys have higher thermal and mechanical properties than other matrix alloys such as AlSi.
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Corrosion of Stainless-Steel Tubing in a Spacecraft Launch Environment
NASA Technical Reports Server (NTRS)
Barile, Ronald G.; MacDowell, Louis G.; Curran, Joe; Calle, Luz Maria; Hodge, Timothy
2001-01-01
This is a report of exposure of various metal tubing to oceanfront launch environments. The objective is to examine various types of corrosion-resistant tubing for Space Shuttle launch sites. The metals were stainless steels (austenitic, low-carbon, Mo-alloy, superaustenitic, duplex, and superferritic), Ni-Cr-Mo alloy, Ni-Mo-Cr-Fe-W alloy, and austenitic Ni-base superalloy.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Stillman, J. A.; Feldman, E. E.; Wilson, E. H.
This report contains the results of reactor accident analyses for the University of Missouri Research Reactor (MURR). The calculations were performed as part of the conversion from the use of highly-enriched uranium (HEU) fuel to the use of low-enriched uranium (LEU) fuel. The analyses were performed by staff members of the Global Threat Reduction Initiative (GTRI) Reactor Conversion Program at the Argonne National Laboratory (ANL), the MURR Facility, and the Nuclear Engineering Program – College of Engineering, University of Missouri-Columbia. The core conversion to LEU is being performed with financial support from the U. S. government. This report contains themore » results of reactor accident analyses for the University of Missouri Research Reactor (MURR). The calculations were performed as part of the conversion from the use of highly-enriched uranium (HEU) fuel to the use of low-enriched uranium (LEU) fuel. The analyses were performed by staff members of the Global Threat Reduction Initiative (GTRI) Reactor Conversion Program at the Argonne National Laboratory (ANL), the MURR Facility, and the Nuclear Engineering Program – College of Engineering, University of Missouri-Columbia. The core conversion to LEU is being performed with financial support from the U. S. government. In the framework of non-proliferation policies, the international community presently aims to minimize the amount of nuclear material available that could be used for nuclear weapons. In this geopolitical context most research and test reactors, both domestic and international, have started a program of conversion to the use of LEU fuel. A new type of LEU fuel based on an alloy of uranium and molybdenum (U-Mo) is expected to allow the conversion of U.S. domestic high performance reactors like MURR. This report presents the results of a study of core behavior under a set of accident conditions for MURR cores fueled with HEU U-Alx dispersion fuel or LEU monolithic U-Mo alloy fuel with 10 wt% Mo (U-10Mo).« less
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Song, Jeong-Gyu; Ryu, Gyeong Hee; Lee, Su Jeong; Sim, Sangwan; Lee, Chang Wan; Choi, Taejin; Jung, Hanearl; Kim, Youngjun; Lee, Zonghoon; Myoung, Jae-Min; Dussarrat, Christian; Lansalot-Matras, Clement; Park, Jusang; Choi, Hyunyong; Kim, Hyungjun
2015-01-01
The effective synthesis of two-dimensional transition metal dichalcogenides alloy is essential for successful application in electronic and optical devices based on a tunable band gap. Here we show a synthesis process for Mo1−xWxS2 alloy using sulfurization of super-cycle atomic layer deposition Mo1−xWxOy. Various spectroscopic and microscopic results indicate that the synthesized Mo1−xWxS2 alloys have complete mixing of Mo and W atoms and tunable band gap by systematically controlled composition and layer number. Based on this, we synthesize a vertically composition-controlled (VCC) Mo1−xWxS2 multilayer using five continuous super-cycles with different cycle ratios for each super-cycle. Angle-resolved X-ray photoemission spectroscopy, Raman and ultraviolet–visible spectrophotometer results reveal that a VCC Mo1−xWxS2 multilayer has different vertical composition and broadband light absorption with strong interlayer coupling within a VCC Mo1−xWxS2 multilayer. Further, we demonstrate that a VCC Mo1−xWxS2 multilayer photodetector generates three to four times greater photocurrent than MoS2- and WS2-based devices, owing to the broadband light absorption. PMID:26204328
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Phase development in a U-7 wt.% Mo vs. Al-7 wt.% Ge diffusion couple
NASA Astrophysics Data System (ADS)
Perez, E.; Keiser, D. D.; Sohn, Y. H.
2013-10-01
Fuel development for the Reduced Enrichment for Research and Test Reactors (RERTR) program has demonstrated that U-Mo alloys in contact with Al develop interaction regions with phases that have poor irradiation behavior. The addition of Si to the Al has been considered with positive results. In this study, compositional modification is considered by replacing Si with Ge to determine the effect on the phase development in the system. The microstructural and phase development of a diffusion couple of U-7 wt.% Mo in contact with Al-7 wt.% Ge was examined by transmission electron microscopy, scanning electron microscopy and energy dispersive spectroscopy. The interdiffusion zone developed a microstructure that included the cubic-UGe3 phase and amorphous phases. The UGe3 phase was observed with and without Mo and Al solid solution developing a (U,Mo)(Al,Ge)3 phase.
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Keiser, Jr., Dennis D.; Jue, Jan -Fong; Gan, Jian; ...
2017-02-27
The Material Management and Minimization (M3) Reactor Conversion Program, in the past called the Reduced Enrichment for Research and Test Reactor (RERTR) Program, is developing low-enriched uranium (LEU) fuels for application in research reactors. U–Mo alloy dispersion fuel is one type being developed. Blister testing has been performed on different fuel plate samples to determine the margin to failure for fuel plates irradiated to different fission densities. Microstructural characterization was performed using scanning electron microscopy and transmission electron microscopy on a sample taken from a U-7Mo/AA4043 matrix dispersion fuel plate irradiated in the RERTR-6 experiment that was blister-tested up tomore » a final temperature of 500°C. The results indicated that two types of grain/cell boundaries were observed in the U- 7Mo fuel particles, one with a relatively low Mo content and fission gas bubbles and a second type enriched in Si, due to interdiffusion from the Si-containing matrix, with little evidence of fission gas bubbles. With respect to the behavior of the major fission gas Xe, a significant amount of the Xe was still observed within the U-7Mo fuel particle, along with microns into the AA4043 matrix. For the fuel/matrix interaction layers that form during fabrication and then grow during irradiation, they change from the as-irradiated amorphous structure to one that is crystalline after blister testing. In the AA4043 matrix, the original Si-rich precipitates, which are typically observed in as-irradiated U-Mo dispersion fuel, get consumed due to interdiffusion with the U-7Mo fuel particles during the blister test. Lastly, the fission gas bubbles that were originally around 2 nm in diameter and resided on a fission gas superlattice in the intragranular regions of as-irradiated U-7Mo fuel grew in size (up to ~20 nm diameter) during blister testing.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Keiser, Jr., Dennis D.; Jue, Jan -Fong; Gan, Jian
The Material Management and Minimization (M3) Reactor Conversion Program, in the past called the Reduced Enrichment for Research and Test Reactor (RERTR) Program, is developing low-enriched uranium (LEU) fuels for application in research reactors. U–Mo alloy dispersion fuel is one type being developed. Blister testing has been performed on different fuel plate samples to determine the margin to failure for fuel plates irradiated to different fission densities. Microstructural characterization was performed using scanning electron microscopy and transmission electron microscopy on a sample taken from a U-7Mo/AA4043 matrix dispersion fuel plate irradiated in the RERTR-6 experiment that was blister-tested up tomore » a final temperature of 500°C. The results indicated that two types of grain/cell boundaries were observed in the U- 7Mo fuel particles, one with a relatively low Mo content and fission gas bubbles and a second type enriched in Si, due to interdiffusion from the Si-containing matrix, with little evidence of fission gas bubbles. With respect to the behavior of the major fission gas Xe, a significant amount of the Xe was still observed within the U-7Mo fuel particle, along with microns into the AA4043 matrix. For the fuel/matrix interaction layers that form during fabrication and then grow during irradiation, they change from the as-irradiated amorphous structure to one that is crystalline after blister testing. In the AA4043 matrix, the original Si-rich precipitates, which are typically observed in as-irradiated U-Mo dispersion fuel, get consumed due to interdiffusion with the U-7Mo fuel particles during the blister test. Lastly, the fission gas bubbles that were originally around 2 nm in diameter and resided on a fission gas superlattice in the intragranular regions of as-irradiated U-7Mo fuel grew in size (up to ~20 nm diameter) during blister testing.« less
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U-Mo Monolithic Fuel for Nuclear Research and Test Reactors
DOE Office of Scientific and Technical Information (OSTI.GOV)
Prabhakaran, Ramprashad
The metallic fuel selected to replace the current HEU fuels in the research and test reactors is the LEU-10 weight % Mo alloy in the form of a thin sheet or foil encapsulated in AA6061 aluminum alloy with a zirconium interlayer. In order to effectively lead this pursuit, new developments in processing and fabrication of the fuel elements have been initiated, along with a better understanding of material behavior before and after irradiation as a result of these new developments. This editorial note gives an introduction about research and test reactors, need for HEU to LEU conversion, fuel requirements, highmore » uranium density monolithic fuel development and an overview of the four articles published in the December 2017 issue of JOM under a special topic titled “U-Mo Monolithic Fuel for Nuclear Research and Test Reactors”.« less
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NASA Technical Reports Server (NTRS)
Stephens, J. R.; Witzke, W. R.; Devletian, J. H.
1981-01-01
Mechanical properties of weldments in two Fe-12Mn experimental alloys designed for cryogenic service were evaluated. Weldments were made using the GTA welding process. Tests to evaluate the weldments were conducted at -196 C and included: equivalent energy fracture toughness tests; autogenous transverse weld, notched transverse weld, and longitudinal weld tensile tests; and all-weld-metal tensile tests. The Fe-12Mn-0.2Ti and Fe-12Mn-1Mo-0.2Ti alloys proved weldable for cryogenic service, with weld metal and heat-affected zone properties comparable with those of the base metal. Optimum properties were achieved in the base alloys, weld metals, and heat-affected zones after a two-step heat treatment consisting of austenitizing at 900 C followed by tempering at 500 C. The Mo-containing alloy offered a marked improvement in cryogenic properties over those of the Mo-free alloy. Molybdenum increased the amount of retained austenite and reduced the amount of epsilon martensite observed in the microstructure of the two alloys.
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Aerospace Structural Metals Handbook. Volume 5. Supplement XI. Nonferrous Alloys
1978-12-01
4140 Sep 74 1204 fe-(0.3C)-l.8,Ni-0.8Cr-0.4Mo-0.07V...IN CIAD WITH! FOILS OF Ni-20Cr-4AI-1.251 OF V C.-• LLA C LADDIN ALLOY ~THICKiNESS ,002. .005, AND .01 INCH U.SING (SUBSTRATE SAE ALLOY FACE SHEEKTS...31, 87, D54 ’est 0 .15xU Bar Electron Beamn Welded In Similar S~cmOJDesrilbed Below ha letNcie AsWn ,elded IlHeat Treat (t,, resterngthen apao
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2011-07-01
research seems to emphasize alloys based Approved for public release; distribution unlimited. 2 on the late transition metals such as Cr, Mn, Fe, Co, Ni ...of the Nb25Mo25Ta25W25 alloy , with larger grains at the regions experiencing slower solidification , i.e. near the surfaces not contacting with the...20-30 µm, indicating similar solidification conditions. 3.2.3 Fractography of samples deformed at room temperature The high entropy alloy
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Yang, Chao; Muránsky, Ondrej; Zhu, Hanliang; Thorogood, Gordon J.; Avdeev, Maxim; Huang, Hefei; Zhou, Xingtai
2017-01-01
A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5–2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni3Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo2C particles during sintering. The amount of grain boundaries greatly increases the Hall–Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process. PMID:28772747
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DOE Office of Scientific and Technical Information (OSTI.GOV)
McDeavitt, Sean; Shao, Lin; Tsvetkov, Pavel
2014-04-07
Advanced fast reactor systems being developed under the DOE's Advanced Fuel Cycle Initiative are designed to destroy TRU isotopes generated in existing and future nuclear energy systems. Over the past 40 years, multiple experiments and demonstrations have been completed using U-Zr, U-Pu-Zr, U-Mo and other metal alloys. As a result, multiple empirical and semi-empirical relationships have been established to develop empirical performance modeling codes. Many mechanistic questions about fission as mobility, bubble coalescience, and gas release have been answered through industrial experience, research, and empirical understanding. The advent of modern computational materials science, however, opens new doors of development suchmore » that physics-based multi-scale models may be developed to enable a new generation of predictive fuel performance codes that are not limited by empiricism.« less
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NASA Astrophysics Data System (ADS)
Soba, A.; Denis, A.
2007-03-01
The codes PLACA and DPLACA, elaborated in this working group, simulate the behavior of a plate-type fuel containing in its core a foil of monolithic or dispersed fissile material, respectively, under normal operation conditions of a research reactor. Dispersion fuels usually consist of ceramic particles of a uranium compound in a high thermal conductivity matrix. The use of particles of a U-Mo alloy in a matrix of Al requires especially devoted subroutines able to simulate the growth of the interaction layer that develops between the particles and the matrix. A model is presented in this work that gives account of these particular phenomena. It is based on the assumption that diffusion of U and Al through the layer is the rate-determining step. Two moving interfaces separate the growing reaction layer from the original phases. The kinetics of these boundaries are solved as Stefan problems. In order to test the model and the associated code, some previous, simpler problems corresponding to similar systems for which analytical solutions or experimental data are known were simulated. Experiments performed with planar U-Mo/Al diffusion couples are reported in the literature, which purpose is to obtain information on the system parameters. These experiments were simulated with PLACA. Results of experiments performed with U-Mo particles disperse in Al either without or with irradiation, published in the open literature were simulated with DPLACA. A satisfactory prediction of the whole reaction layer thickness and of the individual fractions corresponding to alloy and matrix consumption was obtained.
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NASA Astrophysics Data System (ADS)
Shi, Qianying; An, Ning; Huo, Jiajie; Ding, Xianfei; Zheng, Yunrong; Feng, Qiang
2017-11-01
In current study, two sets of Ni-based alloys (Ni-Cr-Mo and Ni-Cr-Re series) containing 0 to 15 at. pct of Co addition were investigated to understand the formation behavior of TCP phases. Significant difference on the formation behavior of TCP phases and corresponding Co effect was found in two series alloys. TCP precipitates ( P and µ phase) were observed in both grain interiors and boundaries in Ni-Cr-Mo series alloys. Higher levels of Co addition increased the supersaturation of Mo in the γ matrix, which explained that Co addition promoted µ phase formation. In contrast, the TCP precipitates ( σ phase) formed by the manner of discontinuous precipitation transformation in the grain boundaries in Ni-Cr-Re series alloys. More Co additions suppressed the formation of σ phase, which was mainly attributed to the decreased supersaturation of Re in thermodynamically metastable γ matrix. The information obtained from simplified alloy systems in this study is helpful for the design of multicomponent Ni-based superalloys.
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Open-Cellular Co-Base and Ni-Base Superalloys Fabricated by Electron Beam Melting
Murr, Lawrence; Li, Shujun; Tian, Yuxing; Amato, Krista; Martinez, Edwin; Medina, Frank
2011-01-01
Reticulated mesh samples of Co-29Cr-6Mo alloy and Ni-21Cr-9Mo-4Nb alloy (625) and stochastic foam samples of Co-29Cr-6Mo alloy fabricated by electron beam melting were characterized by optical metallography, and the dynamic stiffness (Young’s modulus) was measured by resonant frequency analysis. The relative stiffness (E/Es) versus relative density (ρ/ρs) plotted on a log-log basis resulted in a fitted straight line with a slope n ≅ 2, consistent with that for ideal open cellular materials. PMID:28879949
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Solution treatment-delayed zirconium-strengthening behavior in Ti-7.5Mo-xZr alloy system
NASA Astrophysics Data System (ADS)
Chern Lin, Jiin-Huey; Fu, Yen-Han; Chen, Yen-Chun; Peng, Yu-Po; Ju, Chien-Ping
2018-01-01
The present study was devoted to investigate and compare the Zr-strengthening behavior in as-cast (AC) and solution-treated (ST) Ti-7.5Mo-xZr alloys. The experimental results indicated that AC Ti-7.5Mo and AC Ti-7.5Mo-1Zr alloys substantially had an orthorhombic {α }\\prime\\prime phase with a fine, acicular morphology. The content of equi-axed β phase continued to increase with increased Zr content at the expense of {α }\\prime\\prime phase. The threshold Zr content for the formation of β phase in the ST Ti-7.5Mo-xZr alloys was apparently higher than that in the AC Ti-7.5Mo-xZr alloys. The β granular structure was revealed in ST Ti-7.5Mo-5Zr alloy, which increased with increased Zr content. Unlike AC Ti-7.5Mo-9Zr alloy, within each grain of ST Ti-7.5Mo-9Zr alloy were still observed a significant portion of {α }\\prime\\prime morphology. AC Ti-7.5Mo alloy had the lowest YS, lowest tensile modulus and highest elongation among all AC Ti-7.5Mo-xZr alloys. When Zr content increased, both YS and modulus significantly increased while the elongation significantly decreased. Compared to AC Ti-7.5Mo alloy, AC Ti-7.5Mo-9Zr alloy had almost double YS, indicating the effectiveness of Zr-induced strengthening in the AC Ti-7.5Mo-xZr alloys. Compared to AC Ti-7.5Mo, ST Ti-7.5Mo alloys had lower YS, UTS and tensile modulus with almost the same elongation. All the XRD, metallography and tensile test results consistently indicated that the presence of Zr could accelerate the formation of β phase and effectively strengthen the AC Ti-7.5Mo-xZr alloys. A phenomenon of delayed β formation and delayed strengthening was noted in the ST Ti-7.5Mo-xZr alloys, compared to the AC Ti-7.5Mo-xZr alloys.
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NASA Technical Reports Server (NTRS)
Zaplatynsky, I.; Barrett, C. A.
1986-01-01
The influence of varying the content of Co, Cr, Mo, Ta, and Al in a series of cast Ni-based gamma/gamma'superalloys on the behavior of aluminide coatings was studied in burner rig cyclic oxidation tests at 1100 C. The alloys had nominally fixed levels of Ti, W, Cb, Zr, C, and B. The alloy compositions were based on a full 2(sup 5)-fractional statistical design supplemented by 10 star point alloys and a center point alloy. This full central composite design of 43 alloys plus two additional alloys with extreme Al levels allowed a complete second degree estimating equation to be derived from the 5-compositional variables. The weight change/time data for the coated samples fitted well to the paralinear oxidation model and enabled a modified oxidation attack parameter, K'(sub a) to be derived to rank the alloys and log K' (sub a ) to be used as the dependent variable in the estimating equation to determine the oxidation resistance of the coating as a function of the underlying alloy content. The most protective aluminide coatings are associated with the highest possible base ally contents of CR and Al and at a 4 percent Ta level. The Mo and Co effects interact but at fixed levels of 0, 5, or 10% Co. A 4% Mo level is optimum.
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Yang, Chao; Muránsky, Ondrej; Zhu, Hanliang; Thorogood, Gordon J; Avdeev, Maxim; Huang, Hefei; Zhou, Xingtai
2017-04-06
A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5-2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni₃Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo₂C particles during sintering. The amount of grain boundaries greatly increases the Hall-Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process.
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[Metallurgical differentiation of cobalt-chromium alloys for implants].
Holzwarth, U; Thomas, P; Kachler, W; Göske, J; Schuh, A
2005-10-01
Cobalt Chromium alloys are used in cemented total hip or knee arthroplasty as well as in metal-on-metal bearings in total hip arthroplasty. An increasing number of publications report about (allergic) reactions to wear particles of Cobalt Chromium alloys. Reactions to nickel are more frequent in comparison to Cobalt or Chromium particles. It is well known that different kinds of Cobalt Chromium alloys contain different amounts of alloying elements; nevertheless. The aim of the current work was to compare the different Cobalt Chromium alloys according to ASTM F or ISO standards in respect to the different alloying elements. Co28Cr6Mo casting alloys according to ASTM F 75 or ISO 5832-4 as well as forging alloy types according to ASTM F 799 and ISO 5832 such as Co20Cr15W10Ni, Co35Ni20Cr, Fe40Co20Cr10Ni, Co20Cr20Ni, and Co28Cr6Mo were analyzed in respect to their element content of Co, Cr, Ni, Mo, Fe, W, and Mn. In 1935 the Cobalt based alloy "Vitallium" Co30Cr5Mo basically used in the aircraft industry was introduced into medicine. The chemical composition of this alloy based on Cobalt showed 30 wt.% Chromium and 5 wt.% Molybdenum. The differentiation using alloy names showed no Nickel information in single alloy names. The information given about different alloys can lead to an unprecise evaluation of histopathological findings in respect to alloys or alloying constituents. Therefore, implant manufacturers should give the exact information about the alloys used and adhere to European law, Euronorm 93/42/EWG.
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Cost Estimate for Molybdenum and Tantalum Refractory Metal Alloy Flow Circuit Concepts
NASA Technical Reports Server (NTRS)
Hickman, Robert R.; Martin, James J.; Schmidt, George R.; Godfroy, Thomas J.; Bryhan, A.J.
2010-01-01
The Early Flight Fission-Test Facilities (EFF-TF) team at NASA Marshall Space Flight Center (MSFC) has been tasked by the Naval Reactors Prime Contract Team (NRPCT) to provide a cost and delivery rough order of magnitude estimate for a refractory metal-based lithium (Li) flow circuit. The design is based on the stainless steel Li flow circuit that is currently being assembled for an NRPCT task underway at the EFF-TF. While geometrically the flow circuit is not representative of a final flight prototype, knowledge has been gained to quantify (time and cost) the materials, manufacturing, fabrication, assembly, and operations to produce a testable configuration. This Technical Memorandum (TM) also identifies the following key issues that need to be addressed by the fabrication process: Alloy selection and forming, cost and availability, welding, bending, machining, assembly, and instrumentation. Several candidate materials were identified by NRPCT including molybdenum (Mo) alloy (Mo-47.5 %Re), tantalum (Ta) alloys (T-111, ASTAR-811C), and niobium (Nb) alloy (Nb-1 %Zr). This TM is focused only on the Mo and Ta alloys, since they are of higher concern to the ongoing effort. The initial estimate to complete a Mo-47%Re system ready for testing is =$9,000k over a period of 30 mo. The initial estimate to complete a T-111 or ASTAR-811C system ready for testing is =$12,000k over a period of 36 mo.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Y. Park; J. Yoo; K. Huang
2014-04-01
Phase constituents and microstructure changes in RERTR fuel plate assemblies as functions of temperature and duration of hot-isostatic pressing (HIP) during fabrication were examined. The HIP process was carried out as functions of temperature (520, 540, 560 and 580 °C for 90 min) and time (45–345 min at 560 °C) to bond 6061 Al-alloy to the Zr diffusion barrier that had been co-rolled with U-10 wt.% Mo (U10Mo) fuel monolith prior to the HIP process. Scanning and transmission electron microscopies were employed to examine the phase constituents, microstructure and layer thickness of interaction products from interdiffusion. At the interface betweenmore » the U10Mo and Zr, following the co-rolling, the UZr2 phase was observed to develop adjacent to Zr, and the a-U phase was found between the UZr2 and U10Mo, while the Mo2Zr was found as precipitates mostly within the a-U phase. The phase constituents and thickness of the interaction layer at the U10Mo-Zr interface remained unchanged regardless of HIP processing variation. Observable growth due to HIP was only observed for the (Al,Si)3Zr phase found at the Zr/AA6061 interface, however, with a large activation energy of 457 ± 28 kJ/mole. Thus, HIP can be carried to improve the adhesion quality of fuel plate without concern for the excessive growth of the interaction layer, particularly at the U10Mo-Zr interface with the a-U, Mo2Zr, and UZr2 phases.« less
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NASA Astrophysics Data System (ADS)
Park, Y.; Yoo, J.; Huang, K.; Keiser, D. D.; Jue, J. F.; Rabin, B.; Moore, G.; Sohn, Y. H.
2014-04-01
Phase constituents and microstructure changes in RERTR fuel plate assemblies as functions of temperature and duration of hot-isostatic pressing (HIP) during fabrication were examined. The HIP process was carried out as functions of temperature (520, 540, 560 and 580 °C for 90 min) and time (45-345 min at 560 °C) to bond 6061 Al-alloy to the Zr diffusion barrier that had been co-rolled with U-10 wt.% Mo (U10Mo) fuel monolith prior to the HIP process. Scanning and transmission electron microscopies were employed to examine the phase constituents, microstructure and layer thickness of interaction products from interdiffusion. At the interface between the U10Mo and Zr, following the co-rolling, the UZr2 phase was observed to develop adjacent to Zr, and the α-U phase was found between the UZr2 and U10Mo, while the Mo2Zr was found as precipitates mostly within the α-U phase. The phase constituents and thickness of the interaction layer at the U10Mo-Zr interface remained unchanged regardless of HIP processing variation. Observable growth due to HIP was only observed for the (Al,Si)3Zr phase found at the Zr/AA6061 interface, however, with a large activation energy of 457 ± 28 kJ/mole. Thus, HIP can be carried to improve the adhesion quality of fuel plate without concern for the excessive growth of the interaction layer, particularly at the U10Mo-Zr interface with the α-U, Mo2Zr, and UZr2 phases.
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Laser-assisted development of titanium alloys: the search for new biomedical materials
NASA Astrophysics Data System (ADS)
Almeida, Amelia; Gupta, Dheeraj; Vilar, Rui
2011-02-01
Ti-alloys used in prosthetic applications are mostly alloys initially developed for aeronautical applications, so their behavior was not optimized for medical use. A need remains to design new alloys for biomedical applications, where requirements such as biocompatibility, in-body durability, specific manufacturing ability, and cost effectiveness are considered. Materials for this application must present excellent biocompatibility, ductility, toughness and wear and corrosion resistance, a large laser processing window and low sensitivity to changes in the processing parameters. Laser deposition has been investigated in order to access its applicability to laser based manufactured implants. In this study, variable powder feed rate laser cladding has been used as a method for the combinatorial investigation of new alloy systems that offers a unique possibility for the rapid and exhaustive preparation of a whole range of alloys with compositions variable along a single clad track. This method was used as to produce composition gradient Ti-Mo alloys. Mo has been used since it is among the few elements biocompatible, non-toxic β-Ti phase stabilizers. Alloy tracks with compositions in the range 0-19 wt.%Mo were produced and characterized in detail as a function of composition using microscale testing procedures for screening of compositions with promising properties. Microstructural analysis showed that alloys with Mo content above 8% are fully formed of β phase grains. However, these β grains present a cellular substructure that is associated to a Ti and Mo segregation pattern that occurs during solidification. Ultramicroindentation tests carried out to evaluate the alloys' hardness and Young's modulus showed that Ti-13%Mo alloys presented the lowest hardness and Young's modulus (70 GPa) closer to that of bone than common Ti alloys, thus showing great potential for implant applications.
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Evaluation of an advanced directionally solidified gamma/gamma'-alpha Mo eutectic alloy
NASA Technical Reports Server (NTRS)
Henry, M. F.; Jackson, M. R.; Gigliotti, M. F. X.; Nelson, P. B.
1979-01-01
An attempt was made to improve on the properties of the candidate jet engine turbine blade material AG-60, a gamma/gamma prime-alpha Mo eutectic composite. Alloy 38 (AG-170) was evaluated in the greatest detail. This alloy, Ni-5.88 A1-29.74 Mo-1.65 V-1.2C Re (weight percent), represents an improvement beyond AG-60, based on mechanical testing of the transverse and/or longitudinal orientations over a range of temperatures in tension, shear, rupture, and rupture after thermal exposure. It is likely that other alloys in the study represent a similar improvement.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Y. Q. Wu; K. N. Allahar; J. Burns
2013-08-01
Nanoscale oxides play an important role in oxide dispersion strengthened (ODS) alloys for improved high temperature creep resistance and enhanced radiation damage tolerance. In this study, transmission electron microscopy (TEM) and atom probe tomography (APT) were combined to investigate two novel Fe-16Cr-3Mo (wt.%) based ODS alloys. Spark plasma sintering (SPS) was used to consolidate the ODS alloys from powders that were milled with 0.5 wt.% Y2O3 powder only or with Y2O3 powder and 1 wt.% Ti. TEM characterization revealed that both alloys have a bimodal structure of nanometer-size (~ 100 – 500 nm) and micron-size grains with nanostructured oxide precipitatesmore » formed along and close to grain boundaries with diameters ranging from five to tens of nanometers. APT provides further quantitative analyses of the oxide precipitates, and also reveals Mo segregation at grain boundaries next to oxide precipitates. The alloys with and without Ti are compared based on their microstructures.« less
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Microstructural characteristics of HIP-bonded monolithic nuclear fuels with a diffusion barrier
NASA Astrophysics Data System (ADS)
Jue, Jan-Fong; Keiser, Dennis D.; Breckenridge, Cynthia R.; Moore, Glenn A.; Meyer, Mitchell K.
2014-05-01
Due to the limitation of maximum uranium load achievable by dispersion fuel type, the Global Threat Reduction Initiative is developing an advanced monolithic fuel to convert US high-performance research reactors to low-enriched uranium. Hot-isostatic-press (HIP) bonding was the single process down-selected to bond monolithic U-Mo fuel meat to aluminum alloy cladding. A diffusion barrier was applied to the U-Mo fuel meat by roll-bonding process to prevent extensive interaction between fuel meat and aluminum-alloy cladding. Microstructural characterization was performed on fresh fuel plates fabricated at Idaho National Laboratory. Interfaces between the fuel meat, the cladding, and the diffusion barrier, as well as between the U-10Mo fuel meat and the Al-6061 cladding, were characterized by scanning electron microscopy. Preliminary results indicate that the interfaces contain many different phases while decomposition, second phases, and chemical banding were also observed in the fuel meat. The important attributes of the HIP-bonded monolithic fuel are:
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The effect of copper doping on martensite shear stress in porous TiNi(Mo,Fe,Cu) alloys
NASA Astrophysics Data System (ADS)
Khodorenko, V. N.; Kaftaranova, M. I.; Gunther, V. E.
2015-03-01
The properties of alloys based on porous nickel-titanium (TiNi) with copper additives have been studied. It is established that the copper doping of porous TiNi(Mo,Fe,Cu) alloys fabricated by the method of self-propagating high-temperature synthesis leads to a significant decrease in the martensite shear stress (below 30 MPa). Low values of the martensite shear stress (σmin) in copper-doped TiNi-based alloys allows medical implants of complex shapes to be manufactured for various purposes, including oral surgery. The optimum concentration of copper additives (within 3-6 at %) has been determined that ensures high performance characteristics of TiNi-based porous alloys for medical implants.
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Alloy softening in binary molybdenum alloys
NASA Technical Reports Server (NTRS)
Stephens, J. R.; Witzke, W. R.
1972-01-01
An investigation was conducted to determine the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to Mo, while those elements having an equal number or fewer s+d electrons than Mo failed to produce alloy softening. Alloy softening and hardening can be correlated with the difference in number of s+d electrons of the solute element and Mo.
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Effect of the environment on wear ranking and corrosion of biomedical CoCrMo alloys.
Muñoz, A Igual; Mischler, S
2011-03-01
The corrosion behaviour and the wear ranking of biomedical high carbon (HC) and low carbon (LC) CoCrMo alloys sliding against an alumina ball in four different simulated body fluids [NaCl and phosphate buffered solutions (PBS) with and without albumin] has been analyzed by tribocorrosion and electrochemical techniques. The effects of alloy and of albumin on corrosion depend on the base electrolyte: differences between LC and HC alloy were only observed in NaCl solutions but not in PBS. Albumin increased significantly corrosion of both alloys in PBS solutions while its effect in NaCl was smaller. The wear ranking of the HC and LC alloys also depends on the environment. In the present study, HC CoCrMo alloy had lower wear resistance in NaCl and PBS + albumin than the LC alloy, while no differences between both alloys were found in the other solutions. This was attributed to surface chemical effects affecting third body behaviour.
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RECENT DEVELOPMENT IN TEM CHARACTERIZATION OF IRRADIATED RERTR FUELS
DOE Office of Scientific and Technical Information (OSTI.GOV)
J. Gan; B.D. Miller; D.D. Keiser Jr.
2011-10-01
The recent development on TEM work of irradiated RERTR fuels includes microstructural characterization of the irradiated U-10Mo/alloy-6061 monolithic fuel plate, the RERTR-7 U-7Mo/Al-2Si and U-7Mo/Al-5Si dispersion fuel plates. It is the first time that a TEM sample of an irradiated nuclear fuel was prepared using the focused-ion-beam (FIB) lift-out technical at the Idaho National Laboratory. Multiple FIB TEM samples were prepared from the areas of interest in a SEM sample. The characterization was carried out using a 200kV TEM with a LaB6 filament. The three dimensional orderings of nanometer-sized fission gas bubbles are observed in the crystalline region of themore » U-Mo fuel. The co-existence of bubble superlattice and dislocations is evident. Detailed microstructural information along with composition analysis is obtained. The results and their implication on the performance of these fuels are discussed.« less
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NASA Astrophysics Data System (ADS)
Chakraborty, Gopa; Das, C. R.; Albert, S. K.; Bhaduri, A. K.; Murugesan, S.; Dasgupta, Arup
2016-04-01
Dashpot piston, made up of modified 9Cr-1Mo steel, is a part of diverse safety rod used for safe shutdown of a nuclear reactor. This component was hardfaced using nickel base AWS ER NiCr-B alloy and extensive cracking was experienced during direct deposition of this alloy on dashpot piston. Cracking reduced considerably and the component was successfully hardfaced by application of Inconel 625 as buffer layer prior to hardface deposition. Hence, a separate study was undertaken to investigate the role of buffer layer in reducing the cracking and on the microstructure of the hardfaced deposit. Results indicate that in the direct deposition of hardfacing alloy on modified 9Cr-1Mo steel, both heat-affected zone (HAZ) formed and the deposit layer are hard making the thickness of the hard layer formed equal to combined thickness of both HAZ and deposit. This hard layer is unable to absorb thermal stresses resulting in the cracking of the deposit. By providing a buffer layer of Alloy 625 followed by a post-weld heat treatment, HAZ formed in the modified 9Cr-1Mo steel is effectively tempered, and HAZ formed during the subsequent deposition of the hardfacing alloy over the Alloy 625 buffer layer is almost completely confined to Alloy 625, which does not harden. This reduces the cracking susceptibility of the deposit. Further, unlike in the case of direct deposition on modified 9Cr-1Mo steel, dilution of the deposit by Ni-base buffer layer does not alter the hardness of the deposit and desired hardness on the deposit surface could be achieved even with lower thickness of the deposit. This gives an option for reducing the recommended thickness of the deposit, which can also reduce the risk of cracking.
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Zhang, Qi; Li, Kewen; Yan, Jinhong; Wang, Zhuo; Wu, Qi; Bi, Long; Yang, Min; Han, Yisheng
2018-03-18
The objective was to investigate whether a graphene coating could improve the surface bioactivity of a cobalt-chromium-molybdenum-based alloy (CoCrMo). Graphene was produced by chemical vapor deposition and transferred to the surface of the CoCrMo alloy using an improved wet transfer approach. The morphology of the samples was observed, and the adhesion force and stabilization of graphene coating were analyzed by a nanoscratch test and ultrasonication test. In an in vitro study, the adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs) cultured on the samples were quantified via an Alamar Blue assay and cell counting kit-8 (CCK-8) assay. The results showed that it is feasible to apply graphene to modify the surface of a CoCrMo alloy, and the enhancement of the adhesion and proliferation of BMSCs was also shown in the present study. In conclusion, graphene exhibits considerable potential for enhancing the surface bioactivity of CoCrMo alloy. Copyright © 2018 Elsevier Inc. All rights reserved.
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Schaeffler-Type Phase Diagram of Ti-Based Alloys
NASA Astrophysics Data System (ADS)
Ishida, K.
2017-10-01
The α(hcp)/β(bcc) phase equilibria of Ti-based multi-component alloys can be described by a Schaeffler-type diagram, where Al and Mo equivalents (Aleq and Moeq) are used. Aleq is thermodynamically defined by the ratio of partial molar free energy changes transfer of one mole of each α forming element and Al from a dilute solution of α to β phases, while Moeq is also deduced by similar thermodynamic quantities of β forming element and Mo. Aleq and Moeq for 40 alloying elements are estimated from the thermodynamic parameters assessed by Kaufman and Murray. It is shown that three types of Ti alloys, i.e., α and near α, α+β, and β alloys, can be exactly classified using Aleq and Moeq. The Ms and β transus temperatures can also be predicted by Aleq and Moeq. The proposed Aleq and Moeq are very useful for alloy design, heat treatment, and microstructural evolution of Ti-based alloys.
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Atomistic Simulation of High-Density Uranium Fuels
Garcés, Jorge Eduardo; Bozzolo, Guillermo
2011-01-01
We apply an atomistic modeling approach to deal with interfacial phenomena in high-density uranium fuels. The effects of Si, as additive to Al or as U-Mo-particles coating, on the behavior of the Al/U-Mo interface is modeled by using the Bozzolo-Ferrante-Smith (BFS) method for alloys. The basic experimental features characterizing the real system are identified, via simulations and atom-by-atom analysis. These include (1) the trend indicating formation of interfacial compounds, (2) much reduced diffusion of Al into U-Mo solid solution due to the high Si concentration, (3) Si depletion in the Al matrix, (4) an unexpected interaction between Mo and Simore » which inhibits Si diffusion to deeper layers in the U-Mo solid solution, and (5) the minimum amount of Si needed to perform as an effective diffusion barrier. Simulation results related to alternatives to Si dispersed in the Al matrix, such as the use of C coating of U-Mo particles or Zr instead of the Al matrix, are also shown. Recent experimental results confirmed early theoretical proposals, along the lines of the results reported in this work, showing that atomistic computational modeling could become a valuable tool to aid the experimental work in the development of nuclear fuels.« less
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Microstructure of RERTR DU-Alloys Irradiated with Krypton Ions
DOE Office of Scientific and Technical Information (OSTI.GOV)
J. Gan; D. Keiser; D. Wachs
2009-11-01
Fuel development for reduced enrichment research and test reactor (RERTR) program is tasked with the development of new low enrichment uranium fuels that can be employed to replace existing high enrichment uranium fuels currently used in many research and test reactors worldwide. Radiation stability of the interaction product formed at fuel-matrix interface has a strong impact on fuel performance. Three depleted uranium alloys are cast that consist of the following 5 phases of interest to be investigated: U(Si,Al)3, (U,Mo)(Si,Al)3, UMo2Al20, U6Mo4Al43 and UAl4. Irradiation of TEM disc samples with 500 keV Kr ions at 200?C to high doses up tomore » ~100 dpa were conducted using an intermediate voltage electron microscope equipped with an ion accelerator. The irradiated microstructure of the 5 phases is characterized using transmission electron microscopy. The results will be presented and the implication of the observed irradiated microstructure on the fuel performance will be discussed.« less
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Song, Dandan; Li, Qian; Lu, Xiong; Li, Yanshan; Li, Yan; Wang, Yuanzhe; Gao, Faming
2018-06-18
A novel electrochemical biosensor was designed for sensitive detection of organophosphate pesticides based on three-dimensional porous bimetallic alloy architecture with ultrathin nanowires (PdCo NWs, PdCu NWs, PdNi NWs) and monolayer MoS 2 nanosheet (m-MoS 2 ). The bimetallic alloy NWs/m-MoS 2 nanomaterials were used as a sensing platform for electrochemical analysis of omethoate, a representative organophosphate pesticide, via acetylcholinesterase inhibition pathway. We demonstrated that all three bimetallic alloy NWs enhanced electrochemical responses of enzymatic biosensor, benefited from bimetallic synergistic action and porous structure. In particular, PdNi NWs outperformed other two bimetallic alloy. Moreover, PdNi NWs/m-MoS 2 as an electronic transducer is superior to the corresponding biosensor in the absence of monolayer MoS 2 nanosheet, which arise from synergistic signal amplification effect between different components. Under optimized conditions, the developed biosensor on the basis of PdNi NWs/m-MoS 2 shows outstanding performance for the electrochemical assay of omethoate, such as a wide linear range (10 -13 M∼10 -7 M), a low detection limit of 0.05 pM at a signal-to-noise ratio of 3, high sensitivity and long-time stability. The results demonstrate that bimetallic alloy NWs/m-MoS 2 nanocomposites could be excellent transducers to promote electron transfer for the electrochemical reactions, holding great potentials in the construction of current and future biosensing devices. Copyright © 2018 Elsevier B.V. All rights reserved.
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Elastic modulus of phases in Ti–Mo alloys
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhang, Wei-dong; Liu, Yong, E-mail: yonliu11@aliyun.com; Wu, Hong
2015-08-15
In this work, a series of binary Ti–Mo alloys with the Mo contents ranging from 3.2 to 12 at.% were prepared using non-consumable arc melting. The microstructures were investigated by X-ray diffraction and transmission electron microscope, and the elastic modulus was evaluated by nanoindentation testing technique. The evolution of the volume fractions of ω phase was investigated using X-ray photoelectron spectroscopy. The results indicated that the phase constitution and elastic modulus of the Ti–Mo alloys are sensitive to the Mo content. Ti–3.2Mo and Ti–8Mo alloys containing only α and β phases, respectively, have a low elastic modulus. In contrast, Ti–4.5Mo,more » Ti–6Mo, Ti–7Mo alloys, with different contents of ω phase, have a high elastic modulus. A simple micromechanical model was used to calculate the elastic modulus of ω phase (E{sub ω}), which was determined to be 174.354 GPa. - Highlights: • Ti–Mo alloys with the Mo contents ranging from 3.2 to 12 at.% were investigated. • XPS was used to investigate the volume fractions of ω phase. • The elastic modulus of Ti–Mo alloys is sensitive to the Mo content. • The elastic modulus of ω phase was determined to be 174.354 GPa.« less
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NASA Astrophysics Data System (ADS)
Ma, Jingling; Li, Wuhui; Wang, Guangxin; Li, Yaqiong; Guo, Hongbo; Zhao, Zeliang; Li, Wei
2017-10-01
In order to study the effects of La2O3 content and rolling on microstructure and mechanical properties of Mo-La2O3 alloys, Mo-0.5% (1%) La2O3 alloys were prepared by liquid-solid doping technique, subsequently rolled either by a single-direction rolling or a cross-rolling. As a result, three different materials were prepared for this study. After being annealed at 1800 °C, the single-directionally rolled Mo-1% La2O3 alloy shows the best mechanical properties in terms of strength, hardness, and sagging deformation among the three materials. This is attributed to the observation that the alloy is only recovered with a microstructure of subgrains and dislocations. The single-directionally rolled Mo-0.5% La2O3 exhibits the worst mechanical property among the three materials. In this material, coarse grains, but no subgrains and dislocations, can be observed after annealing, indicating that it is fully recrystallized. For the cross-rolled Mo-1% La2O3 alloy, grains of dispersed sizes, but no dislocations, are visible after annealing, implying that this alloy is partially recrystallized. Accordingly, the mechanical property of this material is in between the other two materials. Thus, the mechanical properties of the three materials can be well understood based on OM, SEM, and TEM results. Overall, the single-directionally rolled Mo-1% La2O3 alloy possesses good mechanical properties and is more suitable for high-temperature applications.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wade, C.S.; Park, H.G.; Hoagland, R.G.
This paper considers the relation between microstructure and mechanical properties of two Ni-base and two Fe-base Boride-Dispersion-Strengthened Microcrystalline (BDSM) alloys. In these very fine grained materials the borides were primarily Cr, Mo, and MoFe in a fcc matrix in three of the alloys, and a bcc in one of the Fe-base alloys. Strength data and resistance to stress corrosion cracking are reported and, in the latter case, extraordinary resistance to SCC in NaCl, Na{sub 2}S{sub 2}O{sub 3} and boiling MgCl{sub 2} environments was observed in every case. The fcc BDSM alloys also demonstrated excellent thermal stability in terms of strengthmore » and fracture roughness up to 1000 C. The bcc alloy suffered severe loss of toughness. The fracture mode involved ductile rupture in all alloys and they display a reasonably linear correlation between K{sub Ic} and the square root of particle spacing.« less
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Obtaining and Mechanical Properties of Ti-Mo-Zr-Ta Alloys
NASA Astrophysics Data System (ADS)
Bălţatu, M. S.; Vizureanu, P.; Geantă, V.; Nejneru, C.; Țugui, C. A.; Focşăneanu, S. C.
2017-06-01
Ti-based alloys are successfully used in the area of orthopedic biomaterials for their enhanced biocompatibility, good corrosion and mechanical properties. The most suitable metals as an alloying element for orthopedic biomaterials are zirconium, molybdenum and tantalum because are non toxic and have good properties. The paper purpose development of two alloys of Ti-Mo-Zr-Ta (TMZT) prepared by arc-melting with several mechanical properties determined by microindentation. The mechanical properties analyzed was Vickers hardness and dynamic elasticity modulus. The investigated alloys presents a low Young’s modulus, an important condition of biomaterials for preventing stress shielding phenomenon.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
I. Glagolenko; D. Wachs; N. Woolstenhulme
2010-10-01
Based on the results of the reactor physics assessment, conversion of the Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL) can be potentially accomplished in two ways, by either using U-10Mo monolithic or U-7Mo dispersion type plates in the ATR fuel element. Both designs, however, would require incorporation of the burnable absorber in several plates of the fuel element to compensate for the excess reactivity and to flatten the radial power profile. Several different types of burnable absorbers were considered initially, but only borated compounds, such as B4C, ZrB2 and Al-B alloys, were selected for testing primarily duemore » to the length of the ATR fuel cycle and fuel manufacturing constraints. To assess and compare irradiation performance of the U-Mo fuels with different burnable absorbers we have designed and manufactured 28 RERTR miniplates (20 fueled and 8 non-fueled) containing fore-mentioned borated compounds. These miniplates will be tested in the ATR as part of the RERTR-13 experiment, which is described in this paper. Detailed plate design, compositions and irradiations conditions are discussed.« less
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MoRe-based tunnel junctions and their characteristics
NASA Astrophysics Data System (ADS)
Shaternik, V.; Larkin, S.; Noskov, V.; Chubatyy, V.; Sizontov, V.; Miroshnikov, A.; Karmazin, A.
2008-02-01
Perspective Josephson Mo-Re alloy-oxide-Pb, Mo-Re alloy-normal metal-oxide-Pb and Mo-Re alloy-normal metal-oxide-normal metal-Mo-Re alloy junctions have been fabricated and investigated. Thin (~50-100 nm) MoRe superconducting films are deposited on Al2O3 substrates by using a dc magnetron sputtering of MoRe target. Normal metal (Sn, Al) thin films are deposited on the MoRe films surfaces by thermal evaporation of metals in vacuum and oxidized to fabricate junctions oxide barriers. Quasiparticle I-V curves of the fabricated junctions were measured in wide range of voltages. To investigate a transparency spread for the fabricated junctions barriers the computer simulation of the measured quasiparticle I-V curves have been done in framework of the model of multiple Andreev reflections in double-barrier junction interfaces. It's demonstrated the investigated junctions can be described as highly asymmetric double-barrier Josephson junctions with great difference between the two barrier transparencies. The result of the comparison of experimental quasiparticle I-V curves and calculated ones is proposed and discussed. Also I-V curves of the fabricated junctions have been measured under microwave irradiation with 60 GHz frequency, clear Shapiro steps in the measured I-V curves were observed and discussed.
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Finite-element model to predict roll-separation force and defects during rolling of U-10Mo alloys
NASA Astrophysics Data System (ADS)
Soulami, Ayoub; Burkes, Douglas E.; Joshi, Vineet V.; Lavender, Curt A.; Paxton, Dean
2017-10-01
A major goal of the Convert Program of the U.S. Department of Energy's National Nuclear Security Administration (DOE/NNSA) is to enable high-performance research reactors to operate with low-enriched uranium rather than the high-enriched uranium currently used. To this end, uranium alloyed with 10 wt% molybdenum (U-10Mo) represents an ideal candidate because of its stable gamma phase, low neutron caption cross section, acceptable swelling response, and predictable irradiation behavior. However, because of the complexities of the fuel design and the need for rolled monolithic U-10Mo foils, new developments in processing and fabrication are necessary. This study used a finite-element code, LS-DYNA, as a predictive tool to optimize the rolling process. Simulations of the hot rolling of U-10Mo coupons encapsulated in low-carbon steel were conducted following two different schedules. Model predictions of the roll-separation force and roll pack thicknesses at different stages of the rolling process were compared with experimental measurements. The study reported here discussed various attributes of the rolled coupons revealed by the model (e.g., waviness and thickness non-uniformity like dog-boning). To investigate the influence of the cladding material on these rolling defects, other cases were simulated: hot rolling with alternative can materials, namely, 304 stainless steel and Zircaloy-2, and bare-rolling. Simulation results demonstrated that reducing the mismatch in strength between the coupon and can material improves the quality of the rolled sheet. Bare-rolling simulation results showed a defect-free rolled coupon. The finite-element model developed and presented in this study can be used to conduct parametric studies of several process parameters (e.g., rolling speed, roll diameter, can material, and reduction).
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Characteristics of HY-180 and Ti-100 for Welded High Strength Structures
1974-12-01
materials in welded structures are reported. The 10Ni-8Co-2Cr-lMo steel arid the Ti- 6Al -2Cb-lTa-0. 8Mo titanium alloy were selected as candidate...only li- 6Al -iCb-na-0.»Mo (Ti-6-2-1-1) and’Ii- 6Al - 4V are competitive with 10Ni-8Co-2Cr-lMo steel on a strength-weight basis, while possessing ade...Ti- 6Al -2Cb-lTa-0. 8Mo has better toughness in plate form, based upon dynamic tear properties. There- fore the Ti- 6Al -2Cb-lTa-0.8Mo titanium alloy
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NASA Technical Reports Server (NTRS)
Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.
2002-01-01
Despite nickel aluminide (NiAl) alloys' attractive combination of oxidation and thermophysical properties, their development as replacements for superalloy airfoils in gas turbine engines has been largely limited by difficulties in developing alloys with an optimum combination of elevated-temperature creep resistance and room-temperature fracture toughness. Alternatively, research has focused on developing directionally solidified NiAl-based in situ eutectic composites composed of NiAl and (Cr,Mo) phases in order to obtain a desirable combination of properties a systematic investigation was undertaken at the NASA Glenn Research Center to examine the effects of small additions of 11 alloying elements (Co, Cu, Fe, Hf, Mn, Nb, Re, Si, Ta, Ti, and Zr) in amounts varying from 0.25 to 1.0 at.% on the elevated-temperature strength and room-temperature fracture toughness of directionally solidified Ni-33Al-31Cr-3Mo eutectic alloy. The alloys were grown at 12.7 mm/hr, where the unalloyed eutectic base alloy exhibited a planar eutectic microstructure. The different microstructures that formed because of these fifth-element additions are included in the table. The additions of these elements even in small amounts resulted in the formation of cellular microstructures, and in some cases, dendrites and third phases were observed. Most of these elemental additions did not improve either the elevated-temperature strength or the room-temperature fracture toughness over that of the base alloy. However, small improvements in the compression strength were observed between 1200 and 1400 K when 0.5 at.% Hf and 0.25 at.% Ti were added to the base alloy. The results of this study suggest that the microalloying of Ni-33Al-31Cr-3Mo will not significantly improve either its elevatedtemperature strength or its room-temperature fracture toughness. Thus, any improvements in these properties must be acquired by changing the processing conditions.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Baek, K.K.; Sung, H.J.; Im, C.S.
1998-12-31
For successful application of high-alloyed stainless steels for Flue Gas Desulfurization (FGD) plants, pitting corrosion resistance of arc welds of N-added 6%Mo austenitic stainless steels (UNS N 08367) and super duplex stainless steels (UNS S 32550) made with various filler metals were evaluated using the Green Death solution. For Gas Tungsten Arc (GTA) and Gas Metal Arc (GMA) welds of N 08367, Critical Pitting Temperature (CPT) of base metal was 65--70 C, whereas weld made by ERNiCrMo-3 filler metal yielded CPT of 50 C. Welds made by ERNiCrMo-10 or ERNiCrMo-4 filler metals showed CPT of 60--65 C and 65--70C, respectively.more » For GTA and GMA welds of S 32550, CPT of welds made by ERNiCrMo-3 was 45--50 C, indicating that the filler metal can provide pitting corrosion resistance matching the S 32550 alloy. Thus, a proper pitting corrosion resistance of weldments of high-alloy stainless steels can be achieved by selecting filler metals having at least +10 higher Pitting Resistance Equivalent Number (PRE{sub N}) value than the base metal regardless of the type of arc welding process. The over-alloyed filler metals would compensate preferential segregation of Cr, MO along the dendrite boundary, which made the dendrite core more susceptible to pitting. Nitrogen addition to the GTA welds of N 08367 made with ERNiCrMo-3 failed to improve pitting corrosion resistance, which was attributed to the precipitation of nitrogen in the weld metal in the form of Nb-nitride.« less
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The influence of cladding on fission gas release from irradiated U-Mo monolithic fuel
NASA Astrophysics Data System (ADS)
Burkes, Douglas E.; Casella, Amanda J.; Casella, Andrew M.
2017-04-01
The monolithic uranium-molybdenum (U-Mo) alloy has been proposed as a fuel design capable of converting the world's highest power research reactors from use of high enriched uranium to low enriched uranium. However, a zirconium (Zr) diffusion barrier must be used to eliminate interactions that form between the U-Mo monolith and aluminum alloy 6061 (AA6061) cladding during fabrication and are enhanced during irradiation. One aspect of fuel development and qualification is to demonstrate an appropriate understanding of the extent of fission product release from the fuel under anticipated service environments. An exothermic reaction has previously been observed between the AA6061 cladding and Zr diffusion layer. In this paper, two fuel segments with different irradiation history were subjected to specified thermal profiles under a controlled atmosphere using a thermogravimetric/differential thermal analyzer coupled with a mass spectrometer inside a hot cell. Samples from each segment were tested with cladding and without cladding to investigate the effect, if any, that the exothermic reaction has on fission gas release mechanisms. Measurements revealed there is an instantaneous effect of the cladding/Zr exothermic reaction, but not necessarily a cumulative effect above approximately 973 K (700 °C). The mechanisms responsible for fission gas release events are discussed.
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The influence of cladding on fission gas release from irradiated U-Mo monolithic fuel
DOE Office of Scientific and Technical Information (OSTI.GOV)
Burkes, Douglas E.; Casella, Amanda J.; Casella, Andrew M.
2017-04-01
The monolithic uranium-molybdenum (U-Mo) alloy has been proposed as a fuel design capable of converting the world’s highest power research reactors from use of high enriched uranium to low enriched uranium. However, a zirconium (Zr) diffusion barrier must be used to eliminate interactions that form during fabrication and are enhanced during irradiation between the U-Mo monolith and aluminum alloy 6061 (AA6061) cladding. One aspect of fuel development and qualification is to demonstrate appropriate understanding of the extent of fission product release from the fuel under anticipated service environments. An exothermic reaction has previously been observed between the AA6061 cladding andmore » Zr diffusion layer. In this paper, two fuel segments with different irradiation history were subjected to specified thermal profiles under a controlled atmosphere using a thermogravimetric/differential thermal analyzer coupled with a mass spectrometer inside a hot cell. Samples from each segment were tested with cladding and without cladding to investigate the effect, if any, that the exothermic reaction has on fission gas release mechanisms. Measurements revealed there is an instantaneous effect of the cladding/Zr exothermic reaction, but not necessarily a cumulative effect above approximately 973 K (700 oC). The mechanisms responsible for fission gas release events are discussed.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Liang, Linyun; Mei, Zhi -Gang; Kim, Yeon Soo
A mesoscale model is developed by integrating the rate theory and phase-field models and is used to study the fission-induced recrystallization in U-7Mo alloy. The rate theory model is used to predict the dislocation density and the recrystallization nuclei density due to irradiation. The predicted fission rate and temperature dependences of the dislocation density are in good agreement with experimental measurements. This information is used as input for the multiphase phase-field model to investigate the fission-induced recrystallization kinetics. The simulated recrystallization volume fraction and bubble induced swelling agree well with experimental data. The effects of the fission rate, initial grainmore » size, and grain morphology on the recrystallization kinetics are discussed based on an analysis of recrystallization growth rate using the modified Avrami equation. Here, we conclude that the initial microstructure of the U-Mo fuels, especially the grain size, can be used to effectively control the rate of fission-induced recrystallization and therefore swelling.« less
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NASA Astrophysics Data System (ADS)
Li, Ruidi; Yuan, Tiechui; Qiu, Zili
2014-07-01
A gradient-nanograin surface layer of Co-base alloy was prepared by friction stir processing (FSP) of laser-clad coating in this work. However, it is lack of a quantitatively function relationship between grain refinement and FSP conditions. Based on this, an analytic model is derived for the correlations between carbide size, hardness and rotary speed, layer depth during in-situ FSP of laser-clad Co-Cr-Ni-Mo alloy. The model is based on the principle of typical plastic flow in friction welding and dynamic recrystallization. The FSP experiment for modification of laser-clad Co-based alloy was conducted and its gradient nanograin and hardness were characterized. It shows that the model is consistent with experimental results.
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Säubert, Steffen; Jungwirth, Rainer; Zweifel, Tobias; Hofmann, Michael; Hoelzel, Markus; Petry, Winfried
2016-01-01
Exposing uranium–molybdenum alloys (UMo) retained in the γ phase to elevated temperatures leads to transformation reactions during which the γ-UMo phase decomposes into the thermal equilibrium phases, i.e. U2Mo and α-U. Since α-U is not suitable for a nuclear fuel exposed to high burn-up, it is necessary to retain the γ-UMo phase during the production process of the fuel elements for modern high-performance research reactors. The present work deals with the isothermal transformation kinetics in U–8 wt%Mo alloys for temperatures between 673 and 798 K and annealing durations of up to 48 h. Annealed samples were examined at room temperature using either X-ray or neutron diffraction to determine the phase composition after thermal treatment, and in situ annealing studies disclosed the onset of phase decomposition. While for temperatures of 698 and 673 K the start of decomposition is delayed, for higher temperatures the first signs of transformation are already observable within 3 h of annealing. The typical C-shaped curves in a time–temperature–transformation (TTT) diagram for both the start and the end of phase decomposition could be determined in the observed temperature regime. Therefore, a revised TTT diagram for U–8 wt%Mo between 673 and 798 K and annealing durations of up to 48 h is proposed. PMID:27275139
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Iron-Based Amorphous Metals: High-Performance Corrosion-Resistant Material Development
NASA Astrophysics Data System (ADS)
Farmer, Joseph; Choi, Jor-Shan; Saw, Cheng; Haslam, Jeffrey; Day, Dan; Hailey, Phillip; Lian, Tiangan; Rebak, Raul; Perepezko, John; Payer, Joe; Branagan, Daniel; Beardsley, Brad; D'Amato, Andy; Aprigliano, Lou
2009-06-01
An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was cosponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the U.S. Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition, materials synthesis, thermal stability, corrosion resistance, environmental cracking, mechanical properties, damage tolerance, radiation effects, and important potential applications. Amorphous alloys identified as SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) and SAM1651 (Fe48Mo14Cr15Y2C15B6) have been produced as meltspun ribbons (MSRs), dropcast ingots, and thermal-spray coatings. Chromium (Cr), molybdenum (Mo), and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of MSRs and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently, thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests; good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while the open-circuit corrosion potentials (OCPs) were simultaneously monitored; reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber and suitable for criticality-control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional stainless steel and Ni-based materials, and are proving to have excellent wear properties, sufficient to warrant their use in earth excavation, drilling, and tunnel-boring applications. Large areas have been successfully coated with these materials, with thicknesses of approximately 1 cm. The observed corrosion resistance may enable applications of importance in industries such as oil and gas production, refining, nuclear power generation, shipping, etc.
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NASA Astrophysics Data System (ADS)
Byun, Jong Min; Bang, Su-Ryong; Choi, Won June; Kim, Min Sang; Noh, Goo Won; Kim, Young Do
2017-01-01
In recent years, refractory materials with excellent high-temperature properties have been in the spotlight as a next generation's high-temperature materials. Among these, Mo-Si-B alloys composed of two intermetallic compound phases (Mo5SiB2 and Mo3Si) and a ductile α-Mo phase have shown an outstanding thermal properties. However, due to the brittleness of the intermetallic compound phases, Mo-Si-B alloys were restricted to apply for the structural materials. So, to enhance the mechanical properties of Mo-Si-B alloys, many efforts to add rare-earth oxide particles in the Mo-Si-B alloy were performed to induce the improvement of strength and fracture toughness. In this study, to investigate the effect of adding nano-sized Y2O3 particles in Mo-Si-B alloy, a core-shell powder consisting of intermetallic compound phases as the core and nano-sized α-Mo and Y2O3 particles surrounding the core was fabricated. Then pressureless sintering was carried out at 1400 °C for 3 h, and the mechanical properties of sintered bodies with different amounts of Y2O3 particles were evaluated by Vickers hardness and 3-point bending test. Vickers hardness was improved by dispersed Y2O3 particles in the Mo-Si-B alloy. Especially, Mo-3Si-1B-1.5Y2O3 alloy had the highest value, 589 Hv. The fracture toughness was measured using Mo-3Si-1B-1.5Y2O3 alloy and the value indicated as 13.5 MPa·√m.
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Concept Feasibility Report for Electroplating Zirconium onto Uranium Foil - Year 2
DOE Office of Scientific and Technical Information (OSTI.GOV)
Coffey, Greg W.; Meinhardt, Kerry D.; Joshi, Vineet V.
2015-03-01
The Fuel Fabrication Capability within the U.S. High Performance Research Reactor Conversion Program is funded through the National Nuclear Security Administration (NNSA) NA-26 (Office of Material Management and Minimization). An investigation was commissioned to determine the feasibility of using electroplating techniques to apply a coating of zirconium onto depleted uranium/molybdenum alloy (U-10Mo). Electroplating would provide an alternative method to the existing process of hot roll-bonding zirconium foil onto the U-10Mo fuel foil during the fabrication of fuel elements for high-performance research reactors. The objective of this research was to develop a reproducible and scalable plating process that will produce amore » uniform, 25 μm thick zirconium metal coating on U-10Mo foil. In previous work, Pacific Northwest National Laboratory (PNNL) established a molten salt electroplating apparatus and protocol to plate zirconium metal onto molybdenum foil (Coffey 2015). During this second year of the research, PNNL furthered this work by moving to the U-10Mo alloy system (90 percent uranium:10 percent molybdenum). The original plating apparatus was disassembled and re-assembled in a laboratory capable of handling low-level radioactive materials. Initially, the work followed the previous year’s approach, and the salt bath composition was targeted at the eutectic composition (LiF:NaF:ZrF4 = 26:37:37 mol%). Early results indicated that the formation of uranium fluoride compounds would be problematic. Other salt bath compositions were investigated in order to eliminate the uranium fluoride production (LiF:NaF = 61:39 mol% and LiF:NaF:KF = 46.5:11.5:42 mol% ). Zirconium metal was used as the crucible for the molten salt. Three plating methods were used—isopotential, galvano static, and pulsed plating. The molten salt method for zirconium metal application provided high-quality plating on molybdenum in PNNL’s previous work. A key advantage of this approach is that plating can be performed under conditions that would greatly reduce the quantity of intermetallics that form at the interface between the zirconium and U-10Mo; unlike roll bonding, the molten salt plating approach would allow for complete coverage of the U-10Mo foil with zirconium. When utilizing the experimental parameters developed for zirconium plating onto molybdenum, a uranium fluoride reaction product was formed at the Zr/U-10Mo interface. By controlling the initial plating potential, the uranium fluoride could be prevented; however, the targeted zirconium thickness (25 ±12.5 μm) could not be achieved while maintaining 100% coverage.« less
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NASA Astrophysics Data System (ADS)
Liu, Min; Zheng, Junyi; Lu, Yanling; Li, Zhijun; Zou, Yang; Yu, Xiaohan; Zhou, Xingtai
2013-09-01
Ni-based alloys have been selected as the structural materials in molten-salt reactors due to their high corrosion resistance and excellent mechanical properties. In this paper, the corrosion behavior of some Ni-based superalloys including Inconel 600, Hastelloy X and Hastelloy C-276 were investigated in molten fluoride salts at 750 °C. Morphology and microstructure of corroded samples were analyzed using scanning electron microscope (SEM), synchrotron radiation X-ray microbeam fluorescence (μ-XRF) and synchrotron radiation X-ray diffraction (SR-XRD) techniques. Results from μ-XRF and SR-XRD show that the main depleted alloying element of Ni-based alloys in molten fluoride salt is Cr. In addition, the results indicate that Mo can enhance the corrosion resistance in molten FLiNaK salts. Among the above three Ni-based alloys, Hastelloy C-276 exhibits the best corrosion resistance in molten fluoride salts 750 °C. Higher-content Mo and lower-content Cr in Hastelloy C-276 alloy were responsible for the better anti-corrosive performance, compared to the other two alloys.
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NASA Astrophysics Data System (ADS)
Li, Y. K.; Chen, Y. W.; Cheng, X. W.; Wu, C.; Cheng, B.
2018-05-01
In this paper, the valence electron structure parameters of Zr(x)Ti(x)Hf(x)Nb(x)Mo(x) alloys were calculated based on the empirical electron theory of solids and molecules (EET), and their performance through these parameters were predicted. Subsequently, the alloys with special valence electron structure parameters were prepared byarc melting. The hardness and high-temperature mechanical properties were analyzed to verify the prediction. Research shows that the influence of shared electron number nA on the strongest bond determines the strength of these alloys and the experiments are consistent with the theoretical prediction.
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Thermophysical properties of undercooled liquid Co-Mo alloys
NASA Astrophysics Data System (ADS)
Han, X. J.; Wei, B.
2003-05-01
Using electromagnetic levitation in combination with the oscillating drop technique and drop calorimeter method, the surface tensions and specific heats of undercooled liquid Co-10 wt% Mo, Co-26.3 wt% Mo, and Co-37.6 wt% Mo alloys were measured. The containerless state during levitation produces substantial undercoolings up to 223 K (0.13TL), 213 K (0.13TL) and 110 K (0.07TL) respectively for these three alloys. In their respective undercooling ranges, the surface tensions were determined to be 1895 m 0.31(T m 1744), 1932 m 0.33(T m 1682), and 1989 m 0.34(T m 1607) mN mу. According to the Butler equation, the surface tensions of these three Co-Mo alloys were also calculated, and the results agree well with the experimental data. The specific heats of these three alloys are determined to be 41.85, 43.75 and 44.92 J molу Kу. Based on the determined surface tensions and specific heats, the changes in thermodynamics functions such as enthalpy, entropy and Gibbs free energy are predicted. Furthermore, the crystal nucleation, dendrite growth and Marangoni convection of undercooled Co-Mo alloys are investigated in the light of these measured thermophysical properties.
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Quantitative in vivo biocompatibility of new ultralow-nickel cobalt-chromium-molybdenum alloys.
Sonofuchi, Kazuaki; Hagiwara, Yoshihiro; Koizumi, Yuichiro; Chiba, Akihiko; Kawano, Mitsuko; Nakayama, Masafumi; Ogasawara, Kouetsu; Yabe, Yutaka; Itoi, Eiji
2016-09-01
Nickel (Ni) eluted from metallic biomaterials is widely accepted as a major cause of allergies and inflammation. To improve the safety of cobalt-chromium-molybdenum (Co-Cr-Mo) alloy implants, new ultralow-Ni Co-Cr-Mo alloys with and without zirconium (Zr) have been developed, with Ni contents of less than 0.01%. In the present study, we investigated the biocompatibility of these new alloys in vivo by subcutaneously implanting pure Ni, conventional Co-Cr-Mo, ultralow-Ni Co-Cr-Mo, and ultralow-Ni Co-Cr-Mo with Zr wires into the dorsal sides of mice. After 3 and 7 days, tissues around the wire were excised, and inflammation; the expression of IL-1β, IL-6, and TNF-α; and Ni, Co, Cr, and Mo ion release were analyzed using histological analyses, qRT-PCR, and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Significantly larger amounts of Ni eluted from pure Ni wires than from the other wires, and the degree of inflammation depended on the amount of eluted Ni. Although no significant differences in inflammatory reactions were identified among new alloys and conventional Co-Cr-Mo alloys in histological and qRT-PCR analyses, ICP-MS analysis revealed that Ni ion elution from ultralow-Ni Co-Cr-Mo alloys with and without Zr was significantly lower than from conventional Co-Cr-Mo alloys. Our study, suggests that the present ultralow-Ni Co-Cr-Mo alloys with and without Zr have greater safety and utility than conventional Co-Cr-Mo alloys. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1505-1513, 2016. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.
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Wu, Fan; Chen, Tao; Wang, Haojun; Liu, Defu
2017-09-06
Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt % Mo, 4 wt % Mo and 8 wt % Mo additions are studied comparatively. Results indicate that Ti(C,N) is formed by the in situ metallurgical reaction, the (Ti,Mo)(C,N) rim phase surrounding the Ti(C,N) ceramic particle is synthesized with the addition of Mo, and the increase of Mo content is beneficial to improve the wear properties of the cladding coatings. Because of the effect of Mo, the grains are remarkably refined and a unique core-rim structure that is uniformly dispersed in the matrix appears; meanwhile, the composite coatings with Mo addition exhibit high hardness and excellent wear resistance due to the comprehensive action of dispersion strengthening, fine grain strengthening and solid solution strengthening.
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Chen, Tao; Wang, Haojun
2017-01-01
Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt % Mo, 4 wt % Mo and 8 wt % Mo additions are studied comparatively. Results indicate that Ti(C,N) is formed by the in situ metallurgical reaction, the (Ti,Mo)(C,N) rim phase surrounding the Ti(C,N) ceramic particle is synthesized with the addition of Mo, and the increase of Mo content is beneficial to improve the wear properties of the cladding coatings. Because of the effect of Mo, the grains are remarkably refined and a unique core-rim structure that is uniformly dispersed in the matrix appears; meanwhile, the composite coatings with Mo addition exhibit high hardness and excellent wear resistance due to the comprehensive action of dispersion strengthening, fine grain strengthening and solid solution strengthening. PMID:28878190
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Computational modeling of high-entropy alloys: Structures, thermodynamics and elasticity
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gao, Michael C.; Gao, Pan; Hawk, Jeffrey A.
This study provides a short review on computational modeling on the formation, thermodynamics, and elasticity of single-phase high-entropy alloys (HEAs). Hundreds of predicted single-phase HEAs were re-examined using various empirical thermo-physical parameters. Potential BCC HEAs (CrMoNbTaTiVW, CrMoNbReTaTiVW, and CrFeMoNbReRuTaVW) were suggested based on CALPHAD modeling. The calculated vibrational entropies of mixing are positive for FCC CoCrFeNi, negative for BCC MoNbTaW, and near-zero for HCP CoOsReRu. The total entropies of mixing were observed to trend in descending order: CoCrFeNi > CoOsReRu > MoNbTaW. Calculated lattice parameters agree extremely well with averaged values estimated from the rule of mixtures (ROM) if themore » same crystal structure is used for the elements and the alloy. The deviation in the calculated elastic properties from ROM for select alloys is small but is susceptible to the choice used for the structures of pure components.« less
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Computational modeling of high-entropy alloys: Structures, thermodynamics and elasticity
Gao, Michael C.; Gao, Pan; Hawk, Jeffrey A.; ...
2017-10-12
This study provides a short review on computational modeling on the formation, thermodynamics, and elasticity of single-phase high-entropy alloys (HEAs). Hundreds of predicted single-phase HEAs were re-examined using various empirical thermo-physical parameters. Potential BCC HEAs (CrMoNbTaTiVW, CrMoNbReTaTiVW, and CrFeMoNbReRuTaVW) were suggested based on CALPHAD modeling. The calculated vibrational entropies of mixing are positive for FCC CoCrFeNi, negative for BCC MoNbTaW, and near-zero for HCP CoOsReRu. The total entropies of mixing were observed to trend in descending order: CoCrFeNi > CoOsReRu > MoNbTaW. Calculated lattice parameters agree extremely well with averaged values estimated from the rule of mixtures (ROM) if themore » same crystal structure is used for the elements and the alloy. The deviation in the calculated elastic properties from ROM for select alloys is small but is susceptible to the choice used for the structures of pure components.« less
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NASA Astrophysics Data System (ADS)
Xiang, Dingding; Song, Jian; Wang, Song; Liao, Zhenhua; Liu, Yuhong; Tyagi, Rajnesh; Liu, Weiqiang
2018-02-01
CoCrMo alloys are believed to be a kind of potential material for artificial cervical disc. However, the tribological properties of CoCrMo alloys against different metals and ceramics are not systematically studied. In this study, the tribological behaviors of CoCrMo alloys against metals (316L, Ti6Al4V) and ceramics (Si3N4, ZrO2) were focused under dry friction and 25 wt.% newborn calf serum (NCS)-lubricated conditions using a ball-on-disc apparatus under reciprocating motion. The microstructure, composition and hardness of CoCrMo alloys were characterized using x-ray diffraction, scanning electron microscopy (SEM) and hardness testers, respectively. The contact angles of the CoCrMo alloys with deionized water and 25 wt.% NCS were measured by the OCA contact angle measuring instrument. The maximum wear width, wear depth and wear volume were measured by three-dimensional white light interference. The morphology and the EDX analysis of the wear marks on CoCrMo alloys were examined by SEM to determine the basic mechanism of friction and wear. The dominant wear mechanism in dry friction for CoCrMo alloys against all pairings was severe abrasive wear, accompanied with a lot of material transfer. Under 25 wt.% NCS-lubricated condition, the wear mechanism for CoCrMo alloys against ceramics (Si3N4, ZrO2) was also mainly severe abrasive wear. However, severe abrasive wear and electrochemical corrosion occurred for the CoCrMo-316L pairing under lubrication. Severe abrasive wear, adhesive wear and electrochemical corrosion occurred for the CoCrMo-Ti6Al4V pairing under lubrication. According to the results, the tribological properties of CoCrMo alloys against ceramics were better than those against metals. The CoCrMo-ZrO2 pairing displayed the best tribological behaviors and could be taken as a potential candidate bearing material for artificial cervical disc.
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Hydrogen Induced Intergranular Cracking of Nickel-Base Alloys.
1982-02-01
alloys are discussed. Experimental The steel used in the present investigation is a fully bainitic 2 1/4 Cr-lMo pressure vessel steel , ASTM A542 Class 3...Appendix A describes recent experiments performed in order to study the influence of plastic deformation on hydrogen transport in a 214 Cr-lMo steel (8...PLASTIC DEFORMATION ON HYDROGEN TRANSPORT IN 2 1/4 Cr-lMo STEEL M. Kurkela, G.S. Frankel, and R.M. Latanision Department of Materials Science and
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NASA Astrophysics Data System (ADS)
Václavová, K.; Stráský, J.; Zháňal, P.; Veselý, J.; Polyakova, V.; Semenova, I.; Janeček, M.
2017-05-01
Processing of metastable titanium alloys by severe plastic deformation provides an opportunity to achieve exceptional grain refinement, to enhance the strength and to affect phase transformations occurring during thermal treatment. The main aim of this study is to investigate the microstructure of ultra-fine grained (UFG) material and effect of microstructural changes on phase transformations in metastable β-Ti alloy Ti-15Mo. Metastable β-Ti alloys are currently the most studied Ti-based materials with prospective use in medicine. Ti-15Mo alloy after solution treatment contains metastable β-phase. Metastable ω-phase and stable α-phase particles are formed upon annealing,. Solution treated Ti-15Mo alloy was deformed by high pressure torsion (HPT) at room temperature. Severely deformed structure after HPT with grain size of ~200 nm was studied by transmission electron microscopy. In-situ electrical resistance measurements showed significant changes in undergoing phase transformations when compared to coarse-grained (CG) material. Scanning electron microscopy revealed heterogeneous precipitation of α-particles at grain boundaries (GB). Due to the high density of GBs in UFG structure, these precipitates are very fine and equiaxed. The study demonstrates that SPD is capable of enhancing mechanical properties due to grain refinement and via affecting precipitation processes in metastable β-Ti alloys.
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Shield materials recommended for space power nuclear reactors
NASA Technical Reports Server (NTRS)
Kaszubinski, L. J.
1973-01-01
Lithium hydride is recommended for neutron attenuation and depleted uranium is recommended for gamma ray attenuation. For minimum shield weights these materials must be arranged in alternate layers to attenuate the secondary gamma rays efficiently. In the regions of the shield near the reactor, where excessive fissioning occurs in the uranium, a tungsten alloy is used instead. Alloys of uranium such as either the U-0.5Ti or U-8Mo are available to accommodate structural requirements. The zone-cooled casting process is recommended for lithium hydride fabrication. Internal honeycomb reinforcement to control cracks in the lithium hydride is recommended.
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Processability evaluation of a Mo-containing FeCrAl alloy for seamless thin-wall tube fabrication
Sun, Zhiqian; Yamamoto, Yukinori
2017-06-10
The processability of a Mo-containing FeCrAl alloy (Fe-13Cr-5.2Al-2Mo base, in wt%), developed for accident-tolerant nuclear fuel claddings, was evaluated through a stepwise rolling process at 400 °C under two different inter-pass annealing conditions (i.e., 650 °C for 1 h and at 870 °C for 30 min). The inter-pass annealing at 870 °C easily softened the FeCrAl alloy; however, it led to the formation of coarse grains of ~200 µm. On the other hand, the FeCrAl alloy maintained elongated, deformed grains with the inter-pass annealing at 650 °C, but the annealed samples showed relatively high deformation resistance and strong texture. Importantmore » aspects concerning the processability and microstructural control of FeCrAl alloys, such as deformation inhomogeneity, texture development, and grain coarsening, were discussed. Optimized processing conditions were recommended, based on the results, to achieve desirable microstructures with balanced processability and mechanical properties.« less
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Hidroxyapatite Coating on CoCrMo Alloy Titanium Nitride Coated Using Biomimetic Method
NASA Astrophysics Data System (ADS)
Charlena; Sukaryo, S. G.; Fajar, M.
2016-11-01
Bone implants is a way to cure broken bones which is being developed. The implants can be made of metals, ceramics and polymers. Metallic materials commonly used are titanium (Ti), stainless steel, and metal alloys. This study used Co-based alloys, i.e. CoCrMo coated with titanium nitride (TiN) which was then coated on hidroxyapatite (HAp). The HAp coating on the surface of CoCrMo alloy was done by biomimetic methods, first by soaking the metal alloys in simulated body fluid (SBF) solution for 18, 24, and 36 hours. The immersion in the SBF solution produced white coat on the surface of the metal alloy. The layers formed were analyzed by scanning electron microscope (SEM) and characterized by x-ray diffractometer (XRD). Based on the SEM results of 36 hours treatment, the morphology of apatite crystal formed fine grains. According to XRD result, there were HAp peaks at angles 2θ 31.86, 32.25, dan 39.48. However, there were also CaCO3 peaks at angles 2θ 29.46, 36.04, and 46.79. It indicated the pure HAp is not yet formed.
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NASA Astrophysics Data System (ADS)
He, Hu; Du, Xueming; Huang, Xiaokai; Xu, Weijian; Yao, Zhenhua
2018-05-01
Reliable brazing of Ti(C,N)-based cermet and 45 steel was successfully achieved by using the Mo-particle-reinforced Ag-Cu-Ti composite filler. The effects of Mo content on the interfacial microstructure and mechanical properties of Ti(C,N)-based cermet/45 steel joints were analyzed. The results showed that the joint microstructure was primarily composed of Ni3Ti+Cu3Ti2, Ag(s,s)+Cu(s.s), CuTi+Mo, Ti-based solid solution, and FeTi+Fe2Ti. With the increase in Mo content in filler, the thickness of the Ni3Ti+Cu3Ti2 layer adjacent to the Ti(C,N)-based cermet decreases, while more blocky Ti-Cu intermetallic were observed in the brazing seam. The shear strength of the joint could be significantly improved by adding suitable amounts of Mo into the Ag-Cu-Ti filler, and the peak value of 263 MPa was achieved when the alloys were brazed with Ag-Cu-Ti+8wt.%Mo composite filler at 920 °C for 20 min.
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NASA Astrophysics Data System (ADS)
Park, Sang-Gyu; Kim, Min-Chul; Lee, Bong-Sang; Wee, Dang-Moon
2010-12-01
SA508 Gr.4N Ni-Mo-Cr low alloy steel has improved fracture toughness and strength compared to commercial low alloy steels such as SA508 Gr.3 Mn-Mo-Ni low alloy steel, which has less than 1% Ni. Higher strength and fracture toughness of low alloy steels can be achieved by increasing the Ni and Cr contents. In this study, the effects of the alloying elements of Ni and Cr on the microstructural characteristics and mechanical properties of SA508 Gr.4N Ni-Mo-Cr low alloy steel are evaluated. Changes in the stable phases of SA508 Gr.4N low alloy steel with these alloying elements were evaluated using thermodynamic calculation software. These values were then compared with the observed microstructural results. Additionally, tensile tests and Charpy impact test were carried out to evaluate the mechanical properties. The thermodynamic calculations show that Ni mainly affects the change of the matrix phase of γ and α rather than the carbide phase. Contrary to the Ni effect, Cr and Mo primarily affect the precipitation behavior of the carbide phases of Cr 23C 6, Cr 7C 3 and Mo 2C. In the microscopic observations, the lath martensitic structure becomes finer as the Ni content increases without affecting the carbides. When the Cr content decreases, the Cr carbide becomes unstable and carbide coarsening occurs. Carbide Mo 2C in the form of fine needles were observed in the high-Mo alloy. Greater strength was obtained after additions of Ni and Mo and the transition properties were improved as the Ni and Cr contents increased. These results were correlated with the thermodynamic calculation results.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Jana, S.; Devaraj, A.; Kovarik, L.
Transformation kinetics of metastable body-centered cubic γ-UMo phase in U-10 wt.percent Mo alloy during annealing at sub-eutectoid temperatures of 500C and 400C has been determined as a function of time using detailed microstructural characterization by scanning electron microscopy, X-ray diffraction analysis, scanning transmission electron microscopy, and atom probe tomography. Based on the results, we found that the phase transformation is initiated by cellular transformation at both the temperatures, which results in formation of a lamellar microstructure along prior γ-UMo grain boundaries.
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[Study on high temperature oxidation of Ni-Cr ceramic alloys. Effects of Cr and Mo].
Mizutani, M
1990-03-01
The effects of Cr and Mo addition to Ni-Cr alloys on high temperature oxidation were investigated. The alloys were prepared with the composition of Cr ranging from 5 to 40 wt%. Also 2, 4 and 9 wt% of Mo was added to both Ni-5% Cr and Ni-20% Cr binary alloys. The alloys were heated at 800 degrees C, 900 degrees C and 1000 degrees C for 15 minutes in air, and the weight change after heat treatment was measured by electric automatic balance. The weight change during heating was measured by thermogravimetric measurement (TG). The products after heat treatment were characterized by X-ray diffraction and scanning electron microscopy (SEM). The results are summarized as follows: The Ni-Cr binary alloys were classified into three types of Cr ranging from 5 to 20 wt%, Cr 25% and Cr from 30 wt% to 40 wt% according to the weight gains with oxidation. In the case of the more than 25 wt% Cr content of the Ni-Cr binary alloys, the weight gain was extremely low and the heating temperature effects on the weight change were also small. X-ray diffraction study showed that NiO, NiCr2O4 and Cr2O3 formed on the surface of the Ni-Cr binary alloys whose composition of Cr ranged from 5 to 25 wt%, whereas NiO and NiCr2O4 rarely formed on the Ni-Cr binary alloys whose composition of Cr ranged from 30 to 40 wt%. This suggests that the formation of Cr2O3 prevents the formation of NiO on the alloy with a high Cr content. The weight gain of the Ni-Cr-Mo ternary alloys was smaller than that of the Ni-Cr binary alloys without Mo, and the temperature effects on the weight gain of the Ni-Cr-Mo ternary alloys were different for each Cr content. However, the effect of the amounts of Mo was small. NiO, NiCr2O4, Cr2O3 and MoO2 were identified by X-ray diffraction on the surface of the Ni-Cr-Mo ternary alloys. According to the SEM observation, it seems that NiO was formed at the outermost layer, both NiCr2O4 and Cr2O3 at the inside layer, and MoO2 at the innermost layer. The formation of both NiO and Cr2O3 on the Ni-Cr-Mo ternary alloys was restrained compared with that of the Ni-Cr binary alloys. However, the adhesion of oxides to the Ni-Cr-Mo ternary alloys was lower than that of the Ni-Cr binary alloys.
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The irradiation hardening of Ni-Mo-Cr and Ni-W-Cr alloy under Xe26+ ion irradiation
NASA Astrophysics Data System (ADS)
Chen, Huaican; Hai, Yang; Liu, Renduo; Jiang, Li; Ye, Xiang-xi; Li, Jianjian; Xue, Wandong; Wang, Wanxia; Tang, Ming; Yan, Long; Yin, Wen; Zhou, Xingtai
2018-04-01
The irradiation hardening of Ni-Mo-Cr and Ni-W-Cr alloy was investigated. 7 MeV Xe26+ ion irradiation was performed at room temperature and 650 °C with peak damage dose from 0.05 to 10 dpa. With the increase of damage dose, the hardness of Ni-Mo-Cr and Ni-W-Cr alloy increases, and reaches saturation at damage dose ≥1 dpa. Moreover, the damage dose dependence of hardness in both alloys can be described by the Makin and Minter's equation, where the effective critical volume of obstacles can be used to represent irradiation hardening resistance of the alloys. Our results also show that Ni-W-Cr alloy has better irradiation hardening resistance than Ni-Mo-Cr alloy. This is ascribed to the fact that the W, instead of Mo in the alloy, can suppress the formation of defects under ion irradiation.
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Hiromoto, Sachiko; Onodera, Emi; Chiba, Akihiko; Asami, Katsuhiko; Hanawa, Takao
2005-08-01
Corrosion behaviour and microstructure of developed low-Ni Co-29Cr-(6, 8)Mo (mass%) alloys and a conventional Co-29Cr-6Mo-1Ni alloy (ASTM F75-92) were investigated in saline solution (saline), Hanks' solution (Hanks), and cell culture medium (E-MEM + FBS). The forging ratios of the Co-29Cr-6Mo alloy were 50% and 88% and that of the Co-29Cr-8Mo alloy was 88%. Ni content in the air-formed surface oxide film of the low-Ni alloys was under the detection limit of XPS. The passive current densities of the low-Ni alloys were of the same order of magnitude as that of the ASTM alloy in all the solutions. The passive current densities of all the alloys did not significantly change with the inorganic ions and the biomolecules. The anodic current densities in the secondary passive region of the low-Ni alloys were lower than that of the ASTM alloy in the E-MEM + FBS. Consequently, the low-Ni alloys are expected to show as high corrosion resistance as the ASTM alloy. On the other hand, the passive current density of the Co-29Cr-6Mo alloy with a forging ratio of 50% was slightly lower than that with a forging ratio of 88% in the saline. The refining of grains by further forging causes the increase in the passive current density of the low-Ni alloy.
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NASA Astrophysics Data System (ADS)
Keiser, Dennis D.; Williams, Walter; Robinson, Adam; Wachs, Dan; Moore, Glenn; Crawford, Doug
2017-10-01
The Materials Management and Minimization program is developing fuel designs to replace highly enriched fuel with fuels of low enrichment. Swelling is an important irradiation behavior that needs to be well understood. Data from high resolution thickness measurements performed on U-7Mo dispersion fuel plates with Al-Si alloy matrices that were irradiated at high power is sparse. This paper reports the results of detailed thickness measurements performed on two dispersion fuel plates that were irradiated at relatively high power to high fission densities in the Advanced Test Reactor in the same RERTR-9B experiment. Both plates were irradiated to similar fission densities, but one was irradiated at a higher power than the other. The goal of this work is to identify any differences in the swelling behavior when fuel plates are irradiated at different powers to the same fission densities. Based on the results of detailed thickness measurments, more swelling occurs when a U-7Mo dispersion fuel with Al-3.5Si matrix is irradiated to a high fission density at high power compared to one irradiated at a lower power to high fission density.
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NASA Astrophysics Data System (ADS)
Keyvani, A.; Yeganeh, M.; Rezaeyan, H.
2017-04-01
In this study, Zn-Co-Mo coatings were deposited on the steel substrate from a citrate bath after adjusting pH, concentration, and current density. The morphology, the content of alloying elements, and the thickness of deposits were studied. Deposition behavior of these ternary coatings was examined by cathodic polarization and cyclic voltammetry (CV) techniques. The synthesized deposits were investigated by scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) analysis, x-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization methods. The results showed that the deposition potential of Zn-Co-Mo alloy was feasible in negative potentials higher than about -1.25 V versus Ag/AgCl. Moreover, the corrosion behavior of these coatings was found to be related to the extent of Mo as well as the local anodes and cathodes. The amount of molybdenum in the Zn-Co-Mo coating varied from 2.6 to 14 wt.% as a result of changing the pH. Based on the experimental findings, a narrow range of pH values between 5 and 5.5 could contribute to the high quality of coating in conjunction with the corrosion resistant alloy. Besides, the coatings with Mo element could show a passive-like behavior in the anodic region.
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Xie, Hongmei; Jiang, Bin; Liu, Bo; Wang, Qinghang; Xu, Junyao; Pan, Fusheng
2016-12-01
Hybrid nano-materials offer potential scope for an increasing numerous novel applications when engineered to deliver availably functional properties. In the present study, the SiO2/MoS2 hybrid nanoparticles with different mass ratios were employed as lubricant additives in the base oil, and their tribological properties were evaluated using a reciprocating ball-on-plate tribometer for magnesium alloy-steel contacts. The results demonstrate that the SiO2/MoS2 hybrid nanoparticles exhibit superior lubrication performances than individual nano-SiO2 or nano-MoS2 even in high load and diverse velocity cases. The optimal SiO2/MoS2 mixing ratio and the concentration of SiO2/MoS2 hybrid nanoparticles in the base oil are 0.25:0.75 and 1.00-1.25 wt%, respectively. The excellent lubrication properties of the SiO2/MoS2 hybrid nanoparticles are attributed to the physical synergistic lubricating actions of nano-SiO2 and nano-MoS2 during the rubbing process.
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NASA Astrophysics Data System (ADS)
Xie, Hongmei; Jiang, Bin; Liu, Bo; Wang, Qinghang; Xu, Junyao; Pan, Fusheng
2016-07-01
Hybrid nano-materials offer potential scope for an increasing numerous novel applications when engineered to deliver availably functional properties. In the present study, the SiO2/MoS2 hybrid nanoparticles with different mass ratios were employed as lubricant additives in the base oil, and their tribological properties were evaluated using a reciprocating ball-on-plate tribometer for magnesium alloy-steel contacts. The results demonstrate that the SiO2/MoS2 hybrid nanoparticles exhibit superior lubrication performances than individual nano-SiO2 or nano-MoS2 even in high load and diverse velocity cases. The optimal SiO2/MoS2 mixing ratio and the concentration of SiO2/MoS2 hybrid nanoparticles in the base oil are 0.25:0.75 and 1.00-1.25 wt%, respectively. The excellent lubrication properties of the SiO2/MoS2 hybrid nanoparticles are attributed to the physical synergistic lubricating actions of nano-SiO2 and nano-MoS2 during the rubbing process.
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Fuel Thermo-physical Characterization Project. Fiscal Year 2014 Final Report
DOE Office of Scientific and Technical Information (OSTI.GOV)
Burkes, Douglas; Casella, Andrew M.; Buck, Edgar C.
2015-03-15
The Office of Material Management and Minimization (M3) Reactor Conversion Fuel Thermo-Physical Characterization Project at Pacific Northwest National Laboratory (PNNL) was tasked with using PNNL facilities and processes to receive irradiated low enriched uranium–molybdenum (LEU-Mo) fuel plate samples and perform analysis in support of the M3 Reactor Conversion Program. This work is in support of the M3 Reactor Conversion Fuel Development Pillar that is managed by Idaho National Laboratory. The primary research scope was to determine the thermo-physical properties as a function of temperature and burnup. Work conducted in Fiscal Year (FY) 2014 complemented measurements performed in FY 2013 onmore » four additional irradiated LEU-Mo fuel plate samples. Specifically, the work in FY 2014 investigated the influence of different processing methods on thermal property behavior, the absence of aluminum alloy cladding on thermal property behavior for additional model validation, and the influence of higher operating surface heat flux / more aggressive irradiation conditions on thermal property behavior. The model developed in FY 2013 and refined in FY 2014 to extract thermal properties of the U-Mo alloy from the measurements conducted on an integral fuel plate sample (i.e., U-Mo alloy with a thin Zr coating and clad in AA6061) continues to perform very well. Measurements conducted in FY 2014 on samples irradiated under similar conditions compare well to measurements performed in FY 2013. In general, there is no gross influence of fabrication method on thermal property behavior, although the difference in LEU-Mo foil microstructure does have a noticeable influence on recrystallization of grains during irradiation. Samples irradiated under more aggressive irradiation conditions, e.g., higher surface heat flux, revealed lower thermal conductivity when compared to samples irradiated at moderate surface heat fluxes, with the exception of one sample. This report documents thermal property measurements conducted in FY 2014 and compares results to values obtained from literature and measurements performed in FY 2013, where applicable, along with appropriate discussion.« less
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Structure and Mechanical Properties of As-Cast Ti-5Sn-xMo Alloys.
Yu, Hsing-Ning; Hsu, Hsueh-Chuan; Wu, Shih-Ching; Hsu, Shih-Kuang; Ho, Wen-Fu
2017-04-27
Ti-5Sn- x Mo ( x = 0, 1, 3, 5, 7.5, 10, 12.5, 15, 17.5, and 20 wt %) alloys were designed and prepared for application as implant materials with superior mechanical properties. The results demonstrated that the crystal structure and mechanical properties of Ti-5Sn- x Mo alloys are highly affected by their Mo content. The as-cast microstructures of Ti-5Sn- x Mo alloys transformed in the sequence of phases α' → α″ → β, and the morphologies of the alloys changed from a lath structure to an equiaxed structure as the Mo content increased. The α″-phase Ti-5Sn-7.5Mo (80 GPa) and β-phase Ti-5Sn-10Mo (85 GPa) exhibited relatively low elastic moduli and had excellent elastic recovery angles of 27.4° and 37.8°, respectively. Furthermore, they exhibited high ductility and moderate strength, as evaluated using the three-point bending test. Search for a more suitable implant material by this study, Ti-5Sn- x Mo alloys with 7.5 and 10 wt % Mo appear to be promising candidates because they demonstrate the optimal combined properties of microhardness, ductility, elastic modulus, and elastic recovery capability.
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Structure and Mechanical Properties of As-Cast Ti–5Sn–xMo Alloys
Yu, Hsing-Ning; Hsu, Hsueh-Chuan; Wu, Shih-Ching; Hsu, Shih-Kuang; Ho, Wen-Fu
2017-01-01
Ti–5Sn–xMo (x = 0, 1, 3, 5, 7.5, 10, 12.5, 15, 17.5, and 20 wt %) alloys were designed and prepared for application as implant materials with superior mechanical properties. The results demonstrated that the crystal structure and mechanical properties of Ti–5Sn–xMo alloys are highly affected by their Mo content. The as-cast microstructures of Ti–5Sn–xMo alloys transformed in the sequence of phases α′ → α″ → β, and the morphologies of the alloys changed from a lath structure to an equiaxed structure as the Mo content increased. The α″-phase Ti–5Sn–7.5Mo (80 GPa) and β-phase Ti–5Sn–10Mo (85 GPa) exhibited relatively low elastic moduli and had excellent elastic recovery angles of 27.4° and 37.8°, respectively. Furthermore, they exhibited high ductility and moderate strength, as evaluated using the three-point bending test. Search for a more suitable implant material by this study, Ti–5Sn–xMo alloys with 7.5 and 10 wt % Mo appear to be promising candidates because they demonstrate the optimal combined properties of microhardness, ductility, elastic modulus, and elastic recovery capability. PMID:28772820
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First-Principles Study of Mo Segregation in MoNi(111): Effects of Chemisorbed Atomic Oxygen
Yu, Yanlin; Xiao, Wei; Wang, Jianwei; Wang, Ligen
2015-01-01
Segregation at metal alloy surfaces is an important issue because many electrochemical and catalytic properties are directly correlated to the surface composition. We have performed density functional theory calculations for Mo segregation in MoNi(111) in the presence of chemisorbed atomic oxygen. In particular, the coverage dependence and possible adsorption-induced segregation phenomena are addressed by investigating segregation energies of the Mo atom in MoNi(111). The theoretical calculated results show that the Mo atom prefers to be embedded in the bulk for the clean MoNi(111), while it segregates to the top-most layer when the oxygen coverage is thicker than 1/9 monolayer (ML). Furthermore, we analyze the densities of states for the clean and oxygen-chemisorbed MoNi(111), and see a strong covalent bonding between Mo d-band states and O p-states. The present study provides valuable insight for exploring practical applications of Ni-based alloys as hydrogen evolution electrodes. PMID:28787811
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NASA Technical Reports Server (NTRS)
Barrett, C. A.
1985-01-01
Multiple linear regression analysis was used to determine an equation for estimating hot corrosion attack for a series of Ni base cast turbine alloys. The U transform (i.e., 1/sin (% A/100) to the 1/2) was shown to give the best estimate of the dependent variable, y. A complete second degree equation is described for the centered" weight chemistries for the elements Cr, Al, Ti, Mo, W, Cb, Ta, and Co. In addition linear terms for the minor elements C, B, and Zr were added for a basic 47 term equation. The best reduced equation was determined by the stepwise selection method with essentially 13 terms. The Cr term was found to be the most important accounting for 60 percent of the explained variability hot corrosion attack.
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NASA Technical Reports Server (NTRS)
Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.
2000-01-01
Efforts are underway to replace superalloys used in the hot sections of gas turbine engines with materials possessing better mechanical and physical properties. Alloys based on the intermetallic NiAl have demonstrated potential; however, they generally suffer from low fracture resistance (toughness) at room temperature and from poor strength at elevated temperatures. Directional solidification of NiAl alloyed with both Cr and Mo has yielded materials with useful toughness and elevated-temperature strength values. The intermetallic alloy NiAl has been proposed as an advanced material to extend the maximum operational temperature of gas turbine engines by several hundred degrees centigrade. This intermetallic alloy displays a lower density (approximately 30-percent less) and a higher thermal conductivity (4 to 8 times greater) than conventional superalloys as well as good high-temperature oxidation resistance. Unfortunately, unalloyed NiAl has poor elevated temperature strength (approximately 50 MPa at 1027 C) and low room-temperature fracture toughness (about 5 MPa). Directionally solidified NiAl eutectic alloys are known to possess a combination of high elevated-temperature strength and good room-temperature fracture toughness. Research has demonstrated that a NiAl matrix containing a uniform distribution of very thin Cr plates alloyed with Mo possessed both increased fracture toughness and elevated-temperature creep strength. Although attractive properties were obtained, these alloys were formed at low growth rates (greater than 19 mm/hr), which are considered to be economically unviable. Hence, an investigation was warranted of the strength and toughness behavior of NiAl-(Cr,Mo) directionally solidified at faster growth rates. If the mechanical properties did not deteriorate with increased growth rates, directional solidification could offer an economical means to produce NiAl-based alloys commercially for gas turbine engines. An investigation at the NASA Glenn Research Center at Lewis Field was undertaken to study the effect of the directional solidification growth rate on the microstructure, room temperature fracture toughness, and strength at 1027 C of a Ni-33Al-31Cr-3Mo eutectic alloy. The directionally solidified rates varied between 7.6 and 508 millimeters per hour Essentially fault-free, alternating (Cr, Mo)/NiAl lamellar plate microstructures (left photograph) were formed during growth at and below 12.7 mm/hr, whereas cellular microstructures (right photograph) with the (Cr, Mo) phase in a radial spokelike pattern were developed at faster growth rates. The compressive strength at 1027 C continuously increased with increasing growth rate and did not indicate a maxima as was reported for directionally solidified Ni-33Al-34Cr. Surprisingly, samples with the lamellar plate microstructure (left photograph) possessed a room-temperature fracture toughness of approximately 12 MPa(sup square root of m), whereas all the alloys with a cellular microstructure had a toughness of about 17 MPa(sup square root of m). These results are significant since they clearly demonstrate that Ni-33Al-31Cr-3Mo can be directionally solidified at much faster growth rates without any observable deterioration in its mechanical properties. Thus, the potential to produce strong, tough NiAl-based eutectics at commercially acceptable growth rates exists. Additional testing and alloy optimization studies are underway.
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Influence of carbides and microstructure of CoCrMo alloys on their metallic dissolution resistance.
Valero-Vidal, C; Casabán-Julián, L; Herraiz-Cardona, I; Igual-Muñoz, A
2013-12-01
CoCrMo alloys are passive and biocompatible materials widely used as joint replacements due to their good mechanical properties and corrosion resistance. Electrochemical behaviour of thermal treated CoCrMo alloys with different carbon content in their bulk alloy composition has been analysed. Both the amount of carbides in the CoCrMo alloys and the chemical composition of the simulated body fluid affect the electrochemical properties of these biomedical alloys, thus passive dissolution rate was influenced by the mentioned parameters. Lower percentage of carbon in the chemical composition of the bulk alloy and thermal treatments favour the homogenization of the surface (less amount of carbides), thus increasing the availability of Cr to form the oxide film and improving the corrosion resistance of the alloy. © 2013.
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Intergranular diffusion and embrittlement of a Ni-16Mo-7Cr alloy in Te vapor environment
NASA Astrophysics Data System (ADS)
Cheng, Hongwei; Li, Zhijun; Leng, Bin; Zhang, Wenzhu; Han, Fenfen; Jia, Yanyan; Zhou, Xingtai
2015-12-01
Nickel and some nickel-base alloys are extremely sensitive to intergranular embrittlement and tellurium (Te) enhanced cracking, which should be concerned during their serving in molten salt reactors. Here, a systematic study about the effects of its temperature on the reaction products at its surface, the intergranular diffusion of Te in its body and its embrittlement for a Ni-16Mo-7Cr alloy contacting Te is reported. For exposed to Te vapor at high temperature (823-1073 K), the reaction products formed on the surface of the alloy were Ni3Te2, CrTe, and MoTe2, and the most serious embrittlement was observed at 1073 K. The kinetic measurement in terms of Te penetration depth in the alloy samples gives an activation energy of 204 kJ/mol. Electron probe microanalysis confirmed the local enrichment of Te at grain boundaries. And clearly, the embrittlement was results from the intergranular diffusion and segregation of element Te.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Devaraj, Arun; Nag, Soumya; Banerjee, Rajarshi
2013-10-19
The benefit of direct coupling of APT with TEM dark field imaging to investigate early stages of phase transformation in multicomponent alloys is demonstrated by analyzing alpha phase precipitated in a model Ti-10 at% Mo-10 at% Al alloy during annealing at 400oC. Through such a direct coupling approach a thermodynamically unexpected solute partitioning trend between beta matrix and alpha precipitate is observed in the early stages of precipitation, which is explained based on possible nucleation of alpha phase in the Ti rich (Mo and Al depleted regions) created as a result of phase separation in beta matrix. On further highermore » temperature annealing at 600oC for 1 hour, the alpha precipitates were shown to grow and get enriched in Al and further depleted in Mo reaching the thermodynamic equilibrium.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Morrison, M. L.; Buchanan, R. A.; Leon, R. V.
2005-01-01
Bulk metallic glasses (BMGs) represent an emerging class of materials with an amorphous structure and a unique combination of properties. The objectives of this investigation were to define the electrochemical behavior of a specific Zr-based BMG alloy in a physiologically relevant environment and to compare these properties to standard, crystalline biomaterials as well as other Zr-based BMG compositions. Cyclic-anodic-polarization studies were conducted with a Zr{sub 52.5}Cu{sub 17.9}Ni{sub 14.6}Al{sub 10.0}Ti{sub 5.0} (at %) BMG in a phosphate-buffered saline electrolyte with a physiologically relevant oxygen content at 37 C. The results were compared to three common, crystalline biomaterials: CoCrMo, 316L stainless steel,more » and Ti-6Al-4V. The BMG alloy was found to have a lower corrosion penetration rate (CPR), as compared to the 316L stainless steel, and an equivalent CPR, as compared to the CoCrMo and Ti-6Al-4V alloys. Furthermore, the BMG alloy demonstrated better localized corrosion resistance than the 316L stainless steel. However, the localized corrosion resistance of the BMG alloy was not as high as those of the CoCrMo and Ti-6Al-4V alloys in the tested environment. The excellent electrochemical properties demonstrated by the BMG alloy are combined with a low modulus and unparalleled strength. This unique combination of properties dramatically demonstrates the potential for amorphous alloys as a new generation of biomaterials.« less
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2012-01-01
submitted to Metallurgical Transactions. This document contains color. 14. ABSTRACT While the role of borides on the microstructure of titanium...Ohio, U.S.A. Abstract While the role of borides on the microstructure of titanium alloys has been discussed in many previous reports, this paper...morphology of precipitates nucleating from boride precipitates present in the matrix of a titanium alloy; and (b) to investigate the role of presence or
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NASA Astrophysics Data System (ADS)
Shah, Shreya; Marin-Flores, Oscar G.; Norton, M. Grant; Ha, Su
2015-10-01
In this study, NiMo alloys supported on Mo2C are synthesized by wet impregnation for partial oxidation of methyl oleate, a surrogate biodiesel, to produce syngas. When compared to single phase Mo2C, the H2 yield increases from 70% up to >95% at the carbon conversion of ∼100% for NiMo alloy nanoparticles that are dispersed over the Mo2C surface. Supported NiMo alloy samples are prepared at two different calcination temperatures in order to determine its effect on particle dispersion, crystalline phase and catalytic properties. The reforming test data indicate that catalyst prepared at lower calcination temperature shows better nanoparticle dispersion over the Mo2C surface, which leads to higher initial performance when compared to catalysts synthesized at higher calcination temperature. Activity tests using the supported NiMo alloy on Mo2C that are calcined at the lower temperature of 400 °C shows 100% carbon conversion with 90% H2 yield without deactivation due to coking over 24 h time-on-stream.
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NASA Astrophysics Data System (ADS)
Que, Like
Wear is one of the major causes of artificial total knee arthroplasty (TKA) failure. Wear debris can cause adverse reactions to the surrounding tissue which can ultimately lead to loosening of the prosthesis. The wear behavior of UHMWPE tibial components have been studied extensively, but relatively little attention has been paid to the CoCrMo femoral component. The goal of the present study was to investigate the wear mechanisms of CoCrMo femoral components, to study the effect of CoCrMo alloy surface roughness on the wear of UHMWPE, and to determine the effect of heat treatments on the wear resistance of the CoCrMo implant alloys. The surface roughness of twenty-seven retrieved CoCrMo femoral components was analyzed. A multiple station wear testing machine and a wear fixture attached to an MTS 858 bionix system were built and used for in vitro wear studies of the CoCrMo/UHMWPE bearing couple. Solution and aging treatments were applied to the CoCrMo alloys. A white light interference surface profilometer (WLISP) and a scanning electron microscope (SEM) were used to measure the surface roughness and to study wear mechanisms of CoCrMo alloy. An optical microscope was used for alloy microstructure study. X-ray diffraction tests were performed to identify alloy phase transformation after aging. The micro-structure, hardness, and wear resistance of the alloys were studied. Surface roughness was used to quantify alloy wear, and the minimum number of surface roughness measurements required to obtain a reliable and repeatable characterization of surface roughness for a worn alloy surface was determined. The surfaces of the retrieved CoCrMo femoral components appeared to be damaged by metal particles embedded in the UHMWPE tibial component and metal-on-metal wear due to UHMWPE tibial component through-wear. Surface roughness of the femoral components was not correlated with patient age, weight, sex, or length of implantation. In vitro wear tests showed that when the CoCrMo alloy surface roughness was higher than 0.022 mum Ra (surface roughness average), UHMWPE wear increased with increasing CoCrMo alloy surface roughness. Bone and poly(methyl methacrylate) (PMMA) bone cement abrasive particles created scratches on the alloy via a ploughing mechanism, and resulted in significantly rougher surfaces than controls without particles (P < 0.01). Solution treatments at 1230sp°C and 1245sp°C reduced the hardness and wear resistance of the as-cast F75 CoCrMo alloy. Aging at 700sp°C caused recrystallization of the forged F799 alloy and improved wear resistance. Thermo-mechanical treatments have the potential to increase the lifetime of artificial joints by increasing the wear resistance of CoCrMo components.
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Electrochemical Hydrogen Evolution at Ordered Mo 7 Ni 7
DOE Office of Scientific and Technical Information (OSTI.GOV)
Csernica, Peter M.; McKone, James R.; Mulzer, Catherine R.
2017-04-11
Ni–Mo alloys containing up to ~15 mol % Mo are excellent non-noble electrocatalysts for the hydrogen evolution reaction (HER) in alkaline aqueous electrolytes. To date, studies have not addressed the details of HER activity of ordered Ni–Mo intermetallic compounds, which can contain a significantly larger fraction of Mo (up to 50 mol %) than can be accessed through high-temperature alloying. Here, we present a straightforward and facile synthesis of three phase-pure electrocatalyst powders using a precipitation–reduction approach: ordered Mo7Ni7, disordered Ni0.92Mo0.08, and pure Ni. The Ni0.92Mo0.08 alloy exhibited a nearly 10-fold higher mass-specific HER activity than either pure Ni ormore » Mo7Ni7, where much of the difference could be attributed to relative surface area. Therefore, we attempted to quantify and account for differences in surface areas using electron microscopy, impedance spectroscopy, and gas adsorption measurements. These data suggest that Ni–Mo alloys and intermetallic compounds exhibit substantial pseudocapacitance at potentials near the onset of hydrogen evolution, which can cause impedance spectroscopy to overestimate the interfacial capacitance, and thus the electrochemically active surface area, of these materials. From these observations, we postulate Mo redox activity as the chemical basis for the observed pseudocapacitance of Ni–Mo composites. Furthermore, using gas adsorption measurements, rather than capacitance, to estimate active surface area, we find that ordered Mo7Ni7 is more intrinsically active than the Ni0.92Mo0.08 alloy, implying that Mo7Ni7 intermetallics with high surface area will also give higher mass-specific activities than alloys with comparable roughness.« less
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Chao, Yong-lie; Lui, Chang-hong; Li, Ning; Yang, Xiao-yu
2005-02-01
To investigate a kind of Co-Cr-Mo alloys used for both porcelain fused to metal (PFM) restorations and casting framework of removable partial dentures. The Co-Cr-Mo alloy underwent the design for elementary compositions of the alloys and the production from the raw materials by means of a vacuum melt furnace. The strength, hardness, plasticity and casting ability of the alloy were examined with metal tensile test. Vickers hardness test and grid casting were examined respectively. The microstructure of the Co-Cr-Mo alloy was also inspected by scanning electron microscope and X-ray diffraction analysis. The elementary composition of DA9-4 alloy mainly consisted of Co 54%-67%, Cr 21%-26%, Mo 5%-8%, W 5%-8%, Si 1%-3%, Mn 0.1%-0.25% and trace elements. The yield strength of the alloy was 584 MPa, while the tensile strength was 736 MPa. The coefficient of expansion was 15.0%, the Vickers hardness reached 322, and the casting ratio exibited 100%. The DA9-4 Co-Cr-Mo alloy used for PFM and framework shown in this paper can meet the clinical demands and have reached the objects of the experiment plan.
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Glass Formation, Chemical Properties and Surface Analysis of Cu-Based Bulk Metallic Glasses
Qin, Chunling; Zhao, Weimin; Inoue, Akihisa
2011-01-01
This paper reviews the influence of alloying elements Mo, Nb, Ta and Ni on glass formation and corrosion resistance of Cu-based bulk metallic glasses (BMGs). In order to obtain basic knowledge for application to the industry, corrosion resistance of the Cu–Hf–Ti–(Mo, Nb, Ta, Ni) and Cu–Zr–Ag–Al–(Nb) bulk glassy alloy systems in various solutions are reported in this work. Moreover, X-ray photoelectron spectroscopy (XPS) analysis is performed to clarify the surface-related chemical characteristics of the alloy before and after immersion in the solutions; this has lead to a better understanding of the correlation between the surface composition and the corrosion resistance. PMID:21731441
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Microstructure and Room-Temperature Mechanical Properties of FeCrMoVTi x High-Entropy Alloys
NASA Astrophysics Data System (ADS)
Guo, Jun; Huang, Xuefei; Huang, Weigang
2017-07-01
FeCrMoVTi x ( x values represent the molar ratio, where x = 0, 0.5, 1.0, 1.5, and 2.0) high-entropy alloys were prepared by a vacuum arc melting method. The effects of Ti element on the microstructure and room-temperature mechanical properties of the as-cast FeCrMoVTi x alloys were investigated. The results show that the prepared alloys exhibited typical dendritic microstructure and the size of the microstructure became fine with increasing Ti content. The FeCrMoV alloy exhibited a single body-centered cubic structure (BCC1) and the alloys prepared with Ti element exhibited BCC1 + BCC2 mixed structure. The new BCC2 phase is considered as (Fe, Ti)-rich phase and was distributed in the dendrite region. With the increase of Ti content, the volume fraction of the BCC2 phase increased and its shape changed from a long strip to a network. For the FeCrMoV alloy, the fracture strength, plastic strain, and hardness reached as high as 2231 MPa, 28.2%, and 720 HV, respectively. The maximum hardness of 887 HV was obtained in the FeCrMoVTi alloy. However, the fracture strength, yield stress, and plastic strain of the alloys decreased continuously as Ti content increased. In the room-temperature compressive test, the alloys showed typical brittle fracture characteristics.
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TEM and XAS investigation of fission gas behaviors in U-Mo alloy fuels through ion beam irradiation
NASA Astrophysics Data System (ADS)
Zang, Hang; Yun, Di; Mo, Kun; Wang, Kunpeng; Mohamed, Walid; Kirk, Marquis A.; Velázquez, Daniel; Seibert, Rachel; Logan, Kevin; Terry, Jeffrey; Baldo, Peter; Yacout, Abdellatif M.; Liu, Wenbo; Zhang, Bo; Gao, Yedong; Du, Yang; Liu, Jing
2017-10-01
In this study, smaller-grained (hundred nano-meter size grain) and larger-grained (micro-meter size grain) U-10Mo specimens have been irradiated (implanted) with 250 keV Xe+ beam and were in situ characterized by TEM. Xe bubbles were not seen in the specimen after an implantation fluence of 2 × 1020 ions/m2 at room temperature. Nucleation of Xe bubbles happened during heating of the specimen to a final temperature of 300 °C. By comparing measured Xe bubble statistics, the nucleation and growth behaviors of Xe bubbles were investigated in smaller-grained and larger-grained U-10Mo specimens. A multi-atom kind of nucleation mechanism has been observed in both specimens. X-ray Absorption spectroscopy showed the edge position in the bubbles to be the same as that of Xe gas. The size of Xe bubbles has been shown to be bigger in larger-grained specimens than in smaller-grained specimens at the same implantation conditions.
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Kr ion irradiation study of the depleted-uranium alloys
NASA Astrophysics Data System (ADS)
Gan, J.; Keiser, D. D.; Miller, B. D.; Kirk, M. A.; Rest, J.; Allen, T. R.; Wachs, D. M.
2010-12-01
Fuel development for the reduced enrichment research and test reactor (RERTR) program is tasked with the development of new low enrichment uranium nuclear fuels that can be employed to replace existing high enrichment uranium fuels currently used in some research reactors throughout the world. For dispersion type fuels, radiation stability of the fuel-cladding interaction product has a strong impact on fuel performance. Three depleted-uranium alloys are cast for the radiation stability studies of the fuel-cladding interaction product using Kr ion irradiation to investigate radiation damage from fission products. SEM analysis indicates the presence of the phases of interest: U(Al, Si) 3, (U, Mo)(Al, Si) 3, UMo 2Al 20, U 6Mo 4Al 43 and UAl 4. Irradiations of TEM disc samples were conducted with 500 keV Kr ions at 200 °C to ion doses up to 2.5 × 10 19 ions/m 2 (˜10 dpa) with an Kr ion flux of 10 16 ions/m 2/s (˜4.0 × 10 -3 dpa/s). Microstructural evolution of the phases relevant to fuel-cladding interaction products was investigated using transmission electron microscopy.
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NASA Astrophysics Data System (ADS)
Guo, Lili; Qin, Lin; Kong, Fanyou; Yi, Hong; Tang, Bin
2016-12-01
Molybdenum, an alloying element, was deposited and diffused on Ti-5Zr-3Sn-5Mo-15Nb (TLM) substrate by double glow plasma surface alloying technology at 900, 950 and 1000 °C. The microstructure, composition distribution and micro-hardness of the Mo modified layers were analyzed. Contact angles on deionized water and wear behaviors of the samples against corundum balls in simulated human body fluids were investigated. Results show that the surface microhardness is significantly enhanced after alloying and increases with treated temperature rising, and the contact angles are lowered to some extent. More importantly, compared to as-received TLM alloy, the Mo modified samples, especially the one treated at 1000 °C, exhibit the significant improvement of tribological properties in reciprocating wear tests, with lower specific wear rate and friction coefficient. To conclude, Mo alloying treatment is an effective approach to obtain excellent comprehensive properties including optimal wear resistance and improved wettability, which ensure the lasting and safety application for titanium alloys as the biomedical implants.
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Ren, Fuzeng; Zhu, Weiwei; Chu, Kangjie
2016-07-01
Nickel and carbides free Co-28Cr-6Mo alloy was fabricated by combination of mechanical alloying and warm pressing. The microstructure, mechanical properties, pin-on-disk dry sliding wear and corrosion behavior in simulated physiological solution were investigated. The produced Co-28Cr-6Mo alloy has elongated ultra-fine grained (UFG) structure of ε-phase with average grain size of 600nm in length and 150nm in thickness. The hardness and modulus were determined to be 8.87±0.56GPa and 198.27±7.02GPa, respectively. The coefficient of friction upon dry sliding against alumina is pretty close to that of the forged Co-29Cr-6Mo alloy. The initial ε-phase and UFG microstructure contribute to reduce the depth of severe plastic deformation region during wear and enable the alloy with excellent wear resistance. The corrosion potential of such UFG Co-Cr-Mo alloy has more positive corrosion potential and much lower corrosion current density than those of ASTM alloy. Copyright © 2016 Elsevier Ltd. All rights reserved.
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Mechanical properties and the electronic structure of transition of metal alloys
NASA Technical Reports Server (NTRS)
Arsenault, R. J.; Drew, H. D.
1977-01-01
This interdiscipline research program was undertaken in an effort to investigate the relationship between the mechanical strength of Mo based alloys with their electronic structure. Electronic properties of these alloys were examined through optical studies, and the classical solid solution strengthening mechanisms were considered, based on size and molecular differences to determine if these mechanisms could explain the hardness data.
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Singh, Prashant; Smirnov, A. V.; Johnson, Duane D.
2018-05-31
From electronic-structure-based thermodynamic linear response, we establish chemical ordering behavior in complex solid solutions versus how Gibbs' space is traversed—applying it on prototype refractory A2 Ta-Nb-Mo-W high-entropy alloys. Near ideal stoichiometry, this alloy has anomalous, intricate chemical ordering tendencies, with long-ranged chemical interactions that produce competing short-range order (SRO) with a crossover to spinodal segregation. This atypical SRO arises from canonical band behavior that, with alloying, creates features near the Fermi surface (well defined even with disorder) that change to simple commensurate SRO with (un)filling of these states. In conclusion, our results reveal how complexity and competing electronic effects controlmore » ordering in these alloys.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Singh, Prashant; Smirnov, A. V.; Johnson, Duane D.
From electronic-structure-based thermodynamic linear response, we establish chemical ordering behavior in complex solid solutions versus how Gibbs' space is traversed—applying it on prototype refractory A2 Ta-Nb-Mo-W high-entropy alloys. Near ideal stoichiometry, this alloy has anomalous, intricate chemical ordering tendencies, with long-ranged chemical interactions that produce competing short-range order (SRO) with a crossover to spinodal segregation. This atypical SRO arises from canonical band behavior that, with alloying, creates features near the Fermi surface (well defined even with disorder) that change to simple commensurate SRO with (un)filling of these states. In conclusion, our results reveal how complexity and competing electronic effects controlmore » ordering in these alloys.« less
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Compressive creep behavior of alloys based on B2 FeAl
NASA Technical Reports Server (NTRS)
Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.
1986-01-01
Alloys based on FeAl are attractive alternate materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.
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Compressive creep behavior of alloys based on B2 FeAl
NASA Technical Reports Server (NTRS)
Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.
1987-01-01
Alloys based on FeAl are attractive alternative materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.
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Alloying effect on bright-dark exciton states in ternary monolayer Mo x W1-x Se2
NASA Astrophysics Data System (ADS)
Liu, Yanping; Tom, Kyle; Zhang, Xiaowei; Lou, Shuai; Liu, Yin; Yao, Jie
2017-07-01
Binary transition metal dichalcogenides (TMDCs) in the class MX2 (M = Mo, W; X = S, Se) have been widely investigated for potential applications in optoelectronics and nanoelectronics. Recently, alloy-based monolayers of TMDCs have provided a stable and versatile technique to tune the physical properties and optimize them for potential applications. Here, we present experimental evidence for the existence of an intermediate alloy state between the MoSe2-like and the WSe2-like behavior of the neutral exciton (X 0) using temperature-dependent photoluminescence (PL) of the monolayer Mo x W1-x Se2 alloy. The existence of a maximum PL intensity around 120 K can be explained by the competition between the thermally activated bright states and the non-radiative quenching of the bright states. Moreover, we also measured localized exciton (XB ) PL peak in the alloy and the observed behavior agrees well with a model previously proposed for the 3D case, which indicates the theory also applies to 2D systems. Our results not only shed light on bright-dark states and localized exciton physics of 2D semiconductors, but also offer a new route toward the control of the bright-dark transition and tailoring optical properties of 2D semiconductors through defect engineering.
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NASA Astrophysics Data System (ADS)
Keiser, Dennis D.; Jue, Jan-Fong; Woolstenhulme, Nicolas E.; Ewh, Ashley
2011-12-01
Low-enriched uranium-molybdenum (U-Mo) alloy particles dispersed in aluminum alloy (e.g., dispersion fuels) are being developed for application in research and test reactors. To achieve the best performance of these fuels during irradiation, optimization of the starting microstructure may be required by utilizing a heat treatment that results in the formation of uniform, Si-rich interaction layers between the U-Mo particles and Al-Si matrix. These layers behave in a stable manner under certain irradiation conditions. To identify the optimum heat treatment for producing these kinds of layers in a dispersion fuel plate, a systematic annealing study has been performed using actual dispersion fuel samples, which were fabricated at relatively low temperatures to limit the growth of any interaction layers in the samples prior to controlled heat treatment. These samples had different Al matrices with varying Si contents and were annealed between 450 and 525 °C for up to 4 h. The samples were then characterized using scanning electron microscopy (SEM) to examine the thickness, composition, and uniformity of the interaction layers. Image analysis was performed to quantify various attributes of the dispersion fuel microstructures that related to the development of the interaction layers. The most uniform layers were observed to form in fuel samples that had an Al matrix with at least 4 wt.% Si and a heat treatment temperature of at least 475 °C.
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Copper modified austenitic stainless steel alloys with improved high temperature creep resistance
Swindeman, R.W.; Maziasz, P.J.
1987-04-28
An improved austenitic stainless steel that incorporates copper into a base Fe-Ni-Cr alloy having minor alloying substituents of Mo, Mn, Si, T, Nb, V, C, N, P, B which exhibits significant improvement in high temperature creep resistance over previous steels. 3 figs.
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First-principles studies of chromium line-ordered alloys in a molybdenum disulfide monolayer
NASA Astrophysics Data System (ADS)
Andriambelaza, N. F.; Mapasha, R. E.; Chetty, N.
2017-08-01
Density functional theory calculations have been performed to study the thermodynamic stability, structural and electronic properties of various chromium (Cr) line-ordered alloy configurations in a molybdenum disulfide (MoS2) hexagonal monolayer for band gap engineering. Only the molybdenum (Mo) sites were substituted at each concentration in this study. For comparison purposes, different Cr line-ordered alloy and random alloy configurations were studied and the most thermodynamically stable ones at each concentration were identified. The configurations formed by the nearest neighbor pair of Cr atoms are energetically most favorable. The line-ordered alloys are constantly lower in formation energy than the random alloys at each concentration. An increase in Cr concentration reduces the lattice constant of the MoS2 system following the Vegard’s law. From density of states analysis, we found that the MoS2 band gap is tunable by both the Cr line-ordered alloys and random alloys with the same magnitudes. The reduction of the band gap is mainly due to the hybridization of the Cr 3d and Mo 4d orbitals at the vicinity of the band edges. The band gap engineering and magnitudes (1.65 eV to 0.86 eV) suggest that the Cr alloys in a MoS2 monolayer are good candidates for nanotechnology devices.
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Interface characterization of Cu-Mo coating deposited on Ti-Al alloys by arc spraying
NASA Astrophysics Data System (ADS)
Bai, Shengqiang; Li, Fei; Wu, Ting; Yin, Xianglin; Shi, Xun; Chen, Lidong
2015-03-01
Cu-Mo pseudobinary alloys are promising candidates as electrode materials in CoSb3-based skutterudite thermoelectric (TE) devices for TE power generation. In this study, Cu-Mo coatings were deposited onto Ti-Al substrates by applying a dual-wire electric arc spraying coating technique. The microstructure of the surfaces, cross sections and coating interfaces were analyzed by scanning electron microscopy (SEM) and energy dispersion spectrometry (EDS). Cu-Mo coatings showed a typical banded splat with compact microstructures, and have no coarse pores nor micro-cracks. The thermal shock resistance of the Cu-Mo coating was also investigated to show good combinations with Ti-Al substrates. After 50 thermal shock cycles, there were no cracks observed at the interface. In contrast, the test of the thermal shock resistance of the Cu coating on the Ti-Al substrate was also investigated. Due to a large difference in the thermal expansion coefficients between Cu and Ti-Al alloys, the Cu coating flaked from the Ti-Al substrate completely after 10 thermal shock cycles. The contact resistivity of the Ti-Al/Cu-Mo interface was about 1.6 μΩṡcm2 and this value was unchanged after 50 thermal shock cycles, indicating the low electric resistance and high thermal stability of the Cu-Mo/Ti-Al interface.
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A model for recovery of scrap monolithic uranium molybdenum fuel by electrorefining
NASA Astrophysics Data System (ADS)
Van Kleeck, Melissa A.
The goal of the Reduced Enrichment for Research and Test Reactors program (RERTR) is toreduce enrichment at research and test reactors, thereby decreasing proliferation risk at these facilities. A new fuel to accomplish this goal is being manufactured experimentally at the Y12 National Security Complex. This new fuel will require its own waste management procedure,namely for the recovery of scrap from its manufacture. The new fuel is a monolithic uraniummolybdenum alloy clad in zirconium. Feasibility tests were conducted in the Planar Electrode Electrorefiner using scrap U-8Mo fuel alloy. These tests proved that a uranium product could be recovered free of molybdenum from this scrap fuel by electrorefining. Tests were also conducted using U-10Mo Zr clad fuel, which confirmed that product could be recovered from a clad version of this scrap fuel at an engineering scale, though analytical results are pending for the behavior of Zr in the electrorefiner. A model was constructed for the simulation of electrorefining the scrap material produced in the manufacture of this fuel. The model was implemented on two platforms, Microsoft Excel and MatLab. Correlations, used in the model, were developed experimentally, describing area specific resistance behavior at each electrode. Experiments validating the model were conducted using scrap of U-10Mo Zr clad fuel in the Planar Electrode Electrorefiner. The results of model simulations on both platforms were compared to experimental results for the same fuel, salt and electrorefiner compositions and dimensions for two trials. In general, the model demonstrated behavior similar to experimental data but additional refinements are needed to improve its accuracy. These refinements consist of a function for surface area at anode and cathode based on charge passed. Several approximations were made in the model concerning areas of electrodes which should be replaced by a more accurate function describing these areas.
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Design of refractory high-entropy alloys
Gao, M. C.; Carney, C. S.; Dogan, O. N.; ...
2015-09-15
Here, this report presents a design methodology for refractory high-entropy alloys with a body-centered cubic (bcc) structure using select empirical parameters (i.e., enthalpy of mixing, atomic size difference, Ω-parameter, and electronegativity difference) and CALPHAD approach. Sixteen alloys in equimolar compositions ranging from quinary to ennead systems were designed with experimental verification studies performed on two alloys using x-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. Two bcc phases were identified in the as-cast HfMoNbTaTiVZr, whereas multiple phases formed in the as-cast HfMoNbTaTiVWZr. Observed elemental segregation in the alloys qualitatively agrees with CALPHAD prediction. Comparisons of the thermodynamic mixing properties formore » liquid and bcc phases using the Miedema model and CALPHAD are presented. This study demonstrates that CALPHAD is more effective in predicting HEA formation than empirical parameters, and new single bcc HEAs are suggested: HfMoNbTiZr, HfMoTaTiZr, NbTaTiVZr, HfMoNbTaTiZr, HfMoTaTiVZr, and MoNbTaTiVZr.« less
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Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys
Yang, Ying; Tan, Lizhen; Busby, Jeremy T.
2015-06-12
Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed intomore » the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.« less
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Iron rich low cost superalloys. Ph.D. Thesis. Final Report
NASA Technical Reports Server (NTRS)
Wayne, S. F.
1985-01-01
An iron-rich low-cost superalloy was developed. The alloy, when processed by conventional chill casting, has physical and mechanical properties that compare favorably with existing nickel and cobalt based superalloys while containing significantly lower amounts of strategic elements. Studies were also made on the properties of Cr(20)-Mn(10)-C(3.4)-Fe(bal.), a eutectic alloy processed by chill casting and directional solidification which produced an aligned microstructure consisting of M7C3 fibers in a gamma-Fe matrix. Thermal expansion of the M7C3 (M = Fe, Cr, Mn) carbide lattice was measured up to 800 C and found to be highly anisotropic, with the a-axis being the predominant mode of expansion. Repetitive impact sliding wear experiments performed with the Fe rich eutectic alloy showed that the directionally solidified microstructure greatly improved the alloy's wear resistance as compared to the chill cast microstructure and conventional nickel base superalloys. Studies on the molybdenum cementite phase prove that the crystal structure of the xi phase is not orthorhombic. The crystal structure of the xi phase is made up of octahedra building elements consisting of four Mo and two Fe atoms and trigonal prisms consisting of four Fe and two Mo atoms. The voids are occupied by carbon atoms. The previous chemical formula for the molybdenum cementite MoFe2C is now clearly seen to be Mo12Fe22C10.
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Electrodeposition of Ni-Mo alloy coatings for water splitting reaction
NASA Astrophysics Data System (ADS)
Shetty, Akshatha R.; Hegde, Ampar Chitharanjan
2018-04-01
The present study reports the development of Ni-Mo alloy coatings for water splitting applications, using a citrate bath the inducing effect of Mo (reluctant metal) on electrodeposition, its relationship with their electrocatalytic efficiency were studied. The alkaline water splitting efficiency of Ni-Mo alloy coatings, for both hydrogen evolution reaction (HER) and oxygen evolution reaction were tested using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Moreover, the practical utility of these electrode materials were evaluated by measuring the amount of H2 and O2 gas evolved. The variation in electrocatalytic activity with composition, structure, and morphology of the coatings were examined using XRD, SEM, and EDS analyses. The experimental results showed that Ni-Mo alloy coating is the best electrode material for alkaline HER and OER reactions, at lower and higher deposition current densities (c. d.'s) respectively. This behavior is attributed by decreased Mo and increased Ni content of the alloy coating and the number of electroactive centers.
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Chemical Reduction of SIM MOX in Molten Lithium Chloride Using Lithium Metal Reductant
NASA Astrophysics Data System (ADS)
Kato, Tetsuya; Usami, Tsuyoshi; Kurata, Masaki; Inoue, Tadashi; Sims, Howard E.; Jenkins, Jan A.
2007-09-01
A simulated spent oxide fuel in a sintered pellet form, which contained the twelve elements U, Pu, Am, Np, Cm, Ce, Nd, Sm, Ba, Zr,Mo, and Pd, was reduced with Li metal in a molten LiCl bath at 923 K. More than 90% of U and Pu were reduced to metal to form a porous alloy without significant change in the Pu/U ratio. Small fractions of Pu were also combined with Pd to form stable alloys. In the gap of the porous U-Pu alloy, the aggregation of the rare-earth (RE) oxide was observed. Some amount of the RE elements and the actinoides leached from the pellet. The leaching ratio of Am to the initially loaded amount was only several percent, which was far from about 80% obtained in the previous ones on simple MOX including U, Pu, and Am. The difference suggests that a large part of Am existed in the RE oxide rather than in the U-Pu alloy. The detection of the RE elements and actinoides in the molten LiCl bath seemed to indicate that they dissolved into the molten LiCl bath containing the oxide ion, which is the by-product of the reduction, as solubility of RE elements was measured in the molten LiCl-Li2O previously.
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Surface alloying of aluminum with molybdenum by high-current pulsed electron beam
NASA Astrophysics Data System (ADS)
Xia, Han; Zhang, Conglin; Lv, Peng; Cai, Jie; Jin, Yunxue; Guan, Qingfeng
2018-02-01
The surface alloying of pre-coated molybdenum (Mo) film on aluminum (Al) substrate by high-current pulsed electron beam (HCPEB) was investigated. The microstructure and phase analysis were conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that Mo particles were dissolved into Al matrix to form alloying layer, which was composed of Mo, Al and acicular or equiaxed Al5Mo phases after surface alloying. Meanwhile, various structure defects such as dislocation loops, high-density dislocations and dislocation walls were observed in the alloying surface. The corrosion resistance was tested by using potentiodynamic polarization curves and electrochemical impedance spectra (EIS). Electrochemical results indicate that all the alloying samples had better corrosion resistance in 3.5 wt% NaCl solution compared to initial sample. The excellent corrosion resistance is mainly attributed to the combined effect of the structure defects and the addition of Mo element to form a more stable passive film.
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Tribological characterisation of Zr-based bulk metallic glass in simulated physiological media
NASA Astrophysics Data System (ADS)
Chen, Q.; Chan, K. C.; Liu, L.
2011-10-01
Due to their excellent wear resistant properties and high strength, as well as a low Young's modulus, Zr-based bulk metallic glasses (BMGs) are potentially suitable biomaterials for low-friction arthroplasty. The wear characteristics of the Zr60.14Cu22.31Fe4.85Al9.7Ag3 bulk amorphous alloy against ultra-high-molecular-weight polyethylene (UHMWPE) compared to a CoCrMo/UHMWPE combination were investigated in two different wear screening test devices, reciprocating and unidirectional. Hank's solution and sterile calf bovine serum were selected as the lubricant fluid media. It was found that different fluid media had insignificant effect on polyethylene wear against BMG counterfaces. The wear behaviour obtained on both test devices demonstrated that Zr-based BMG achieved UHMWPE counterface wear rates superior to conventional cast CoCrMo alloy, where the wear rate of UHMWPE is decreased by over 20 times. The tribological performance of these joints is superior to that of conventional metal-on-polymer designs. Contact angle measurements suggested that the advantage of BMG over a CoCrMo alloy counterface is attributed to its highly hydrophilic surfaces.
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Bahrami, M; Fathi, M H; Ahmadian, M
2015-03-01
The goal of the present research was to fabricate, characterize, and evaluate mechanical and biological properties of Co-base alloy composites with different amounts of hydroxyapatite (HA) nanopowder reinforcement. The powder of Co-Cr-Mo alloy was mixed with different amounts of HA by ball milling and it was then cold pressed and sintered. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used. Microhardness measurement and compressive tests were also carried out. Bioactivity behavior was evaluated in simulated body fluid (SBF). A significant decrease in modulus elasticity and an increase in microhardness of the sintered composites were observed. Apatite formation on the surface of the composites showed that it could successfully convert bioinert Co-Cr-Mo alloy to bioactive type by adding 10, 15, and 20wt.% HA which have lower modulus elasticity and higher microhardness. Copyright © 2014 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Kolotova, L. N.; Starikov, S. V.
2017-11-01
In irradiation of swift heavy ions, the defects formation frequently takes place in crystals. High energy transfer into the electronic subsystem and relaxations processes lead to the formation of structural defects and cause specific effects, such as the track formation. There is a large interest to understanding of the mechanisms of defects/tracks formation due to the heating of the electron subsystem. In this work, the atomistic simulation of defects formation and structure transitions in U-Mo alloys in irradiation of swift heavy ions has been carried out. We use the two-temperature atomistic model with explicit account of electron pressure and electron thermal conductivity. This two-temperature model describes ionic subsystem by means of molecular dynamics while the electron subsystem is considered in the continuum approach. The various mechanisms of structure changes in irradiation are examined. In particular, the simulation results indicate that the defects formation may be produced without melting and subsequent crystallization. Threshold stopping power of swift ions for the defects formation in irradiation in the various conditions are calculated.
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Isothermal and cyclic oxidation resistance of pack siliconized Mo-Si-B alloy
NASA Astrophysics Data System (ADS)
Majumdar, Sanjib
2017-08-01
Oxidation behaviour of MoSi2 coated Mo-9Si-8B-0.75Y (at.%) alloy has been investigated at three critical temperatures including 750, 900 and 1400 °C in static air. Thermogravimetric analysis (TGA) data indicates a remarkable improvement in the oxidation resistance of the silicide coated alloy in both isothermal and cyclic oxidation tests. The cross-sectional scanning electron microscopy and energy dispersive spectroscopic analysis reveal the occurrence of internal oxidation particularly at the crack fronts formed in the outer MoSi2 layer during thermal cycling. The dominant oxidation mechanisms at 750-900 °C and 1400 °C are identified. Development of MoB inner layer further improves the oxidation resistance of the silicide coated alloy.
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The effect of alloying on gamma and gamma prime in nickel-base superalloys
NASA Technical Reports Server (NTRS)
Dreshfield, R. L.; Wallace, J. F.
1972-01-01
An investigation was conducted to determine the compositional limits of gamma and gamma prime phases in nickel-base superalloys. Fifty-one nickel-base alloys were melted under vacuum and heat treated for 4 hours at 1190 C followed by 1008 hours at 850 C. The alloys had the following composition ranges: A1 4.0 to 13 atomic percent, Cr 6.5 to 20.5 percent, Ti 0.25 to 4.75 percent, Mo 0.0 to 6.0 percent, and W 0.0 to 4.0 percent. The residues from the ammonium sulfate electrolytic extraction for the two-phase alloys were analyzed chemically and by X-ray diffraction. The results of the investigation were used to assemble a mathematical model of the gamma-gamma prime region of the Ni-Al-Cr-Ti-Mo-W system. A computer program was written to analyze the model of the phase diagram. Some of these results are also presented graphically. The resulting model is capable of satisfactorily predicting the compositions of conjugate gamma-gamma prime phases in the alloys investigated and twelve of fifteen commercial superalloys studied.
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Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system
DOE Office of Scientific and Technical Information (OSTI.GOV)
Teng, Zhenke; Zhang, F; Miller, Michael K
2012-01-01
NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model inmore » the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.« less
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Processing of U-2.5Zr-7.5Nb and U-3Zr-9Nb alloys by sintering process
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dos Santos, A. M. M.; Ferraz, W. B.; Lameiras, F. S.
2012-07-01
To minimize the risk of nuclear proliferation, there is worldwide interest in reducing fuel enrichment of research and test reactors. To achieve this objective while still guaranteeing criticality and cycle length requirements, there is need of developing high density uranium metallic fuels. Alloying elements such as Zr, Nb and Mo are added to uranium to improve fuel performance in reactors. In this context, the Centro de Desenvolvimento da Tecnologia Nuclear (CDTN) is developing the U-2.5Zr-7.5Nb and U-3Zr-9Nb (weight %) alloys by the innovative process of sintering that utilizes raw materials in the form of powders. The powders were pressed atmore » 400 MPa and then sintered under a vacuum of about 1x10{sup -4} Torr at temperatures ranging from 1050 deg. to 1500 deg.C. The densities of the alloys were measured geometrically and by hydrostatic method and the phases identified by X ray diffraction (XRD). The microstructures of the pellets were observed by scanning electron microscopy (SEM) and the alloying elements were analyzed by energy dispersive X-ray spectroscopy (EDS). The results obtained showed the fuel density to slightly increase with the sintering temperature. The highest density achieved was approximately 80% of theoretical density. It was observed in the pellets a superficial oxide layer formed during the sintering process. (authors)« less
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Atomistic modeling and simulation of the role of Be and Bi in Al diffusion in U-Mo fuel
NASA Astrophysics Data System (ADS)
Hofman, G. L.; Bozzolo, G.; Mosca, H. O.; Yacout, A. M.
2011-07-01
Within the RERTR program, previous experimental and modeling studies identified Si as the alloying addition to the Al cladding responsible for inhibiting Al interdiffusion in the UMo fuel. However, difficulties with reprocessing have rendered this choice inappropriate, leading to the need to study alternative elements. In this work, we discuss the results of an atomistic modeling effort which allows for the systematic study of several possible alloying additions. Based on the behavior observed in the phase diagrams, beryllium or bismuth additions suggest themselves as possible options to replace Si. The results of temperature-dependent simulations using the Bozzolo-Ferrante-Smith (BFS) method for the energetics for varying concentrations of either element are shown, indicating that Be could have a substantial effect in stopping Al interdiffusion, while Bi does not. Details of the calculations and the dependence of the role of each alloying addition as a function of temperature and concentration (of beryllium or bismuth in Al) are shown.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, Ying
This work aims at developing computational tools for modeling thermal and radiation effects on solute segregation at grain boundaries (GBs) and precipitation. This report described two major efforts. One is the development of computational tools on integrated modeling of thermal equilibrium segregation (TES) and radiation-induced segregation (RIS), from which synergistic effects of thermal and radiation, pre-existing GB segregation have been taken into consideration. This integrated modeling was used in describing the Cr and Ni segregation in the Fe-Cr-Ni alloys. The other effort is thermodynamic modeling on the Fe-Cr-Ni-Mo system which includes the major alloying elements in the investigated alloys inmore » the Advanced Radiation Resistant Materials (ARRM) program. Through thermodynamic calculation, we provide baseline thermodynamic stability of the hardening phase Ni2(Cr,Mo) in selected Ni-based super alloys, and contribute knowledge on mechanistic understanding on the formation of Ni2(Cr,Mo) in the irradiated materials. The major outcomes from this work are listed in the following: 1) Under the simultaneous thermal and irradiation conditions, radiation-induced segregation played a dominant role in the GB segregation. The pre-existing GB segregation only affects the subsequent radiation-induced segregation in the short time. For the same element, the segregation tendency of Cr and Ni due to TES is opposite to it from RIS. The opposite tendency can lead to the formation of W-shape profile. These findings are consistent with literature observation of the transitory W-shape profile. 2) While TES only affects the distance of one or two atomic layers from GBs, the RIS can affect a broader distance from GB. Therefore, the W-shape due to pre-existing GB segregation is much narrower than that due to composition gradient formed during the transient state. Considering the measurement resolution of Auger or STEM analysis, the segregation tendency due to RIS should play a dominant role in the measured values. However, The GB segregation due to pre-existing GB segregation may affect the chemical potential of element at GB, and subsequently the corrosion resistance. 3) Based on the newly developed thermodynamic database of Fe-Cr-Ni-Mo, we predicted the Ni2(Cr,Mo) as a thermodynamically stable phase in all investigated low Fe-content Ni-based alloys. The calculated phase amount decreases with the increasing Fe content, being consistent with that observed in the irradiated materials. 4) The formation of the Ni2(Cr,Mo) phase in irradiated materials is due to irradiation enhanced diffusion. The calculated equilibrium Ni2(Cr,Mo) amount is more than that observed in the irradiated materials, suggesting that the amount of Ni2(Cr,Mo) is likely to increase more with further irradiation.« less
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NASA Technical Reports Server (NTRS)
Deadmore, D. L.
1984-01-01
The effects of Cr, Al, Ti, Mo, Ta, Nb, and W content on the hot corrosion of nickel base alloys were investigated. The alloys were tested in a Mach 0.3 flame with 0.5 ppmw sodium at a temperature of 900 C. One nondestructive and three destructive tests were conducted. The best corrosion resistance was achieved when the Cr content was 12 wt %. However, some lower-Cr-content alloys ( 10 wt%) exhibited reasonable resistance provided that the Al content alloys ( 10 wt %) exhibited reasonable resistance provided that the Al content was 2.5 wt % and the Ti content was Aa wt %. The effect of W, Ta, Mo, and Nb contents on the hot-corrosion resistance varied depending on the Al and Ti contents. Several commercial alloy compositions were also tested and the corrosion attack was measured. Predicted attack was calculated for these alloys from derived regression equations and was in reasonable agreement with that experimentally measured. The regression equations were derived from measurements made on alloys in a one-quarter replicate of a 2(7) statistical design alloy composition experiment. These regression equations represent a simple linear model and are only a very preliminary analysis of the data needed to provide insights into the experimental method.
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Influence of molybdenum on the creep properties of nickel-base superalloy single crystals
NASA Technical Reports Server (NTRS)
Mackay, R. A.; Nathal, M. V.; Pearson, D. D.
1990-01-01
The Mo content of an alloy series based on Ni-6 wt pct Al-6 wt pct Ta was systematically varied from 9.8 to 14.6 wt pct, in order to ascertain the influence of Mo on the creep properties of single crystals. The optimum initial gamma-gamma prime microstructure for raft development and creep strength was established in each alloy before testing. It was found that, as the Mo content increased from 9.8 to 14.0 percent, the magnitude of the lattice mismatch increased; upon reaching 14.6 percent, a degradation of mechanical properties occurred due to the precipitation of a third phase. These results suggest that small refractory metal content and initial gamma-prime variations can profoundly affect mechanical properties.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hill, Mary Ann; Dombrowski, David E.; Clarke, Kester Diederik
U-10 wt. % Mo (U-10Mo) alloys are being developed as low enrichment monolithic fuel for the CONVERT program. Optimization of processing for the monolithic fuel is being pursued with the use of electrical discharge machining (EDM) under CONVERT HPRR WBS 1.2.4.5 Optimization of Coupon Preparation. The process is applicable to manufacturing experimental fuel plate specimens for the Mini-Plate-1 (MP-1) irradiation campaign. The benefits of EDM are reduced machining costs, ability to achieve higher tolerances, stress-free, burr-free surfaces eliminating the need for milling, and the ability to machine complex shapes. Kerf losses are much smaller with EDM (tenths of mm) comparedmore » to conventional machining (mm). Reliable repeatability is achievable with EDM due to its computer-generated machining programs.« less
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Fracture & Fatigue Characteristics in Titanium Alloys.
1982-06-01
7 AD-All7 155 ROCKWELL INTERNATIONAL THOUSAND OAKS CA SCIENCE CENTER FIG 1i/ 6 FRACTURE & FATI6UE CHARACTERISTICS IN TITANIUM ALLOYS.(U) JUN 82 C 6 ...RECIPIENT’S CATALOG NUMBER 2!, !/,/ S 4 . TITLE (mod Subi.le) S. TYPE OF REPORT & PERIOD COVERED Fracture and Fatigue Characteristics in Final Report Titanium ...tempera- ture fracture toughness of Ti-6A)--4V ( 6 - 4 ) and Ti-4.5A,9-5Mo-l.5Cr (CORONA-5) has been studied as a function of elemental partition- ing and
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2009-09-01
Alloy Ti-6Al-4V; ARL-MR- 486; U.S. Army Research Laboratory: Aberdeen Proving Ground, MD, July 2000. Donachie, M. J., Jr. Titanium: A Technical...Tests of Armor Materials. TOP-2-2-710 (AD A137873), Aberdeen Proving Ground, MD, 8 July 1993. Veeck, S.; Lee, D.; Boyer, R.; Briggs, R. The...195 BEAR HILL RD WALTHAM MA 02451 1 RMI TITANIUM CO W PALLANTE PO BOX 269 1000 WARREN AVE NILES OH 44446 2 SOUTHWEST RSRCH INST
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Phase Transformations and Microstructural Evolution of Mo-Bearing Stainless Steels
NASA Astrophysics Data System (ADS)
Anderson, T. D.; Dupont, J. N.; Perricone, M. J.; Marder, A. R.
2007-01-01
The good corrosion resistance of superaustenitic stainless steel (SASS) alloys has been shown to be a direct consequence of high concentrations of Mo, which can have a significant effect on the microstructural development of welds in these alloys. In this research, the microstructural development of welds in the Fe-Ni-Cr-Mo system was analyzed over a wide variety of Cr/Ni ratios and Mo contents. The system was first simulated by construction of multicomponent phase diagrams using the CALPHAD technique. Data from vertical sections of these diagrams are presented over a wide compositional range to produce diagrams that can be used as a guide to understand the influence of composition on microstructural development. A large number of experimental alloys were then prepared via arc-button melting for comparison with the diagrams. Each alloy was characterized using various microscopy techniques. The expected δ-ferrite and γ-austenite phases were accompanied by martensite at low Cr/Ni ratios and by σ phase at high Mo contents. A total of 20 possible phase transformation sequences are proposed, resulting in various amounts and morphologies of the γ, δ, σ, and martensite phases. The results were used to construct a map of expected phase transformation sequence and resultant microstructure as a function of composition. The results of this work provide a working guideline for future base metal and filler metal development of this class of materials.
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The Electrochemical Behavior of Mo-Ta Alloy in Phosphoric Acid Solution for TFT-LCD Application.
Lee, Sang-Hyuk; Kim, Byoung O; Seo, Jong Hyun
2015-10-01
Molybdenum-tantalum alloy thin film is a suitable material for the higher corrosion resistance and low resistivity for gate and data metal lines. In this study, Mo-Ta alloy thin films were prepared by using a DC magnetron co-sputtering system on a glass substrate. An abrupt increase in the etching rates of low Mo-Ta alloys was observed. From the observed impedance analysis, the defect densities in the MoTa oxide films increased from 5.4 x 10(21) (cm(-3)) to 8.02 x 10(21) (cm(-3)) up to the 6 at% of tantalum level; and above the 6 at% of tantalum level, the defect densities decreased. This electrochemical behavior is explained by the mechanical instability of the MoTa oxide film.
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TEM characterization of irradiated U-7Mo/Mg dispersion fuel
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gan, J.; Keiser, D. D.; Miller, B. D.
This paper presents the results of transmission electron microscopy (TEM) characterization on neutron-irradiated samples taken from the low-flux and high-flux sides of the same fuel plate with U-7Mo fuel particles dispersed in Mg matrix with aluminum alloy Al6061 as cladding material that was irradiated edge-on to the core in the Advanced Test Reactor. The corresponding local fission density and fission rate of the fuel particles and the average fuel-plate centerline temperature for the low-flux and high-flux samples are estimated to be 3.7 × 10 21 f/cm 3, 7.4 × 10 14 f/cm 3/s and 123 °C, and 5.5 × 10more » 21 f/cm3, 11.0 × 10 14 f/cm 3/s and 158 °C, respectively. Complex interaction layers developed at the Al-Mg interface, consisting of Al 3Mg 2 and Al 12Mg 17 along with precipitates of MgO, Mg 2Si and FeAl 5.3. No interaction between Mg matrix and U-Mo fuel particle was identified. For the U-Mo fuel particles, at low fission density, small elongated bubbles wrapped around the clean areas with a fission gas bubble superlattice, which suggests that bubble coalescence is an important mechanism for converting the fission gas bubble superlattice to large bubbles. At high fission density, no bubbles or porosity were observed in the Mg matrix, and pockets of residual fission gas bubble superlattice were observed in the U-Mo fuel particle interior.« less
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TEM characterization of irradiated U-7Mo/Mg dispersion fuel
Gan, J.; Keiser, D. D.; Miller, B. D.; ...
2017-07-15
This paper presents the results of transmission electron microscopy (TEM) characterization on neutron-irradiated samples taken from the low-flux and high-flux sides of the same fuel plate with U-7Mo fuel particles dispersed in Mg matrix with aluminum alloy Al6061 as cladding material that was irradiated edge-on to the core in the Advanced Test Reactor. The corresponding local fission density and fission rate of the fuel particles and the average fuel-plate centerline temperature for the low-flux and high-flux samples are estimated to be 3.7 × 10 21 f/cm 3, 7.4 × 10 14 f/cm 3/s and 123 °C, and 5.5 × 10more » 21 f/cm3, 11.0 × 10 14 f/cm 3/s and 158 °C, respectively. Complex interaction layers developed at the Al-Mg interface, consisting of Al 3Mg 2 and Al 12Mg 17 along with precipitates of MgO, Mg 2Si and FeAl 5.3. No interaction between Mg matrix and U-Mo fuel particle was identified. For the U-Mo fuel particles, at low fission density, small elongated bubbles wrapped around the clean areas with a fission gas bubble superlattice, which suggests that bubble coalescence is an important mechanism for converting the fission gas bubble superlattice to large bubbles. At high fission density, no bubbles or porosity were observed in the Mg matrix, and pockets of residual fission gas bubble superlattice were observed in the U-Mo fuel particle interior.« less
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Two phase titanium aluminide alloy
Deevi, Seetharama C.; Liu, C. T.
2001-01-01
A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.
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Microstructural control of FeCrAl alloys using Mo and Nb additions
Sun, Zhiqian; Bei, Hongbin; Yamamoto, Yukinori
2017-08-14
The effects of Mo and Nb additions on the microstructure and mechanical properties of two FeCrAl alloys were studied in this paper. Fine and uniform recrystallized grain structures (~ 20–30 μm) were achieved in both alloys through suitable annealing after warm-rolling. The formation of Fe 2Nb-type Laves phase precipitates in the Nb-containing FeCrAl alloy effectively stabilized the deformed and recrystallized microstructures. The Mo-containing FeCrAl alloy exhibited strong γ texture fiber after annealing at 650–900 °C, whereas the annealed Nb-containing FeCrAl alloy had much weaker texture. Finally, both strength and ductility decreased as the grain size increased in both alloys.
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DEVELOPMENT OF FERRITIC STEELS FOR HIGH TEMPERATURE SODIUM SERVICE. PART II
DOE Office of Scientific and Technical Information (OSTI.GOV)
Anderson, W.J.; Sheffield, G.S.; Birkle, A.J.
1963-11-30
The suitability of modified 2.25 Cr--1 Mo alloy steels for sodium service was investigated. Eleven modifications were examined to establish heat treatment behavior, mechanical properties, resistance to decarburization in liquid sodium, and weldability. Two of the alloys, 4S8 (2.25 Cr--1 Mo--0.6 V-- 0.1 Cb) and 4S4 (2.25 Cr--1 Mo-0.8 V), were found to have the best combination of properties. When heat treated by normalizing and tempering, their mechanical properties to 1200 deg F were found to be comparable to those of Type 304 stainless steel. A low chromium, nickel-base alloy was developed for welding the steels, to give either fullymore » heat treatable joints or to apply the butter-weld technique useful in field welding. It provides high joint efficiency without sacrifice in joint ductility. (auth)« less
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Molybdenum-rhenium alloy based high-Q superconducting microwave resonators
DOE Office of Scientific and Technical Information (OSTI.GOV)
Singh, Vibhor, E-mail: v.singh@tudelft.nl; Schneider, Ben H.; Bosman, Sal J.
2014-12-01
Superconducting microwave resonators (SMRs) with high quality factors have become an important technology in a wide range of applications. Molybdenum-Rhenium (MoRe) is a disordered superconducting alloy with a noble surface chemistry and a relatively high transition temperature. These properties make it attractive for SMR applications, but characterization of MoRe SMR has not yet been reported. Here, we present the fabrication and characterization of SMR fabricated with a MoRe 60–40 alloy. At low drive powers, we observe internal quality-factors as high as 700 000. Temperature and power dependence of the internal quality-factors suggest the presence of the two level systems from themore » dielectric substrate dominating the internal loss at low temperatures. We further test the compatibility of these resonators with high temperature processes, such as for carbon nanotube chemical vapor deposition growth, and their performance in the magnetic field, an important characterization for hybrid systems.« less
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Xu, Jiaqi; Li, Xiaodong; Liu, Wei; Sun, Yongfu; Ju, Zhengyu; Yao, Tao; Wang, Chengming; Ju, Huanxin; Zhu, Junfa; Wei, Shiqiang; Xie, Yi
2017-07-24
Structural parameters of ternary transition-metal dichalcogenide (TMD) alloy usually obey Vegard law well, while interestingly it often exhibits boosted electrocatalytic performances relative to its two pristine binary TMDs. To unveil the underlying reasons, we propose an ideal model of ternary TMDs alloy monolayer. As a prototype, MoSeS alloy monolayers are successfully synthesized, in which X-ray absorption fine structure spectroscopy manifests their shortened Mo-S and lengthened Mo-Se bonds, helping to tailor the d-band electronic structure of Mo atoms. Density functional theory calculations illustrate an increased density of states near their conduction band edge, which ensures faster electron transfer confirmed by their lower work function and smaller charge-transfer resistance. Energy calculations show the off-center charge around Mo atoms not only benefits for stabilizing COOH* intermediate confirmed by its most negative formation energy, but also facilitates the rate-limiting CO desorption step verified by CO temperature programmed desorption and electro-stripping tests. As a result, MoSeS alloy monolayers attain the highest 45.2 % Faradaic efficiency for CO production, much larger than that of MoS 2 monolayers (16.6 %) and MoSe 2 monolayers (30.5 %) at -1.15 V vs. RHE. This work discloses how the partially delocalized charge in ternary TMDs alloys accelerates electrocatalytic performances at atomic level, opening new horizons for manipulating CO 2 electroreduction properties. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yun, Di, E-mail: diyun1979@xjtu.edu.cn; Xi'an Jiao Tong University, 28 Xian Ning West Road, Xi'an 710049; Mo, Kun
2015-12-15
U–Mo metallic alloys have been extensively used for the Reduced Enrichment for Research and Test Reactors (RERTR) program, which is now known as the Office of Material Management and Minimization under the Conversion Program. This fuel form has also recently been proposed as fast reactor metallic fuels in the recent DOE Ultra-high Burnup Fast Reactor project. In order to better understand the behavior of U–10Mo fuels within the fast reactor temperature regime, a series of annealing and characterization experiments have been performed. Annealing experiments were performed in situ at the Intermediate Voltage Electron Microscope (IVEM-Tandem) facility at Argonne National Laboratorymore » (ANL). An electro-polished U–10Mo alloy fuel specimen was annealed in situ up to 700 °C. At an elevated temperature of about 540 °C, the U–10Mo specimen underwent a relatively slow microstructure transition. Nano-sized grains were observed to emerge near the surface. At the end temperature of 700 °C, the near-surface microstructure had evolved to a nano-crystalline state. In order to clarify the nature of the observed microstructure, Laue diffraction and powder diffraction experiments were carried out at beam line 34-ID of the Advanced Photon Source (APS) at ANL. Phases present in the as-annealed specimen were identified with both Laue diffraction and powder diffraction techniques. The U–10Mo was found to recrystallize due to thermally-induced recrystallization driven by a high density of pre-existing dislocations. A separate in situ annealing experiment was carried out with a Focused Ion Beam processed (FIB) specimen. A similar microstructure transition occurred at a lower temperature of about 460 °C with a much faster transition rate compared to the electro-polished specimen. - Highlights: • TEM annealing experiments were performed in situ at the IVEM facility up to fast reactor temperature. • At 540 °C, the U-10Mo specimen underwent a slow microstructure transition where nano-sized grains were observed to emerge. • UO{sub 2} phase exists at the thin area of the as-annealed specimen whereas U-10Mo γ phase dominated at the thicker part. • Bcc γ U-10Mo recrystallized to become nano-meter sized crystallites near the specimen surface. • A separateannealing experiment was conducted with a FIB processed specimen where similar transition occurred at a lower temperature of 460 °C with a faster rate.« less
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First-principles studies of Te line-ordered alloys in a MoS2 monolayer
NASA Astrophysics Data System (ADS)
Andriambelaza, N. F.; Mapasha, R. E.; Chetty, N.
2018-04-01
The thermodynamic stability, structural and electronic properties of Te line-ordered alloys are investigated using density functional theory (DFT) methods. Thirty four possible Te line-ordered alloy configurations are found in a 5×5 supercell of a MoS2 monolayer. The calculated formation energies show that the Te line-ordered alloy configurations are thermodynamically stable at 0 K and agree very well with the random alloys. The lowest energy configurations at each concentration correspond to the configuration where the Te atom rows are far apart from each other (avoiding clustering) within the supercell. The variation of the lattice constant at different concentrations obey Vegard's law. The Te line-ordered alloys fine tune the band gap of a MoS2 monolayer although deviating from linearity behavior. Our results suggest that the Te line-ordered alloys can be an effective way to modulate the band gap of a MoS2 monolayer for nanoelectronic, optoelectronic and nanophotonic applications.
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Microstructure and Tribological Properties of Mo-40Ni-13Si Multiphase Intermetallic Alloy.
Song, Chunyan; Wang, Shuhuan; Gui, Yongliang; Cheng, Zihao; Ni, Guolong
2016-12-06
Intermetallic compounds are increasingly being expected to be utilized in tribological environments, but to date their implementation is hindered by insufficient ductility at low and medium temperatures. This paper presents a novel multiphase intermetallic alloy with the chemical composition of Mo-40Ni-13Si (at %). Microstructure characterization reveals that a certain amount of ductile Mo phases formed during the solidification process of a ternary Mo-Ni-Si molten alloy, which is beneficial to the improvement of ductility of intermetallic alloys. Tribological properties of the designed alloy-including wear resistance, friction coefficient, and metallic tribological compatibility-were evaluated under dry sliding wear test conditions at room temperature. Results suggest that the multiphase alloy possesses an excellent tribological property, which is attributed to unique microstructural features and thereby a good combination in hardness and ductility. The corresponding wear mechanism is explained by observing the worn surface, subsurface, and wear debris of the alloy, which was found to be soft abrasive wear.
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NASA Astrophysics Data System (ADS)
Drozdov, A. A.; Povarova, K. B.; Morozov, A. E.; Antonova, A. V.; Bulakhtina, M. A.; Alad'ev, N. A.
2015-07-01
The character of dendrite segregation in Ni3Al-based intermetallic VKNA-type alloy single crystals with a dendritic-cellular structure is studied. Distribution coefficient k d of an alloying element (AE) in the alloy during solidification k d = c d.a.I/ c 0 ( c 0 is the AE content in the alloy (liquid phase composition), c d.a.I is the AE content in primary dendrite arms of the alloy (in the solid phase)) and segregation coefficient k s = c d.a.I/ c i.d ( c i.d is the AE content in the interdendritic space) have been found. A comparative study of the dendrite segregation parameters in VKNA-nype Ni3Al-based intermetallic alloys and the well-known ZhS36-type nickel superalloy shows that the intermetallic alloys satisfy to the rule deduced for two- and three-component nickel-based superalloys: if an introduced AE increases the melting temperature of the basic metal, we have k d > 1 (Co, W, Re); if it decreases the melting temperature, we have k d < 1 (Al, Ti, Cr, Mo). Dendrite segregation coefficients k s are dependent on the proportion of the AE contents in the alloys. In nickel superalloys, the dendrite segregation of aluminum, tungsten, and rhenium is higher than that in the intermetallic alloys. The dendrite segregation coefficients of tungsten and rhenium is higher by a factor of 1.5-2 than that in the VKNA-type intermetallic alloys with a low content of refractory metals. This can be due to the retardation of diffusion of refractory metals in the solid phase of a nickel superalloy highly alloyed with these elements.
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Development of oxide dispersion strengthened turbine blade alloy by mechanical alloying
NASA Technical Reports Server (NTRS)
Merrick, H. F.; Curwick, L. R. R.; Kim, Y. G.
1977-01-01
There were three nickel-base alloys containing up to 18 wt. % of refractory metal examined initially for oxide dispersion strengthening. To provide greater processing freedom, however, a leaner alloy was finally selected. This base alloy, alloy D, contained 0.05C/15Cr / 2Mo/4W/2Ta/4.5Al/2.Ti/015Zr/0.01-B/Bal. Ni. Following alloy selection, the effect of extrusion, heat treatment, and oxide volume fraction and size on microstructure and properties were examined. The optimum structure was achieved in zone annealed alloy D which contained 2.5 vol. % of 35 mm Y2O3 and which was extruded 16:1 at 1038 C.
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Elastoplastic properties of a low-modulus titanium-based β alloy
NASA Astrophysics Data System (ADS)
Betekhtin, V. I.; Kolobov, Yu. R.; Golosova, O. A.; Kardashev, B. K.; Kadomtsev, A. G.; Narykova, M. V.; Ivanov, M. B.; Vershinina, T. N.
2013-10-01
The elastoplastic properties (elastic modulus, amplitude-independent damping ratio, microplastic flow stress) of a Ti-26Nb-7Mo-12Zr titanium β alloy are determined using an acoustic resonance method. The effect of the strain during thermomechanical treatment on the structural features of the micro-crystalline alloy and, hence, its elastoplastic properties is analyzed.
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NASA Astrophysics Data System (ADS)
Chen, Y. W.; Li, Y. K.; Cheng, X. W.; Wu, C.; Cheng, B.
2018-05-01
Refractory high entropy alloys (RHEAs), with excellent properties at high temperature, have several applications. In this work, the ZrTiHfNbMox (x=0.5, 1.0, 1.5) alloys were prepared by arc melting. All these alloys form body centered cubic (BCC) structure without other intermediate phases. The Mo element contributes to the strength of alloys at high temperature, but too much of Mo decreases the plasticity severely and enhances the strength. The ZrTiHfNbMo alloy, whose compressive stress is 1099 MPa at 800° C, is a promising material for high-temperature applications.
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Improved Mo-Re VPS Alloys for High-Temperature Uses
NASA Technical Reports Server (NTRS)
Hickman, Robert; Martin, James; McKechnie, Timothy; O'Dell, John Scott
2011-01-01
Dispersion-strengthened molybdenum- rhenium alloys for vacuum plasma spraying (VPS) fabrication of high-temperature-resistant components are undergoing development. In comparison with otherwise equivalent non-dispersion-strengthened Mo-Re alloys, these alloys have improved high-temperature properties. Examples of VPS-fabricated high-temperature-resistant components for which these alloys are expected to be suitable include parts of aircraft and spacecraft engines, furnaces, and nuclear power plants; wear coatings; sputtering targets; x-ray targets; heat pipes in which liquid metals are used as working fluids; and heat exchangers in general. These alloys could also be useful as coating materials in some biomedical applications. The alloys consist of 60 weight percent Mo with 40 weight percent Re made from (1) blends of elemental Mo and Re powders or (2) Re-coated Mo particles that have been subjected to a proprietary powder-alloying-and-spheroidization process. For most of the dispersion- strengthening experiments performed thus far in this development effort, 0.4 volume percent of transition-metal ceramic dispersoids were mixed into the feedstock powders. For one experiment, the proportion of dispersoid was 1 volume percent. In each case, the dispersoid consisted of either ZrN particles having sizes <45 m, ZrO2 particles having sizes of about 1 m, HfO2 particles having sizes <45 m, or HfN particles having sizes <1 m. These materials were chosen for evaluation on the basis of previously published thermodynamic stability data. For comparison, Mo-Re feedstock powders without dispersoids were also prepared.
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Ion, Raluca; Drob, Silviu Iulian; Ijaz, Muhammad Farzik; Vasilescu, Cora; Osiceanu, Petre; Gordin, Doina-Margareta; Cimpean, Anisoara; Gloriant, Thierry
2016-01-01
A new superelastic Ti-23Hf-3Mo-4Sn biomedical alloy displaying a particularly large recovery strain was synthesized and characterized in this study. Its native passive film is very thick (18 nm) and contains very protective TiO2, Ti2O3, HfO2, MoO2, and SnO2 oxides (XPS analysis). This alloy revealed nobler electrochemical behavior, more favorable values of the corrosion parameters and open circuit potentials in simulated body fluid in comparison with commercially pure titanium (CP-Ti) and Ti-6Al-4V alloy taken as reference biomaterials in this study. This is due to the favorable influence of the alloying elements Hf, Sn, Mo, which enhance the protective properties of the native passive film on alloy surface. Impedance spectra showed a passive film with two layers, an inner, capacitive, barrier, dense layer and an outer, less insulating, porous layer that confer both high corrosion resistance and bioactivity to the alloy. In vitro tests were carried out in order to evaluate the response of Human Umbilical Vein Endothelial Cells (HUVECs) to Ti-23Hf-3Mo-4Sn alloy in terms of cell viability, cell proliferation, phenotypic marker expression and nitric oxide release. The results indicate a similar level of cytocompatibility with HUVEC cells cultured on Ti-23Hf-3Mo-4Sn substrate and those cultured on the conventional CP-Ti and Ti-6Al-4V metallic materials. PMID:28773939
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Effect of mo Content on Microstructure and Properties of Laser Cladding Fe-BASED Alloy Coatings
NASA Astrophysics Data System (ADS)
Xiaoli, Ma; Kaiming, Wang; Hanguang, Fu; Jiang, Ju; Yongping, Lei; Dawei, Yi
Mo alloying Fe-based coating was fabricated on the surface of Q235 steel by using 6 kW fiber laser. The effects of Mo additions on the microstructure, microhardness and wear resistance of the cladding layer were studied by means of optical microscopy (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), Vickers hardness tester and M-200 ring block wear tester. Research results showed that the microstructure of Mo-free cladding layer mainly consisted of matrix and eutectic structure. The matrix was martensite and retained austenite. The eutectic structure mainly consisted of M2(B,C) and M7(C,B)3 type of eutectic borocarbides. With the increase of Mo content, there was no significant change in the matrix. However, the eutectic structure was transformed from M2(B,C)- and M7(C,B)3-type borocarbides into M2(B,C)-, M7(C,B)3- and M23(C,B)6-type borocarbides. When the content of Mo is 4.0wt.%, the Mo2C-type carbide appear on the matrix, and parts of the borocarbide networks are broken. The change of microhardness of the cladding layer was not obvious with the increase of Mo content. But the increase of Mo content increases the wear resistance of the cladding layer. The wear resistance of cladding layer with 4.0wt.% Mo is 2.4 times as much as the cladding layer which is Mo-free.
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Microstructural characterization of as-cast biocompatible Co-Cr-Mo alloys
DOE Office of Scientific and Technical Information (OSTI.GOV)
Giacchi, J.V., E-mail: jgiacchi@exa.unicen.edu.ar; Instituto de Fisica de Materiales Tandil; Morando, C.N.
2011-01-15
The microstructure of a cobalt-base alloy (Co-Cr-Mo) obtained by the investment casting process was studied. This alloy complies with the ASTM F75 standard and is widely used in the manufacturing of orthopedic implants because of its high strength, good corrosion resistance and excellent biocompatibility properties. This work focuses on the resulting microstructures arising from samples poured under industrial environment conditions, of three different Co-Cr-Mo alloys. For this purpose, we used: 1) an alloy built up from commercial purity constituents, 2) a remelted alloy and 3) a certified alloy for comparison. The characterization of the samples was achieved by using opticalmore » microscopy (OM) with a colorant etchant to identify the present phases and scanning electron microscopy (SE-SEM) and energy dispersion spectrometry (EDS) techniques for a better identification. In general the as-cast microstructure is a Co-fcc dendritic matrix with the presence of a secondary phase, such as the M{sub 23}C{sub 6} carbides precipitated at grain boundaries and interdendritic zones. These precipitates are the main strengthening mechanism in this type of alloys. Other minority phases were also reported and their presence could be linked to the cooling rate and the manufacturing process variables and environment. - Research Highlights: {yields}The solidification microstructure of an ASTM-F75 type alloy were studied. {yields}The alloys were poured under an industrial environment. {yields}Carbides and sigma phase identified by color metallography and scanning microscopy (SEM and EDS). {yields}Two carbide morphologies were detected 'blocky type' and 'pearlite type'. {yields}Minority phases were also detected.« less
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Corrosion behaviour of Ti-15Mo alloy for dental implant applications.
Kumar, Satendra; Narayanan, T S N Sankara
2008-07-01
The corrosion behaviour of Ti-15Mo alloy in 0.15M NaCl solution containing varying concentrations of fluoride ions (190, 570, 1140 and 9500 ppm) is evaluated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and chronoamperometric/current-time transient (CTT) studies to ascertain its suitability for dental implant applications. The study reveals that there is a strong dependence of the corrosion resistance of Ti-15Mo alloy on the concentration of fluoride ions in the electrolyte medium. Increase in fluoride ion concentration from 0 to 9500 ppm shifts the corrosion potential (E(corr)) from -275 to -457 mV vs. SCE, increases the corrosion current density (i(corr)) from 0.31 to 2.30 microA/cm(2), the passive current density (i(pass)) from 0.07 to 7.32 mA/cm(2) and the double-layer capacitance (C(dl)) from 9.63 x 10(-5) to 1.79 x 10(-4)F and reduces the charge transfer resistance (R(ct)) from 6.58 x 10(4) to 6.64 x 10(3)Omega cm(2). In spite of the active dissolution, the Ti-15Mo alloy exhibit passivity at anodic potentials at all concentrations of the fluoride ions studied. In dental implants since the exposure of the alloy will be limited only to its 'neck', the amount of Mo ions released from Ti-15Mo alloy is not likely to have an adverse and hence, in terms of biocompatibility this alloy seems to be acceptable for dental implant applications. The results of the study suggest that Ti-15Mo alloy can be a suitable alternative for dental implant applications.
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Development of new ferritic steels as cladding material for metallic fuel fast breeder reactor
NASA Astrophysics Data System (ADS)
Tokiwai, Moriyasu; Horie, Masaaki; Kako, Kenji; Fujiwara, Masayuki
1993-09-01
The excellent thermal, chemical and neutronic properties of metallic fuel (U-Pu-Zr alloy) will lead to drastic improvements in fast reactor safety and the related fuel cycle economy. Some new high molybdenum 12Cr ferritic stainless steel candidate cladding alloys have been designed to achieve the mechanical properties required for high performance metallic fuel elements. These candidate claddings were irradiated by ion bombardment and tested to determine their strength and creep rupture properties. A 12Cr-8Mo and a 12Cr-8Mo-0.1Y 2O 3 steel were fabricated into cladding via a powder metallurgy process and by a mechanical alloying process, respectively. These claddings had two and three times the creep rupture strength (pressurized at 650°C for 10000 h) of a conventional 12Cr ferritic steel (HT-9). These two steels also showed no void formation up to 350 dpa by Ni 3+ irradiation. A zircaloy-2 lined steel cladding tube has also been fabricated for the purpose of reducing fuel-cladding interdiffusion and chemical interaction.
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NASA Astrophysics Data System (ADS)
Li, Hutian; Guo, Jianting; Huai, Kaiwen; Ye, Hengqiang
2006-04-01
The microstructure and room temperature compressive deformation behavior of a rapidly solidified NiAl-Cr(Mo)-Dy eutectic alloy fabricated by water-cooled copper mold method were studied by a combination of SEM, EDS and compressive tests. The morphology stability after hot isostatic pressing (HIP) treatment was evaluated. Rapid solidification resulted in a shift in the coupled zone for the eutectic growth towards the Cr(Mo) phase, indicating a hypoeutectic composition, hence increasing the volume fraction of primary dendritic NiAl. Meanwhile, significantly refined microstructure and lamellar/rod-like Cr(Mo) transition were observed due to trace rare earth (RE) element Dy addition and rapid solidification effects. Compared with the results in literature [H.E. Cline, J.L. Walter, Metall. Trans. 1(1970)2907-2917; P. Ferrandini, W.W. Batista, R. Caram, J. Alloys Comp. 381(2004)91-98], an interesting phenomenon, viz., NiAl halos around the primary Cr(Mo) dendrites in solidified NiAl-Cr(Mo) hypereutectic alloy, was not observed in this study. This difference was interpreted in terms of their different reciprocal nucleation ability. In addition, it was proposed that the localized destabilization of morphology after HIP treatment is closely related to the presence of primary NiAl dendrites. The improved mechanical properties can be attributed to the synergistic effects of rapid solidification and Dy addition, which included refined microstructure, suppression of the crack development along eutectic grain boundaries, enhancement of density of geometrically necessary dislocations located at NiAl/Cr(Mo) interfaces and the Cr solubility extension in NiAl.
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Primary arm spacing in chill block melt spun Ni-Mo alloys
NASA Technical Reports Server (NTRS)
Tewari, S. N.; Glasgow, T. K.
1986-01-01
Chill block melt spun ribbons of Ni-Mo binary alloys containing 8.0 to 41.8 wt % Mo have been prepared under carefully controlled processing conditions. The growth velocity has been determined as a function of distance from the quench surface from the observed ribbon thickness dependence on the melt puddle residence time. Primary arm spacings measured at the midribbon thickness locations show a dependence on growth velocity and alloy composition which is expected from dendritic growth models for binary alloys directionally solidified in a positive temperature gradient.
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Primary arm spacing in chill block melt spun Ni-Mo alloys
NASA Technical Reports Server (NTRS)
Tewari, S. N.; Glasgow, T. K.
1987-01-01
Chill block melt spun ribbons of Ni-Mo binary alloys containing 8.0 to 41.8 wt pct Mo have been prepared under carefully controlled processing conditions. The growth velocity has been determined as a function of distance from the quench surface from the observed ribbon thickness dependence on the melt puddle residence time. Primary arm spacing measured at the midribbon thickness locations show a dependence on growth velocity and alloy composition which is expected from dendritic growth models for binary alloys directionally solidified in a positive temperature gradient.
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Surface Characterization of New Biomaterials
NASA Astrophysics Data System (ADS)
Minciuna, M. G.; Vizureanu, P.; Abdullah, M. M. B.; Achitei, D. C.; Istrate, B.; Cimpoesu, R.; Focsaneanu, S. C.
2017-06-01
This paper presents the characterization of new alloys CoCrMoSi6, CoCrMoSi7, CoCrMoSi10, in terms of hardness determinations, fractographic analysis and surface analysis. The original version of the alloy was obtained by casting process in a vacuum arc furnace. Experimental results obtained from this study confirms that by increasing content of silicon, the mechanical properties are superior and the positive results obtained at surface studies favoring the formation of compounds, that lead to the reduction of alloying grade for α solid solution and the plasticity of the alloys.
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NASA Technical Reports Server (NTRS)
Hebsur, M. G.; Choi, S. R.; Whittenberger, J. D.; Salem, J. A.; Noebe, R. D.
2001-01-01
A new MoSi2-base composite was developed that contains in-situ reinforcement of whisker-type beta-Si3N4 grains in a MoSi2 matrix. The advantages of this in-situ reinforced MoSi2-Si3N4 are lower density, higher fracture toughness and better strength than typical MoSi2 alloys, combined with excellent environmental and pest resistance. The average fracture toughness of the in-situ reinforced material determined by one technique was 12.2 MPa.m(exp 1/2) compared to 4.9 to 5.5 MPa.m(exp 1/2) for similar materials with the exception that the beta-Si3N4 had a blocky morphology as opposed to the whisker-like morphology typical of the in-situ toughened material. This MoSi2-(beta)Si3N4 was also resistant to pesting at intermediate temperatures (400 to 600 C) even when precracked or under applied load; conditions that would quickly reduce typical MoSi2 alloys to oxidized powder.
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Mo-Si-B alloys for ultrahigh-temperature structural applications.
Lemberg, J A; Ritchie, R O
2012-07-10
A continuing quest in science is the development of materials capable of operating structurally at ever-increasing temperatures. Indeed, the development of gas-turbine engines for aircraft/aerospace, which has had a seminal impact on our ability to travel, has been controlled by the availability of materials capable of withstanding the higher-temperature hostile environments encountered in these engines. Nickel-base superalloys, particularly as single crystals, represent a crowning achievement here as they can operate in the combustors at ~1100 °C, with hot spots of ~1200 °C. As this represents ~90% of their melting temperature, if higher-temperature engines are ever to be a reality, alternative materials must be utilized. One such class of materials is Mo-Si-B alloys; they have higher density but could operate several hundred degrees hotter. Here we describe the processing and structure versus mechanical properties of Mo-Si-B alloys and further document ways to optimize their nano/microstructures to achieve an appropriate balance of properties to realistically compete with Ni-alloys for elevated-temperature structural applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Superconducting properties of molybdenum ruthenium alloy Mo0.63Ru0.37
NASA Astrophysics Data System (ADS)
Wei, Wensen; Ge, Min; Wang, Shasha; Zhang, Lei; Han, Yuyan; Du, Haifeng; Tian, Mingliang; Zhang, Yuheng
2018-03-01
Resistance, magnetization and specific heat measurements were performed on Mo0.63Ru0.37 alloy. All of them confirm that Mo0.63Ru0.37 becomes superconducting at about 7.0 K with bulk nature. Its upper critical field behavior fits to Werthamer-Helfand-Hohenberg (WHH) model quite well, with an upper critical field of μ0Hc2(0) = 8.64 T, less than its Pauli limit. Its electronic specific heat is reproduced by Bardeen-Cooper-Schriffer (BCS)-based α-model with a gap ratio Δ0 = 1.88kBTc, which is a little larger than the standard BCS value of 1.76. We concluded that Mo0.63Ru0.37 is a fully gapped isotropic s-wave superconductor, with its features are mostly consistent with the conventional theory.
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Isoelectronic tungsten doping in monolayer MoSe 2 for carrier type modulation
Li, Xufan; Lin, Ming -Wei; Basile, Leonardo; ...
2016-07-06
Doping and alloying are effective ways to engineer the band structure and modulate the optoelectronic functionality of monolayer transition metal dichalcogenides (TMDs). In this work, we explore the synthesis and electronic properties of monolayer Mo 1-xW xSe 2 (0 < x < 0.18) alloys with almost 100% alloying degree. The isoelectronic substitutional doping of tungsten for molybdenum in the monolayer MoSe 2 is shown to suppress its intrinsically n-type conduction behavior, with p-type conduction gradually emerging to become dominant with increasing W concentration in the alloys. Atomic resolution Z-contrast electron microscopy show that W is shown to substitute directly formore » Mo without the introduction of noticeable vacancy or interstitial defects, however with randomly-distributed W-rich regions ~2 nm in diameter. Scanning tunneling microscopy/spectroscopy measurements reveal that these W-rich regions exhibit a local band structure with the valence band maximum (VBM) closer to the Fermi level as compared with the Mo-rich regions in the monolayer Mo 1-xW xSe 2 crystal. These localized upshifts of the VBM in the local band structure appear responsible for the overall p-type behavior observed for the monolayer Mo 1-xW xSe 2 crystals. Stacked monolayers of n-type MoSe 2 and p-type Mo 1-xW xSe 2 were demonstrated to form atomically thin, vertically stacked p n homojunctions with gate-tunable characteristics, which appear useful for future optoelectronic applications. Lastly, these results indicate that alloying with isoelectronic dopant atoms appears to be an effective and advantageous alternate strategy to doping or alloying with electron donors or acceptors in two-dimensional TMDs.« less
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NASA Astrophysics Data System (ADS)
Awasthi, Reena; Abraham, Geogy; Kumar, Santosh; Bhattacharyya, Kaustava; Keskar, Nachiket; Kushwaha, R. P.; Rao, Ramana; Tewari, R.; Srivastava, D.; Dey, G. K.
2017-06-01
In this study, corrosion characteristics of a nickel-based Ni-Mo-Cr-Si hardfacing alloy having 32Mo, 15Cr, and 3Si (wt pct) as alloying elements, deposited on stainless steel SS316L substrate by laser cladding, have been presented. Corrosion behavior of the laser clad layer was evaluated in reducing (0.1 M HCl) and oxidizing (0.5 M HNO3) environments, in comparison with the reference substrate SS316L, using electrochemical potentiodynamic technique at room temperature. The corrosion mechanisms have been evaluated on the basis of microstructural and microchemical analysis using scanning electron microscopy attached with energy-dispersive spectrometry. Passivity behavior of the laser clad layer was studied in 0.5 M H2SO4, using the potentiostatic technique and analyzing the passive layer by X-ray photoelectron spectroscopy. Laser clad layer of Ni-Mo-Cr-Si exhibited higher pitting corrosion resistance in chloride (reducing) environment, indicated by much higher breakdown potential ( 0.8 VSCE) and the absence of pitting as compared to substrate SS316L ( 0.3 VSCE). However, in oxidizing (0.5 M HNO3) environment, both the laser clad layer and substrate SS316L showed excellent and similar corrosion resistance exhibiting high breakdown potential ( 0.85 VSCE) and wide passivation range ( 0.8 VSCE) with low passive current density ( 4 to 7 × 10-6 A/cm2). The stable passive layer formed on laser clad layer of Ni-Mo-Cr-Si after exposure in 0.5 M H2SO4 solution at constant potential 0.6 VSCE (within the passive range), consisted oxides of Mo as Mo+4 (MoO2) and Mo+6 (MoO4)-2, Cr as Cr3+ (mixture of both Cr2O3 and Cr (OH)3), and Si as Si4+(SiO2), which have contributed to passivation and repassivation and therefore excellent corrosion behavior.
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NASA Astrophysics Data System (ADS)
Noli, Fotini; Pichon, Luc; Öztürk, Orhan
2018-04-01
Plasma-based nitriding and/or oxidizing treatments were applied to CoCrMo alloy to improve its surface mechanical properties and corrosion resistance for biomedical applications. Three treatments were performed. A set of CoCrMo samples has been subjected to nitriding at moderate temperatures ( 400 °C). A second set of CoCrMo samples was oxidized at 395 °C in pure O2. The last set of CoCrMo samples was nitrided and subsequently oxidized under the experimental conditions of previous sets (double treatment). The microstructure and morphology of the layers formed on the CoCrMo alloy were investigated by X-ray diffraction, Atomic Force Microscopy, and Scanning Electron Microscopy. In addition, nitrogen and oxygen profiles were determined by Glow Discharge Optical Emission Spectroscopy, Rutherford Backscattering Spectroscopy, Energy-Dispersive X-ray, and Nuclear Reaction Analysis. Significant improvement of the Vickers hardness of the CoCrMo samples after plasma nitriding was observed due to the supersaturated nitrogen solution and the formation of an expanded FCC γ N phase and CrN precipitates. In the case of the oxidized samples, Vickers hardness improvement was minimal. The corrosion behavior of the samples was investigated in simulated body fluid (0.9 pct NaCl solution at 37 °C) using electrochemical techniques (potentiodynamic polarization and cyclic voltammetry). The concentration of metal ions released from the CoCrMo surfaces was determined by Instrumental Neutron Activation Analysis. The experimental results clearly indicate that the CoCrMo surface subjected to the double surface treatment consisting in plasma nitriding and plasma oxidizing exhibited lower deterioration and better resistance to corrosion compared to the nitrided, oxidized, and untreated samples. This enhancement is believed to be due to the formation of a thicker and more stable layer.
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NASA Astrophysics Data System (ADS)
Shin, Soon-Gi
2000-06-01
The grain growth behaviors of TiC and WC particles in TiC-Ni, TiC-Mo2C-Ni, WC-Co and WC-VC-Co alloys during liquid phase sintering were investigated for different Ni or Co contents and compared with the results of Monte Carlo simulations. In the experimental study, TiC-Ni and WC-Co alloys had a maximum grain size at a certain liquid volume fraction, while the grain size in TiC-Mo2C-Ni and WC-VC-Co alloys increased monotonically with an increasing liquid volume fraction. These results mean that the grain growth of these alloys cannot be explained by the conventional mechanisms for Ostwald ripening, namely diffusion or reaction controlled processes. Monte Carlo simulations with different energy relationships between solidliquid interfaces predicted the effect of the liquid volume fraction on grain size similar to the experimental results. The contiguous boundaries between solid (carbide) particles appear to influence the grain growth behavior in TiC- and WC-based alloys during liquid phase sintering.
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Structural Phase Transformation in Strained Monolayer MoWSe2 Alloy.
Apte, Amey; Kochat, Vidya; Rajak, Pankaj; Krishnamoorthy, Aravind; Manimunda, Praveena; Hachtel, Jordan A; Idrobo, Juan Carlos; Syed Amanulla, Syed Asif; Vashishta, Priya; Nakano, Aiichiro; Kalia, Rajiv K; Tiwary, Chandra Sekhar; Ajayan, Pulickel M
2018-04-24
Two-dimensional (2D) materials exhibit different mechanical properties from their bulk counterparts owing to their monolayer atomic thickness. Here, we have examined the mechanical behavior of 2D molybdenum tungsten diselenide (MoWSe 2 ) precipitation alloy grown using chemical vapor deposition and composed of numerous nanoscopic MoSe 2 and WSe 2 regions. Applying a bending strain blue-shifted the MoSe 2 and WSe 2 A 1g Raman modes with the stress concentrated near the precipitate interfaces predominantly affecting the WSe 2 modes. In situ local Raman measurements suggested that the crack propagated primarily thorough MoSe 2 -rich regions in the monolayer alloy. Molecular dynamics (MD) simulations were performed to study crack propagation in an MoSe 2 monolayer containing nanoscopic WSe 2 regions akin to the experiment. Raman spectra calculated from MD trajectories of crack propagation confirmed the emergence of intermediate peaks in the strained monolayer alloy, mirroring experimental results. The simulations revealed that the stress buildup around the crack tip caused an irreversible structural transformation from the 2H to 1T phase both in the MoSe 2 matrix and WSe 2 patches. This was corroborated by high-angle annular dark-field images. Crack branching and subsequent healing of a crack branch were also observed in WSe 2 , indicating the increased toughness and crack propagation resistance of the alloyed 2D MoWSe 2 over the unalloyed counterparts.
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Influence of graphite-alloy interactions on corrosion of Ni-Mo-Cr alloy in molten fluorides
NASA Astrophysics Data System (ADS)
Ai, Hua; Hou, Juan; Ye, Xiang-Xi; Zeng, Chao Liu; Sun, Hua; Li, Xiaoyun; Yu, Guojun; Zhou, Xingtai; Wang, Jian-Qiang
2018-05-01
In this study, the effects of graphite-alloy interaction on corrosion of Ni-Mo-Cr alloy in molten FLiNaK salt were investigated. The corrosion tests of Ni-Mo-Cr alloys were conducted in graphite crucibles, to examine the differences of test specimens in conditions of electric contact and isolated with graphite, respectively. The corrosion attack is severer with more weight loss and deeper Cr depletion layer in samples electric contact with graphite than those isolated with graphite. The occurrence of galvanic corrosion between alloy specimens and graphite container was confirmed by electrochemical measurement. The corrosion is controlled by nonelectric transfer in isolated test while electrochemical reaction accelerated corrosion in electric contact test.
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Electrochemical stability and corrosion resistance of Ti-Mo alloys for biomedical applications.
Oliveira, N T C; Guastaldi, A C
2009-01-01
Electrochemical behavior of pure Ti and Ti-Mo alloys (6-20wt.% Mo) was investigated as a function of immersion time in electrolyte simulating physiological media. Open-circuit potential values indicated that all Ti-Mo alloys studied and pure Ti undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the chloride-containing solution. It also indicated that the addition of Mo to pure Ti up to 15wt.% seems to improve the protection characteristics of its spontaneous oxides. Electrochemical impedance spectroscopy (EIS) studies showed high impedance values for all samples, increasing with immersion time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The fit obtained suggests a single passive film present on the metals' surface, improving their resistance with immersion time, presenting the highest values to Ti-15Mo alloy. Potentiodynamic polarization showed a typical valve-metal behavior, with anodic formation of barrier-type oxide films, without pitting corrosion, even in chloride-containing solution. In all cases, the passive current values were quite small, and decrease after 360h of immersion. All these electrochemical results suggest that the Ti-15Mo alloy is a promising material for orthopedic devices, since electrochemical stability is directly associated with biocompatibility and is a necessary condition for applying a material as biomaterial.
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Tribological coating of titanium alloys by laser processing
NASA Astrophysics Data System (ADS)
Pang, Wang
Titanium-based alloys have been used for aerospace materials for many years. Recently, these alloys are now being increasingly considered for automotive, industrial and consumer applications. Their excellent creep resistance, corrosion resistance and relative higher specific strength ratio are attractive for many applications. However, the main obstacle for the wide adoption of Ti alloys in various industries is their poor tribological properties. In slide wear, Ti deforms and adhesive wear readily occurs. Their poor tribological properties are mainly due to low hardness and absolute values of tensile and shear strength. Different surface modification techniques have been studied in order to improve the tribological characteristics of Ti alloys, i.e. PVD, nitrding, carburizing, boriding, plating etc. Coatings produced by these techniques have their own limitations such as thermal distortion and grain growth. A different approach is to introduce hard particles in the Ti alloy matrix to form a MMC coating, which has tailor-made hardness and wear resistance properties. Laser cladding or laser alloying techniques facilitate the fabrication of surface MMC on Ti alloys without thermal distortion to the substrate. In this project, the fabrication of hard and wear resistant layers of metal matrix composite on titanium alloys substrate by laser surface alloying was investigated. Powder mixtures of Mo and WC were used to form the MMC layer. By optimizing the processing parameters and pre-placed powder mixture compositions, surface MMC of different properties have been successfully fabricated on CP-Ti and Ti6A14V respectively. The structure and characteristics of the MMC surface were investigated by metallography, SEM, XRD, and E-DAX. It was found that the hardness of the laser alloyed Mo/WC MMC surface was 300% higher than that of the CP-Ti substrate Excellent metallurgical bonding with the MMC layer of the substrate has been achieved. The relative kinetic frictional tests were carried out and the results showed that the kinetic coefficient of friction of the laser fabricated Ti-Mo-WC MMC coatings was much lower than that of the CP-Ti and Ti6A14V substrate. The wear resistance of this Ti-Mo-WC MMC was found to be between 60 to 150 times better than those of CP-Ti. The experimental results also identified a key issue of mixing efficiency that the density of WC was much higher than that of Ti and Mo and this rendered poor mixing between the different constituents. This resulted in a relatively poor repeatability of the coating quality. To solve this issue, a lower density carbide phase, TiC, was used. The hardness and dry sliding wear resistance of the Ti-Mo-TiC MMC was found to be lower than those of Ti-Mo-WC MMC. The mixing efficiency of the TiC in the Ti-Mo-MMC was found to be better than the WC in Ti-Mo-WC MMC. This combination gave a harder and more wear resistant MMC with more uniform properties across the width and depth of the alloyed layer formed. A mathematical model for predicting the melt depth of the alloyed MMC layer was developed together with a heat transfer mechanism between layers of powders under the laser irradiation. The model facilitates the prediction of melt depth of the alloyed layer and the dilution ratio of the MMC layer. It thus enabled the composition of the MMC layer to be predicted and tailor made. The project results contribute significantly to the knowledge of improving the wear and frictional properties of one of the most important engineering metals for the automobile and aerospace industries.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Sun, Zhiqian; Yamamoto, Yukinori
The processability of a Mo-containing FeCrAl alloy (Fe-13Cr-5.2Al-2Mo base, in wt%), developed for accident-tolerant nuclear fuel claddings, was evaluated through a stepwise rolling process at 400 °C under two different inter-pass annealing conditions (i.e., 650 °C for 1 h and at 870 °C for 30 min). The inter-pass annealing at 870 °C easily softened the FeCrAl alloy; however, it led to the formation of coarse grains of ~200 µm. On the other hand, the FeCrAl alloy maintained elongated, deformed grains with the inter-pass annealing at 650 °C, but the annealed samples showed relatively high deformation resistance and strong texture. Importantmore » aspects concerning the processability and microstructural control of FeCrAl alloys, such as deformation inhomogeneity, texture development, and grain coarsening, were discussed. Optimized processing conditions were recommended, based on the results, to achieve desirable microstructures with balanced processability and mechanical properties.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Kirby, Brent W.
The crucibles used currently for microwave melting of U-Mo alloy at the Y-12 Complex contain silicon carbide (SiC) in a mullite (3Al 2O 3-2SiO 2) matrix with an erbia coating in contact with the melt. Due to observed silicon contamination, Pacific Northwest National Laboratory has investigated alternative crucible materials that are susceptible to microwave radiation and are chemically compatible with molten U-Mo at 1400 1500C. Recommended crucibles for further testing are: 1) high-purity alumina (Al 2O 3); 2) yttria-stabilized zirconia (ZrO 2); 3) a composite of alumina and yttria-stabilized zirconia; 4) aluminum nitride (AlN). Only AlN does not require anmore » erbia coating. The recommended secondary susceptor, for heating at low temperature, is SiC in a “picket fence” arrangement.« less
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Short communication on Kinetics of grain growth and particle pinning in U-10 wt.% Mo
NASA Astrophysics Data System (ADS)
Frazier, William E.; Hu, Shenyang; Overman, Nicole; Lavender, Curt; Joshi, Vineet V.
2018-01-01
The alloy U-10 wt% Mo was annealed at temperatures ranging from 700 °C to 900 °C for periods lasting up to 24 h. Annealed microstructures were examined using Electron Backscattered Diffraction (EBSD) to obtain average grain sizes and grain size distributions. From the temporal evolution of the average grain size, the activation energy of grain growth was determined to be 172.4 ± 0.961 kJ/mol. Grain growth over the annealing period stagnated after a period of 1-4 h. This stagnation is apparently caused by the pinning effect of second-phase particles in the materials. Back-scattered electron imaging (BSE) was used to confirm that these particles do not appreciably coarsen or dissolve during annealing at the aforementioned temperatures.
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High damping Al-Fe-Mo-Si/Zn-Al composites produced by rapidly solidified powder metallurgy process
DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, P.Y.; Dai, S.L.; Chai, S.C.
2000-05-10
The metallic materials commonly used in aircraft and aerospace fields, such as aluminum and titanium alloys, steels, etc., show extremely low damping capacity (usually of the order of or less than 10{sup {minus}3}). Thus, some problems related to vibration may emerge and influence the reliability, safety and life of airplanes, satellites, etc. It has been reported that almost two thirds of errors for rockets and satellites are related to vibration and noise. One effective way to solve these vibration-related problems is to adopt high damping metallic materials. Conventional high damping alloys exhibit damping capacity above 10{sup {minus}2}, however, their densitiesmore » are usually great than 5 x 10{sup 3} kg m{sup {minus}3}, or their strengths are less than 200 MPa (for alloys based on dislocation damping), making them impossible to be applied to aircraft and aerospace areas. Recently, some low-density high-damping metal/metal composites based on aluminum and high damping alloys have been developed in Beijing Institute of Aeronautical Materials (BIAM) by the rapidly solidified power metallurgy process. This paper aims to report the properties of the composites based on a high temperature Al-Fe-Mo-Si alloy and a high damping Zn-Al alloy, and compare them with that of 2618-T61 alloy produced by the ingot metallurgy process.« less
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Summary Abstract: Growth and Alloying of Pd Films on Mo(110) Surfaces
NASA Technical Reports Server (NTRS)
Park, Ch. E.; Poppa, H.; Bauer, E.
1985-01-01
Alloying in small metal particles and in very thin films has recently received considerable attention. In the past it has been generally assumed that alloying is insignificant up to temperatures. Thus many epitaxy experiments of metals on metals with complete miscibility were performed at temperatures between 200 and 400 C and analyzed assuming no alloying. In particular, alloying was not suspected if the film material was not soluble in the substrate. In the present study, which was stimulated by annealing-induced CO adsorption anomalies on thin film surfaces, it has become evident that low temperature alloying can occur in thin films on a metal substrate which is refractory and has very strong interatomic bonds (as evidenced by a high sublimation energy) provided that the substrate is soluble in the film material. A good example of such a film-substrate combination is Pd on Mo. The solubility of Pd in Mo is very at temperatures below 1000 K but Pd can dissolve slightly more than 40 at. % Mo even at low temperatures.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ozaltun, Hakan; Medvedev, Pavel G
2015-06-01
Monolithic plate-type fuel is a fuel form being developed for high performance research and test reactors to minimize the use of enriched material. These fuel elements are comprised of a high density, low enrichment, U-Mo alloy based fuel foil, sandwiched between Zirconium liners and encapsulated in Aluminum cladding. The use of a high density fuel in a foil form presents a number of fabrication and operational concerns, such as: foil centering, flatness of the foil, fuel thickness variation, geometrical tilting, foil corner shape etc. To benchmark this new design, effects of various geometrical and operational variables on irradiation performance havemore » been evaluated. As a part of these series of sensitivity studies, the shape of the foil corners were studied. To understand the effects of the corner shapes of the foil on thermo-mechanical performance of the plates, a behavioral model was developed for a selected plate from RERTR-12 experiments (Plate L1P785). Both fabrication and irradiation processes were simulated. Once the thermo-mechanical behavior the plate is understood for the nominal case, the simulations were repeated for two additional corner shapes to observe the changes in temperature, displacement and stress-strain fields. The results from the fabrication simulations indicated that the foil corners do not alter the post-fabrication stress-strain magnitudes. Furthermore, the irradiation simulations revealed that post-fabrication stresses of the foil would be relieved very quickly in operation. While, foils with chamfered and filleted corners yielded stresses with comparable magnitudes, they are slightly lower in magnitudes, and provided a more favorable mechanical response compared with the foil with sharp corners.« less
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Corrosion behavior of high-nickel and chromium alloys in natural Baltic seawater
DOE Office of Scientific and Technical Information (OSTI.GOV)
Birn, J.; Janik-Czachor, M.; Wolowik, A.
Effect of Cl{sup {minus}} ion concentration (O M sodium chloride [NaCl] to 2 M NaCl) and temperature (25 C to 75 C) on stability of the passive state of high-Ni and Cr alloys: NI-1 ({approximately} 16% Mo), CR-2 ({approximately} 6.2% Mo), and NI-3 (3.5% Mo) were investigated in acidic and neutral electrolytes in strictly controlled electrochemical conditions. The anodic behavior of the alloys appeared to depend mostly upon Mo content in the alloy. Thus, the NI-1 was the most stable alloy under the applied experimental conditions. The other alloys were also quite resistant, undergoing pitting only at elevated temperatures, atmore » high anodic potentials, and at a chloride concentration not lower than 1 M. In natural Baltic seawater, these alloys did not exhibit any tendency to pitting, in qualitative agreement with the accelerated electrochemical tests. Complementary microscopic and surface analytical (AES) investigations were carried out to correlate the anodic and corrosion behavior of these materials with their composition and structure, and the composition of the passivating films formed at their surfaces.« less
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METALLURGY DIVISION QUARTERLY REPORT FOR JULY, AUGUST, AND SEPTEMBER 1957
DOE Office of Scientific and Technical Information (OSTI.GOV)
None
1958-10-01
Advanced Water Reactor Program. Three firings were made of initial closed-porosity fuel pellet bodies. Each firing coatained pellets of the composition 90 wt.% ThO/sub 2/-10 wt.%fl U0/sub 2/ with various additives and firing variables. Fast Power Breeder Reactor Program. To determine the potential usefulness of a Zr-5 wt. % Pu alloy, the fabricability of the alloy was tested. The manufacture of rod stock from which fuel and blanket elements for the Mark III loading of the EBR-1 were prcduced has been completed. The effect of irradiation on extruded and heat-treated U-2 wt.% Zr alloy for the EBR- 1 is reported.more » Fabrication procedures for making graphite-U/sub 3/O/sub 8/ test specimens for the TREAT Reactor were investigated. Advanced Engineering and Development. Ultrasonic bond tests were conducted on 590 EBR-1 Mark III blanket fuel elemeats. The blanket rods and part of the fuel rcds for the EBR-1 Mark III loading are being checked for cladding thickness by an eddy current system. Investigations of corrosionresistant Zr-Nb alloy were coatinued. Corrosion of MR alloys is being studied Ln support of the Mighty Mouse reactor program. Dynamic corrosion tests were performed on aluminum alloys, and results are included. Prcduction, Treatment, and Properties of Materials. The progress of the program of preparing highpurity Pu by fused salt electrolysis is summarized. Velocities of ultrasonic waves propagated in directions suitable for determining the room- temperature elastic moduli C/sub 12/, C/sub 13/, and C/sub 23/ of alpha U were determined. investigation of recrystallization in heavily coldrolled alpha- uranium sheet without a texture change was essentially concluded during this quarter. Selfdiffasion runs in polycrystalline uranium in the gamma phase, using the sputtering technique, have yielded a tentative value for the diffusion coefficient between 10/sup -8/ and 10/sup -7/ cm/sup 2/second. The preparation of high-purity U-Pan alloys is reponted. The data for the alpha-tobeta transformation temperatures in high-purity U and U-C alloys were confirmed by experiments on new specimens. Microstructure, density, and thermal arrest data were obtained for several injection cast, nominal U-5 wt.%fl fissium and U-8 wt.%fl fissium alloys. Phase diagrams are preseated for U-Mo and U-Ru alloys. Alloy Theory and The Nature of Solids. Four new isomorphs of Ti/sub 2/Ni have been discovered. Effects of Irradiation on Materials. The experimental and analytical work on the radial distribution of thermal neutrons within cylindrically shaped fuel specimens during irradiation was completed. (For preceding period see ANL-5790.) (W.L.H.)« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Soulami, Ayoub; Lavender, Curt A.; Paxton, Dean M.
2014-04-23
Pacific Northwest National Laboratory (PNNL) has been investigating manufacturing processes for the uranium-10% molybdenum (U-10Mo) alloy plate-type fuel for the U.S. high-performance research reactors. This work supports the Convert Program of the U.S. Department of Energy’s National Nuclear Security Administration (DOE/NNSA) Global Threat Reduction Initiative. This report documents modeling results of PNNL’s efforts to perform finite-element simulations to predict roll separating forces and rolling defects. Simulations were performed using a finite-element model developed using the commercial code LS-Dyna. Simulations of the hot rolling of U-10Mo coupons encapsulated in low-carbon steel have been conducted following two different schedules. Model predictions ofmore » the roll-separation force and roll-pack thicknesses at different stages of the rolling process were compared with experimental measurements. This report discusses various attributes of the rolled coupons revealed by the model (e.g., dog-boning and thickness non-uniformity).« less
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Multi-component solid solution alloys having high mixing entropy
Bei, Hongbin
2015-10-06
A multi-component high-entropy alloy includes a composition selected from the following group: VNbTaTiMoWRe, VNbTaTiMoW, VNbTaTiMoRe, VNbTaTiWRe, VNbTaMoWRe, VNbTiMoWRe, VTaTiMoWRe, NbTaTiMoWRe, VNbTaTiMo, VNbTaTiW, VNbTaMoW, VNbTiMoW, VTaTiMoW, NbTaTiMoW, VNbTaTiRe, VNbTaMoRe, VNbTiMoRe, VTaTiMoRe, NbTaTiMoRe, VNbTaWRe, VNbTiWRe, VTaTiWRe, NbTaTiWRe, VNbMoWRe, VTaMoWRe, NbTaMoWRe, VTiMoWRe, NbTiMoWRe, TaTiMoWRe, wherein relative amounts of each element vary by no more than .+-.15 atomic %.
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[Corrosion property and oxide film of dental casting alloys before and after porcelain firing].
Ma, Qian; Wu, Feng-ming
2011-03-01
To evaluate the types and compositions of oxide films formed during porcelain-fused-to-metal (PFM) firing on three kinds of dental casting alloys, and to investigate the corrosion property of these alloys in Dulbecco's modification of Eagle's medium (DMEM) cell culture fluid, before and after PFM firing. Specimens of three dental casting alloys (Ni-Cr, Co-Cr and Ni-Ti) before and after PFM firing were prepared, and were immersed in DMEM cell culture fluid. After 30 days, the type and concentration of released metal ions were measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES). X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used for analysis of oxide film on the alloys. One way-ANOVA was adopted in data analysis. The total amount of metal ions released from the three dental alloys was found to be highest in Ni-Cr alloy [(2.829 ± 0.694) mg/L], followed by Co-Cr [(2.120 ± 0.418) mg/L] and Ni-Ti alloy [(1.211 ± 0.101) mg/L]. The amount of Ni ions released from Ni-Cr alloys [(1.531 ± 0.392) mg/L] was higher than that from Ni-Ti alloys [(0.830 ± 0.052) mg/L]. The amount of Cr, Mo ions released from Co-Cr alloy [Cr: (0.048 ± 0.011) mg/L, Mo: (1.562 ± 0.333) mg/L] was higher than that from Ni-Cr alloy [Cr: (0.034 ± 0.002) mg/L, Mo: (1.264 ± 0.302) mg/L] and Ni-Ti alloy [Cr: (0.013 ± 0.006) mg/L, Mo: (0.151 ± 0.026) mg/L] (P < 0.05). After PFM firing, the total amount of metal irons released from the three dental alloys decreased [Ni-Cr: (0.861 ± 0.054) mg/L, Co-Cr: (0.695 ± 0.327) mg/L, Ni-Ti: (0.892 ± 0.115) mg/L] (P < 0.05). In addition, XPS showed increase of Cr(2)O(3) and Mo-Ni oxide on the surface of all the alloys after PFM firing. The amount of ions released from Ni-Cr alloy was the highest among the three dental casting alloys, this means Ni-Cr alloy is prone to corrode. The PFM firing process changed the alloys' surface composition. Increased Ni, Cr and Mo were found in oxide film, and the increase in Cr(2)O(3) can improve the corrosion-resistance of alloys.
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NASA Astrophysics Data System (ADS)
Santa Coloma, P.; Izagirre, U.; Belaustegi, Y.; Jorcin, J. B.; Cano, F. J.; Lapeña, N.
2015-08-01
Novel chromium-free conversion coatings based on Zr/Ti/Mn/Mo compounds were developed at a pilot scale to improve the corrosion resistance of the AA2024-T3 and AA7075-T6 aluminum alloys for aircraft applications. The influence of the presence of Zr and Ti in the Zr/Ti/Mn/Mo conversion bath's formulation on the corrosion resistance of the coated alloys was investigated. The corrosion resistance provided by the conversion coatings was evaluated by salt spray exposure and potentiodynamic sweeps. Optical and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) and atomic force microscopy (AFM) operating in the Kelvin Probe mode (SKPFM) were used to provide microstructural information of the coated samples that achieved the best results in the corrosion tests. The salt spray test evidenced the higher corrosion resistance of the coated samples compared to the bare surfaces for both alloys. The potentiodynamic tests showed that the corrosion current density decreased for coated AA7075-T6 and AA2024-T3 alloys, which indicated an obvious improvement of the corrosion resistance with all the processes for both alloys. Although the corrosion resistance of the coated samples appeared to be higher for the alloy AA7075-T6 than for the alloy AA2024-T3, both alloys achieved the best corrosion protection with the coatings deposited from conversion bath formulations containing no titanium salts. The microscopy analysis on the coated AA7075-T6 samples revealed that a local deposition of Zr compounds and, possibly, an oxidation process occurred in the vicinity of the alloy's intermetallic particles. The amount of the Zr deposits at these locations increased with coating's formulations without Ti, which provided the best corrosion resistance. The Cr-free conversion coatings developed in this study for the AA7075-T6 and AA2024-T3 alloys do not meet yet the strict requirements of the aircraft industry. However, they significantly improved the corrosion performance with respect to the bare alloys and could be a good starting point for further studies and optimization.
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Reaction of Unalloyed and Cr-Mo Alloyed Steels with Nitrogen from the Sintering Atmosphere
NASA Astrophysics Data System (ADS)
Dlapka, Magdalena; Gierl-Mayer, Christian; Calderon, Raquel de Oro; Danninger, Herbert; Bengtsson, Sven; Dudrova, Eva
2016-12-01
Nitrogen is usually regarded as an inert sintering atmosphere for PM steels; however, this cannot be taken for granted in particular for steels alloyed with nitride forming elements. Among those elements, chromium has become more and more important as an alloying element in sintered low alloy structural steels in the last decade due to the moderate alloying cost and the excellent mechanical properties obtainable, in particular when sinter hardening is applied. The high affinity of Cr to oxygen and the possible ways to overcome related problems have been the subject of numerous studies, while the fact that chromium is also a fairly strong nitride forming element has largely been neglected at least for low alloy steel grades, although frequently used materials like steels from Cr and Cr-Mo prealloyed powders are commonly sintered in atmospheres consisting mainly of nitrogen. In the present study, nitrogen pickup during sintering at different temperatures and for varying times has been studied for Cr-Mo prealloyed steel grades as well as for unalloyed carbon steel. Also the effect of the cooling rate and its influence on the properties, of the microstructure and the composition have been investigated. It showed that the main nitrogen uptake occurs not during isothermal sintering but rather during cooling. It could be demonstrated that a critical temperature range exists within which the investigated CrM-based steel is particularly sensitive to nitrogen pickup.
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NASA Astrophysics Data System (ADS)
Waseda, O.; Goldenstein, H.; Silva, G. F. B. Lenz e.; Neiva, A.; Chantrenne, P.; Morthomas, J.; Perez, M.; Becquart, C. S.; Veiga, R. G. A.
2017-10-01
The thermal stability of nanocrystalline Ni due to small additions of Mo or W (up to 1 at%) was investigated in computer simulations by means of a combined Monte Carlo (MC)/molecular dynamics (MD) two-steps approach. In the first step, energy-biased on-lattice MC revealed segregation of the alloying elements to grain boundaries. However, the condition for the thermodynamic stability of these nanocrystalline Ni alloys (zero grain boundary energy) was not fulfilled. Subsequently, MD simulations were carried out for up to 0.5 μs at 1000 K. At this temperature, grain growth was hindered for minimum global concentrations of 0.5 at% W and 0.7 at% Mo, thus preserving most of the nanocrystalline structure. This is in clear contrast to a pure Ni model system, for which the transformation into a monocrystal was observed in MD simulations within 0.2 μs at the same temperature. These results suggest that grain boundary segregation of low-soluble alloying elements in low-alloyed systems can produce high-temperature metastable nanocrystalline materials. MD simulations carried out at 1200 K for 1 at% Mo/W showed significant grain boundary migration accompanied by some degree of solute diffusion, thus providing additional evidence that solute drag mostly contributed to the nanostructure stability observed at lower temperature.
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NASA Astrophysics Data System (ADS)
Saha, Biswadeep
Rare-earth-free Fe-Ga magnetostrictive alloys exhibit an excellent combination of large low-field magnetostriction, strength, ductility, wide operating temperature range, and low cost. Various observations in these and other alpha-Fe-based magnetostrictive alloys suggest that lattice strain modulations that are influenced by solute elements, near neighbor atomic environments around Fe atoms, coherent and incoherent precipitates, and structural defects such as dislocations likely play an important role in their magnetostrictive behavior. In the first part, the effect of dislocations on the magnetostriction of Fe-Ga single crystals was examined. The [001]- and [126]-oriented Fe-20 at.% Ga single crystal samples were deformed in a controlled way to introduce dislocation arrays with two different array geometries. Magnetostriction values showed a much lower decrease after deformation for the case of a [001]-oriented crystal, where eight different slip systems were operative and consequently eight different sets of dislocation arrays are expected. A drastic drop in magnetostriction measured along the sample axis is observed in the sample subjected to a small strain by deformation of a [126]-oriented crystal during which slip occurred on only one slip system. The nature of strain modulation introduced in this case was spatially asymmetric. The [126] deformation was accompanied by an acoustic emission during the formation of slip band. Transmission electron microscopy was carried out to examine the nature of dislocation distribution. The results show that the nature of strain modulation introduced by the dislocation arrays has a strong influence on the magnetostrictive behavior of magnetostrictive alloys. In the second part of this research, the effect of Mo addition to Fe was examined in detail. Addition of Mo to Fe increased the magnetostriction (3/2)lambda100 Fe very rapidly to 137 ppm at 10 at.% Mo, the highest value observed in these alloys. Further Mo additions decreased the magnetostriction. Magnetization data show a drastic drop in magnetization to 63 emu/gm for Fe-20 at.% Mo from 176 emu/gm for Fe-10 at.% Mo suggesting the formation large amounts of nonmagnetic second phase and reduction in total Fe content of the alloy. The drop in magnetostriction at higher Mo contents is associated with the formation of a second phase.
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Atomic scale modelling of hexagonal structured metallic fission product alloys
Middleburgh, S. C.; King, D. M.; Lumpkin, G. R.
2015-01-01
Noble metal particles in the Mo-Pd-Rh-Ru-Tc system have been simulated on the atomic scale using density functional theory techniques for the first time. The composition and behaviour of the epsilon phases are consistent with high-entropy alloys (or multi-principal component alloys)—making the epsilon phase the only hexagonally close packed high-entropy alloy currently described. Configurational entropy effects were considered to predict the stability of the alloys with increasing temperatures. The variation of Mo content was modelled to understand the change in alloy structure and behaviour with fuel burnup (Mo molar content decreases in these alloys as burnup increases). The predicted structures compare extremely well with experimentally ascertained values. Vacancy formation energies and the behaviour of extrinsic defects (including iodine and xenon) in the epsilon phase were also investigated to further understand the impact that the metallic precipitates have on fuel performance. PMID:26064629
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CORROSION STUDIES FOR A FUSED SALT-LIQUID METAL EXTRACTION PROCESS FOR THE LIQUID METAL FUEL REACTOR
DOE Office of Scientific and Technical Information (OSTI.GOV)
Susskind, H.; Hill, F.B.; Green, L.
1960-06-30
Corrosion screening tests were carried out on potential materials of construction for use in a fused salt-liquid metal extraction process plant. The corrodents of interest were NaCl--KCl-- MgCl/sub 2/ eutectic, LiCl--KCl eutectic, Bi-- U fuel, and BiCl/sub 3/, either separately or in various combinations. Screening tests to determine the resistance of a wide range of commercial alloys to the corrodents were performed in static and tilting-furnace capsules. Some ceramic materials were tested in static capsules. Largerscale tests of metallic materials were conducted in thermal convection loops and in a forced circulation loop. Some of the tests were conducted isothermally atmore » 500 deg C, and others were performed under 40 to 50 deg C temperature differences at roughly the same teinperature level. On the basis of metallographic examination of exposed test tabs and chemical analyses of corrodents, it was found that the binary and ternary eutectics by themselves produced little attack on any of the materials tested. A wide variety of materials including 1020 mild steel, 2 1/4 Cr--1 Mo alloy steel, types 304 (ELC), 310, 316, 347, 430, and 446 stainless steel, 16-1 Croloy, Inconel, Hastelloy C, Inor-8, Mo, and Ta is, therefore, available for further study. Corrosion by the ternary salt-fuel system was characteristic of that produced by the fuel alone. Alloys such as 1020 mild steel, and 1 1/4 Cr--1/ 2 Mo, and 2 1/4 Cr--1 Mo alloy steel, which are resistant to fuel, would be likely choices at present for container materials. BiCl/sub 3/ produced extensive attack on ternary salt-fuel containers when the fuel contained insufficient concentrations of oxidizable solutes. Au and Al/sub 2/O/sub 3/ were the only materials not attacked by BiCl/sub 3/ in ternary salt alone. (auth)« less
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Advanced nickel base alloys for high strength, corrosion applications
Flinn, John E.
1998-01-01
Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0-20Fe, 10-30Cr, 2-12Mo, 6 max. Nb, 0.05-3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01-0.08C, less than 0.2N, 0.1 max. 0, bal. Ni.
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Advanced nickel base alloys for high strength, corrosion applications
Flinn, J.E.
1998-11-03
Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0--20Fe, 10--30Cr, 2--12Mo, 6 max. Nb, 0.05--3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01--0.08C, less than 0.2N, 0.1 max. 0, bal. Ni. 3 figs.
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A long-term ultrahigh temperature application of layered silicide coated Nb alloy in air
NASA Astrophysics Data System (ADS)
Sun, Jia; Fu, Qian-Gang; Li, Tao; Wang, Chen; Huo, Cai-Xia; Zhou, Hong; Yang, Guan-Jun; Sun, Le
2018-05-01
Nb-based alloy possessed limited application service life at ultrahigh temperature (>1400 °C) in air even taking the effective protective coating strategy into consideration for last decades. In this work a long duration of above 128 h at 1500 °C in air was successfully achieved on Nb-based alloy thanked to multi-layered silicide coating. Through optimizing interfaces, the MoSi2/NbSi2 silicide coating with Al2O3-adsorbed-particles layer exhibited three-times higher of oxidation resistance capacity than the one without it. In MoSi2-Al2O3-NbSi2 multilayer coating, the Al2O3-adsorbed-particles layer playing as an element-diffusion barrier role, as well as the formed porous Nb5Si3 layer as a stress transition zone, contributed to the significant improvement.
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Kwon, J.; Bowers, M. L.; Brandes, M. C.; ...
2015-02-26
In this paper, directionally solidified (DS) NiAl–Mo eutectic composites were strained to plastic strain values ranging from 0% to 12% to investigate the origin of the previously observed stochastic versus deterministic mechanical behaviors of Mo-alloy micropillars in terms of the development of dislocation structures at different pre-strain levels. The DS composites consist of long, [1 0 0] single-crystal Mo-alloy fibers with approximately square cross-sections embedded in a [1 0 0] single-crystal NiAl matrix. Scanning transmission electron microscopy (STEM) and computational stress state analysis were conducted for the current study. STEM of the as-grown samples (without pre-straining) reveal no dislocations inmore » the investigated Mo-alloy fibers. In the NiAl matrix, on the other hand, a(1 0 0)-type dislocations exist in two orthogonal orientations: along the [1 0 0] Mo fiber axis, and wrapped around the fiber axis. They presumably form to accommodate the different thermal contractions of the two phases during cool down after eutectic solidification. At intermediate pre-strain levels (4–8%), a/2(1 1 1)-type dislocations are present in the Mo-alloy fibers and the pre-existing dislocations in the NiAl matrix seem to be swept toward the interphase boundary. Some of the dislocations in the Mo-alloy fibers appear to be transformed from a(1 0 0)-type dislocations present in the NiAl matrix. Subsequently, the transformed dislocations in the fibers propagate through the NiAl matrix as a(1 1 1) dislocations and aid in initiating additional slip bands in adjacent fibers. Thereafter, co-deformation presumably occurs by (1 1 1) slip in both phases. With a further increase in the pre-strain level (>10%), multiple a/2(1 1 1)-type dislocations are observed in many locations in the Mo-alloy fibers. Interactions between these systems upon subsequent deformation could lead to stable junctions and persistent dislocation sources. Finally, the transition from stochastic to deterministic, bulk-like behavior in sub-micron Mo-alloy pillars may therefore be related to an increasing number of multiple a(1 1 1) dislocation systems within the Mo fibers with increasing pre-strain, considering that the bulk-like behavior is governed by the forest hardening of these junctions.« less
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Mechanical Alloying of W-Mo-V-Cr-Ta High Entropy Alloys
NASA Astrophysics Data System (ADS)
Das, Sujit; Robi, P. S.
2018-04-01
Recent years have seen the emergence of high-entropy alloys (HEAs) consisting of five or more elements in equi-atomic or near equi-atomic ratios. These alloys in single phase solid solution exhibit exceptional mechanical properties viz., high strength at room and elevated temperatures, reasonable ductility and stable microstructure over a wide range of temperatures making it suitable for high temperature structural materials. In spite of the attractive properties, processing of these materials remains a challenge. Reports regarding fabrication and characterisation of a few refractory HEA systems are available. The processing of these alloys have been carried out by arc melting of small button sized materials. The present paper discusses the development of a novel refractory W-Mo-V-Cr-Ta HEA powder based on a new alloy design concept. The powder mixture was milled for time periods up to 64 hours. Single phase alloy powder having body centred cubic structure was processed by mechanical alloying. The milling characteristics and extent of alloying during the ball milling were characterized using X-ray diffractiometre (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). A single phase solid solution alloy powder having body-centred cubic (BCC) structure with a lattice parameter of 3.15486 Å was obtained after milling for 32 hours.
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Alloy Design Challenge: Development of Low Density Superalloys for Turbine Blade Applications
NASA Technical Reports Server (NTRS)
MacKay, Rebecca A.; Gabb, Timothy P.; Smialek, James L.; Nathal, Michael V.
2009-01-01
New low density single crystal (LDS) alloys have been developed for turbine blade applications, which have the potential for significant improvements in the thrust to weight ratio over current production alloys. An innovative alloying strategy was identified to achieve high temperature creep resistance, alloy density reductions, microstructural stability, and cyclic oxidation resistance. The approach relies on the use of molybdenum (Mo) as a potent solid solution strengthener for the nickel (Ni)-base superalloy; Mo has a density much closer to Ni than other refractory elements, such as rhenium (Re) or tungsten (W). A host of testing and microstructural examinations was conducted on the superalloy single crystals, including creep rupture testing, microstructural stability, cyclic oxidation, and hot corrosion. The paper will provide an overview of the single crystal properties that were generated in this new superalloy design space. The paper will also demonstrate the feasibility of this innovative approach of low density single crystal superalloy design. It will be shown that the best LDS alloy possesses the best attributes of three generations of single crystal alloys: the low density of first-generation single crystal alloys, the excellent oxidation resistance of second-generation single crystal alloys, and a creep strength which exceeds that of second and third generation alloys.
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Physical properties of monolithic U8 wt.%-Mo
NASA Astrophysics Data System (ADS)
Hengstler, R. M.; Beck, L.; Breitkreutz, H.; Jarousse, C.; Jungwirth, R.; Petry, W.; Schmid, W.; Schneider, J.; Wieschalla, N.
2010-07-01
As a possible high density fuel for research reactors, monolithic U8 wt.%-Mo ("U8Mo") was examined with regard to its structural, thermal and electric properties. X-ray diffraction by the Bragg-Brentano method was used to reveal the tetragonal lattice structure of rolled U8Mo. The specific heat capacity of cast U8Mo was determined by differential scanning calorimetry, its thermal diffusivity was measured by the laser flash method and its mass density by Archimedes' principle. From these results, the thermal conductivity of U8Mo in the temperature range from 40 °C to 250 °C was calculated; in the measured temperature range, it is in good accordance with literature data for UMo with 8 and 9 wt.% Mo, is higher than for 10 wt.% Mo and lower than for 5 wt.% Mo. The electric conductivity of rolled and cast U8Mo was measured by a four-wire method and the electron based part of the thermal conductivity calculated by the Wiedemann-Frantz law. Rolled and cast U8Mo was irradiated at about 150 °C with 80 MeV 127I ions to receive the same iodine ion density in the damage peak region as the fission product density in the fuel of a typical high flux reactor after the targeted nuclear burn-up. XRD analysis of irradiated U8Mo showed a change of the lattice parameters as well as the creation of UO 2 in the superficial sample regions; however, a phase change by irradiation was not observed. The determination of the electron based part of the thermal conductivity of the irradiated samples failed due to high measurement errors which are caused by the low thickness of the damage region in the ion irradiated samples.
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Microstructure of As-cast Co-Cr-Mo Alloy Prepared by Investment Casting
NASA Astrophysics Data System (ADS)
Park, Jong Bum; Jung, Kyung-Hwan; Kim, Kang Min; Son, Yong; Lee, Jung-Il; Ryu, Jeong Ho
2018-04-01
The microstructure of a cobalt-base alloy (Co-Cr-Mo) obtained by an investment casting process was studied. This alloy complies with the ASTM F75 standard and is widely used in the manufacturing of orthopedic implants owing to its high strength, good corrosion resistance, and excellent biocompatibility. This work focuses on the resulting microstructures arising from normal industrial environmental conditions. The characterization of the samples was carried out using optical microscopy, field emission scanning electron microscopy and energy-dispersive spectroscopy. In this study, the as-cast microstructure is an γ-Co (face-centered cubic) dendritic matrix with the presence of a secondary phase, such as M23C6 carbides precipitated at grain boundaries and interdendritic zones. These precipitates are the main strengthening mechanism in this type of alloy. Other minority phases, such as the σ phase, were also detected, and their presence could be linked to the manufacturing process and environment.
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Evaluation of directionally solidified eutectic superalloys for turbine blade applications
NASA Technical Reports Server (NTRS)
Henry, M. E.; Jackson, M. R.; Walter, J. L.
1978-01-01
Alloys from the following systems were selected for property evaluation: (1) gamma/gamma-Mo (Ni-base, rods of Mo); (2) gamma-beta (Ni-base, lamellae or rods of (Ni, Fe/Co Al); and (3) gamma-gamma (Ni-base rods of Ni3Al gamma). The three alloys were subjected to longitudinal and transverse tensile and rupture tests from 750 C to 1100 C, longitudinal shear strength was measured at several temperatures, resistance to thermal cycling to 1150 C was determined, cyclic oxidation resistance was evaluated at 750 C and 1100 C, and each system was directionally solidified in an alumina shell mold turbine shape to evaluate mold/metal reactivity. The gamma/gamma Mo system has good rupture resistance, transverse properties and processability, and is a high potential system for turbine blades. The gamma-beta system has good physical properties and oxidation resistance, and is a potential system for turbine vanes. The gamma-gamma system has good high temperature rupture resistance and requires further exploratory research.
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Surface chemistry and microstructure of metallic biomaterials for hip and knee endoprostheses
NASA Astrophysics Data System (ADS)
Jenko, Monika; Gorenšek, Matevž; Godec, Matjaž; Hodnik, Maxinne; Batič, Barbara Šetina; Donik, Črtomir; Grant, John T.; Dolinar, Drago
2018-01-01
The surface chemistry and microstructures of titanium alloys (both new and used) and CoCrMo alloys used for hip and knee endoprostheses were determined using SEM (morphology), EBSD (phase analysis), AES and XPS (surface chemistry). Two new and two used endoprostheses were studied. The SEM SE and BE images showed their microstructures, while the EBSD provided the phases of the materials. During the production of the hip and knee endoprostheses, these materials are subject to severe thermomechanical treatments and physicochemical processes that are decisive for CoCrMo alloys. The AES and XPS results showed that thin oxide films on (a) Ti6Al4V are primarily a mixture of TiO2 with a small amount of Al2O3, while the V is depleted, (b) Ti6Al7Nb is primarily a mixture of TiO2 with a small amount of Al2O3 and Nb2O5, and (c) the CoCrMo alloy is primarily a mixture of Cr2O3 with small amounts of Co and Mo oxides. The thin oxide film on the CoCrMo alloy should prevent intergranular corrosion and improve the biocompatibility. The thin oxide films on the Ti alloys prevent further corrosion, improve the biocompatibility, and affect the osseointegration.
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Khaksar, Ladan; Shirokoff, John
2017-04-20
The chemical degradation of alloy components in sulfur-containing environments is a major concern in oil and gas production. This paper discusses the effect of elemental sulfur and its simplest anion, sulfide, on the corrosion of Cr-Mo alloy steel at pH 2 and 5 during 10, 20 and 30 h immersion in two different solutions. 4130 Cr-Mo alloy steel is widely used as tubing and tubular components in sour services. According to the previous research in aqueous conditions, contact of solid sulfur with alloy steel can initiate catastrophic corrosion problems. The corrosion behavior was monitored by the potentiodynamic polarization technique during the experiments. Energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) have been applied to characterize the corrosion product layers after each experiment. The results show that under the same experimental conditions, the corrosion resistance of Cr-Mo alloy in the presence of elemental sulfur is significantly lower than its resistance in the presence of sulfide ions.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Bretscher, M.M.; Matos, J.E.
At the Reduced Enrichment for Research and Test Reactors (RERTR) meeting in September 1994, Durand reported that the maximum uranium loading attainable with U{sub 3}Si{sub 2} fuel is about 6.0 g U/cm{sup 3}. The French Commissariat a l`Energie Atomique (CEA) plan to perform irradiation tests with 5 plates at this loading. Compagnie pour L`Etude et La Realisation de Combustibles Atomiques (CERCA) has also fabricated a few uranium nitride (UN) plates with a uranium density in the fuel meat of 7.0 g/cm{sup 3} and found that UN is compatible with the aluminum matrix at temperatures below 500 C. High density dispersionmore » fuels proposed for development include U-Zr(4 wt%)-Nb(2 wt%), U-Mo(5 wt%), and U-Mo(9 wt%). The purpose of this note is to examine the relative neutronic behavior of these high density fuels in a typical light water-reflected and water-moderated MTR-type research reactor. The results show that a dispersion of the U-Zr-Nb alloy has the most favorable neutronic properties and offers the potential for uranium densities greater than 8.0 g/cm{sup 3}. On the other hand, UN is the least reactive fuel because of the relatively large {sup 14}N(n,p) cross section. For a fixed value of k{sub eff}, the required {sup 235}U loading per fuel element is least for the U-Zr-Nb fuel and steadily increases for the U-Mo(5%), U-Mo(9%), and UN fuels. Because of volume fraction limitations, the UO{sub 2} dispersions are only useful for uranium densities below 5.0 g/cm{sup 3}. In this density range, however, UO{sub 2} is more reactive than U{sub 3}Si{sub 2}.« less
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Fabrication and testing of U-7Mo monolithic plate fuel with Zircaloy cladding
NASA Astrophysics Data System (ADS)
Pasqualini, E. E.; Robinson, A. B.; Porter, D. L.; Wachs, D. M.; Finlay, M. R.
2016-10-01
Nuclear fuel designs are being developed to replace highly enriched fuel used in research and test reactors with fuels of low enrichment. In the most challenging cases, U-(7-10 wt%)Mo monolithic plate fuels are proposed. One of the considered designs includes aluminum-alloy cladding, which provides some challenges in fabrication and fuel/cladding interaction during service. Zircaloy cladding, specifically Zry-4, was investigated as an alternative cladding, and development of a fabrication method was performed by researchers with the Comisión Nacionalde Energia Atómica (CNEA) in Argentina, resulting in test fuel plates (Zry-4 clad U-7Mo) which were subsequently tested in the Advanced Test Reactor in Idaho. Because Zry-4 and U-(7-10)Mo have similar high-temperature mechanical properties, fabrication was simplified in that the fuel foil and cladding could be co-rolled and bonded. The challenge was to prevent a thermal-expansion mismatch, which could destroy the fuel/cladding bond before complete bonding was achieved; the solution was to prevent the composites from cooling significantly during or between roll passes. The final product performed very well in-reactor, showing good bonding, very little fuel/cladding interaction-either from fabrication or in-reactor testing-and little swelling, especially no detectable heterogeneous bubble formation at the fuel/cladding interface tested to a fission density of up to 2.7E+21 (average) fissions/cm3, 3.8E+21 (peak).
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Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2
NASA Technical Reports Server (NTRS)
Ray, Ranjan; Jha, Sunil C.
1987-01-01
Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.
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NASA Astrophysics Data System (ADS)
Dobriţa, S.; Istrate, B.; Cimpoeşu, N.; Stanciu, S.; Apostol, V.; Cimpoeşu, R.; Ioniţă, I.; Paraschiv, P.
2018-06-01
The class of biomaterials (metallic, polymer or ceramics) has applications as implants with a temporary function. Among magnezium (high corrosion rate) and iron (slow corrosion rate) based biodegradable alloys a new class based on zinc try to fullfill the gap between the first two alloy systems concerning the degradation rate. The role of these alloys is to provide some specific characteristics for a limited period of time. In this article preliminary results based on microstructural and chemical characteristics of a Zn-Mg alloy are presented. The results were obtained using optical and electronic microscopy (MO and SEM) and dispersive energy spectroscpy (EDS) and X-ray difraction (XRD).
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The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)
NASA Technical Reports Server (NTRS)
Schuon, S. R.
1982-01-01
The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.
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Oxidation resistant Mo-Mo2B-silica and Mo-Mo2B-silicate composites for high temperature applications
NASA Astrophysics Data System (ADS)
Cochran, J. K.; Daloz, W. L.; Marshall, P. E.
2011-12-01
Development of Mo composites based on the Mo-Si-B system has been demonstrated as a possible new route to achieving a high temperature Mobased material. In this new system, the silicide phases are replaced directly with silica or other silicate materials. These composites avoid the high ductile to brittle transition temperature observed for Mo-Si-B alloys by removing the Si that exists in solid solution in Mo at equilibrium with its silicides. A variety of compositions is tested for room temperature ductility and oxidation resistance. A system based upon Mo, Mo2B, and SrO·Al2O3·(SiO2)2 is shown to possess both ductility at 80 vol.% Mo and oxidation resistance at 60 vol.%. These composites can be produced using a powder processing approach and fired to greater than 95% theoretical density with a desirable microstructure of isolated boride and silicate phases within a ductile Mo matrix.
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Rodrigues, A V; Oliveira, N T C; dos Santos, M L; Guastaldi, A C
2015-01-01
The electrochemical behavior and corrosion resistance of Ti-15Mo alloy to applications as biomaterials in solutions 0.15 mol L(-1) Ringer, 0.15 mol L(-1) Ringer plus 0.036 mol L(-1) NaF and 0.036 mol L(-1) NaF (containing 1,500 ppm of fluoride ions, F(-)) were investigated using open-circuit potential, cyclic voltammetry, and electrochemical impedance spectroscopy techniques, X-ray photoelectron spectroscopy and scanning electron microscope. Corrosion resistance and electrochemical stability of the Ti-15Mo alloy decreased in solutions containing F(-) ions. In all cases, there were formation and growth of TiO2 and MoO3 (a protector film), not being observed pitting corrosion, which might enable Ti-15Mo alloys to be used as biomedical implant, at least in the studied conditions, since the electrochemical stability and corrosion resistance of the passive films formed are necessary conditions for osseointegration.
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Effects of hot-salt stress corrosion on titanium alloys.
NASA Technical Reports Server (NTRS)
Gray, H. R.
1972-01-01
Susceptibility of titanium alloys to hot-salt stress-corrosion cracking increased as follows: Ti-2Al-11Sn-5Zr-1Mo-0.2Si (679), Ti-6Al-2Sn-4Zr-2Mo (6242), Ti-6Al-4V (64), Ti-6Al-4V-3Co (643), Ti-8Al-1Mo-1V (811), and Ti-13V-11Cr-3Al (13-11-3). The Ti-5Al-6Sn-2Zr-1Mo-0.25Si (5621S) alloy was both the least and most susceptible, depending on heat treatment. Such rankings can be drastically altered by heat-to-heat variations and processing conditions. Residual compressive stresses reduce susceptibility to stress-corrosion. Detection of substantial concentrations of hydrogen in all corroded alloys confirmed the generality of a previously proposed hydrogen embrittlement mechanism.
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Laser surface processing on sintered PM alloys
NASA Astrophysics Data System (ADS)
Reiter, Wilfred; Daurelio, Giuseppe; Ludovico, Antonio D.
1997-08-01
Usually the P.M. alloys are heat treated like case hardening, gas nitriding or plasma nitriding for a better wear resistance of the product surface. There is an additional method for gaining better tribological properties and this is the surface hardening (or remelting or alloying) of the P.M. alloy by laser treatment on a localized part of the product without heating the whole sample. This work gives a cured experimentation about the proper sintering powder alloys for laser surface processing from the point of view of wear, fatigue life and surface quality. As concerns the materials three different basic alloy groups with graduated carbon contents were prepared. Regarding these sintered powder alloys one group holds Fe, Mo and C and other group holds Fe, Ni, Mo and C and the last one holds Fe, Ni, Cu, Mo and C contents. Obviously each group has a different surface hardness, different porosity distribution, different density and diverse metallurgical structures (pearlite or ferrite-pearlite, etc.). ON the sample surfaces a colloidal graphite coating, in different thicknesses, has been sprayed to increase laser energy surface absorption. On some other samples a Mo coating, in different thicknesses, has been produced (on the bulk alloy) by diverse deposition techniques (D.C. Sputtering, P.V.D. and Flame Spraying). Only a few samples have a Mo coating and also an absorber coating, that is a bulk material- Mo and a colloidal graphite coating. All these sintered alloys have been tested by laser technology; so that, many laser working parameters (covering gas, work-speed, focussed and defocussed spot, rastered and integrated beam spots, square and rectangular beam shapes and so on) have been experimented for two different processes at constant laser power and at constant surface temperature (by using a temperature surface sensor and a closed controlled link). For all experiments a transverse fast axial flow CO2 2.5 kW c.w. laser source has been employed.
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Vajpai, Sanjay Kumar; Sawangrat, Choncharoen; Yamaguchi, Osamu; Ciuca, Octav Paul; Ameyama, Kei
2016-01-01
In the present work, Co-Cr-Mo alloy compacts with a unique bimodal microstructural design, harmonic structure design, were successfully prepared via a powder metallurgy route consisting of controlled mechanical milling of pre-alloyed powders followed by spark plasma sintering. The harmonic structured Co-Cr-Mo alloy with bimodal grain size distribution exhibited relatively higher strength together with higher ductility as compared to the coarse-grained specimens. The harmonic Co-Cr-Mo alloy exhibited a very complex deformation behavior wherein it was found that the higher strength and the high retained ductility are derived from fine-grained shell and coarse-grained core regions, respectively. Finally, it was observed that the peculiar spatial/topological arrangement of stronger fine-grained and ductile coarse-grained regions in the harmonic structure promotes uniformity of strain distribution, leading to improved mechanical properties by suppressing the localized plastic deformation during straining. Copyright © 2015 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Li, Jin-Feng; Wang, Xin; Liu, Xue; Zhao, Shao-Fan; Yao, Ke-Fu
2018-01-01
The effect of fluxing treatment on the properties of Fe66Co15Mo1P7.5C5.5B2Si3bulk amorphous alloy (BAA) has been investigated. Prepared by a combination method of flux treatment and water quenching, the Fe66Co15Mo1P7.5C5.5B2Si3 BAA exhibits better glass-forming ability, thermal stability, soft magnetic properties and ductility than those of the one prepared by direct water quenching. This indicates that fluxing treatment can play a potential role in improving the properties of Fe-based BAA due to the effective elimination of the impurities within the alloy.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Tsipas, Sophia A., E-mail: stsipas@ing.uc3m.es; Go
Wear and high temperature oxidation resistance of some titanium-based alloys needs to be enhanced, and this can be effectively accomplished by surface treatment. Molybdenizing is a surface treatment where molybdenum is introduced into the surface of titanium alloys causing the formation of wear-resistant surface layers containing molybdenum, while aluminizing of titanium-based alloys has been reported to improve their high temperature oxidation properties. Whereas pack cementation and other surface modification methods have been used for molybdenizing or aluminizing of wrought and/or cast pure titanium and titanium alloys, such surface treatments have not been reported on titanium alloys produced by powder metallurgymore » (PM). Also a critical understanding of the process parameters for simultaneous one step molybdeno-aluminizing of titanium alloys by pack cementation and the predominant mechanism for this process have not been reported. The current research work describes the surface modification of titanium and Ti-6Al-4V prepared by PM by molybdeno-aluminizing and analyzes thermodynamic aspects of the deposition process. Similar coatings are also deposited to wrought Ti-6Al-4V and compared. Characterization of the coatings was carried out using scanning electron microscopy and x-ray diffraction. For both titanium and Ti-6Al-4V, the use of a powder pack containing ammonium chloride as activator leads to the deposition of molybdenum and aluminium into the surface but also introduces nitrogen causing the formation of a thin titanium nitride layer. In addition, various titanium aluminides and mixed titanium aluminium nitrides are formed. The appropriate conditions for molybdeno-aluminizing as well as the phases expected to be formed were successfully determined by thermodynamic equilibrium calculations. - Highlights: •Simultaneous co-deposition of Mo-Al onto powder metallurgy and wrought Ti alloy •Thermodynamic calculations were used to optimize deposition conditions •External TiN and internal a Mo-rich layer on all alloy substrates •Titanium aluminides and Ti-Al mixed nitrides are formed on Ti-6Al-4V •The presence of Al and V alloying elements modifies the diffusion of Mo.« less
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Microstructural Characteristics of HIP-bonded Monolithic Nuclear Fuels with a Diffusion Barrier
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jan-Fong Jue; Dennis D. Keiser, Jr.; Cynthia R. Breckenridge
Due to the limitation of maximum uranium load achievable by dispersion fuel type, the Global Threat Reduction Initiative (GTRI) is developing an advanced monolithic fuel to convert US high performance research reactors to low-enriched uranium. Hot-isostatic-press bonding was the single process down-selected to bond monolithic U-Mo fuel meat to aluminum alloy cladding. A diffusion barrier was applied to the U–Mo fuel meat by roll-bonding process to prevent extensive interaction between fuel meat and aluminum-alloy cladding. Microstructural characterization was performed on fresh fuel plates fabricated at Idaho National Laboratory. Interfaces between fuel meat, cladding, and diffusion barrier, as well as U–10Momore » fuel meat and Al–6061 cladding were characterized by scanning electron microscopy. Preliminary results indicate that the interfaces contain many different phases while decomposition, second phases, and chemical banding were also observed in the fuel meat. The important attributes of the HIP-bonded monolithic fuel are • A typical Zr diffusion barrier of thickness 25 µm • Transverse cross section that exhibits relatively equiaxed grains with an average grain diameter of 10 µm • Chemical banding, in some areas more than 100 µm in length, that is very pronounced in longitudinal (i.e., rolling) direction with Mo concentration varying from 7–13 wt% • Decomposed areas containing plate-shaped low-Mo phase • A typical Zr/cladding interaction layer of thickness 1-2 µm • A visible UZr2 bearing layer of thickness 1-2 µm • Mo-rich precipitates (mainly Mo2Zr, forming a layer in some areas) followed by a Mo-depleted sub-layer between the visible UZr2-bearing layer and the U–Mo matrix • No excessive interaction between cladding and the uncoated fuel edge • Cladding-to-cladding bonding that exhibits no cracks or porosity with second phases high in Mg, Si, and O decorating the bond line. • Some of these attributes might be critical to the irradiation performance of monolithic U-10Mo nuclear fuel. There are several issues or concerns that warrant more detailed study, such as precipitation along cladding-to-cladding bond line, chemical banding, uncovered fuel-zone edge, and interaction layer between U–Mo fuel meat and zirconium. Future post-irradiation examination results will focus, among other things, on identifying in-reactor failure mechanisms and, eventually, directing further fresh fuel characterization efforts.« less
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NASA Astrophysics Data System (ADS)
Ijiri, Masataka; Yoshimura, Toshihiko
2018-02-01
Low-alloy steels are based on carbon steel in combination with several percent or less (in many cases, 1 mass%) alloying elements, and they offer improved resistance to corrosion at a cost slightly higher than that of carbon steel. However, these materials do not exhibit the same corrosion resistance as stainless steel. The authors have previously developed a novel multifunction cavitation (MFC) technique, which combines ultrasonic cavitation with water jet cavitation. In this study, MFC was used to modify the surface of Cr-Mo steel (SCM435) and Ni-Cr-Mo steel (SNCM630). MFC was found to improve the residual stress value of the material as the result of surface modification while also imparting high strength and superior corrosion resistance.
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NASA Astrophysics Data System (ADS)
Sheng, L. Y.; Du, B. N.; Guo, J. T.
2017-01-01
NiAl based materials has been considered as most potential candidate of turbine blade, due to its excellent high-temperature properties. However the bad room-temperature properties handicap its application. In the present paper, the zirconium doped NiAl/Cr(Mo) hypoeutectic alloy is fabricated by conventional casting and injection casting technology to improve its room-temperature properties. The microstructure and compressive properties at different temperatures of the conventionally-cast and injection-cast were investigated. The results exhibit that the conventionally-cast alloy comprises coarse primary NiAl phase and eutectic cell, which is dotted with irregular Ni2AlZr Heusler phase. Compared with the conventionally-cast alloy, the injection-cast alloy possesses refined the primary NiAl, eutectic cell and eutectic lamella. In addition, the Ni2AlZr Heusler phase become smaller and distribute uniformly. Moreover, the injection casting decrease the area fraction of primary NiAl phase at the cell interior or cell boundaries. The compressive ductility and yield strength of the injection-cast alloy at room temperature increase by about 100% and 35% over those of conventionally-cast alloy, which should be ascribed to the microstructure optimization.
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Microstructure of as atomized and annealed U-Mo7 particles: A SEM/EBSD study of grain growth
NASA Astrophysics Data System (ADS)
Iltis, X.; Zacharie-Aubrun, I.; Ryu, H. J.; Park, J. M.; Leenaers, A.; Yacout, A. M.; Keiser, D. D.; Vanni, F.; Stepnik, B.; Blay, T.; Tarisien, N.; Tanguy, C.; Palancher, H.
2017-11-01
Significant progresses in the performances under in-pile irradiation of particular U-Mo based fuels have been observed over the last fifteen years. One of the remaining issues has still to be tackled for use as a LEU fuel in the high power research reactors: the U-Mo recrystallization and its associated swelling have to be controlled or delayed. One way to mitigate this problem would be to optimize the initial microstructure of U-Mo atomized particle, by homogenizing Mo concentration and increasing grain size. This paper mainly focuses on U-Mo grain growth. Based on samples prepared in the framework of KOMO-5 and EMPIrE tests, a methodological work based on the use of EBSD is presented. In particular, surface preparation procedures are proposed for powders and rods, this last one being most likely readily applicable for plate analysis. As-atomized microstructures are analyzed in detail and subsequently compared to those obtained on particles annealed at 1000 °C under various conditions. It is found that 1 h annealing under vacuum is a good compromise of temperature and time to meet the development goals, provided that few impurity precipitates are present within U-Mo particles, since these can impact grain growth.
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2005-02-16
alloy is also given. The solidification mode of martensitic samples has been omitted and replaced with ’M’. Mo Ni +Cr Cr Ni ... alloys composed predominately of austenite. The four solidification modes present in the remaining 64 alloys , in order of increasing Cr/ Ni content, were...result in Fe- Ni -Cr-Mo alloys from the arc-melt condition. Solidification Solidification Primar- Secondar- Final microstrncture Mode
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NASA Astrophysics Data System (ADS)
Hamdani, Fethi; Das, Nishith K.; Shoji, Tetsuo
2018-06-01
The design of ultra-high purity (UHP) Fe-based model alloys for advanced ultra-supercritical (A-USC) technology is attempted in this work. Creep testing has been performed in air at 700 °C and a stress level of 150 MPa. Analysis of the fracture surface and cross section of the crept specimen was performed. To evaluate the oxidation resistance in A-USC conditions, oxidation testing was performed in supercritical water (SCW) at 700 °C and 25 MPa. Weight gain (WG) measurements and meticulous characterization of the oxide scale were carried out. Based on thermodynamics and density functional theory calculations, some reactive elements in the Fe-Cr-Ni system were designated to promote precipitation strengthening and to improve the hydrogen-accelerated oxidation resistance. The addition of a 2 wt pct Mo into Fe-22Cr-22Ni-0.6Nb wt pct-based matrix did not significantly improve the creep resistance. The addition of 0.26 wt pct Zr coupled with cold working was effective for improving creep properties. The Mo-modified model alloy showed almost the same WG value as SUS310, while the Zr-modified alloy showed a higher WG value. Meanwhile, a Cr-enriched continuous oxide layer was formed at the oxidation front of the Zr-modified alloy and SUS310S after exposure to SCW conditions.
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NASA Astrophysics Data System (ADS)
Hamdani, Fethi; Das, Nishith K.; Shoji, Tetsuo
2018-03-01
The design of ultra-high purity (UHP) Fe-based model alloys for advanced ultra-supercritical (A-USC) technology is attempted in this work. Creep testing has been performed in air at 700 °C and a stress level of 150 MPa. Analysis of the fracture surface and cross section of the crept specimen was performed. To evaluate the oxidation resistance in A-USC conditions, oxidation testing was performed in supercritical water (SCW) at 700 °C and 25 MPa. Weight gain (WG) measurements and meticulous characterization of the oxide scale were carried out. Based on thermodynamics and density functional theory calculations, some reactive elements in the Fe-Cr-Ni system were designated to promote precipitation strengthening and to improve the hydrogen-accelerated oxidation resistance. The addition of a 2 wt pct Mo into Fe-22Cr-22Ni-0.6Nb wt pct-based matrix did not significantly improve the creep resistance. The addition of 0.26 wt pct Zr coupled with cold working was effective for improving creep properties. The Mo-modified model alloy showed almost the same WG value as SUS310, while the Zr-modified alloy showed a higher WG value. Meanwhile, a Cr-enriched continuous oxide layer was formed at the oxidation front of the Zr-modified alloy and SUS310S after exposure to SCW conditions.
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A model to predict thermal conductivity of irradiated U-Mo dispersion fuel
NASA Astrophysics Data System (ADS)
Burkes, Douglas E.; Huber, Tanja K.; Casella, Andrew M.
2016-05-01
Numerous global programs are focused on the continued development of existing and new research and test reactor fuels to achieve maximum attainable uranium loadings to support the conversion of a number of the world's remaining high-enriched uranium fueled reactors to low-enriched uranium fuel. Some of these programs are focused on assisting with the development and qualification of a fuel design that consists of a uranium-molybdenum (U-Mo) alloy dispersed in an aluminum matrix as one option for reactor conversion. Thermal conductivity is an important consideration in determining the operational temperature of the fuel and can be influenced by interaction layer formation between the dispersed phase and matrix and upon the concentration of the dispersed phase within the matrix. This paper extends the use of a simple model developed previously to study the influence of interaction layer formation as well as the size and volume fraction of fuel particles dispersed in the matrix, Si additions to the matrix, and Mo concentration in the fuel particles on the effective thermal conductivity of the U-Mo/Al composite during irradiation. The model has been compared to experimental measurements recently conducted on U-Mo/Al dispersion fuels at two different fission densities with acceptable agreement. Observations of the modeled results indicate that formation of an interaction layer and subsequent consumption of the matrix reveals a rather significant effect on effective thermal conductivity. The modeled interaction layer formation and subsequent consumption of the high thermal conductivity matrix was sensitive to the average dispersed fuel particle size, suggesting this parameter as one of the most effective in minimizing thermal conductivity degradation of the composite, while the influence of Si additions to the matrix in the model was highly dependent upon irradiation conditions.
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Brady, Michael P.; Muralidharan, Govindarajan; Leonard, Donovan .; ...
2014-08-29
Here, the oxidation behavior of SiMo cast iron, Ni-resist D 5S cast iron, cast chromia-forming austenitic stainless steels of varying Cr/Ni content based on CF8C plus, HK, and HP, and a developmental cast alumina-forming austenitic (AFA) stainless steel of interest for diesel exhaust system components were studied for up to 5000 h at 650-800 °C in air with 10% H 2O. At 650 °C, the Ni-resist D5S exhibited moderately better oxidation resistance than did the SiMo cast iron. However, the D5S suffered from oxide scale spallation issues at 700 °C and higher, whereas the oxide scales formed on SiMo castmore » iron remained adherent from 700-800 °C despite oxide scales hundreds of microns thick. The oxidation of the SiMo cast iron exhibited unusual temperature dependence, with periods of slower oxidation kinetics at 750-800 °C compared to 650-700 °C due to continuous silica-rich scale formation at the higher temperatures. The oxidation of the cast chromia-forming austenitics trended with the level of Cr and Ni additions, with small mass losses consistent with Cr oxy-hydroxide volatilization processes for the higher 25Cr/25-35Ni HK and HP type alloys, and transition to rapid Fe-base oxide formation and scale spallation in the lower 19Cr/12Ni CF8C plus type alloy. In contrast, small positive mass changes consistent with protective alumina scale formation were observed for the cast AFA alloy under all conditions studied. Implications of these findings for diesel exhaust system components are discussed.« less
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Effect of Aluminum Alloying on the Hot Deformation Behavior of Nano-bainite Bearing Steel
NASA Astrophysics Data System (ADS)
Yang, Z. N.; Dai, L. Q.; Chu, C. H.; Zhang, F. C.; Wang, L. W.; Xiao, A. P.
2017-12-01
Interest in using aluminum in nano-bainite steel, especially for high-carbon bearing steel, is gradually growing. In this study, GCr15SiMo and GCr15SiMoAl steels are introduced to investigate the effect of Al alloying on the hot deformation behavior of bearing steel. Results show that the addition of Al not only notably increases the flow stress of steel due to the strong strengthening effect of Al on austenite phase, but also accelerates the strain-softening rates for its increasing effect on stacking fault energy. Al alloying also increases the activation energy of deformation. Two constitutive equations with an accuracy of higher than 0.99 are proposed. The constructed processing maps show the expanded instability regions for GCr15SiMoAl steel as compared with GCr15SiMo steel. This finding is consistent with the occurrence of cracking on the GCr15SiMoAl specimens, revealing that Al alloying reduces the high-temperature plasticity of the bearing steel. On the contrary, GCr15SiMoAl steel possesses smaller grain size than GCr15SiMo steel, manifesting the positive effect of Al on bearing steel. Attention should be focused on the hot working process of bearing steel with Al.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Takida, T.; Mabuchi, M.; Nakamura, M.
2000-03-01
The tensile properties of a ZrC particle-dispersed Mo, which was processed by spark plasma sintering with mechanically alloyed powder, were investigated at room temperature and at elevated temperatures of 1,170 to 1,970 K. The Mo-ZrC alloy showed much higher strength at room temperature than a fully recrystallized pure Mo. The high strength of Mo-ZrC is mainly attributed to a very small grain size (about 3 {micro}m). The main role of the ZrC particle is not to increase strength due to the particle-dislocation interaction, but to limit grain growth during sintering and to attain the very small grain size. The elongationmore » at room temperature of No-ZrC was much lower than that of pure Mo. This is probably related to the higher interstitial contents. However, Mo-ZrC showed a large elongation of 180 pct at 1,970 K and 6.7 x 10{sup {minus}4} s{sup {minus}1}. It was suggested that the ZrC particles stabilized the fine-grained microstructure yet provided no cavitation sites at 1,970 K; as a result, the large elongation was attained.« less
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Interaction of Al with O2 exposed Mo2BC
NASA Astrophysics Data System (ADS)
Bolvardi, Hamid; Music, Denis; Schneider, Jochen M.
2015-03-01
A Mo2BC(0 4 0) surface was exposed to O2. The gas interaction was investigated using ab initio molecular dynamics and X-ray photoelectron spectroscopy (XPS) of air exposed surfaces. The calculations suggest that the most dominating physical mechanism is dissociative O2 adsorption whereby Mosbnd O, Osbnd Mosbnd O and Mo2sbnd Csbnd O bond formation is observed. To validate these results, Mo2BC thin films were synthesized utilizing high power pulsed magnetron sputtering and air exposed surfaces were probed by XPS. MoO2 and MoO3 bond formation is observed and is consistent with here obtained ab initio data. Additionally, the interfacial interactions of O2 exposed Mo2BC(0 4 0) surface with an Al nonamer is studied with ab initio molecular dynamics to describe on the atomic scale the interaction between this surface and Al to mimic the interface present during cold forming processes of Al based alloys. The Al nonamer was disrupted and Al forms chemical bonds with oxygen contained in the O2 exposed Mo2BC(0 4 0) surface. Based on the comparison of here calculated adsorption energy with literature data, Alsbnd Al bonds are shown to be significantly weaker than the Alsbnd O bonds formed across the interface. Hence, Alsbnd Al bond rupture is expected for a mechanically loaded interface. Therefore the adhesion of a residual Al on the native oxide layer is predicted. This is consistent with experimental observations. The data presented here may also be relevant for other oxygen containing surfaces in a contact with Al or Al based alloys for example during forming operations.
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Development of β Type Ti23Mo-45S5 Bioglass Nanocomposites for Dental Applications
Jurczyk, Karolina; Miklaszewski, Andrzej; Jurczyk, Mieczyslawa U.; Jurczyk, Mieczyslaw
2015-01-01
Titanium β-type alloys attract attention as biomaterials for dental applications. The aim of this work was the synthesis of nanostructured β type Ti23Mo-x wt % 45S5 Bioglass (x = 0, 3 and 10) composites by mechanical alloying and powder metallurgy methods and their characterization. The crystallization of the amorphous material upon annealing led to the formation of a nanostructured β type Ti23Mo alloy with a grain size of approximately 40 nm. With the increase of the 45S5 Bioglass contents in Ti23Mo, nanocomposite increase of the α-phase is noticeable. The electrochemical treatment in phosphoric acid electrolyte resulted in a porous surface, followed by bioactive ceramic Ca-P deposition. Corrosion resistance potentiodynamic testing in Ringer solution at 37 °C showed a positive effect of porosity and Ca-P deposition on nanostructured Ti23Mo 3 wt % 45S5 Bioglass nanocomposite. The contact angles of glycerol on the nanostructured Ti23Mo alloy were determined and show visible decrease for bulk Ti23Mo 3 wt % 45S5 Bioglass and etched Ti23Mo 3 wt % 45S5 Bioglass nanocomposites. In vitro tests culture of normal human osteoblast cells showed very good cell proliferation, colonization, and multilayering. The present study demonstrated that porous Ti23Mo 3 wt % 45S5 Bioglass nanocomposite is a promising biomaterial for bone tissue engineering. PMID:28793695
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Fe-based bulk amorphous alloys with iron contents as high as 82 at%
NASA Astrophysics Data System (ADS)
Li, Jin-Feng; Liu, Xue; Zhao, Shao-Fan; Ding, Hong-Yu; Yao, Ke-Fu
2015-07-01
Fe-based bulk amorphous alloys (BAAs) with high Fe contents are advantageous due to their high saturation magnetization and low cost. However, preparing Fe-based BAAs with Fe contents higher than 80 at% is difficult due to their poor glass forming abilities (GFA). In this study, an Fe81P8.5C5.5B2Si3 BAA with a diameter of 1 mm and a saturation magnetization of 1.56 T was successfully prepared using the fluxing and copper mold casting methods. In addition, by introducing a small amount of elemental Mo to the alloy, an Fe82Mo1P6.5C5.5B2Si3 BAA rod with a diameter of 1 mm, a high saturation magnetization of 1.59 T, a high yield stress of 3265 MPa, and a clear plasticity of 1.3% was prepared in the same way. The cost effectiveness and good magnetic properties of these newly-developed Fe-based BAAs with Fe contents as high as 82 at% would be advantageous and promising for industrial applications.
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Wang, C C; Hsu, C S
1996-06-01
The use of base metal alloys for porcelain fused to a metal crown and bridges has increased recently because of lower price, high hardness, high tensile strength and high elastic modulus. The addition of beryllium to base metal alloys increased fluidity and improved casting fitness. Beryllium also controlled surface oxidation and bonding strength. The bonding agent and gold bonding agent also affected the bonding strength between porcelain and metal alloys. Four commercially available ceramic base alloys were studied (two alloys contained beryllium element, another two did not). The purpose of this investigation was to study the microstructure between porcelain matrix, bonding agent and alloy matrix interfaces. A scanning electron micro-probe analyzer and energy dispersive X-ray spectroscopy (EDXS) were used to study the distribution of elements (Ni, Cr, Mo, Cu, O, Si, Sn, Al) in four base alloys. The following results were obtained: 1. The thickness of the oxidized layer of Rexillium III alloy and Unitbond alloy (contained beryllium) was thinner than Unibond alloy and Wiron 88 alloy (no beryllium). 2. The thickness of the oxidized layer of alloys in air (10 minutes and 30 minutes) was thinner in Unitbond (2.45 microns and 3.80 microns) and thicker in Wiron 88 (4.39 microns and 5.96 microns). 3. The thickness of the oxidized layer occurring for a duration of ten minutes (in vaccum) showed that the Rexillium III alloy was the thinnest (1.93 microns), and Wiron 88 alloy was the thickest (2.30 microns). But in thirty minutes (vacuum), Unitbond alloy was the thinnest (3.37 microns), and Wiron 88 alloy was the thickest (5.51 microns). 4. The intensity of Cr elements was increased obviously near the interface between Unitbond alloy, Wiron 88 alloy (no beryllium) and oxidized layer, but the intensity of Ni and Mo elements was slightly increased. The intensity of Cr element was not increased markedly between Rexillium III alloy, Unitbond alloy (beryllium) and oxidized layer. 5. A white-grayish oxidized layer appeared at the metal-ceramic interfaces but the thickness of oxidized layer was not obviously different. 6. The use of bonding agent at metal-ceramic interface leads to the deposition of many Sn elements at about 40 microns range within the porcelain surface. 7. Second interaction phases at the porcelain layer appeared when gold bonding agent was used, and a 50-100 microns microleakage occurred at the metal-ceramic interface.
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Mechanically Activated Combustion Synthesis of MoSi 2-Based Composites
DOE Office of Scientific and Technical Information (OSTI.GOV)
Shafirovich, Evgeny
2015-09-30
The thermal efficiency of gas-turbine power plants could be dramatically increased by the development of new structural materials based on molybdenum silicides and borosilicides, which can operate at temperatures higher than 1300 °C with no need for cooling. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. One approach is based on the fabrication of MoSi2-Mo5Si3 composites that combine high oxidation resistance of MoSi2 and good mechanical properties of Mo5Si3. Another approach involves the addition of boron to Mo-rich silicides for improving their oxidation resistance through the formation of a borosilicatemore » surface layer. In particular, materials based on Mo5SiB2 phase are promising materials that offer favorable combinations of high temperature mechanical properties and oxidation resistance. However, the synthesis of Mo-Si-B multi-phase alloys is difficult because of their extremely high melting temperatures. Mechanical alloying has been considered as a promising method, but it requires long milling times, leading to large energy consumption and contamination of the product by grinding media. In the reported work, MoSi2-Mo5Si3 composites and several materials based on Mo5SiB2 phase have been obtained by mechanically activated self-propagating high-temperature synthesis (MASHS). Short-term milling of Mo/Si mixture in a planetary mill has enabled a self-sustained propagation of the combustion front over the mixture pellet, leading to the formation of MoSi2-T1 composites. Combustion of Mo/Si/B mixtures for the formation of T2 phase becomes possible if the composition is designed for the addition of more exothermic reactions leading to the formation of MoB, TiC, or TiB2. Upon ignition, Mo/Si/B and Mo/Si/B/Ti mixtures exhibited spin combustion, but the products were porous, contained undesired secondary phases, and had low oxidation resistance. It has been shown that use of SHS compaction (quasi-isostatic pressing after combustion) significantly improves oxidation resistance of the obtained MoSi2-Mo5Si3 composites. The “chemical oven” technique has been successfully employed to fabricate low-porous Mo5SiB2–TiC, Mo5SiB2–TiB2, and Mo–Mo5SiB2–Mo3Si materials. Among them, Mo5SiB2–TiB2 material possesses good mechanical properties and simultaneously exhibits excellent oxidation resistance at temperatures up to 1500 °C.« less
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NASA Astrophysics Data System (ADS)
Eason, Paul Duane
The Mo(Si,Al)2 C40 compound was chosen for investigation as a possible high temperature structural material. To produce the C40 phase, several processing routes were explored with emphasis on obtaining microstructure/property relationships (i.e. control of grain size and minimization of secondary phases). To facilitate processing of single phase material, the phase equilibria of the Mo-Si-Al ternary system were reevaluated with respect to the phases adjacent to the C40 compound. An anomalous environmental degradation appeared to be the primary obstacle to further study of the compound and was investigated accordingly. Several processing routes were assessed for the production of dense, nearly single-phase Mo(Si,Al)2. Hot powder compaction was chosen as the method of sample production as is the case with many refractory silicide based materials. Therefore, variations in the processing techniques came from the choice of precursor materials and methods of powder production. Mechanical alloying, arc-melting and comminution, and blending of both elemental and compound powders were all employed to produce charges for hot uniaxial pressing. The final compacts were compared on the basis of density, grain size and presence of secondary phases. Establishment of a Mo-Si-Al ternary isothermal phase diagram at 1400°C was performed. Multiphase alloy compositions were selected to identify the phase boundaries of the C40, C54, T1 and Mo3Al8 phase fields, as well as to verify the existence of the C54 phase at 1400°C. The alloys were equilibrated by heat treatment and analyzed for phase identification and quantitative compositional information. The environmental degradation phenomenon was approached as a classical "pest" with an emphasis of study on grain boundary chemistry and atmospheric dependence of attack. Both Auger spectroscopy and electron microscopy revealed carbon-impurity-induced grain boundary segregation responsible for the embrittlement and material loss. Means of preventing the attack by alloying techniques used in traditional alloys were explored.
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NASA Technical Reports Server (NTRS)
Smeggil, J. G.; Bornstein, N. S.
1983-01-01
Thermogravimetric, metallographic, and X-ray studies of a model alloy, Ni-(17 a/o)Al-(10 a/o)Mo+W, oxidized in dry air at 600-1200 C and in air with 10 ppm NaCl gas at 900 C, are reported. The alloy was melted under Ar and pretreated in flowing H2 for 24 h at 1300 C. Polished 1.3 x 1.3 x 0.2-cm specimens were washed and degreased prior to oxidation in a quartz tube within a furnace for up to 120 hr. The oxidation activation energy of the alloy is determined to be about 30 kcal/mole. The specimens oxidized at 900 C and hotter exhibited oxidized and nitrided phases covered by complex NiMoO4, NiWO4, and NiAl2O4 scales and a porous, nonprotective outer layer of NiO. The oxidation behavior is found to be determined by the formation and growth of the scale, especially the (Mo,W)O2 component. Al2O3 scale layers were not formed, and further runs with pure O2 or Ar-(20 percent)O2 ruled out an explanation of this phenomenon based on aluminum nitride formation. The oxidation was accelerated by the addition of NaCl gas, a finding attributed to the reaction of NaCl with external locally protective Al2O3 scales and with the internal(Mo, W)O2 layers.
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Silicide Coating Fabricated by HAPC/SAPS Combination to Protect Niobium Alloy from Oxidation.
Sun, Jia; Fu, Qian-Gang; Guo, Li-Ping; Wang, Lu
2016-06-22
A combined silicide coating, including inner NbSi2 layer and outer MoSi2 layer, was fabricated through a two-step method. The NbSi2 was deposited on niobium alloy by halide activated pack cementation (HAPC) in the first step. Then, supersonic atmospheric plasma spray (SAPS) was applied to obtain the outer MoSi2 layer, forming a combined silicide coating. Results show that the combined coating possessed a compact structure. The phase constitution of the combined coating prepared by HAPC and SAPS was NbSi2 and MoSi2, respectively. The adhesion strength of the combined coating increased nearly two times than that for single sprayed coating, attributing to the rougher surface of the HAPC-bond layer whose roughness increased about three times than that of the grit-blast substrate. After exposure at 1200 °C in air, the mass increasing rate for single HAPC-silicide coating was 3.5 mg/cm(2) because of the pest oxidation of niobium alloy, whereas the combined coating displayed better oxidation resistance with a mass gain of only 1.2 mg/cm(2). Even more, the combined coating could significantly improve the antioxidation ability of niobium based alloy at 1500 °C. The good oxidation resistance of the combined silicide coating was attributed to the integrity of the combined coating and the continuous SiO2 protective scale provided by the oxidation of MoSi2.
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Summer, Burkhard; Fink, Ulrich; Zeller, Richard; Rueff, Franziska; Maier, Sonja; Roider, Gabriele; Thomas, Peter
2007-07-01
Nickel, chromium, and cobalt released from stainless steel and CoCrMo alloys have been postulated to trigger hypersensitivity reactions. The objective of this study was to assess the ion release from a CoCrMo alloy and stainless steel in vitro and the cutaneous reactivity to it by patch test. 52 metal-allergic patients and 48 non-allergic controls were patch tested to stainless steel and CoCrMo discs. In addition, using atomic absorption spectrometry, the release of nickel, cobalt, and chromium from both materials was assessed upon 2-day exposure to distilled water, artificial sweat (AS), and cell culture medium. There was low nickel ion release from stainless steel (0.3-0.46 microg/cm(2)/2 days) and CoCrMo discs (up to 0.33 microg/cm(2)/2 days) into the different elution media. Chromium release from the 2 materials was also very low (0.06-0.38 microg/cm(2)/2 days from stainless steel and 0.52-1.36 microg/cm(2)/2 days from CoCrMo alloy). In contrast, AS led to abundant cobalt release (maximally 18.94 microg/cm(2)/2 days) from the CoCrMo discs, with concomitant eczematous reaction upon patch testing: 0 of the 52 metal-allergic patients reacted to stainless steel discs and 5 of the 52 patients to CoCrMo discs (all 5 patients were cobalt allergic and 3 also nickel and chromium allergic). None of the controls reacted to the discs. Apart from nickel being a focus of allergological research, our results point to the possibly underestimated association of cobalt release and potential hyperreactivity to CoCrMo alloy.
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Structural, electronic, magnetic and optical properties of semiconductor Zn1-xMoxTe compound
NASA Astrophysics Data System (ADS)
Feng, Zhong-Ying; Zhang, Jian-Min
2018-03-01
The structural, electronic, magnetic and optical properties of the Zn1-xMoxTe (x = 0.00, 0.25, 0.50, 0.75, 1.00) have been investigated by the spin-polarized first-principles calculations. The Zn0.50Mo0.50Te has tetragonal structure while the Zn1-xMoxTe (x = 0.00, 0.25, 0.75, 1.00) crystallize in cubic structures. For Zn1-xMoxTe (x = 0.25, 0.50, 0.75, 1.00) alloys, the lattice constant and the volume are found larger than those of pure ZnTe alloy. The Zn1-xMoxTe (x = 0.25, 0.50, 0.75, 1.00) is magnetic and the Mo element is found dominant in the bands crossing the Fermi level in the spin-up channel. The Zn0.75Mo0.25Te and MoTe have half-metallic (HM) behavior. In spin-down channel of the Zn0.75Mo0.25Te, the Zn atom mainly contributed to the conduction band minimum (CBM), while the valence band maximum (VBM) appears mainly due to contribution of Te element. A positive spin splitting and crystal field splitting of d-states of Mo atom has been observed for Zn0.75Mo0.25Te alloy. The maximum values of the absorption coefficients αMAX(ω) of the Zn0.50Mo0.50Te alloy along a or b axes are smaller than the absorption coefficient along c axis. The first absorption peak appearing in the energy range of 0.000-1.000 eV for Zn1-xMoxTe (x = 0.25, 0.50, 0.75 or 1.00) alloys is the new peak which is not observed in ZnTe.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Field, Kevin G.; Gussev, Maxim N.; Hu, Xunxiang
2015-09-30
The present report summarizes and discusses the recent results on developing a modern, nuclear grade FeCrAl alloy designed to have enhanced radiation tolerance and weldability. The alloys used for these investigations are modern FeCrAl alloys based on a Fe-13Cr-5Al-2Mo-0.2Si-0.05Y alloy (in wt.%, designated C35M). Development efforts have focused on assessing the influence of chemistry and microstructure on the fabricability and performance of these newly developed alloys. Specific focus was made to assess the weldability, thermal stability, and radiation tolerance.
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Puskar, Tatjana; Jevremovic, Danimir; Williams, Robert J.; Eggbeer, Dominic; Vukelic, Djordje; Budak, Igor
2014-01-01
Dental alloys for direct metal laser sintering (DMLS) are available on the market today, but there is little scientific evidence reported on their characteristics. One of them is the release of ions, as an indicator of the corrosion characteristics of a dental alloy. Within this research, the difference in the elution of metals from DMLS and cast (CM) samples of Co-Cr-Mo dental alloy in saliva-like medium of three different pH was examined by inductively-coupled plasma mass spectrometry (ICP-MS). The obtained results show that the metal elution in artificial saliva from the DMLS alloy was lower than the elution from the CM alloy. The release of all investigated metal ions was influenced by the acidity, both from the DMLS and CM alloy, throughout the investigated period of 30 days. The change in acidity from a pH of 6.8 to a pH of 2.3 for the cast alloy led to a higher increase of the elution of Co, Cr and Mo from CM than from the DMLS alloy. The greatest release out of Co, Cr and Mo was for Co for both tested alloys. Further, the greatest release of all ions was measured at pH 2.3. In saliva of pH 2.3 and pH 4.5, the longer the investigated period, the higher the difference between the total metal ion release from the CM and DMLS alloys. Both alloys showed a safe level of elution according to the ISO definition in all investigated acidic environments. PMID:28788197
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Puskar, Tatjana; Jevremovic, Danimir; Williams, Robert J; Eggbeer, Dominic; Vukelic, Djordje; Budak, Igor
2014-09-11
Dental alloys for direct metal laser sintering (DMLS) are available on the market today, but there is little scientific evidence reported on their characteristics. One of them is the release of ions, as an indicator of the corrosion characteristics of a dental alloy. Within this research, the difference in the elution of metals from DMLS and cast (CM) samples of Co-Cr-Mo dental alloy in saliva-like medium of three different pH was examined by inductively-coupled plasma mass spectrometry (ICP-MS). The obtained results show that the metal elution in artificial saliva from the DMLS alloy was lower than the elution from the CM alloy. The release of all investigated metal ions was influenced by the acidity, both from the DMLS and CM alloy, throughout the investigated period of 30 days. The change in acidity from a pH of 6.8 to a pH of 2.3 for the cast alloy led to a higher increase of the elution of Co, Cr and Mo from CM than from the DMLS alloy. The greatest release out of Co, Cr and Mo was for Co for both tested alloys. Further, the greatest release of all ions was measured at pH 2.3. In saliva of pH 2.3 and pH 4.5, the longer the investigated period, the higher the difference between the total metal ion release from the CM and DMLS alloys. Both alloys showed a safe level of elution according to the ISO definition in all investigated acidic environments.
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Manifestations of Dynamic Strain Aging in Soft-Oriented NiAl Single Crystals
NASA Technical Reports Server (NTRS)
Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.
1996-01-01
The tensile and compressive properties of six NiAl-base single-crystal alloys have been investigated at temperatures between 77 and 1200 K. The normalized critical resolved shear stresses (CRSS/E) and work-hardening rates (Theta/E) for these alloys generally decreased with increasing temperature. However, anomalous peaks or plateaus for these properties were observed in conventional purity (CPNiAl), Si-doped (NiAl-Si), C-doped low Si (UF-NiAl1), and Mo-doped (NiAl-Mo) alloys at intermediate temperatures (600 to 1000 K). This anomalous behavior was not observed in high-purity, low interstitial material (HP-NiAl). Low or negative strain-rate sensitivities (SRS) also were observed in all six alloys in this intermediate temperature range. Coincident with the occurrence of negative strain-rate sensitivities was the observation of serrated stress-strain curves in the CPNiAl and NiAl-Si alloys. These phenomena have been attributed to dynamic strain aging (DSA). Chemical analysis of the alloys used in this study suggests that the main specie responsible for strain aging in NiAl is C but indicate that residual Si impurities can enhance the strain aging effects. The corresponding dislocation microstructures at low temperatures (300 to 600 K) were composed of well-defined cells. At intermediate temperatures (600 to 900 K), either poorly defined cells or coarse bands of localized slip, reminiscent of the vein structures observed in low-cycle fatigue specimens deformed in the DSA regime, were observed in conventional purity, Si-doped, and in Mo-doped alloys. In contrast, a well-defined cell structure persisted in the low interstitial, high-purity alloy. At elevated temperatures (greater than or equal to 1000 K), more uniformly distributed dislocations and sub-boundaries were observed in all alloys. These observations are consistent with the occurrence of DSA in NiAl single-crystal alloys at intermediate temperatures.
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Nickel aluminide alloy suitable for structural applications
Liu, Chain T.
1998-01-01
Alloys for use in structural applications based upon NiAl to which are added selected elements to enhance room temperature ductility and high temperature strength. Specifically, small additions of molybdenum produce a beneficial alloy, while further additions of boron, carbon, iron, niobium, tantalum, zirconium and hafnium further improve performance of alloys at both room temperature and high temperatures. A preferred alloy system composition is Ni--(49.1.+-.0.8%)Al--(1.0.+-.0.8%)Mo--(0.7.+-.0.5%)Nb/Ta/Zr/Hf--(nearly zero to 0.03%)B/C, where the % is at. % in each of the concentrations. All alloys demonstrated good oxidation resistance at the elevated temperatures. The alloys can be fabricated into components using conventional techniques.
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Alloy Effects on the Gas Nitriding Process
NASA Astrophysics Data System (ADS)
Yang, M.; Sisson, R. D.
2014-12-01
Alloy elements, such as Al, Cr, V, and Mo, have been used to improve the nitriding performance of steels. In the present work, plain carbon steel AISI 1045 and alloy steel AISI 4140 were selected to compare the nitriding effects of the alloying elements in AISI 4140. Fundamental analysis is carried out by using the "Lehrer-like" diagrams (alloy specific Lehrer diagram and nitriding potential versus nitrogen concentration diagram) and the compound layer growth model to simulate the gas nitriding process. With this method, the fundamental understanding for the alloy effect based on the thermodynamics and kinetics becomes possible. This new method paves the way for the development of new alloy for nitriding.
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Ni.sub.3 Al-based intermetallic alloys having improved strength above 850.degree. C.
Liu, Chain T.
2000-01-01
Intermetallic alloys composed essentially of: 15.5% to 17.0% Al, 3.5% to 5.5% Mo, 4% to 8% Cr, 0.04% to 0.2% Zr, 0.04% to 1.5% B, balance Ni, are characterized by melting points above 1200.degree. C. and superior strengths at temperatures above 1000.degree. C.
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Stacking-fault strengthening of biomedical Co-Cr-Mo alloy via multipass thermomechanical processing.
Yamanaka, Kenta; Mori, Manami; Sato, Shigeo; Chiba, Akihiko
2017-09-07
The strengthening of metallic biomaterials, such as Co-Cr-Mo and titanium alloys, is of crucial importance to the improvement of the durability of orthopedic implants. In the present study, we successfully developed a face-centered cubic (fcc) Co-Cr-Mo alloy with an extremely high yield strength (1400 MPa) and good ductility (12%) by multipass hot-rolling, which is suitable for industrial production, and examined the relevant strengthening mechanisms. Using an X-ray diffraction line-profile analysis, we revealed that a substantial increase in the number of stacking faults (SFs) in the fcc γ-matrix occurred at a greater height reduction (r), while physical modeling demonstrated that the contribution of the accumulated SFs (i.e., the reduction in SF spacing) with an increase in r successfully explains the entire strengthening behavior of the hot-rolled alloy. The present study sheds light on the importance of the SF strengthening mechanism, and will help to guide the design and manufacturing strategy for the high-strength Co-Cr-Mo alloys used in highly durable medical devices.
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Mori, Manami; Yamanaka, Kenta; Sato, Shigeo; Tsubaki, Shinki; Satoh, Kozue; Kumagai, Masayoshi; Imafuku, Muneyuki; Shobu, Takahisa; Chiba, Akihiko
2015-12-01
Further strengthening of biomedical Co-Cr-Mo alloys is desired, owing to the demand for improvements to their durability in applications such as artificial hip joints, spinal rods, bone plates, and screws. Here, we present a strategy-multipass "low-strain-per-pass" thermomechanical processing-for achieving high-strength biomedical Co-Cr-Mo alloys with sufficient ductility. The process primarily consists of multipass hot deformation, which involves repeated introduction of relatively small amounts of strain to the alloy at elevated temperatures. The concept was verified by performing hot rolling of a Co-28 Cr-6 Mo-0.13N (mass%) alloy and its strengthening mechanisms were examined. Strength increased monotonically with hot-rolling reduction, eventually reaching 1,400 MPa in 0.2% proof stress, an exceptionally high value. Synchrotron X-ray diffraction (XRD) line-profile analysis revealed a drastic increase in the dislocation density with an increase in hot-rolling reduction and proposed that the significant strengthening was primarily driven by the increased dislocation density, while the contributions of grain refinement were minor. In addition, extra strengthening, which originates from contributions of planar defects (stacking faults/deformation twins), became apparent for greater hot-rolling reductions. The results obtained in this work help in reconsidering the existing strengthening strategy for the alloys, and thus, a novel feasible manufacturing route using conventional hot deformation processing, such as forging, rolling, swaging, and drawing, is realized. The results obtained in this work suggested a novel microstructural design concept/feasible manufacturing route of high-strength Co-Cr-Mo alloys using conventional hot deformation processing. The present strategy focuses on the strengthening due to the introduction of a high density of lattice defects rather than grain refinement using dynamic recrystallization (DRX). The hot-rolled samples obtained by our process exhibited exceptional strength, which is comparable to the highest strength reported for biomedical Co-Cr-Mo alloys. It was also found that the acceptable ductility can be obtained even in such highly distorted Co-Cr-Mo alloys. We described the strengthening mechanisms in detail; this will be helpful for further investigations or industrial realization of the proposed strategy. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Dilawary, Shaikh Asad Ali; Motallebzadeh, Amir; Afzal, Muhammad; Atar, Erdem; Cimenoglu, Huseyin
2018-05-01
Laser surface melting (LSM) process has been applied on the plasma transferred arc (PTA) deposited Stellite 12 and 10 wt% Mo alloyed Stellite 12 in this study. Following the LSM process, structural and mechanical property comparison of the LSM'ed surfaces has been made. Hardness of the LSM'ed surfaces was measured as 549 HV and 623 HV for the Stellite 12 and Stellite 12 + 10 wt% Mo deposits, respectively. Despite their different hardness and structural features, the LSM'ed surfaces exhibited similar tribological performance at room temperature (RT), where fatigue wear mechanism operates. However, the wear at 500 °C promotes tribo-oxide layer formation whose composition depended on the alloying with Mo. Thus, addition of 10 wt% Mo into Stellite 12 PTA deposit has remarkably enhanced the high temperature wear performance of the LSM'ed surface as a result of participation of complex oxide (CoMoO4) in tribo-oxide layer.
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U-based metallic glasses with superior glass forming ability
NASA Astrophysics Data System (ADS)
Xu, Hongyang; Ke, Haibo; Huang, Huogen; Zhang, Pengguo; Pu, Zhen; Zhang, Pei; Liu, Tianwei
2018-02-01
By using Al as the third and B as the fourth but minor alloying elements for the U66.7Co33.3 basic metallic glass, a series of U-Co-Al(-B) alloys were designed. The quaternary U-Co-Al-B alloys exhibit significantly improved glass-forming ability (GFA) than previously reported U-based metallic glasses. Low fragility (∼24) is found for these new U-based metallic glasses. The improvement in GFA would result from denser atomic packing in the undercooled liquids due to the presence of small B atoms. Some U-Co-Al(-B) glasses showed corrosion resistance comparable to that of U64Co34Al2 glass, known for premium anti-corrosive performance among the unveiled U-based glasses.
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Mengucci, P; Barucca, G; Gatto, A; Bassoli, E; Denti, L; Fiori, F; Girardin, E; Bastianoni, P; Rutkowski, B; Czyrska-Filemonowicz, A
2016-07-01
Direct Metal Laser Sintering (DMLS) technology based on a layer by layer production process was used to produce a Co-Cr-Mo-W alloy specifically developed for biomedical applications. The alloy mechanical response and microstructure were investigated in the as-sintered state and after post-production thermal treatments. Roughness and hardness measurements, and tensile and flexural tests were performed to study the mechanical response of the alloy while X-ray diffraction (XRD), electron microscopy (SEM, TEM, STEM) techniques and microanalysis (EDX) were used to investigate the microstructure in different conditions. Results showed an intricate network of ε-Co (hcp) lamellae in the γ-Co (fcc) matrix responsible of the high UTS and hardness values in the as-sintered state. Thermal treatments increase volume fraction of the ε-Co (hcp) martensite but slightly modify the average size of the lamellar structure. Nevertheless, thermal treatments are capable of producing a sensible increase in UTS and hardness and a strong reduction in ductility. These latter effects were mainly attributed to the massive precipitation of an hcp Co3(Mo,W)2Si phase and the contemporary formation of Si-rich inclusions. Copyright © 2016 Elsevier Ltd. All rights reserved.
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Adsorption behavior of glycidoxypropyl-trimethoxy-silane on titanium alloy Ti-6.5Al-1Mo-1V-2Zr
NASA Astrophysics Data System (ADS)
Liu, Jian-hua; Zhan, Zhong-wei; Yu, Mei; Li, Song-mei
2013-01-01
The adsorption behavior of glycidoxypropyl-trimethoxy-silane (GTMS) on titanium alloy Ti-6.5Al-1Mo-1V-2Zr was investigated by using X-ray photoelectron spectroscopy (XPS), Tafel polarization test, and electrochemical impedance spectroscopy (EIS). From the XPS results, it was found that the silane coverage on the titanium surface generally increased with GTMS concentration, with a slight decrease at concentration of 0.1%. Based on the relationship between isoelectronic point (IEP) of titanium surface and the pH values of silane solutions, adsorption mechanisms at different concentrations were proposed. The surface coverage data of GTMS on titanium surface was also derived from electrochemical measurements. By linear fitting the coverage data, it revealed that the adsorption of GTMS on the titanium alloy surface at 30 °C was of a physisorption-based mechanism, and obeyed Langmuir adsorption isotherm. The adsorption equilibrium constant (Kads) and free energy of adsorption process (ΔGads) were calculated to elaborate the mechanism of GTMS adsorption.
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NASA Astrophysics Data System (ADS)
Wang, Qing; Dong, Chuang; Liaw, Peter K.
2015-08-01
Structural stabilities of β-Ti alloys are generally investigated by an empirical Mo equivalent, which quantifies the stability contribution of each alloying element, M, in comparison to that of the major β-Ti stabilizer, Mo. In the present work, a new Mo equivalent (Moeq)Q is proposed, which uses the slopes of the boundary lines between the β and ( α + β) phase zones in binary Ti-M phase diagrams. This (Moeq)Q reflects a simple fact that the β-Ti stability is enhanced, when the β phase zone is enlarged by a β-Ti stabilizer. It is expressed as (Moeq)Q = 1.0 Mo + 0.74 V + 1.01 W + 0.23 Nb + 0.30 Ta + 1.23 Fe + 1.10 Cr + 1.09 Cu + 1.67 Ni + 1.81 Co + 1.42 Mn + 0.38 Sn + 0.34 Zr + 0.99 Si - 0.57 Al (at. pct), where the equivalent coefficient of each element is the slope ratio of the [ β/( α + β)] boundary line of the binary Ti-M phase diagram to that of the Ti-Mo. This (Moeq)Q is shown to reliably characterize the critical stability limit of multi-component β-Ti alloys with low Young's moduli, where the critical lower limit for β stabilization is (Moeq)Q = 6.25 at. pct or 11.8 wt pct Mo.
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Electronic structure of Mo1-x Re x alloys studied through resonant photoemission spectroscopy
NASA Astrophysics Data System (ADS)
Sundar, Shyam; Banik, Soma; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Ganguli, Tapas; Lodha, G. S.; Pandey, Sudhir K.; Phase, D. M.; Roy, S. B.
2016-08-01
We studied the electronic structure of Mo-rich Mo1-x Re x alloys (0≤slant x≤slant 0.4 ) using valence band photoemission spectroscopy in the photon energy range 23-70 eV and density of states calculations. Comparison of the photoemission spectra with the density of states calculations suggests that, with respect to the Fermi level E F, the d states lie mostly in the binding energy range 0 to -6 eV, whereas s states lie in the binding energy range -4 to -10 eV. We observed two resonances in the photoemission spectra of each sample, one at about 35 eV photon energy and the other at about 45 eV photon energy. Our analysis suggests that the resonance at 35 eV photon energy is related to the Mo 4p-5s transition and the resonance at 45 eV photon energy is related to the contribution from both the Mo 4p-4d transition (threshold: 42 eV) and the Re 5p-5d transition (threshold: 46 eV). In the constant initial state plot, the resonance at 35 eV incident photon energy for binding energy features in the range E F (BE = 0) to -5 eV becomes progressively less prominent with increasing Re concentration x and vanishes for x > 0.2. The difference plots obtained by subtracting the valence band photoemission spectrum of Mo from that of Mo1-x Re x alloys, measured at 47 eV photon energy, reveal that the Re d-like states appear near E F when Re is alloyed with Mo. These results indicate that interband s-d interaction, which is weak in Mo, increases with increasing x and influences the nature of the superconductivity in alloys with higher x.
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Particle Characteristics and Densification of W6Mo5Cr4V2Co5Nb Overspray Powder
NASA Astrophysics Data System (ADS)
Pi, Ziqiang; Lu, Xin; Yang, Fei; Liu, Bowen; Jia, Chengchang; Qu, Xuanhui; Zheng, Wei; Wu, Lizhi; Shao, Qingli
2018-05-01
W6Mo5Cr4V2Co5Nb (825 K) alloy was prepared by a two-step sintering process from overspray 825 K alloy powder. The overspray powder characteristics and the microstructure and mechanical properties of the as-sintered 825 K alloy were investigated. Results showed that two types of carbides formed a network structure in the overspray powder, which had spherical or quasispherical shape: one was MC carbide that was rich in vanadium (V), and the other was M2C carbide enriched with vanadium (V) and tungsten (W). The sintered 825 K alloy contained M6C and MC carbides, of which M6C was rich in tungsten (W) and molybdenum (Mo), and both of these two carbides were uniformly distributed in the alloy matrix. The alloy had relative density of 98.43%, hardness of HRC 51.8, and superior bending strength of 2042 MPa. These mechanical properties can meet the requirements of most engineering applications.
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NASA Technical Reports Server (NTRS)
Stephens, J. R.
1975-01-01
A program was conducted to determine if aging embrittlement occurs in the columbium alloys C-103, CB-1Zr, and Cb-752 or in the molybdenum alloy Mo-TZM. Results showed that aging embrittlement does not occur in C-103, Cb-1Zr, or Mo-TZM during long-term (1000 hr) aging at temperatures in the range 700 to 1025 C. In contrast, aging embrittlement did occur in the Cb-752 alloy after similar aging at 900 C. A critical combination of the solute additions W and Zr in Cb-752 led to Zr segregation at grain boundaries during long-term aging. This segregation subsequently resulted in embrittlement as indicated by an increase in the ductile-brittle transition temperature from below -1960 C to about -150 C.
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Rhenium Alloys as Ductile Substrates for Diamond Thin-Film Electrodes.
Halpern, Jeffrey M; Martin, Heidi B
2014-02-01
Molybdenum-rhenium (Mo/Re) and tungsten-rhenium (W/Re) alloys were investigated as substrates for thin-film, polycrystalline boron-doped diamond electrodes. Traditional, carbide-forming metal substrates adhere strongly to diamond but lose their ductility during exposure to the high-temperature (1000°C) diamond, chemical vapor deposition environment. Boron-doped semi-metallic diamond was selectively deposited for up to 20 hours on one end of Mo/Re (47.5/52.5 wt.%) and W/Re (75/25 wt.%) alloy wires. Conformal diamond films on the alloys displayed grain sizes and Raman signatures similar to films grown on tungsten; in all cases, the morphology and Raman spectra were consistent with well-faceted, microcrystalline diamond with minimal sp 2 carbon content. Cyclic voltammograms of dopamine in phosphate-buffered saline (PBS) showed the wide window and low baseline current of high-quality diamond electrodes. In addition, the films showed consistently well-defined, dopamine electrochemical redox activity. The Mo/Re substrate regions that were uncoated but still exposed to the diamond-growth environment remained substantially more flexible than tungsten in a bend-to-fracture rotation test, bending to the test maximum of 90° and not fracturing. The W/Re substrates fractured after a 27° bend, and the tungsten fractured after a 21° bend. Brittle, transgranular cleavage fracture surfaces were observed for tungsten and W/Re. A tension-induced fracture of the Mo/Re after the prior bend test showed a dimple fracture with a visible ductile core. Overall, the Mo/Re and W/Re alloys were suitable substrates for diamond growth. The Mo/Re alloy remained significantly more ductile than traditional tungsten substrates after diamond growth, and thus may be an attractive metal substrate for more ductile, thin-film diamond electrodes.
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Rhenium Alloys as Ductile Substrates for Diamond Thin-Film Electrodes
Halpern, Jeffrey M.; Martin, Heidi B.
2014-01-01
Molybdenum-rhenium (Mo/Re) and tungsten-rhenium (W/Re) alloys were investigated as substrates for thin-film, polycrystalline boron-doped diamond electrodes. Traditional, carbide-forming metal substrates adhere strongly to diamond but lose their ductility during exposure to the high-temperature (1000°C) diamond, chemical vapor deposition environment. Boron-doped semi-metallic diamond was selectively deposited for up to 20 hours on one end of Mo/Re (47.5/52.5 wt.%) and W/Re (75/25 wt.%) alloy wires. Conformal diamond films on the alloys displayed grain sizes and Raman signatures similar to films grown on tungsten; in all cases, the morphology and Raman spectra were consistent with well-faceted, microcrystalline diamond with minimal sp2 carbon content. Cyclic voltammograms of dopamine in phosphate-buffered saline (PBS) showed the wide window and low baseline current of high-quality diamond electrodes. In addition, the films showed consistently well-defined, dopamine electrochemical redox activity. The Mo/Re substrate regions that were uncoated but still exposed to the diamond-growth environment remained substantially more flexible than tungsten in a bend-to-fracture rotation test, bending to the test maximum of 90° and not fracturing. The W/Re substrates fractured after a 27° bend, and the tungsten fractured after a 21° bend. Brittle, transgranular cleavage fracture surfaces were observed for tungsten and W/Re. A tension-induced fracture of the Mo/Re after the prior bend test showed a dimple fracture with a visible ductile core. Overall, the Mo/Re and W/Re alloys were suitable substrates for diamond growth. The Mo/Re alloy remained significantly more ductile than traditional tungsten substrates after diamond growth, and thus may be an attractive metal substrate for more ductile, thin-film diamond electrodes. PMID:25404788
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NASA Astrophysics Data System (ADS)
Qiu, Jianke; Ma, Yingjie; Lei, Jiafeng; Liu, Yuyin; Huang, Aijun; Rugg, David; Yang, Rui
2014-12-01
The dwell effects of Ti624 x ( x = 2 to 6) alloys, including dwell fatigue life debit, fracture mode and strain accumulation, were characterized and compared. With increasing Mo content, the dwell fatigue life debit decreases quickly, and dwell fatigue fracture exhibits a transition from subsurface to surface initiation. Accompanying these changes, the accumulated strain decreases, and the pattern of secondary cracks loses morphological features typical of dwell cracks. These variations in the fatigue behavior of Ti624 x were attributed on the fundamental level to the dual effects of Mo: It decreases the β transus of titanium and, as a slow diffuser, reduces the rate of phase transformation from β to α. A higher Mo content encourages nucleation of multiple variants of α laths and promotes the transition from aligned colonies to basketweave microstructure during cooling after β forging. As a result both the grain size and microtexture intensity of α grains in the two-phase processed and heat treated microstructure are reduced. Smaller grain size of the alloys with higher Mo content produces smaller slip band spacing and reduces accumulated strain during dwell fatigue, thus reducing propensity for crack initiation. Microtexture was shown to be the direct cause of dwell sensitivity, and their relationship was described with the aid of a two-region redistribution model based on a previous two-element redistribution model proposed by Bache.
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Albumin adsorption on CoCrMo alloy surfaces
NASA Astrophysics Data System (ADS)
Yan, Yu; Yang, Hongjuan; Su, Yanjing; Qiao, Lijie
2015-12-01
Proteins can adsorb on the surface of artificial joints immediately after being implanted. Although research studying protein adsorption on medical material surfaces has been carried out, the mechanism of the proteins’ adsorption which affects the corrosion behaviour of such materials still lacks in situ observation at the micro level. The adsorption of bovine serum albumin (BSA) on CoCrMo alloy surfaces was studied in situ by AFM and SKPFM as a function of pH and the charge of CoCrMo alloy surfaces. Results showed that when the specimens were uncharged, hydrophobic interaction could govern the process of the adsorption rather than electrostatic interaction, and BSA molecules tended to adsorb on the surfaces forming a monolayer in the side-on model. Results also showed that adsorbed BSA molecules could promote the corrosion process for CoCrMo alloys. When the surface was positively charged, the electrostatic interaction played a leading role in the adsorption process. The maximum adsorption occurred at the isoelectric point (pH 4.7) of BSA.
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Effects of heat treatment on U–Mo fuel foils with a zirconium diffusion barrier
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jue, Jan-Fong; Trowbridge, Tammy L.; Breckenridge, Cynthia R.
A monolith fuel design based on U–Mo alloy has been selected as the fuel type for conversion of the United States’ high performance research reactors (HPRRs) from highly enriched uranium (HEU) to low-enriched uranium (LEU). In this fuel design, a thin layer of zirconium is used to eliminate the direct interaction between the U–Mo fuel meat and the aluminum-alloy cladding during irradiation. The co-rolling process used to bond the Zr barrier layer to the U–Mo foil during fabrication alters the microstructure of both the U–10Mo fuel meat and the U–Mo/Zr interface. This work studied the effects of post-rolling annealing treatmentmore » on the microstructure of the co-rolled U–Mo fuel meat and the U–Mo/Zr interaction layer. Microscopic characterization shows that the grain size of U–Mo fuel meat increases with the annealing temperature, as expected. The grain sizes were ~9, ~13, and ~20 μm for annealing temperature of 650, 750, and 850 °C, respectively. No abnormal grain growth was observed. The U–Mo/Zr interaction-layer thickness increased with the annealing temperature with an Arrhenius constant for growth of 184 kJ/mole, consistent with a previous diffusion-couple study. The interaction layer thickness was 3.2 ± 0.5 μm, 11.1 ± 2.1 μm, 27.1 ± 0.9 μm for annealing temperature of 650, 750, to 850 °C, respectively. The homogeneity of Mo improves with post rolling annealing temperature and with U–Mo coupon homogenization. The phases in the Zr/U–Mo interaction layer produced by co-rolling, however, differ from those reported in the previous diffusion couple studies.« less
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Thermal fatigue-and-oxidation-resistant alloy
NASA Technical Reports Server (NTRS)
Bizon, P. T.; Waters, W. J.; Spera, D. A.
1976-01-01
Cast nickel-base alloy designated as NASA TAZ-8A has been developed for use in high temperature aircraft engine components. TAZ-8A composition is 8Ta, 6Cr, 6A1, 4Mo, 4W, 2Cb, 0.5Zr, 0.125C, 0.004B, and balance Ni (weight percent). Its specific gravity at room temperature is 8.65.
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Corrosion Studies in Support of Medium Power Lead Alloy Cooled Reactor
DOE Office of Scientific and Technical Information (OSTI.GOV)
Eric Loewen; Ronald Ballinger; Jeongyoun Lim
2004-09-01
The performance of structural materials in lead or lead-bismuth eutectic (LBE) systems is evaluated. The materials evaluated included refractory metals (W, Mo, and Ta), several U.S. steels [austenitic steel (316L), carbon steels (F-22, Fe-Si), ferritic/martensitic steels (HT-9 and 410)], and several experimental Fe-Si-Cr alloys that were expected to demonstrate corrosion resistance. The materials were exposed in either an LBE rotating electrode or a dynamic corrosion cell for periods from 100 to 1000 h at temperatures of 400, 500, 600, and 700°C, depending on material and exposure location. Weight change and optical scanning electron microscopy or X-ray analysis of the specimenmore » were used to characterize oxide film thickness, corrosion depth, microstructure, and composition changes. The results of corrosion tests validate the excellent resistance of refractory metals (W, Ta, and Mo) to LBE corrosion. The tests conducted with stainless steels (410, 316L, and HT-9) produced mass transfer of elements (e.g., Ni and Cr) into the LBE, resulting in degradation of the material. With Fe-Si alloys a Si-rich layer (as SiO2) is formed on the surface during exposure to LBE from the selective dissolution of Fe.« less
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Corrosion Studies in Support of Medium-Power Lead-Alloy-Cooled Reactor
DOE Office of Scientific and Technical Information (OSTI.GOV)
Loewen, Eric P.; Ballinger, Ronald G.; Lim, Jeongyoun
2004-09-15
The performance of structural materials in lead or lead-bismuth eutectic (LBE) systems is evaluated. The materials evaluated included refractory metals (W, Mo, and Ta), several U.S. steels [austenitic steel (316L), carbon steels (F-22, Fe-Si), ferritic/martensitic steels (HT-9 and 410)], and several experimental Fe-Si-Cr alloys that were expected to demonstrate corrosion resistance. The materials were exposed in either an LBE rotating electrode or a dynamic corrosion cell for periods from 100 to 1000 h at temperatures of 400, 500, 600, and 700 deg. C, depending on material and exposure location. Weight change and optical scanning electron microscopy or X-ray analysis ofmore » the specimen were used to characterize oxide film thickness, corrosion depth, microstructure, and composition changes. The results of corrosion tests validate the excellent resistance of refractory metals (W, Ta, and Mo) to LBE corrosion. The tests conducted with stainless steels (410, 316L, and HT-9) produced mass transfer of elements (e.g., Ni and Cr) into the LBE, resulting in degradation of the material. With Fe-Si alloys a Si-rich layer (as SiO{sub 2}) is formed on the surface during exposure to LBE from the selective dissolution of Fe.« less
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Preliminary Tests for Ti-Mo-Zr-Ta Alloys as Potential Biomaterials
NASA Astrophysics Data System (ADS)
Bălţatu, M. S.; Vizureanu, P.; Bălan, T.; Lohan, M.; Ţugui, C. A.
2018-06-01
Nowadays, there is a continuing concern for the research and development of alloys for medical and biomedical applications. In order to check the biocompatible character of a new Ti-Mo-Zr-Ta alloys, it is necessary to carry out preliminary laboratory tests to follow how a biomaterial surface would interact with the host. The paper presents tests for Ti-Mo-Zr-Ta alloys like contact angle and DSC test to identify biocompatible character. Contact angle measurement is an experimental technique used to assess the hydrophilic or hydrophobic character of surfaces by reference to the 90º contact angle value and to characterize the thermal behavior, for temperature range between 36.5-37.2ºC, interval which a biomaterial works inside the healthy human body, was used DSC test.
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Zhang, Hong-Yu; Zhu, Yu-Jiao; Hu, Xiang-Yu; Sun, Yan-Fang; Sun, Yu-Long; Han, Jian-Min; Yan, Yu; Zhou, Ming
2014-01-01
Surface grafting of polyelectrolyte brush, such as 3-sulfopropyl methacrylate potassium salt (SPMK), on hip implant materials has been reported to reduce the wear of the orthopaedic bearing surface. However, the biotribocorrosion behaviour of the SPMK brush has not been taken into consideration in previous research. In the present study, SPMK was grafted on Co28Cr6Mo alloy through photo-induced polymerization, and the biotribocorrosion behaviour was investigated by a series of frictional-electrochemical tests using a universal materials tester combined with an electrochemical measurement (three-electrode) system. Co28Cr6Mo disk and polyethylene (PE) pin were used as the contact pair, and the lubricants were 0.9% saline solution (NaCl) and 0.9% saline solution coupled with 25% bovine serum albumin (BSA). The results showed that SPMK was successfully grafted on Co28Cr6Mo alloy, which was confirmed by the comparison of Raman spectroscopy and static contact angle of the samples before and after surface modification. The greatly reduced electrochemical parameters such as corrosion current and pitting potential indicated that the corrosion rate of Co28Cr6Mo alloy was significantly reduced following SPMK grafting. Additionally, the frictional-electrochemical coupled measurement performed under reciprocating sliding demonstrated that the lowest corrosion current was obtained for the SPMK-grafted Co28Cr6Mo disk, with 0.9% NaCl coupled with 25% BSA as the electrolyte. It is indicated from the present study that SPMK polyelectrolyte brush can greatly improve the anti-biotribocorrosion properties of Co28Cr6Mo alloy, and thus has potential application on surface modification of hip implant materials.
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2007-06-23
6 %AI-2%Sn- 4 %Zr- 6 %Mo in the very high cycle regime. The microstructure is a two-phase structure with primary a grains (ap grains) in a transformed [3...aluminum [2], magnesium [3], nickel-based [ 4 ], and titanium [5,6] alloy systems. Fatigue crack initiation is known to consume the majority of fatigue...microstructural neighborhood affects this process. In fatigue studies of alpha + beta titanium alloys, [ 6 -9] cyclic deformation localization is first observed in
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1300 K Compressive Properties of Directionally Solidified Ni-33Al-33Cr-1Mo
NASA Technical Reports Server (NTRS)
Whittenberger, J. Daniel; Raj, S. V.; Locci, Ivan E.
2000-01-01
The Ni-33Al-33Cr-1Mo eutectic has been directionally solidified by a modified Bridgeman technique at growth rates ranging from 7.6 to 508 mm/h to produce grain/cellular microstructures, containing alternating plates of NiAl and Cr alloyed with Mo. The grains had sharp boundaries for slower growth rates (< 12.7 mm/h), while faster growth rates (> 25.4 mm/h) lead to cells bounded by intercellular regions. Compressive testing at 1300 K indicated that alloys DS'ed at rates between 25.4 to 254 mm/h possessed the best strengths which exceed that for the as-cast alloy.
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Corrosion-resistant amorphous metallic films of Mo49Cr33B18 alloy
NASA Technical Reports Server (NTRS)
Ramesham, R.; Distefano, S.; Fitzgerald, D.; Thakoor, A. P.; Khanna, S. K.
1987-01-01
Corrosion-resistant amorphous metallic alloy films of Mo49Cr33B18 with a crystallization temperature of 590 C were deposited onto glass and quartz substrates by magnetron sputter-quench technique. The amorphous nature of the films was confirmed by their diffuse X-ray diffraction patterns. The deposited films are densely packed (zone T) and exhibit low stress and good adhesion to the substrate. Corrosion current of as-deposited coating of MoCrB amorphous metallic alloy is approximately three orders of magnitude less than the corrosion current of 304 stainless steel in 1N H2SO4 solution.
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Nickel aluminide alloy suitable for structural applications
Liu, C.T.
1998-03-10
Alloys are disclosed for use in structural applications based upon NiAl to which are added selected elements to enhance room temperature ductility and high temperature strength. Specifically, small additions of molybdenum produce a beneficial alloy, while further additions of boron, carbon, iron, niobium, tantalum, zirconium and hafnium further improve performance of alloys at both room temperature and high temperatures. A preferred alloy system composition is Ni--(49.1{+-}0.8%)Al--(1.0{+-}0.8%)Mo--(0.7 + 0.5%)Nb/Ta/Zr/Hf--(nearly zero to 0.03%)B/C, where the % is at. % in each of the concentrations. All alloys demonstrated good oxidation resistance at the elevated temperatures. The alloys can be fabricated into components using conventional techniques. 4 figs.
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Dynamic mechanical properties of straight titanium alloy arch wires.
Kusy, R P; Wilson, T W
1990-10-01
Eight straight-wire materials were studied: an orthodontic titanium-molybdenum (Ti-Mo) product, TMA; three orthodontic nickel-titanium (Ni-Ti) products, Nitinol, Titanal, and Orthonol; three prototype alloys, a martensitic, an austenitic, and a biphasic alloy; and a hybrid shape-memory-effect product, Biometal. Each wire was prepared with a length-to-cross-sectional area of at least 3600 cm-1. With an Autovibron Model DDV-II-C used in the tensile mode, each sample was scanned from -120 to +200 degrees C at 2 degrees C/min. From the data base, plots of the log storage modulus, log tan delta, and percent change in length vs. temperature were generated. Results showed that the dynamic mechanical properties of the alloys within this TI system are quite different. The Ti-Mo alloy, TMA, was invariant with temperature, having a modulus of 7.30 x 10(11) dyne/cm2 (10.6 x 10(6) psi). The three cold-worked alloys--Nitinol, Titanal, and Orthonol--appeared to be similar, having a modulus of 5.74 x 10(11) dyne/cm2 (8.32 x 10(6) psi). The biphasic shape-memory alloy displayed a phase transformation near ambient temperature; whereas the hybrid shape-memory product, Biometal, underwent a 3-5% change in length during its transformation between 95 and 125 degrees C. Among the Ni-Ti wires tested, several different types of alloys were represented by this intermetallic material.
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Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding
NASA Astrophysics Data System (ADS)
Wu, Wei; Jiang, Li; Jiang, Hui; Pan, Xuemin; Cao, Zhiqiang; Deng, Dewei; Wang, Tongmin; Li, Tingju
2015-10-01
A series of Al2CrFeNiMo x ( x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.
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2011-05-01
Mn, Fe, Co, Ni and Cu. Since metallic alloys for high temperature load bearing structures and thermal protection systems remain in high demand for aer...condition. These results indicate that the BCC crystal structure formed in both alloys during solidification is stable upon heating at least up to 1400 C... solidification (Fig. 5b). Higher magnification images reveal a dendritic structure in both alloys (Fig. 5c and d). Uneven Z contrast inside the grains indicates
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Intergranular tellurium cracking of nickel-based alloys in molten Li, Be, Th, U/F salt mixture
NASA Astrophysics Data System (ADS)
Ignatiev, Victor; Surenkov, Alexander; Gnidoy, Ivan; Kulakov, Alexander; Uglov, Vadim; Vasiliev, Alexander; Presniakov, Mikhail
2013-09-01
In Russia, R&D on Molten Salt Reactor (MSR) are concentrated now on fast/intermediate spectrum concepts which were recognized as long term alternative to solid fueled fast reactors due to their attractive features: strong negative feedback coefficients, easy in-service inspection, and simplified fuel cycle. For high-temperature MSR corrosion of the metallic container alloy in primary circuit is the primary concern. Key problem receiving current attention include surface fissures in Ni-based alloys probably arising from fission product tellurium attack. This paper summarizes results of corrosion tests conducted recently to study effect of oxidation state in selected fuel salt on tellurium attack and to develop means of controlling tellurium cracking in the special Ni-based alloys recently developed for molten salt actinide recycler and tranforming (MOSART) system. Tellurium corrosion of Ni-based alloys was tested at temperatures up to 750 °C in stressed and unloaded conditions in molten LiF-BeF2 salt mixture fueled by about 20 mol% of ThF4 and 2 mol% of UF4 at different [U(IV)]/[U(III)] ratios: 0.7, 4, 20, 100 and 500. Following Ni-based alloys (in mass%): HN80М-VI (Mo—12, Cr—7.6, Nb—1.5), HN80МТY (Mo—13, Cr—6.8, Al—1.1, Ti—0.9), HN80МТW (Mo—9.4, Cr—7.0, Ti—1.7, W—5.5) and ЕМ-721 (W—25.2, Cr—5.7, Ti—0.17) were used for the study in the corrosion facility. If the redox state the fuel salt is characterized by uranium ratio [U(IV)]/[U(III)] < 1 the alloys' specimens get a more negative stationary electrode potential than equilibrium electrode potentials of some uranium intermetallic compounds and alloys with nickel and molybdenum. This leads to spontaneous behavior of alloy formation processes on the specimens' surface and further diffusion of uranium deep into the metallic phase. As consequence of this films of intermetallic compounds and alloys of nickel, molybdenum, tungsten with uranium are formed on the alloys specimens' surface, and intergranular corrosion does not take place. In the fuel salt with [U(IV)]/[U(III)] = 4-20 the potentials of uranium alloy formation with the main components of the tested alloys are not reached, that's why alloys and intermetallic compounds are not formed on the surface of the investigated chromium-nickel alloys. Under such conditions any intergranular tellurium corrosion of the selected alloys does not occur. In the fuel salt with [U(IV)/]/[U(III)] = 100 the potentials of uranium alloy formation with the main components of the tested alloys are not also reached. Under such redox conditions any traces intergranular tellurium IGC on the HN80MTY and H80M-VI alloys specimens are not found. Certain signs of incipient IGC in the form of tellurium presence on the grain boundaries in the HN80MTB and EM-721 alloys surface layer and formation of not too deep cracks on HN80MTB alloy surface were revealed at [U(IV)/]/[U(III)] = 100. With this uranium ratio in the presence of corrosion products on the surface of all of the alloys films, containing tellurium, metals of the construction alloys and carbon, are formed. In the melt with [U(IV)]/[U(III)] = 500 in all of the alloys tested the tellurium IGC took place. The HN80MTY alloy shows the maximum resistance to tellurium IGC. The intensity of tellurium IGC of the alloy (the K parameter) is by 3-5 times lower as compared to other alloys. The EM-721 alloy has the minimal resistance to tellurium IGC (K = 9200 pc m/cm, the depth of cracks is up to 434 μm). The studies have shown, that the intensity of the nickel alloys IGC is controlled by the [U(IV)]/[U(III)] ratio, and its dependence on this parameter is of threshold character. Providing the uranium ratio value's monitoring and regulation, it is possible to control the tellurium corrosion and in such a way to eliminate IGC completely or to minimize its value. The alloys strength characteristics and their structure were changed insignificantly after testing within the [U(IV)]/[U(III)] range from 0.7 tо 100. The changes are not linked with the influence of fuel salt, containing tellurium additions, but are stipulated by alloys structure, temperature factor, exposure time and mechanical loads. Significant effect of tellurium cracking on the alloys (excepting HN80MTY) strength characteristics was established after corrosion testing with [U(IV)]/[U(III)] = 500. In the absence of IGC all of the alloys investigated have a good ductility at high strength characteristics. The disrupture of specimens under mechanical tests both before and after corrosion tests of all alloys except for ЕМ-721 proceeds on a ductile mechanism. On the EM-721 alloy specimens, both in their initial state and after corrosion testing, clear signs of brittle destruction, caused by heterogeneity of its structure due to the presence of tungsten phase, are very clearly observed. The presence of such phases increases the alloy IGC and leads to reduction of the alloy resistance tellurium damage. The HN80MTY alloy has the best corrosion and mechanical properties. It does not undergo tellurium IGC in the molten 75LiF-5BeF2-20ThF4 salt mixture fueled by about 2 mol% of UF4 with [U(IV)]/[U(III)] ratio ⩽ 100. The alloy has high resistance to tellurium cracking at [U(IV)]/[U(III)] = 500. The alloy can be recommended as the main construction material for the fuel circuit with selected salt composition up to temperature 750 °С.
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NASA Astrophysics Data System (ADS)
Petica, A.; Brincoveanu, O.; Golgovici, F.; Manea, A. C.; Enachescu, M.; Anicai, L.
2018-03-01
The paper presents some experimental results regarding the functionalization of 3D electroformed Ni and Ni-Mo alloy nanofoams with Pd nanoclusters, as potential cathodic materials suitable for HER during seawater electrolysis. The electrodeposition from aqueous electrolytes containing NiCl2 and NH4Cl has been applied to prepare the 3D Ni nanofoams. Ni-Mo alloys have been electrodeposited involving aqueous ammonium citrate type electrolytes. Pd surface functionalization has been performed using both electroless and electrochemical procedures. Pd content varied in the range of 0.5 – 8 wt.%, depending on the applied procedure and the operation conditions. The use of a porous structure associated with alloying element (i.e. Mo) and Pd surface functionalization facilitated enhanced performances from HER view point in seawater electrolyte (lower Tafel slopes). The determined Tafel slope values ranged from 123 to 105 mV.dec-1, suggesting the Volmer step as rate determining step. The improvement of the HER catalytic activity may be ascribed to a synergistic effect between the high real active area of the 3D electroformed metallic substrate, Ni alloying with a left transition metal and surface modification using Pd noble metal.
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Fabrication of thin film TiO2 nanotube arrays on Co-28Cr-6Mo alloy by anodization.
Ni, Jiahua; Frandsen, Christine J; Noh, Kunbae; Johnston, Gary W; He, Guo; Tang, Tingting; Jin, Sungho
2013-04-01
Titanium oxide (TiO2) nanotube arrays were prepared by anodization of Ti/Au/Ti trilayer thin film DC sputtered onto forged and cast Co-28Cr-6Mo alloy substrate at 400 °C. Two different types of deposited film structures (Ti/Au/Ti trilayer and Ti monolayer), and two deposition temperatures (room temperature and 400 °C) were compared in this work. The concentrations of ammonium fluoride (NH4F) and H2O in glycerol electrolyte were varied to study their effect on the formation of TiO2 nanotube arrays on a forged and cast Co-28Cr-6Mo alloy. The results show that Ti/Au/Ti trilayer thin film and elevated temperature sputtered films are favorable for the formation of well-ordered nanotube arrays. The optimized electrolyte concentration for the growth of TiO2 nanotube arrays on forged and cast Co-28Cr-6Mo alloy was obtained. This work contains meaningful results for the application of a TiO2 nanotube coating to a CoCr alloy implant for potential next-generation orthopedic implant surface coatings with improved osseointegrative capabilities. Copyright © 2013 Elsevier B.V. All rights reserved.
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Ultrasonic investigation of the superconducting properties of the Nb-Mo system
NASA Technical Reports Server (NTRS)
Lacy, L. L.
1972-01-01
The superconducting properties of single crystals of Nb and two alloys of Nb with Mo were investigated by ultrasonic techniques. The results of measurements of the ultrasonic attenuation and velocities as a function of temperature, Mo composition, crystallographic direction, and ultrasonic frequency are reported. The attenuation and small velocity changes associated with the superconductivity of the samples are shown to be dependent on the sample resistivity ratio which varied from 4.3 for Nb-9% Mo to 6500 for pure Nb. The ultrasonic attenuation data are analyzed in terms of the superconducting energy gap term of the BCS theory. A new model is proposed for the analysis of ultrasonic attenuation in pure superconductors with two partially decoupled energy bands. To analyze the attenuation in pure superconducting Nb, the existence of two energy gaps was assumed to be associated with the two partially decoupled energy bands. One of the gaps was found to have the normal BCS value of 3.4 and the other gap was found to have the anomalously large value of 10. No experimental evidence was found to suggest that the second energy gap had a different transition temperature. The interpretation of the results for the Nb-Mo alloys is shown to be complicated by the possible existence of a second superconducting phase in Nb-Mo alloys with a transition temperature of 0.35 of the transition temperature of the first phase. The elastic constants of Nb and Nb-Mo alloys are shown to be approximately independent of Mo composition to nine atomic percent Mo. These results do not agree with the current microscopic theory of transition temperature for the transition elements.
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In vitro biocorrosion of Co-Cr-Mo implant alloy by macrophage cells.
Lin, Hsin-Yi; Bumgardner, Joel D
2004-11-01
We hypothesized that macrophage cells and their released reactive chemical species (RCS) affect Co-Cr-Mo alloy's corrosion properties and that alloy corrosion products change macrophage cell behavior. A custom cell culture corrosion cell was used to evaluate how culture medium, cells, and RCS altered alloy corrosion in 3-day tests. Corrosion was evaluated by measuring total charge transfer at a constant potential using a potentiostat and metal ion release by atomic emission spectroscopy. Viability, proliferation, and NO (nitric oxide) and IL-1beta (interlukin-1beta) release were used to assess cellular response to alloy corrosion products. In the presence of activated cells, total charge transfers and Co ion release were the lowest (p < 0.05). This was attributed to an enhancement of the surface oxide by RCS. Cr and Mo release were not different between cells and activated cells. Low levels of metal ions did not affect cell viability, proliferation, or NO release, though IL-1beta released from the activated cells was higher on the alloy compared to the controls. These data support the hypothesis that macrophage cells and their RCS affect alloy corrosion. Changes in alloy corrosion by cells may be important to the development of host responses to the alloy and its corrosion products.
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Additive Manufacturing of Metastable Beta Titanium Alloys
NASA Astrophysics Data System (ADS)
Yannetta, Christopher J.
Additive manufacturing processes of many alloys are known to develop texture during the deposition process due to the rapid reheating and the directionality of the dissipation of heat. Titanium alloys and with respect to this study beta titanium alloys are especially susceptible to these effects. This work examines Ti-20wt%V and Ti-12wt%Mo deposited under normal additive manufacturing process parameters to examine the texture of these beta-stabilized alloys. Both microstructures contained columnar prior beta grains 1-2 mm in length beginning at the substrate with no visible equiaxed grains. This microstructure remained constant in the vanadium system throughout the build. The microstructure of the alloy containing molybdenum changed from a columnar to an equiaxed structure as the build height increased. Eighteen additional samples of the Ti-Mo system were created under different processing parameters to identify what role laser power and travel speed have on the microstructure. There appears to be a correlation in alpha lath size and power density. The two binary alloys were again deposited under the same conditions with the addition of 0.5wt% boron to investigate the effects an insoluble interstitial alloying element would have on the microstructure. The size of the prior beta grains in these two alloys were reduced with the addition of boron by approximately 50 (V) and 100 (Mo) times.
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Ternary cobalt-molybdenum-zirconium coatings for alternative energies
NASA Astrophysics Data System (ADS)
Yar-Mukhamedova, Gulmira; Ved', Maryna; Sakhnenko, Nikolay; Koziar, Maryna
2017-11-01
Consistent patterns for electrodeposition of Co-Mo-Zr coatings from polyligand citrate-pyrophosphate bath were investigated. The effect of both current density amplitude and pulse on/off time on the quality, composition and surface morphology of the galvanic alloys were determined. It was established the coating Co-Mo-Zr enrichment by molybdenum with current density increasing up to 8 A dm-2 as well as the rising of pulse time and pause duration promotes the content of molybdenum because of subsequent chemical reduction of its intermediate oxides by hydrogen ad-atoms. It was found that the content of the alloying metals in the coating Co-Mo-Zr depends on the current density and on/off times extremely and maximum Mo and Zr content corresponds to the current density interval 4-6 A dm-2, on-/off-time 2-10 ms. Chemical resistance of binary and ternary coatings based on cobalt is caused by the increased tendency to passivity and high resistance to pitting corrosion in the presence of molybdenum and zirconium, as well as the acid nature of their oxides. Binary coating with molybdenum content not less than 20 at.% and ternary ones with zirconium content in terms of corrosion deep index are in a group ;very proof;. It was shown that Co-Mo-Zr alloys exhibits the greatest level of catalytic properties as cathode material for hydrogen electrolytic production from acidic media which is not inferior a platinum electrode. The deposits Co-Mo-Zr with zirconium content 2-4 at.% demonstrate high catalytic properties in the carbon(II) oxide conversion. This confirms the efficiency of materials as catalysts for the gaseous wastes purification and gives the reason to recommend them as catalysts for red-ox processes activating by oxygen as well as electrode materials for red-ox batteries.
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A model to predict thermal conductivity of irradiated U–Mo dispersion fuel
DOE Office of Scientific and Technical Information (OSTI.GOV)
Burkes, Douglas E.; Huber, Tanja K.; Casella, Andrew M.
The Office of Materials Management and Minimization Reactor Conversion Program continues to develop existing and new research and test reactor fuels to achieve maximum attainable uranium loadings to support the conversion of a number of the world’s remaining high-enriched uranium fueled reactors to low-enriched uranium fuel. The program is focused on assisting with the development and qualification of a fuel design that consists of a uranium-molybdenum (U-Mo) alloy dispersed in an aluminum matrix as one option for reactor conversion. Thermal conductivity is an important consideration in determining the operational temperature of the fuel and can be influenced by interaction layermore » formation between the dispersed phase and matrix and upon the concentration of the dispersed phase within the matrix. This paper extends the use of a simple model developed previously to study the influence of interaction layer formation as well as the size and volume fraction of fuel particles dispersed in the matrix, Si additions to the matrix, and Mo concentration in the fuel particles on the effective thermal conductivity of the U-Mo/Al composite during irradiation. The model has been compared to experimental measurements recently conducted on U-Mo/Al dispersion fuels at two different fission densities with acceptable agreement. Observations of the modeled results indicate that formation of an interaction layer and subsequent consumption of the matrix reveals a rather significant effect on effective thermal conductivity. The modeled interaction layer formation and subsequent consumption of the high thermal conductivity matrix was sensitive to the average dispersed fuel particle size, suggesting this parameter as one of the most effective in minimizing thermal conductivity degradation of the composite, while the influence of Si additions to the matrix in the model was highly dependent upon irradiation conditions.« less
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Analysis of the thermal expansivity near the tricritical point in dilute chromium alloys
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yurtseven, H., E-mail: hamit@metu.edu.tr; Tari, Ö., E-mail: ozlemilgin@arel.edu.tr
Chromium (Cr) undergoes a first order Neel transition as an antiferromagnetic material. When V, Mo and Mn atoms are substituted in the Cr lattice, a weak first order Neel transition in pure Cr changes toward a second order transition and a possible tricritical point in CrV occurs close to 0.2 at %V, as observed experimentally from the measurements of the thermal expansivity at various temperatures. In this study, we analyze the experimental data for the thermal expansivity from the literature as a function of temperature using the power - law formula for Cr alloys (Cr - 0.1V, 0.2V, 0.5V andmore » Cr - 0.1Mn, Cr - 0.2Mo, 0.3Mo, 0.4Mo). Our results are interpreted near the tricritical point in dilute chromium alloys.« less
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Redox-Mediated Stabilization in Zinc Molybdenum Nitrides
DOE Office of Scientific and Technical Information (OSTI.GOV)
Arca, Elisabetta; Lany, Stephan; Perkins, John D.
We report on the theoretical prediction and experimental realization of new ternary zinc molybdenum nitride compounds. We used theory to identify previously unknown ternary compounds in the Zn-Mo-N systems, Zn 3MoN 4 and ZnMoN 2, and to analyze their bonding environment. Experiments show that Zn-Mo-N alloys can form in broad composition range from Zn 3MoN 4 to ZnMoN 2 in the wurtzite-derived structure, accommodating very large off-stoichiometry. Interestingly, the measured wurtzite-derived structure of the alloys is metastable for the ZnMoN 2 stoichiometry, in contrast to the Zn 3MoN 4 stoichiometry, where ordered wurtzite is predicted to be the ground state.more » The formation of Zn 3MoN 4-ZnMoN 2 alloy with wurtzite-derived crystal structure is enabled by the concomitant ability of Mo to change oxidation state from +VI in Zn 3MoN 4 to +IV in ZnMoN 2, and the capability of Zn to contribute to the bonding states of both compounds, an effect that we define as 'redox-mediated stabilization.' The stabilization of Mo in both the +VI and +IV oxidation states is due to the intermediate electronegativity of Zn, which enables significant polar covalent bonding in both Zn 3MoN 4 and ZnMoN 2 compounds. The smooth change in the Mo oxidation state between Zn 3MoN 4 and ZnMoN 2 stoichiometries leads to a continuous change in optoelectronic properties - from resistive and semitransparent Zn 3MoN 4 to conductive and absorptive ZnMoN 2. The reported redox-mediated stabilization in zinc molybdenum nitrides suggests there might be many undiscovered ternary compounds with one metal having an intermediate electronegativity, enabling significant covalent bonding, and another metal capable of accommodating multiple oxidation states, enabling stoichiometric flexibility.« less
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Redox-Mediated Stabilization in Zinc Molybdenum Nitrides
Arca, Elisabetta; Lany, Stephan; Perkins, John D.; ...
2018-03-01
We report on the theoretical prediction and experimental realization of new ternary zinc molybdenum nitride compounds. We used theory to identify previously unknown ternary compounds in the Zn-Mo-N systems, Zn 3MoN 4 and ZnMoN 2, and to analyze their bonding environment. Experiments show that Zn-Mo-N alloys can form in broad composition range from Zn 3MoN 4 to ZnMoN 2 in the wurtzite-derived structure, accommodating very large off-stoichiometry. Interestingly, the measured wurtzite-derived structure of the alloys is metastable for the ZnMoN 2 stoichiometry, in contrast to the Zn 3MoN 4 stoichiometry, where ordered wurtzite is predicted to be the ground state.more » The formation of Zn 3MoN 4-ZnMoN 2 alloy with wurtzite-derived crystal structure is enabled by the concomitant ability of Mo to change oxidation state from +VI in Zn 3MoN 4 to +IV in ZnMoN 2, and the capability of Zn to contribute to the bonding states of both compounds, an effect that we define as 'redox-mediated stabilization.' The stabilization of Mo in both the +VI and +IV oxidation states is due to the intermediate electronegativity of Zn, which enables significant polar covalent bonding in both Zn 3MoN 4 and ZnMoN 2 compounds. The smooth change in the Mo oxidation state between Zn 3MoN 4 and ZnMoN 2 stoichiometries leads to a continuous change in optoelectronic properties - from resistive and semitransparent Zn 3MoN 4 to conductive and absorptive ZnMoN 2. The reported redox-mediated stabilization in zinc molybdenum nitrides suggests there might be many undiscovered ternary compounds with one metal having an intermediate electronegativity, enabling significant covalent bonding, and another metal capable of accommodating multiple oxidation states, enabling stoichiometric flexibility.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Bhattacharyya, D., E-mail: dhb@ansto.gov.au; Davis, J.; Drew, M.
2015-07-15
Nickel based alloys of the type Hastelloy-N™ are ideal candidate materials for molten salt reactors, as well as for applications such as pressure vessels, due to their excellent resistance to creep, oxidation and corrosion. In this work, the authors have attempted to understand the effects of welding on the morphology, chemistry and crystal structure of the precipitates in the heat affected zone (HAZ) and the weld zone of a Ni–Cr–Mo–Fe–Si alloy similar to Hastelloy-N™ in composition, by using characterization techniques such as scanning and transmission electron microscopy. Two plates of a Ni–Cr–Mo–Fe–Si alloy GH-3535 were welded together using a TiGmore » welding process without filler material to achieve a joint with a curved molten zone with dendritic structure. It is evident that the primary precipitates have melted in the HAZ and re-solidified in a eutectic-like morphology, with a chemistry and crystal structure only slightly different from the pre-existing precipitates, while the surrounding matrix grains remained unmelted, except for the zones immediately adjacent to the precipitates. In the molten zone, the primary precipitates were fully melted and dissolved in the matrix, and there was enrichment of Mo and Si in the dendrite boundaries after solidification, and re-precipitation of the complex carbides/silicides at some grain boundaries and triple points. The nature of the precipitates in the molten zone varied according to the local chemical composition. - Graphical abstract: Display Omitted - Highlights: • Ni-based alloy with Cr, Mo, Si, Fe and C was welded, examined with SEM, EBSD, and TEM. • Original Ni{sub 2}(Mo,Cr){sub 4}(Si,C) carbides changed from equiaxed to lamellar shape in HAZ. • Composition and crystal structure remained almost unchanged in HAZ. • Original carbides changed to lamellar Ni{sub 3}(Mo,Cr){sub 3}(Si,C) in some cases in weld metal. • Precipitates were mostly incoherent, but semi-coherent in some cases in weld metal.« less
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Microstructure, soft magnetic properties and applications of amorphous Fe-Co-Si-B-Mo-P alloy
NASA Astrophysics Data System (ADS)
Hasiak, Mariusz; Miglierini, Marcel; Łukiewski, Mirosław; Łaszcz, Amadeusz; Bujdoš, Marek
2018-05-01
DC thermomagnetic properties of Fe51Co12Si16B8Mo5P8 amorphous alloy in the as-quenched and after annealing below crystallization temperature are investigated. They are related to deviations in the microstructure as revealed by Mössbauer spectrometry. Study of AC magnetic properties, i.e. hysteresis loops, relative permeability and core losses versus maximum induction was aimed at obtaining optimal initial parameters for simulation process of a resonant transformer for a rail power supply converter. The results obtained from numerical analyses including core losses, winding losses, core mass, and dimensions were compared with the same parameters calculated for Fe-Si alloy and ferrite. Moreover, Steinmetz coefficients were also calculated for the as-quenched Fe51Co12Si16B8Mo5P8 amorphous alloy.
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Microstructures in rapidly solidified Ni-Mo alloys
NASA Technical Reports Server (NTRS)
Jayaraman, N.; Tewari, S. N.; Hemker, K. J.; Glasgow, T. K.
1985-01-01
Ni-Mo alloys of compositions ranging from pure Ni to Ni-40 at % Mo were rapidly solidified by Chill Block Melt Spinning in vacuum and were examined by optical metallography, X-ray diffraction and transmission electron microscopy. Rapid solidification resulted in an extension of molybdenum solubility in nickel from 28 to 37.5 at %. A number of different phases and microstructures were seen at different depths (solidification conditions) from the quenched surface of the melt spun ribbons.
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Mörsdorf, Alexander; Odnevall Wallinder, Inger; Hedberg, Yolanda
2015-08-01
The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
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Kim, J. T.; Hong, S. H.; Park, H. J.; Kim, Y. S.; Suh, J. Y.; Lee, J. K.; Park, J. M.; Maity, T.; Eckert, J.; Kim, K. B.
2017-01-01
In the present study, the microstructural evolution and the modulation of the mechanical properties have been investigated for a Co-Cr-Mo (CCM) ternary eutectic alloy by addition of a small amount of copper (0.5 and 1 at.%). The microstructural observations reveal a distinct dissimilarity in the eutectic structure such as a broken lamellar structure and a well-aligned lamellar structure and an increasing volume fraction of Co lamellae as increasing amount of copper addition. This microstructural evolution leads to improved plasticity from 1% to 10% without the typical tradeoff between the overall strength and compressive plasticity. Moreover, investigation of the fractured samples indicates that the CCMCu alloy exhibits higher plastic deformability and combinatorial mechanisms for improved plastic behavior. The improved plasticity of CCMCu alloys originates from several deformation mechanisms; i) slip, ii) deformation twinning, iii) strain-induced transformation and iv) shear banding. These results reveal that the mechanical properties of eutectic alloys in the Co-Cr-Mo system can be ameliorated by micro-alloying such as Cu addition. PMID:28067248
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Effect of carbide additions on grain growth in TiC-Ni cermets
NASA Astrophysics Data System (ADS)
Shin, Soon-Gi; Lee, Jun-Hee
2006-02-01
The growth of carbide particles in TiC-XC-2 vol.% Ni and TiC-XC-30 vol.% Ni alloys, where X=Zr, Cr, W, Ta and Mo, was fitted to an equation of the form d3-do 3=Kt. The grain growth behavior during liquid phase sintering at 1673K decreased markedly with the addition of Mo2C or WC, changed little for TaC, and increased with the addition of ZrC or Cr3C2. The grain contiguity decreased with increasing Ni content in the TiC-Mo2C-Ni alloy and was greater in the alloys with smaller growth rate constant. Consequently, the effect of carbide addition on the grain growth of 2 vol.% Ni alloys was found to be similar to that of 30 vol.% Ni alloys. The grain growth mechanism could be explained by the effect of contiguous carbide grain boundaries in restricting the overall grain growth, as well as the area of the solid/liquid interfaces in the alloy by the usual solution/reprecipitation model.
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Manufacturing Experience for Oxide Dispersion Strengthened Alloys
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bennett, Wendy D.; Doherty, Ann L.; Henager, Charles H.
2016-09-22
This report documents the results of the development and the manufacturing experience gained at the Pacific Northwest National Laboratories (PNNL) while working with the oxide dispersion strengthened (ODS) materials MA 956, 14YWT, and 9YWT. The Fuel Cycle Research and Development program of the Office of Nuclear Energy has implemented a program to develop a Uranium-Molybdenum metal fuel for light water reactors. ODS materials have the potential to provide improved performance for the U-Mo concept.
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EFFECTS OF COMPOSITION ON THE MECHANICAL PROPERTIES OF NI-CR-MO-CO FILLER METALS.
STEEL, WELDING RODS), CHEMICAL ANALYSIS, CARBON ALLOYS , COBALT ALLOYS , CHROMIUM ALLOYS , MOLYBDENUM ALLOYS , NICKEL ALLOYS , MARAGING STEELS...ALUMINUM COMPOUNDS, TITANIUM , NONMETALS, SHIP HULLS, SHIP PLATES, SUBMARINE HULLS, WELDING , WELDS , MECHANICAL PROPERTIES, STATISTICAL ANALYSIS, MICROSTRUCTURE.
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Thermophysical properties of heat-treated U-7Mo/Al dispersion fuel
NASA Astrophysics Data System (ADS)
Cho, Tae Won; Kim, Yeon Soo; Park, Jong Man; Lee, Kyu Hong; Kim, Sunghwan; Lee, Chong Tak; Yang, Jae Ho; Oh, Jang Soo; Sohn, Dong-Seong
2018-04-01
In this study, the effects of interaction layer (IL) on thermophysical properties of U-7Mo/Al dispersion fuel were examined. Microstructural analyses revealed that ILs were formed uniformly on U-Mo particles during heating of U-7Mo/Al samples. The IL volume fraction was measured by applying image analysis methods. The uranium loadings of the samples were calculated based on the measured meat densities at 298 K. The density of the IL was estimated by using the measured density and IL volume fraction. Thermal diffusivity and heat capacity of the samples after the heat treatment were measured as a function of temperature and volume fractions of U-Mo and IL. The thermal conductivity of IL-formed U-7Mo/Al was derived by using the measured thermal diffusivity, heat capacity, and density. The thermal conductivity obtained in the present study was lower than that predicted by the modified Hashin-Shtrikman model due to the theoretical model's inability to consider the thermal resistance at interfaces between the meat constituents.
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Atom probe study of B2 order and A2 disorder of the FeCo matrix in an Fe-Co-Mo-alloy.
Turk, C; Leitner, H; Schemmel, I; Clemens, H; Primig, S
2017-07-01
The physical and mechanical properties of intermetallic alloys can be tailored by controlling the degree of order of the solid solution by means of heat treatments. FeCo alloys with an appropriate composition exhibit an A2-disorder↔B2-order transition during continuous cooling from the disordered bcc region. The study of atomic order in intermetallic alloys by diffraction and its influence on the material properties is well established, however, investigating magnetic FeCo-based alloys by conventional methods such as X-ray diffraction is quite challenging. Thus, the imaging of ordered FeCo-nanostructures needs to be done with high resolution techniques. Transmission electron microscopy investigations of ordered FeCo domains are difficult, due to the chemical and physical similarity of Fe and Co atoms and the ferromagnetism of the samples. In this work it will be demonstrated, that the local atomic arrangement of ordered and disordered regions in an industrial Fe-Co-Mo alloy can be successfully imaged by atom probe measurements supported by field ion microscopy and transmission Kikuchi diffraction. Furthermore, a thorough atom probe parameter study will be presented and field evaporation artefacts as a function of crystallographic orientation in Fe-Co-samples will be discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.
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Electrochemical corrosion of a noble metal-bearing alloy-oxide composite
Chen, X.; Ebert, W. L.; Indacochea, J. E.
2017-04-27
The effects of added Ru and Pd on the microstructure and electrochemical behaviour of a composite material made by melting those metals with AISI 410 stainless steel, Zr, Mo, and lanthanide oxides were assessed using electrochemical and microscopic methods Furthermore, the lanthanide oxides reacted with Zr to form durable lanthanide zirconates and Mo alloyed with steel to form FeMoCr intermetallics. The noble metals alloyed with the steel to provide solid solution strengthening and inhibit carbide/nitride formation. In a passive film formed during electrochemical tests in acidic NaCl solution, but became less effective as corrosion progressed and regions over the intermetallicsmore » eventually failed.« less
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DFT study of structural and electronic properties of MoS2(1-x)Se2x alloy (x = 0.25)
NASA Astrophysics Data System (ADS)
Gusakova, Julia; Gusakov, Vasilii; Tay, Beng Kang
2018-04-01
First-principles calculations have been performed to study the structural features of the monolayer MoS2(1-x)Se2x (x = 0.25) alloy and its electronic properties. We studied the effects of the relative positions of Se atoms in a real monolayer alloy. It was demonstrated that the distribution of the Se atoms between the top and bottom chalcogen planes was most energetically favorable. For a more probable distribution of Se atoms, a MoS2(1-x)Se2x (x = 0.25) monolayer alloy is a direct semiconductor with a fundamental band gap equal to 2.35 eV (calculated with the GVJ-2e method). We also evaluated the optical band gap of the alloy at 77 K (1.86 eV) and at room temperature (1.80 eV), which was in good agreement with the experimentally measured band gap of 1.79 eV.
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Effect of commercial mouthwashes on the corrosion resistance of Ti-10Mo experimental alloy.
Alves Rezende, Maria Cristina Rosifini; Alves, Ana Paula Rosifini; Codaro, Eduardo Norberto; Dutra, Conceição Aparecida Matsumoto
2007-01-01
The purpose of this work was to evaluate the effect of three commercial mouthwashes on the corrosion resistance of Ti-10Mo experimental alloy. Experiments were made at 37.0 +/- 0.5 degrees C in a conventional three-compartment double wall glass cell containing commercial mouthwashes. Three mouthwashes with different active ingredients were tested: (I) 0.05% sodium fluoride + 0.03% triclosan; (II) 0.5 g/l cetylpyridinium chloride + 0.05% sodium fluoride; (III) 0.12% chlorohexidine digluconate. The assessment of the individual effect of active ingredients was studied by using 0.05% sodium fluoride. Commercially pure titanium (CP Ti) was used as control. Microstructures from Ti-10Mo experimental alloy and CP Ti were also evaluated using optical microscopy. Ti-10Mo as-cast alloy shows the typical rapidly cooled dendrites microstructure (beta phase) while CP Ti has exhibited a metastable martensitic microstructure. Electrochemical behavior of dental materials here studied was more affected by mouthwash type than by Ti alloy composition or microstructure. In both alloys passivation phenomenon was observed. This process may be mainly related to Ti oxides or other Ti species present in spontaneously formed film. Small differences in passive current densities values may be connected with changes in film porosity and thickness. Protective characteristics of this passive film are lower in 0.05% sodium fluoride + 0.03% triclosan mouthwash than in the other two mouthwashes tested.
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McCaughey, Conor; Tsakiropoulos, Panos
2018-06-07
The Nb-silicide-based alloy of near eutectic composition (at.%) Nb-21.1Si-8.3Ti-5.4Mo-4W-0.7Hf (alloy CM1) was studied in the cast and heat-treated (1500 °C/100 h) conditions. The alloy was produced in the form of buttons and bars using three different methods, namely arc-melting, arc-melting and suction casting, and optical floating zone (OFZ) melting. In the former two cases the alloy solidified in water-cooled copper crucibles. Buttons and suction-cast bars of different size, respectively of 10 g and 600 g weight and 6 mm and 8 mm diameter, were produced. The OFZ bars were grown at three different growth rates of 12, 60 and 150 mm/h. It was confirmed that the type of Nb₅Si₃ formed in the cast microstructures depended on the solidification conditions. The primary phase in the alloy CM1 was the βNb₅Si₃. The transformation of βNb₅Si₃ to αNb₅Si₃ had occurred in the as cast large size button and the OFZ bars grown at the three different growth rates, and after the heat treatment of the small size button and the suction-cast bars of the alloy. This transformation was accompanied by subgrain formation in Nb₅Si₃ and the precipitation of Nb ss in the large size as cast button and only by the precipitation of Nb ss in the cast OFZ bars. Subgrains and precipitation of Nb ss in αNb₅Si₃ was observed in the small size button and suction-cast bars after the heat treatment. Subgrains formed in αNb₅Si₃ after the heat treatment of the OFZ bars. The partitioning of solutes and in particular of Mo and Ti was key to this phase transformation. Subgrain formation was not necessary for precipitation of Nb ss in αNb₅Si₃, but the partitioning of solutes was essential for this precipitation.
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Metastable gamma-Iron Nickel Nanostructures for Magnetic Refrigeration Near Room Temperature
NASA Astrophysics Data System (ADS)
Ucar, Huseyin
The observation of a giant magnetocaloric effect in Gd5Ge 1.9Si2Fe0.1 has stimulated the magnetocaloric research in the last two decades. However, the high price of Gd and its proclivity to corrosion of these compounds have prevented their commercial use. To reduce raw materials cost, transition metal-based alloys are investigated to replace rare earth-based materials. Environmental considerations, substitution for scarce and strategic elements, and cost considerations all speak to potential contributions of these new materials to sustainability. Efforts in improving the refrigeration capacity (RC) of refrigerants mainly rely on broadening the magnetic entropy change. One promising technique is to couple two phases of magnetic materials with desirable properties. Second is the investigation of nanoparticle synthesis routes, with ball milling being the most widely used one. The motivation for the nanoparticles synthesis is rooted in their inherent tendency to have distributed exchange coupling, which will broaden the magnetic entropy curve. As proven with the cost analysis, the focus is believed to shift from improving the RC of refrigerants toward finding the most economically advantageous magnetic refrigerant with the highest performance. Mechanically alloyed Fe70Ni30 and Fe72Ni 28 alloys were characterized in terms of their structural and magnetic properties. Previous studies showed that single phase FCC gamma-FeNi alloys with 26-30 at. % Ni have Curie temperatures, TC, near room temperature. Having TC near room temperatures along with large magnetization makes gamma-FeNi alloys attractive for room temperature magnetocaloric cooling technologies. To obtain a single gamma-phase, particles were solution annealed in the gamma-phase field and water quenched. The preferential oxidation of Fe during ball milling was used as a means to tune the TC of the alloy. Refrigeration capacities, RCFWHM, of the Fe70Ni30 and the Fe72Ni28 alloys were calculated to be 470 J/kg and 250 J/kg at 5 T, with peak temperatures 363 K and 333 K, respectively. The RCFW H M for the Fe70Ni30 is higher than the previously reported Nanoperm (Fe70Ni 30)89Zr7B4 type alloy and on the same order of magnitude with other Fe-based alloys. The maximum magnetic entropy change values observed for the Fe70Ni30 and the Fe 72Ni28 are 0.65 and 0.5 Jkg--1K --1, respectively, at a field of 5 T. These are smaller than those of rare earth magnetic refrigerants showing first order transformation behavior. The larger RCFW H M value results mainly from the width of the magnetic entropy curve in these types of materials. In a follow up study, nanocrystalline powders of (Fe70Ni 30)100--xMox (x=1 to x=4) were produced by high energy (SPEX) mechanical alloying. Increasing the Mo content was found to stabilize the FCC phase in mechanically alloyed nanopowders. The TC of the alloys was lowered with Mo additions, without decreasing the Refrigeration Capacity (RC), due to the additional temperature broadening of the magnetic entropy change. Based on the previous study on the role of disorder, the additional temperature broadening was attributed to the increased positional disorder introduced by the Mo additions into the gammaFeNi system. Alloy with (Fe70Ni 30)96Mo4 composition was observed to have RCFW H M of 432 J/kg at 5T which is comparable to other prominent magnetic refrigerants operating near room temperatures. The economic viability of these rare-earth-free alloys, along with respectable magnetocaloric properties and potential for scalable production, make them good candidates for magnetic refrigeration applications.
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Metal- and intermetallic-matrix composites for aerospace propulsion and power systems
NASA Technical Reports Server (NTRS)
Doychak, J.
1992-01-01
The requirements for high specific strength refractory materials of prospective military, civil, and space propulsion systems are presently addressed in the context of emerging capabilities in metal- and intermetallic-matrix composites. The candidate systems encompass composite matrix compositions of superalloy, Nb-Zr refractory alloy, Cu-base, and Ti-base alloy types, as well as such intermetallics as TiAl, Ti3Al, NiAl, and MoSi2. The brittleness of intermetallic matrices remains a major consideration, as does their general difficulty of fabrication.
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NASA Astrophysics Data System (ADS)
Huang, Zhi Xiang; Wang, Ye; Liu, Bo; Kong, Dezhi; Zhang, Jun; Chen, Tupei; Yang, Hui Ying
2017-01-01
The alloying-dealloying reactions of SnS2 proceeds with the initial conversion reaction of SnS2 with lithium that produces Li2S. Unfortunately, due to the electrochemical inactivity of Li2S, the conversion reaction of SnS2 is irreversible, which significantly limit its potential applications in lithium-ion batteries. Herein, a systematic understanding of transition metal molybdenum (Mo) as a catalyst in SnS2 anode is presented. It is found that Mo catalyst is able to efficiently promote the reversible conversion of Sn to SnS2. This leads to the utilization of both conversion and alloying reactions in SnS2 that greatly increases lithium storage capability of SnS2. Mo catalyst is introduced in the form of MoS2 grown directly onto self-assembled vertical SnS2 nanosheets that anchors on three-dimensional graphene (3DG) creating a hierarchal nanostructured named as SnS2/MoS2/3DG. The catalytic effect results in a significantly enhanced electrochemical properties of SnS2/MoS2/3DG; a high initial Coulombic efficiency (81.5%) and high discharge capacities of 960.5 and 495.6 mA h g-1 at current densities of 50 and 1000 mA g-1, respectively. Post cycling investigations using ex situ TEM and XPS analysis verifies the successful conversion reaction of SnS2 mediated by Mo. The successful integration of catalyst on alloying type metal sulfide anode creates a new avenue towards high energy density lithium anodes.
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Huang, Zhi Xiang; Wang, Ye; Liu, Bo; Kong, Dezhi; Zhang, Jun; Chen, Tupei; Yang, Hui Ying
2017-01-19
The alloying-dealloying reactions of SnS 2 proceeds with the initial conversion reaction of SnS 2 with lithium that produces Li 2 S. Unfortunately, due to the electrochemical inactivity of Li 2 S, the conversion reaction of SnS 2 is irreversible, which significantly limit its potential applications in lithium-ion batteries. Herein, a systematic understanding of transition metal molybdenum (Mo) as a catalyst in SnS 2 anode is presented. It is found that Mo catalyst is able to efficiently promote the reversible conversion of Sn to SnS 2 . This leads to the utilization of both conversion and alloying reactions in SnS 2 that greatly increases lithium storage capability of SnS 2 . Mo catalyst is introduced in the form of MoS 2 grown directly onto self-assembled vertical SnS 2 nanosheets that anchors on three-dimensional graphene (3DG) creating a hierarchal nanostructured named as SnS 2 /MoS 2 /3DG. The catalytic effect results in a significantly enhanced electrochemical properties of SnS 2 /MoS 2 /3DG; a high initial Coulombic efficiency (81.5%) and high discharge capacities of 960.5 and 495.6 mA h g -1 at current densities of 50 and 1000 mA g -1 , respectively. Post cycling investigations using ex situ TEM and XPS analysis verifies the successful conversion reaction of SnS 2 mediated by Mo. The successful integration of catalyst on alloying type metal sulfide anode creates a new avenue towards high energy density lithium anodes.
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Complex, Precision Cast Columbium Alloy Gas Turbine Engine Nozzles Coated to Resist Oxidation.
1980-04-01
Microstructures of Sprayed Specimens 64 Table 19 NS-4 Coated C129Y Alloy Specimens Weight Bisque Weight Sintered Weight Silicided Weight Pre-Oxidized...choice of another alloy , while perhaps assisting in the foundry process , would not have yielded a mechanical property data base with advantage over...Mo 250 ppm max; Fe 30 ppm max; Al , Ca, C, Si, Cr, Ni, Cu , Mn, Mg and Sn 10 ppm max each). Molybdenum វim powder (02 2000 ppm max; W 250 ppm max; Fe
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A New Paradigm of Fatigue Variability Behavior and Implications for Life Prediction (Preprint)
2006-06-01
turbine engine materials is discussed. These were: the α+β titanium alloy, Ti-6Al-2Sn-4Zr-6Mo (Ti- 6 -2- 4 - 6 ) and a powder metallurgy (P/M) processed...MATERIALS AND EXPERIMENTAL PROCEDURE The materials in this study were an α+β titanium alloy, Ti- 6 -2- 4 - 6 and a P/M processed nickel-based superalloy. Two...and correlations between microstructure and loading variables vs. the mean behavior have been established in many cases [ 6 -9]. In α+β titanium alloys
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2007-07-01
predicted at lower stress levels as illustrated for the α+β titanium alloy, Ti-6Al-2Sn-4Zr-6Mo (Ti- 6 -2- 4 - 6 ), in Fig. 2((a) and (b)) [7, 8]. The...variability by a bimodal probability density representing the superposition of these dual mechanisms with reference to the α+β titanium alloy, Ti- 6 -2- 4 - 6 ...these trends. 7 The alternate description is illustrated with respect to the α+β titanium alloy, Ti- 6 -2- 4 - 6 . The stress vs. total lifetime behavior
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Lee, S-H; Todai, M; Tane, M; Hagihara, K; Nakajima, H; Nakano, T
2012-10-01
The elastic anisotropy of the Ti-15Mo-5Zr-3Al (mass%) β-Ti alloy, an ISO certified biomedical material, was investigated using its single crystal. It was revealed that the Young's modulus exhibited pronounced anisotropy. The Young's modulus was reduced to 44.4GPa along the 〈100〉 direction in the Ti-15Mo-5Zr-3Al single crystal, that is comparable to that of human cortical bones. We determined the strategy that β-Ti alloys with extremely low moduli can be developed by reducing the electron-atom (e/a) ratio in alloys, and by suppressing the formation of the ω-phase at the same time. This new knowledge must lead to the development of "single crystalline β-Ti implant materials" as hard tissue replacements for reducing the stress shielding effect. Copyright © 2012 Elsevier Ltd. All rights reserved.
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Undercooled and rapidly quenched Ni-Mo alloys
NASA Technical Reports Server (NTRS)
Tewari, S. N.; Glasgow, T. K.
1986-01-01
Hypoeutectic, eutectic, and hypereutectic nickel-molybdenum alloys were rapidly solidified by both bulk undercooling and melt spinning techniques. Alloys were undercooled in both electromagnetic levitation and differential thermal analysis equipment. The rate of recalescence depended upon the degree of initial undercooling and the nature (faceted or nonfaceted) of the primary nucleating phase. Alloy melts were observed to undercool more in the presence of primary Beta (NiMo intermetallic) phase than in gamma (fcc solid solution) phase. Melt spinning resulted in an extension of molybdenum solid solubility in gamma nickel, from 28 to 37.5 at % Mo. Although the microstructures observed by undercooling and melt spinning were similar the microsegregation pattern across the gamma dendries was different. The range of microstructures evolved was analyzed in terms of the nature of the primary phase to nucleate, its subsequent dendritic growth, coarsening and fragmentation, and final solidification of interfenderitic liquid.
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Phase transformation in rapidly quenched Fe-Cr-Co-Mo-Ti-Si-B alloys
NASA Astrophysics Data System (ADS)
Zhukov, D. G.; Shubakov, V. S.; Zhukova, E. Kh; Gorshenkov, M. V.
2018-03-01
The research results of phase transformations in Fe-24Cr-16Co-3Mo-0.2Ti-1Si-B alloys (with a boron content of 1 to 3% by mass) obtained by rapid quenching are presented. The structure formation regularities during the melt spinning and during the subsequent crystallization annealing in rapidly quenched bands of the Fe-Cr-Co-Mo-Ti-Si-B system alloys were studied. The changes in the phase composition of the rapidly quenched Fe-Cr-Co-Mo-Ti- Si-B system alloys after quenching at various quench rates and at different boron concentrations in the alloys are studied. It is shown that during crystallization from an amorphous state, at temperatures above 570 °C, in addition to the α-phase, the σ-phase appears first, followed by the γ-phase. Heat treatment of rapidly quenched bands to high-coercive state was carried out. A qualitative assessment of magnetic properties in a high-coercivity state was carried out. An evaluation of the level of magnetic properties in a high-coercivity state allows us to conclude that the application of a magnetic field during crystallization from an amorphous state leads to anisotropy of the magnetic properties, that is, an anisotropic effect of thermo-magnetic treatment is detected.
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NASA Technical Reports Server (NTRS)
Whittenberger, J. D.; Raj, S. V.; Locci, I. E.; Salem, J. A.
2001-01-01
A study of the effects of small (0.25 to 1.0 at%) fifth element additions to the structure and mechanical properties of directionally solidified (DS) NiAl-31Cr-3Mo has been undertaken. Essentially all the additions changed the as-DS'ed microstructure from lamellar eutectic grains to cells and, in some cases, introduced NiAl dendrites and/or third phases. In general the alloying additions did not improve strength or toughness over that possessed by the base composition; only Hf and, perhaps Ti, gave a minor increase in elevated temperature creep resistance. The lack of improvement in creep properties is probably due to inability to precipitation harden NiAl.
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Development and Processing of Nickel Aluminide-Carbide Alloys
NASA Technical Reports Server (NTRS)
Newport, Timothy Scott
1996-01-01
With the upper temperature limit of the Ni-based superalloys attained, a new class of materials is required. Intermetallics appear as likely candidates because of their attractive physical properties. With a relatively low density, high thermal conductivity, excellent oxidation resistance, high melting point, and simple crystal structure, nickel aluminide (NiAl) appears to be a potential candidate. However, NiAl is limited in structural applications due to its low room temperature fracture toughness and poor elevated temperature strength. One approach to improving these properties has been through the application of eutectic composites. Researchers have shown that containerless directional solidification of NiAl-based eutectic alloys can provide improvement in both the creep strength and fracture toughness. Although these systems have shown improvements in the mechanical properties, the presence of refractory metals increases the density significantly in some alloys. Lower density systems, such as the carbides, nitrides, and borides, may provide NiAl-based eutectic structure. With little or no information available on these systems, experimental investigation is required. The objective of this research was to locate and develop NiAl-carbide eutectic alloys. Exploratory arc-melts were performed in NiAl-refractory metal-C systems. Refractory metal systems investigated included Co, Cr, Fe, Hf, Mo, Nb, Ta, Ti, W, and Zr. Systems containing carbides with excellent stability (i.e.,HfC, NbC, TaC, TiC, and ZrC) produced large blocky cubic carbides in an NiAl matrix. The carbides appeared to have formed in the liquid state and were randomly distributed throughout the polycrystalline NiAl. The Co, Cr, Fe, Mo, and W systems contained NiAl dendrites with a two-phase interdendritic microconstituent present. Of these systems, the NiAl-Mo-C system had the most promising microstructure for in-situ composites. Three processing techniques were used to evaluate the NiAl-Mo-C system: arc-melting, slow cooling, and containerless directional solidification. Arc-melting provided a wide range of compositions in an economical and simple fashion. The slow cooled ingots provided larger ingots and slower cooling rates than arc-melting. Directional solidification was used to produce in-situ composites consisting of NiAl reinforced with molybdenum carbides.
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NASA Astrophysics Data System (ADS)
Zhang, D. C.; Xue, Q.; Lei, J. F.; Ma, Y. J.; Yang, R.; Wang, C.
2018-06-01
Metastable β Ti-12Mo wt pct alloys with controllable grain sizes are successfully produced, and the effect of grain size on mechanical responses has been thoroughly investigated. It is found that target alloys possess concurrent twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) features. Mechanisms governing mechanical properties through well-manipulated tensile experiments, detailed microstructure analysis, as well as strong correlations between triggering stress and twinning/phase transformation are offered.
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Microstructural Effects on the Deformation and Fracture of the Alloy Ti- 25Al-10Nb-3B-1Mo
1992-12-01
Materials Development Branch whose stimulating discussions on titanium aluminide physical and mechanical metallurgy helped immensely. This thesis may not... properties and fracture is somewhat different in the a 2 +0/B2 titanium aluminides from conventional a+13 titanium alloys. When trying to explain the...effects of microstructure and temperature on tensile and fracture behavior were explored for the titanium aluminide alloy Ti-25AI-l0Nb-3V-lMo (atomic
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Fu, Jie; Kim, Hee Young; Miyazaki, Shuichi
2017-01-01
In this study a new superelastic Ti-18Zr-4.5Nb-3Sn-2Mo alloy was prepared by adding 2at% of Mo as a substitute for Nb to the Ti-18Zr-11Nb-3Sn alloy, and heat treatment at different temperatures was conducted. The temperature dependence of superelasticity and annealing texture was investigated. Texture showed a dependence of annealing temperature: the specimen annealed at 923K for 0.3ks exhibited {113} β <47¯1> β type texture which was similar to the deformation texture, while specimens annealed at 973, 1073K, and 1173K showed {001} β <110> β type recrystallization texture which was preferable for recovery strain. The largest recovery strain of 6.2%, which is the same level as that of the Ti-18Zr-11Nb-3Sn alloy, was obtained in the specimen annealed at 1173K for 0.3ks due to the well-developed {001} β <110> β type recrystallization texture. The Ti-18Zr-3Nb-3Sn-2Mo alloy presented a higher tensile strength compared with the Ti-18Zr-11Nb-3Sn alloy when heat treated at 1173K for 0.3ks, which was due to the solid solution strengthening effect of Mo. Annealing at 923K for 0.3ks was effective in obtaining a good combination of a high strength as 865MPa and a large recovery strain as 5.6%. The high recovery strain was due to the high stress at which the maximum recovery stain was obtained which was attributed to the small grain size formed at low annealing temperature. Copyright © 2016 Elsevier Ltd. All rights reserved.
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The structural phases and vibrational properties of Mo1-xWxTe2 alloys
NASA Astrophysics Data System (ADS)
Oliver, Sean M.; Beams, Ryan; Krylyuk, Sergiy; Kalish, Irina; Singh, Arunima K.; Bruma, Alina; Tavazza, Francesca; Joshi, Jaydeep; Stone, Iris R.; Stranick, Stephan J.; Davydov, Albert V.; Vora, Patrick M.
2017-12-01
The structural polymorphism in transition metal dichalcogenides (TMDs) provides exciting opportunities for developing advanced electronics. For example, MoTe2 crystallizes in the 2H semiconducting phase at ambient temperature and pressure, but transitions into the 1T‧ semimetallic phase at high temperatures. Alloying MoTe2 with WTe2 reduces the energy barrier between these two phases, while also allowing access to the T d Weyl semimetal phase. The \\text{M}{{\\text{o}}1-\\text{x}} WxTe2 alloy system is therefore promising for developing phase change memory technology. However, achieving this goal necessitates a detailed understanding of the phase composition in the MoTe2-WTe2 system. We combine polarization-resolved Raman spectroscopy with x-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) to study bulk \\text{M}{{\\text{o}}1-\\text{x}} WxTe2 alloys over the full compositional range x from 0 to 1. We identify Raman and XRD signatures characteristic of the 2H, 1T‧, and T d structural phases that agree with density-functional theory (DFT) calculations, and use them to identify phase fields in the MoTe2-WTe2 system, including single-phase 2H, 1T‧, and T d regions, as well as a two-phase 1T‧ + T d region. Disorder arising from compositional fluctuations in \\text{M}{{\\text{o}}1-\\text{x}} WxTe2 alloys breaks inversion and translational symmetry, leading to the activation of an infrared 1T‧-MoTe2 mode and the enhancement of a double-resonance Raman process in \\text{2H-M}{{\\text{o}}1-\\text{x}} WxTe2 alloys. Compositional fluctuations limit the phonon correlation length, which we estimate by fitting the observed asymmetric Raman lineshapes with a phonon confinement model. These observations reveal the important role of disorder in \\text{M}{{\\text{o}}1-\\text{x}} WxTe2 alloys, clarify the structural phase boundaries, and provide a foundation for future explorations of phase transitions and electronic phenomena in this system.
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NASA Astrophysics Data System (ADS)
Bouamama, Kh.; Djemia, P.; Benhamida, M.
2015-09-01
First-principles pseudo-potentials calculations of the mixing enthalpy, of the lattice constants a0 and of the single-crystal elastic constants cij for ternary metal nitrides TaxMe1-xN (Me=Mo or W) alloys considering the cubic B1-rocksalt structure is carried out. For disordered ternary alloys, we employ the virtual crystal approximation VCA in which the alloy pseudopotentials are constructed within a first-principles VCA scheme. The supercell method SC is also used for ordered structures in order to evaluate clustering effects. We find that the mixing enthalpy still remains negative for TaxMe1-xN alloys in the whole composition range which implies these cubic TaxMo1-xN and TaxW1-xN ordered solid solutions are stable. We investigate the effect of Mo and W alloying on the trend of the mechanical properties of TaN. The effective shear elastic constant c44, the Cauchy pressure (c12-c44), and the shear to bulk modulus G/B ratio are used to discuss, respectively, the mechanical stability of the ternary structure and the brittle/ductile behavior in reference to TaN, MeN alloys. We determine the onset transition from the unstable structure to the stable one B1-rocksalt from the elastic stability criteria when alloying MeN with Ta. In a second stage, in the frame of anisotropic elasticity, we estimate by one homogenization method the averaged constants
of the polycrystalline TaxMe1-xN alloys considering the special case of an isotropic medium with no crystallographic texture. -
El Sawy, Amal A; Shaarawy, Mohammed A
2014-02-01
The aim of this study was to evaluate the amount of ions released from Ti6Al4V and Co-Cr-Mo alloys both in vivo and in vitro. Twenty-one discs of each alloy were constructed and divided into seven groups. Three specimens from each group were immersed in a buffered saline solution over a period of 1, 3, 5, 7, 14, 21, and 28 days. Twenty-eight participants were also included in the study, where the study group consisted of 14 mandibular partially edentulous patients, and the control group consisted of 14 volunteers. The study group was further divided into two equal groups: the first group received removable partial dentures (RPDs) constructed from Co-Cr-Mo alloy, while the second group received RPDs constructed from Ti6Al4V alloy. Saliva samples were collected from each participant over the same study period. The conditioning media and saliva samples were analyzed using a spectrophotometer. One-way ANOVA and Tukey tests were used for statistical analysis (p < 0.05). The concentrations of metal ions released from the studied alloys were significantly higher in the in vitro than in the in vivo study group during the follow-up periods. A statistically significant increase in ion concentrations of the different elements for both alloys was found with time (p < 0.05). The amounts of released metallic ions from Co-Cr-Mo and Ti6Al4V alloys were higher in the buffered saline solutions than in the studied saliva samples and control groups; however, these amounts were still within the physiological limit of trace elements in the human body. © 2013 by the American College of Prosthodontists.
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Characterization of a High Strength, Refractory High Entropy Alloy, AlMo0.5NbTa0.5TiZr
NASA Astrophysics Data System (ADS)
Jensen, Jacob
High entropy alloys (HEAs) are a relatively new class of materials that have garnered significant interest over the last decade due to their intriguing balance of properties including high strength, toughness, and corrosion resistance. In contrast to conventional alloy systems, HEAs are based on four or more principal elements with near equimolar concentrations and tend to have simple microstructures due to the preferential formation of solid solution phases. HEAs appear to offer new pathways to lightweighting in structural applications, new alloys for elevated temperature components, and new magnetic materials, but more thorough characterization studies are needed to assess the viability of the recently developed multicomponent materials. One such HEA, AlMo0.5NbTa0.5TiZr, was selected to be the basis for this characterization study in part due to its strength at elevated temperatures (sigma0.2 = 1600 MPa at T = 800 °C) and low density compared with commercially available Ni-based superalloys. The refractory element containing HEA composition was developed in order to balance the high temperature strength of the refractory elements with the desirable properties achieved by the high entropy alloying design approach for potential use in aerospace thermal protection and structural applications. Ingots of AlMo0.5NbTa0.5TiZr were cast by vacuum arc melting followed by hot isostatic pressing (HIP) and homogenization at 1400 °C for 24 hrs with a furnace cool of 10 °C/min. The resulting microstructure was characterized at multiple length scales using x-ray diffraction (XRD), scanning transmission electron microscopy (SEM), conventional and scanning transmission electron microscopy (TEM and STEM), and x-ray energy dispersive spectroscopy (XEDS). The microstructure was found to consist of a periodic, coherent two phase mixture, where a disordered bcc phase is aligned orthogonally in an ordered B2 phase. Through microstructural evolution heat treatment studies, the nanoscale interpenetrating microstructure was discovered to form via a conditional spinodal reaction pathway involving a congruent ordering transformation preceding spinodal decomposition. In order to gain a comprehensive understanding of the true morphology of these phases and obtain a novel perspective of 3D elemental segregation in the HEA, STEM-high angle annular darkfield (HAADF) micrographs and XEDS spectral images were utilized in the tomographic reconstruction of the microstructure, which was inherently difficult to observe through conventional characterization techniques. The microstructure of the alloy was ultimately refined by incremental variations to the base alloy composition in an effort to remove deleterious intermetallic phases adversely affecting ductility. Despite the excellent compressive strength across a wide range of temperatures and the ability to tailor the microstructure by compositional modifications, microstructural and phase transformations in the desired operating temperature range indicate that the AlMo0.5NbTa0.5TiZr alloy may not be a suitable material for high temperature aerospace structural components.
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Microstructure of as-fabricated UMo/Al(Si) plates prepared with ground and atomized powder
NASA Astrophysics Data System (ADS)
Jungwirth, R.; Palancher, H.; Bonnin, A.; Bertrand-Drira, C.; Borca, C.; Honkimäki, V.; Jarousse, C.; Stepnik, B.; Park, S.-H.; Iltis, X.; Schmahl, W. W.; Petry, W.
2013-07-01
UMo-Al based fuel plates prepared with ground U8wt%Mo, ground U8wt%MoX (X = 1 wt%Pt, 1 wt%Ti, 1.5 wt%Nb or 3 wt%Nb) and atomized U7wt%Mo have been examined. The first finding is that that during the fuel plate production the metastable γ-UMo phases partly decomposed into two different γ-UMo phases, U2Mo and α'-U in ground powder or α″-U in atomized powder. Alloying small amounts of a third element to the UMo had no measurable effect on the stability of the γ-UMo phase. Second, the addition of some Si inside the Al matrix and the presence of oxide layers in ground and atomized samples is studied. In the case with at least 2 wt%Si inside the matrix a Silicon rich layer (SiRL) forms at the interface between the UMo and the Al during the fuel plate production. The SiRL forms more easily when an Al-Si alloy matrix - which is characterized by Si precipitates with a diameter ⩽1 μm - is used than when an Al-Si mixed powder matrix - which is characterized by Si particles with some μm diameter - is used. The presence of an oxide layer on the surface of the UMo particles hinders the formation of the SiRL. Addition of some Si into the Al matrix [7-11]. Application of a protective barrier at the UMo/Al interface by oxidizing the UMo powder [7,12]. Increase of the Mo content or use of UMo alloys with ternary element addition X (e.g. X = Nb, Ti, Pt) to stabilize the γ-UMo with respect to α-U or to control the UMo-Al interaction layer kinetics [9,12-24]. Use of ground UMo powder instead of atomized UMo powder [10,25] The points 1-3 are to limit the formation of the undesired UMo/Al layer. Especially the addition of Si into the matrix has been suggested [3,7,8,10,11,26,27]. It has been often mentioned that Silicon is efficient in reducing the Uranium-Aluminum diffusion kinetics since Si shows a higher chemical affinity to U than Al to U. Si suppresses the formation of brittle UAl4 which causes a huge swelling during the irradiation. Furthermore it enhances the formation of more stable UAl3 within the diffusion layer [14]. In addition, Si will not notably influence the reactor neutronics due to its low absorption cross section for thermal neutrons of σabs = 0.24 barn. Aluminum has σabs = 0.23 barn.Williams [28], Bierlein [29], Green [30] and de Luca [31] showed the first time in the 1950s that alloying Aluminum with some Silicon reduces the Uranium-Aluminum diffusion kinetics in can-type fuel elements. However, up to now uncertainties remained about the most promising Si concentration and the involved mechanisms.Ground powder - possibility 4 - introduces a high density of defects like dislocations, oxide layers and impurities into UMo grains. Fuel prepared with this kind of powder exhibits a larger porosity. It may also be combined with an AlSi matrix. As a consequence, the degree of swelling due to high-burn up is reduced compared to fuel with atomized powder [5,6,25].This study focuses on the metallurgical characterization of as-fabricated samples prepared with ground UMo and UMoX (X = Ti, Nb, Pt) powders and atomized UMo powder. The influence of some Si into the Al matrix and the presence of oxide layers on the UMo is discussed. Details of the differences of samples with ground UMo from atomized UMo will be discussed.The examined samples originate from non-irradiated spare fuel plates from the IRIS-TUM irradiation campaign [5,6]. The samples containing ground UMoX powders and atomized UMo powders with Si addition into the matrix have been produced for this study [32]. Powder mixing: The UMo powder is mixed with Al powder. Compact production: UMo-Al powder is poured into a mould and undergoes compaction under large force. Plate-processing: An AlFeNi frame is placed on an AlFeNi plate and the UMo-Al compact is placed into the frame. Afterwards it is covered with a second AlFeNi plate. This assembly is hot-rolled to reduce the total thickness to 1.4 mm. Subsequently, a blister test (1-2 h at 400-450 °C) ensures that the fuelplate is sealed. After this step, the UMo particles are tightly covered with Al as shown in Fig. 1. To access the meat layer, small samples have been cut from the fuel plates. The AlFeNi cladding has been removed using abrasive paper and diamond polishing paste. Cross sections were prepared from each sample and examined using SEM/EDX and XRD. Laboratory scale XRD Laboratory sealed-tube XRD on a STOE-STADIP diffractometer equipped with an incident beam focusing monochromator and used in reflection geometry with respect to the sample. MoK-α radiation has been used. Details on the systems used can be found in [39]. mu;-XRD using micro-focused synchrotron radiation at the Swiss Light Source μ-XAS beamline (PSI, Switzerland). At SLS, the beam size was 3 × 3 μm2, the energy was 19.7 keV. Further details on the experimental procedure can be found in [40]. Only very small sample volumes are probed with this technique, therefore the results may not be representative for the whole miniplate. The standard deviation of the lattice parameters obtained with this method is ±0.01 Å in case not different given. High-energy XRD (HE-XRD) in transmission mode using synchrotron radiation at the "High Energy Diffraction and Scattering Beamline ID15B" of ESRF. An X-ray energy of 87 keV has been used, the beam size was 0.3 × 0.3 mm2. Details on the experimental procedure are presented in [41,42]. It was possible to determine the average mass fractions of the phases present inside the sample using this technique. The standard deviation of the lattice parameters obtained with this method is ±0.001 Å in case not different given. laser granulometry to determine the size distribution of the particles, XRD for phase identification. Granulometry measurements showed that a significant amount of very fine particles of a few μm to 10 μm size are present in the first class of powder.In both cases, laboratory XRD analyses evidenced only two phases: γ-UMo and UO2. In contrast to observations on the final fuel plates, there are no signs of α-U. Comparing XRD data of atomized UMo powder (taken form the IRIS4 experiment) and ground UMo powder with almost the same Mo content, the peaks are broader in XRD patterns of ground UMo and there is a higher background [44]. This points that the lattice structure of the UMo inside the ground powder is strongly disordered during the grinding process.Complementary investigations were performed in these ground UMo powder samples using HE-XRD. The obtained data can therefore directly be compared to those measured on pre-oxidized atomized UMo powders [45] and IRIS-TUM fuel plates [41]. For both powder samples the γ-UMo lattice constant has been estimated to 3.433 ± 0.002 Å which corresponds to about 7.2 wt% for Mo in the alloy according to Dwight's law [46]. The existence of two UMo phases inside these ground particles (as in atomized case) could not be investigated because of the huge peak broadening (presence of micro distortions). Whatever the sample granulometry, the analysis of the HE-XRD data showed a non-negligible nitride contamination in ground powders (see Fig. 2). Two uranium nitride phases are indeed found in these samples: UN and U2N3+x[47]. Note that the presence of UN has also been found in the as-fabricated plates. These results confirm the high reactivity of UMo with both Oxygen and Nitrogen in the grinding conditions. As a comparison for temperatures in the 200-250 °C range, it seems that UNx phases are more difficult to grow: they were not present in outer layers obtained by heat treatment under air on atomized particles [45]. Finally it can be seen in Table 3 that the weight fractions of UO2 and U2N3+x phases are lower in the sample with larger UMo particles. This suggests the existence of an oxide, nitride outer shell around UMo ground particle with thickness that does not strongly evolve with particle size. This constant outer shell thickness has also been found in pre-oxidized atomized powders [45].The UMoX powder used for the samples MAFIA-I-18 - MAFIA-I-21 has not been investigated prior to plate fabrication. However, since the grinding process is essentially the same as for the pure UMo powder, similar characteristics are assumed. Thin oxide layers with a thickness ⩽1 μm on some of the particles that were not intentionally oxidized. Although the UMo powder was stored and handled under an inert atmosphere over the whole production process, some residual oxygen has reacted with the UMo. Already this thin oxide layers exhibits cracks (Fig. 5). Thicker oxide layers with a thickness up to 5 μm on the UMo particles that were oxidized purposely. This kind of oxide layer is very brittle and shows large cracks (Fig. 6). The oxidized UMo particles tend to detach with the matrix as gaps between the UMo particles and the oxide layer could be observed (Fig. 6). This is most obvious at spots where a UMo particle has been pulled out during polishing. A part of the oxide layer remained inside the resulting hole (Fig. 7). Atomized UMo powder 2 wt%Si in Al matrix, alloyed AlSi 2 wt%Si in Al matrix, mixed AlSi 5 wt%Si in Al matrix, mixed AlSi 7 wt%Si in Al matrix, mixed AlSi Ground UMo powder 2 wt%Si in Al matrix, alloyed AlSi The influence of an oxide layer around the UMo particles on the formation of the SiRL during fuel plate production is further discussed. The growth of a Si rich layer surrounding the UMo particles in the 2 wt%Si alloyed powder (oxidized UMo), as well as the 5 wt% and 7 wt%Si mixed powder (non-oxidized UMo) during production of the miniplates. The presence of Si precipitates in the Al-matrix (large precipitates in case of mixture, small si particles in alloy). No oxide layer: If no oxide layer is present around the UMo particles a homogeneous SiRL grows at the interface UMo-Al (Fig. 15a). Brittle oxide layer: An oxide layer is present around the UMo particles, the SiRL grows always between the UMo particle and the oxide layer (Fig. 15b). In this case the the SiRL is thin and not homogeneous. As presumed by Ripert et al. [7] it is essential that the oxide layer reveals cracks perpendicular the UMo particle surface to make path for the Si diffusion. Dense oxide layer: In case of a thin (≈1 μm) but compact oxide layer no SiRL is formed even at high Si concentrations inside the matrix (Fig. 15c). The observed effects are pronounced when the thickness of the oxide layer is increased, as shown in Fig. 16: UMo particles covered with a thicker oxide layer (>1 μm) inside an Aluminum matrix with 5 wt%Si (mixed Al-Si powder). The oxide layer is dense at the left side of the particle, no Si can be found there (Fig. 16a). In contrast, the brittle and cracked oxide layer on the right side made path for a Si diffusion but the SiRL is thinner than in the sites where the UMo particle is not covered with an oxide layer. EDX maps at different positions of the sample showed that in general no SiRL forms around UMo particles covered by oxide layers with a thickness greater than 1 μm (Fig. 16b). This behavior is identical for the samples with 5 wt%Si and 7 wt%Si added to the Aluminum matrix (mixed Al-Si powder). Obviously the presence of a (dense) oxide layer hampers the formation of a SiRL. different UXSiY phases with strongly overlapping peaks can be found in the SiRL, these phases are characterized by small sizes of the crystallites (a few tens of nanometers) and/or cell parameter gradients. Two different crystallographic phases have been usually identified: U(Al,Si)3 displaying a small lattice parameter of a0 = 4.16 Å. This indicates that about 40% of the Al lattice sites are occupied by Si atoms. The second phase is isostructural to U3Si54 with a different lattice parameter [59-61]. Although the U-Si-Al phase diagram contains a variety of phases, none of the phases reported in literature [62] could be used to fully refine the measured diagram. Therefore, three different hypotheses are suggested to explain the occurence of this unknown phase: The observed compound consists of two phases: Conventional U3Si5 and USi2, as has been suggested by the authors before [58]. However, only one literature source (Brown et al.) describing the occurrence of USi2 below 450 °C could be found [63,64]. Furthermore, it has not been possible to reproduce the experiments described by Brown et al. Therefore, this hypothesis remains doubtful [59]. The observed phase may be a new unknown phase. For example, a cubic phase with lattice constant a0 = 3.96 Å can be used to refine the observed peaks. This hypothesis can neither be confirmed nor refused based on the existing data. The observed phase can be a U3Si5 variant containing Mo and/or Al atoms. This hypothesis is supported by the authors. Hence in the following sections this structure will be denoted as U3Si5. No traces of SiRL phases are found inside the sample with 2 wt%Si mixed-powder matrix (MAFIA-I-3), all the Si remained inside the matrix. A SiRL is present inside the samples with 2.1 wt%Si alloyed powder matrix (MAFIA-I-4) and 5 wt%Si (MAFIA-I-5) and 7 wt%Si (MAFIA-I-7) mixed powder matrix. However, between 76% and 96% of the Si remained inside the matrix in form of precipitates or Si particles. The SiRL is formed readily when the Si is present inside the matrix in form of precipitates (i.e. Al-Si alloy matrix, MAFIA-I-4 and IRIS-TUM 8502) compared to particles (i.e. Al-Si mixed powder matrix, MAFIA-I-3, MAFIA-I-5 and MAFIA-I-7). This behavior can best be observed on the sample prepared with ground powder and with 2.1 wt%Si alloyed powder matrix (IRIS-TUM-8502): The matrix contains no Si, only SiRL phases are found. Since the sample with 5 wt%Si mixed powder matrix (MAFIA-I-5) has the lowest SiRL fraction but by far the highest UO2 content, it is concluded that the presence of UO2 around the UMo kernels tends to hamper the formation of a SiRL. UMo/Al samples prepared with ground powder contain irregularly shaped UMo kernels. They are in general oxidized and also contain oxide stringers. These samples have a high porosity content of around 8 vol%. In contrast, UMo/Al samples prepared with atomized powder contain spherical UMo kernels. Only the surface of the UMo kernels is oxidized in some cases. Thick oxide layers must be grown intentionally while thinner layers are the result of oxidation during the whole process. The oxide layer is in general brittle and exhibits cracks. The Uranium-oxide content of all examined samples (atomized and ground) varies between 2 and 13 wt%. gamma;-UMo present in the fresh UMo powder destabilizes to transform to an α-U-like phase, U2Mo, and two γ-UMo phases with different Mo content during the fuel plate production. For ground powder, α-U content varies in 28-38 wt%, for atomized powder in 11-14 wt%. The degree of γ-phase destabilization is therefore higher for ground powder. Ternary addition of Nb, Ti or Pt to the UMo did not impact the extent of decomposition. The γ-phase decomposition in the atomized and ground powder does not follow the expected in the U8wt%Mo TTT diagram between 400 and 450 °C [41]. According to Repas et al. [65], the route is γ-UMoa → γ-UMob + α-U → γ-UMoc+α-U + U2Mo . γ-UMoa,b,c differ in the Mo content where γ-UMoa has the lowest and γ-UMoc has the highest Mo content. We observe a new route of decomposition of ground powder into two different γ-UMo phases. One of them has approximately the original Mo content and the other has a higher Mo content. Further U2Mo and a phase with deformed lattice parameters compared to pure α-U have been observed. The latter is known as α' in literature.For atomized powder, also two different γ-UMo phases and traces of U2Mo have been found. However, a different α-U like phase has been identified: α″ [41,53-55].Repas et al. used as cast samples that have been examined with conventional XRD and different metallographic methods [65]. The difference to our data can be explained by the superior resolution of the here used HE-XRD diffraction. Most probably, conventional lab X-ray sourcces could not resolve fine differences in the lattice parameters of α-U and may not enable to separate two γ-UMo phase. To overcome this uncertainty it is highly desirable to examine the TTT diagram of UMo with high resolution. When Si is added into the matrix - by using alloyed Al-Si powder as a matrix or blending Al and Si powder - in general a SiRL is formed at the interface between the UMo and the Al matrix. An exception can be found in MAFIA-I-3 in which the overall Si content was to low to form a SiRL. The SiRL consists of U(Al,Si)3 and U3Si5. The SiRL forms less readily in case of mixed Al-Si than in case of alloyed Al-Si powder. In the latter case (MAFIA-I-4), a Si depleted zone has been observed around the UMo particles. For ground powder in combination with an Al-Si alloyed matrix, the entire Si from the matrix has reacted with the UMo forming SiRL phases. The presence of a dense oxide layer around the UMo kernels can prevent the formation of a SiRL. However, as soon as the oxide layer is cracked a SiRL forms between the UMo and the oxide layer. A dense oxide layer isolates the UMo from the Si inside the matrix and occurring cracks make path for the diffusion of Si towards the UMo. U3Si 5 is also called USi2-x or USi1.66 in literature.
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NASA Astrophysics Data System (ADS)
Oh, Seung-Jin; Jun, Joong-Hwan; Lee, Min-Ha; Shon, In-Jin; Lee, Seok-Jae
2018-05-01
In this study, we successfully fabricated highly alloyed FeCrMoVC specimens within 2 min by using the spark plasma sintering (SPS) method. The densities of the sintered specimens were almost identical to their theoretical values. Fine (Mo, V)-rich carbides with lamellar structure were precipitated along the grain boundaries of the as-sintered specimen, whereas relatively large carbides were formed additionally in the transgranular region during the tempering treatment. Compared with the specimen produced by a conventional casting method, the FeCrMoVC specimens from SPS showed smaller grain size with finer carbides and higher hardness values.
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The Structure and Mechanical Properties of Ni-Mo PM Steels with Addition of Mn And Cu
NASA Astrophysics Data System (ADS)
Lichańska, E.; Kulecki, P.; Pańcikiewicz, K.
2017-12-01
The aim of the study was to evaluate the effect of chemical composition on the structure and mechanical properties of Mn-Ni-Mo and Ni-Mo-Cu PM steels. Pre-alloyed powder Astaloy 85Mo, diffusion alloyed powders Distaloy AQ and Distaloy AB produced by Höganäs, low carbon ferromanganese, carbonyl nickel powder T255 with three-dimensional filamentary structure and graphite CU-F have been used as the basic powders. Three mixtures with compositions of Fe-1%Mn-(0.5/1.75)%Ni-(0.5/0.85)%Mo-0.8%C and Fe-1.75%Ni-0.5%Mo-1.5%Cu-0.8%C were prepared in a Turbula mixer. Green compacts were single pressed in a steel die at 660 MPa according to PN-EN ISO 2740 standard. Sinterhardening was carried out at 1250°C in a mixture of 95% N2+5% H2 for 60 minutes. Mechanical tests (tensile, bend, hardness) and microstructural investigations were performed. Additionally, XRD and EDS analysis, fractographic investigations were carried out. The microstructures of steels investigated were mainly bainitic or bainitic-martensitic. Addition 1% Mn to Distaloy AQ based steel caused increase of tensile properties (YS from 422 to 489 MPa, UTS from 522 to 638 MPa, TRS from 901 to 1096 MPa) and decrease of plasticity (elongation from 3.65 to 2.84%).
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PLANE STRAIN FRACTURE TOUGHNESS DATA FOR HANDBOOK PRESENTATION
An experimental program was conducted to determine the plane strain fracture toughness (K sub IC) of the following classes of: (1) AISI Alloy Steels...4340, 4140 ); (2) 5Cr-Mo-V Steels; (3) Precipitation-Hardening Stainless Steels (17-7 PH, PH 15-7 Mo, 17-4, AM355); (4) Titanium Alloy, Ti-6Al-4V. The
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Tantalum-based thin film coatings for wear resistant arthroprostheses.
Balagna, C; Faga, M G; Spriano, S
2011-10-01
Cobalt-chromium-molybdenum alloys with high carbon content (HC-CoCrMo) are widely used as materials for arthroprosthesis, in particular in metal-on-metal (MoM) hip joints. In spite of their good wear and corrosion resistance, production of metallic wear particles and metal ion release will occur on a large time-scale. An enhancement of the metal ion level in the patient's blood and urine is often reported in clinical data. Hypersensitivity, inflammatory response and cell necrosis can occur as consequence. So implants on young patients and women on childbearing age are not so widespread. The aim of this research is the realization of a thin film coating in order to improve the biocompatibility of Co-based alloys and to reduce debris production, ion release and citotoxicity. The innovative process consists of a thermal treatment in molten salts, in order to obtain a tantalum enriched thin film coating. Tantalum is chosen because it is considered a biocompatible metal with high corrosion resistance and low ion release. Three HC-CoCrMo alloys, produced by different manufacturing processes, are tested as substrates. The coating is a thin film of TaC or it can be composed by a multilayer of two tantalum carbides and metallic tantalum, depending on the temperature of the treatment and on the carbon content of the substrate. The thin films as well the substrates are characterized from the structural, chemical and morphological point of view. Moreover mechanical behaviour of treated and untreated materials is analyzed by means of nanohardness, scratch and ball-on-disc wear tests. The coating increases the mechanical and tribological properties of HC-CoCrMo.
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Simulations of Metallic Nanoscale Structures
NASA Astrophysics Data System (ADS)
Jacobsen, Karsten W.
2003-03-01
Density-functional-theory calculations can be used to understand and predict materials properties based on their nanoscale composition and structure. In combination with efficient search algorithms DFT can furthermore be applied in the nanoscale design of optimized materials. The first part of the talk will focus on two different types of nanostructures with an interesting interplay between chemical activity and conducting states. MoS2 nanoclusters are known for their catalyzing effect in the hydrodesulfurization process which removes sulfur-containing molecules from oil products. MoS2 is a layered material which is insulating. However, DFT calculations indicates the exsistence of metallic states at some of the edges of MoS2 nanoclusters, and the calculations show that the conducting states are not passivated by for example the presence of hydrogen gas. The edge states may play an important role for the chemical activity of MoS_2. Metallic nanocontacts can be formed during the breaking of a piece of metal, and atomically thin structures with conductance of only a single quantum unit may be formed. Such open metallic structures are chemically very active and susceptible to restructuring through interactions with molecular gases. DFT calculations show for example that atomically thin gold wires may incorporate oxygen atoms forming a new type of metallic nanowire. Adsorbates like hydrogen may also affect the conductance. In the last part of the talk I shall discuss the possibilities for designing alloys with optimal mechanical properties based on a combination of DFT calculations with genetic search algorithms. Simulaneous optimization of several parameters (stability, price, compressibility) is addressed through the determination of Pareto optimal alloy compositions within a large database of more than 64000 alloys.
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Rao, Ankita; Kumar Sharma, Abhishek; Kumar, Pradeep; Charyulu, M M; Tomar, B S; Ramakumar, K L
2014-07-01
A new method has been developed for separation and purification of fission (99)Mo from neutron activated uranium-aluminum alloy. Alkali dissolution of the irradiated target (100mg) results in aluminum along with (99)Mo and a few fission products passing into solution, while most of the fission products, activation products and uranium remain undissolved. Subsequent purification steps involve precipitation of aluminum as Al(OH)3, iodine as AgI/AgIO3 and molybdenum as Mo-α-benzoin oxime. Ruthenium is separated by volatilization as RuO4 and final purification of (99)Mo was carried out using anion exchange method. The radiochemical yield of fission (99)Mo was found to be >80% and the purity of the product was in conformity with the international pharmacopoeia standards. Copyright © 2014 Elsevier Ltd. All rights reserved.
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Laser Additive Manufacturing of Magnetic Materials
NASA Astrophysics Data System (ADS)
Mikler, C. V.; Chaudhary, V.; Borkar, T.; Soni, V.; Jaeger, D.; Chen, X.; Contieri, R.; Ramanujan, R. V.; Banerjee, R.
2017-03-01
While laser additive manufacturing is becoming increasingly important in the context of next-generation manufacturing technologies, most current research efforts focus on optimizing process parameters for the processing of mature alloys for structural applications (primarily stainless steels, titanium base, and nickel base alloys) from pre-alloyed powder feedstocks to achieve properties superior to conventionally processed counterparts. However, laser additive manufacturing or processing can also be applied to functional materials. This article focuses on the use of directed energy deposition-based additive manufacturing technologies, such as the laser engineered net shaping (LENS™) process, to deposit magnetic alloys. Three case studies are presented: Fe-30 at.%Ni, permalloys of the type Ni-Fe-V and Ni-Fe-Mo, and Fe-Si-B-Cu-Nb (derived from Finemet) alloys. All these alloys have been processed from a blend of elemental powders used as the feedstock, and their resultant microstructures, phase formation, and magnetic properties are discussed in this paper. Although these alloys were produced from a blend of elemental powders, they exhibited relatively uniform microstructures and comparable magnetic properties to those of their conventionally processed counterparts.
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Thermophysical properties of heat-treated U-7Mo/Al dispersion fuel
DOE Office of Scientific and Technical Information (OSTI.GOV)
Cho, Tae Won; Kim, Yeon Soo; Park, Jong Man
In this study, the effects of interaction layer (IL) on thermophysical properties of U-7Mo/Al dispersion fuel were examined. Microstructural analyses revealed that ILs were formed uniformly on U-Mo particles during heating of U-7Mo/Al samples. The IL volume fraction was measured by applying image analysis methods. The uranium loadings of the samples were calculated based on the measured meat densities at 298 K. The density of the IL was estimated by using the measured density and IL volume fraction. Thermal diffusivity and heat capacity of the samples after the heat treatment were measured as a function of temperature and volume fractionsmore » of U-Mo and IL. The thermal conductivity of IL-formed U-7Mo/Al was derived by using the measured thermal diffusivity, heat capacity, and density. The thermal conductivity obtained in the present study was lower than that predicted by the modified Hashin–Shtrikman model due to the theoretical model’s inability to consider the thermal resistance at interfaces between the meat constituents.« less
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Oxidation performance of platinum-clad Mo-47Re alloy
NASA Technical Reports Server (NTRS)
Clark, Ronald K.; Wallace, Terryl A.
1994-01-01
The alloy Mo-47Re has favorable mechanical properties at temperatures above 1400 C, but it undergoes severe oxidation when used in air with no protective coating. To shield the alloy from oxidation, platinum cladding has been evaluated. The unprotected alloy undergoes catastrophic oxidation under static and dynamic oxidation conditions. The platinum cladding provides good protection from static and dynamic oxidation for moderate times at 1260 C. Samples tested for longer times under static oxidation conditions experienced severe oxidation. The data suggest that oxidation results from the transport of oxygen through the grain boundaries and through the pinhole defects of the platinum cladding.
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Atomic and electronic basis for the serrations of refractory high-entropy alloys
NASA Astrophysics Data System (ADS)
Wang, William Yi; Shang, Shun Li; Wang, Yi; Han, Fengbo; Darling, Kristopher A.; Wu, Yidong; Xie, Xie; Senkov, Oleg N.; Li, Jinshan; Hui, Xi Dong; Dahmen, Karin A.; Liaw, Peter K.; Kecskes, Laszlo J.; Liu, Zi-Kui
2017-06-01
Refractory high-entropy alloys present attractive mechanical properties, i.e., high yield strength and fracture toughness, making them potential candidates for structural applications. Understandings of atomic and electronic interactions are important to reveal the origins for the formation of high-entropy alloys and their structure-dominated mechanical properties, thus enabling the development of a predictive approach for rapidly designing advanced materials. Here, we report the atomic and electronic basis for the valence-electron-concentration-categorized principles and the observed serration behavior in high-entropy alloys and high-entropy metallic glass, including MoNbTaW, MoNbVW, MoTaVW, HfNbTiZr, and Vitreloy-1 MG (Zr41Ti14Cu12.5Ni10Be22.5). We find that the yield strengths of high-entropy alloys and high-entropy metallic glass are a power-law function of the electron-work function, which is dominated by local atomic arrangements. Further, a reliance on the bonding-charge density provides a groundbreaking insight into the nature of loosely bonded spots in materials. The presence of strongly bonded clusters and weakly bonded glue atoms imply a serrated deformation of high-entropy alloys, resulting in intermittent avalanches of defects movement.
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Effect of the microstructure of Ti-5Mo on the anodic dissolution in H/sub 2/SO/sub 4/
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kim, Y.J.; Oriani, R.A.
1987-04-01
The effect of microstructure of the Ti-5Mo alloy on its anodic dissolution rate in sulfuric acid solution at various temperatures has been investigated. TiMo alloys exhibit a region of increased dissolution rate in the vicinity of +0.20 V (saturated calomel electrode (SCE)) in 10% H/sub 2/SO/sub 4/, the same potential region in which pure Mo exhibits a large anodic dissolution rate. Aging of Ti-5Mo at 350 C was found to lead to the formation of ..omega.. phase. Heat treatment caused larger passive currents in 10% H/sub 2/SO/sub 4/, but the critical passivation potentials and corrosion potentials were not significantly affected.more » Molybdenum was enriched in the oxide formed on aged Ti-5Mo at +0.23 V (SCE), in comparison with the Mo concentration found in the oxide on as-received Ti-5Mo.« less
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NASA Astrophysics Data System (ADS)
Keshavarz, Mohsen K.; Fattah-Alhosseini, Arash
2018-05-01
The corrosiveness of bismuth telluride-based thermoelectric materials (n-type single-phase alloy and a nanocomposite with MoS2 nanoinclusions), in 0.1 molar solution of sodium chloride (NaCl), was investigated. The electrochemical impedance spectroscopy curves obtained after 1, 24, 48 and 72 h immersion time revealed the enhancement of the corrosion resistance of the nanocomposite specimen in a 0.1 molar NaCl solution in comparison with the single-phase bismuth telluride-based alloys, and the passivity increased by immersion time up to 72 h. The nanocomposite sample with submicron grains provided suitable nucleation sites for passive film nucleation that led to higher protective behavior.
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NASA Technical Reports Server (NTRS)
Dupraw, W. A.
1972-01-01
A simple analytical procedure is described for accurately and precisely determining the zirconium or hafnium content of molybdenum-base alloys. The procedure is based on the reaction of the reagent Arsenazo III with zirconium or hafnium in strong hydrochloric acid solution. The colored complexes of zirconium or hafnium are formed in the presence of molybdenum. Titanium or rhenium in the alloy have no adverse effect on the zirconium or hafnium complex at the following levels in the selected aliquot: Mo, 10 mg; Re, 10 mg; Ti, 1 mg. The spectrophotometric measurement of the zirconium or hafnium complex is accomplished without prior separation with a relative standard deviation of 1.3 to 2.7 percent.
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Voltage effects on cells cultured on metallic biomedical implants
NASA Astrophysics Data System (ADS)
Haerihosseini, Seyed Morteza
Electrochemical voltage shifts in metallic biomedical implants occur in-vivo due to a number of processes including mechanically assisted corrosion. Surface potential of biomedical implants and excursions from resting open circuit potential (OCP), which is the voltage they attain while in contact with an electrolyte, can significantly change the interfacial properties of the metallic surfaces and alter the behavior of the surrounding cells, compromising the biocompatibility of metallic implants. Voltages can also be controlled to modulate cell function and fate. To date, the details of the physico-chemical phenomena and the role of different biomaterial parameters involved in the interaction between cells and metallic surfaces under cathodic bias have not been fully elucidated. In this work, changes in the interfacial properties of a CoCrMo biomedical alloy (ASTM F-1537) in phosphate-buffered saline (PBS) (pH 7.4) at different voltages was studied. Step polarization impedance spectroscopy technique was used to apply 50 mV voltage steps to samples, and the time-based current transients were recorded. A new equation was derived based on capacitive discharge through a Tafel element and generalized to deal with non-ideal impedance behavior. The new function compared to the KWW-Randles function, better matched the time-transient response. The results also showed a voltage dependent oxide resistance and capacitance behavior. Additionally, the in-vitro effect of static voltages on the behavior of MC3T3-E1 pre-osteoblasts cultured on CoCrMo alloy (ASTM-1537) was studied to determine the range of cell viability and mode of cell death beyond the viable range. Cell viability and morphology, changes in actin cytoskeleton, adhesion complexes and nucleus, and mode of cell death (necrosis, or intrinsic or extrinsic apoptosis) were characterized at different voltages ranging from -1000 to +500 mV (Ag/AgCl). Moreover, electrochemical currents and metal ion concentrations at each voltage were measured and related to the observed responses. Results show that cathodic and anodic voltages outside the voltage viability range (-400 < V < +500) lead to primarily intrinsic apoptotic and necrotic cell death, respectively. Cell death is associated with cathodic current densities of 0.1 uAcm-2 and anodic current densities of 10 uAcm-2. Significant increase in metallic ions (Co, Cr, Ni, Mo) was seen at +500 mV, and -1000 mV (Cr only) compared to open circuit potential. The number and total projected area of adhesion complexes was also lower on the polarized alloy (p < 0.05). These results show that reduction reactions on CoCrMo alloys leads to apoptosis of cells on the surface and may be a relevant mode of cell death for metallic implants in-vivo. . On the other hand, we studied how surface oxide thickness of Ti affects its voltage viability range and cellular response and whether anodic oxidation can serve as a means to extend this range. Cellular behavior (cell viability, cytoskeletal organization, and cellular adhesion) on bare and anodized Ti samples, potentiostatically held at voltages at the cathodic edge of the viability range, were assessed. Surfaces were characterized using contact angle (CA) measurement technique and atomic force microscopy (AFM), and the observed cellular response was related to the changes in the electrochemical properties (electrochemical currents, open circuit potential, and impedance spectra) of the samples. Results show that anodization at a low voltage (9 V) in phosphate buffer saline (PBS) generates a compact surface oxide with comparable surface roughness and energy to the starting native oxide on the bare surface. The anodized surface extends the viability range at 24 hours by about a 100 mV in the cathodic region, and preserved the cytoskeletal integrity and cell adhesion. Broadening of the viability range corresponds to an increase in impedance of the anodized surface at -400 mV(Ag/AgCl) and the resulting low average currents (below 0.1 uAcm-2) at the interface, which diminish the harmful cathodic reactions. Finally, cellular dynamics (size, polarity, movement) and temporal changes in the number and total area of focal adhesions in transiently transfected MC3T3-E1 pre-osteoblasts cultured on a CoCrMo alloy polarized at the cathodic and anodic edges of its voltage viability range (-400 and +500 mV(Ag/AgCl) respectively) were studied. Nucleus dynamics (size, circularity, movement) and the release of reactive oxygen species (ROS) was also studied on the polarized metal at -1000, -400, and +500 mV(Ag/AgCl). The results show that at -400 mV(Ag/AgCl) a gradual loss of adhesion occurs over 24 hours while cells shrink in size during this time. At +500 mV, cells become non-viable after 5 hours without showing any significant changes in adhesion behavior right before cell death. Nucleus size of cells at -1000 mV decreased sharply within 15 minutes after electrochemical polarization, which rendered the cells completely non-viable. No significant amount of ROS was released by cells on the polarized CoCrMo at any of these voltages.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wheeling, Rebecca A., E-mail: wheeling.8@osu.edu; Lippold, John C., E-mail: lippold.1@osu.edu
2016-05-15
Additions of niobium (Nb) and molybdenum (Mo) were made to an Alloy 690 base alloy in order to investigate the formation of a eutectic constituent at the end of solidification and to evaluate the effect of the eutectic liquid on backfilling (or healing) of solidification cracks. Solidification cracking was induced using the cast pin tear test (CPTT) and regions of backfilling were located and characterized via optical and electron microscopy. Computational predictions of fraction eutectic and composition of the eutectic constituent were compared to experimental findings and were found to correlate well in both cases. The extent of crack backfillingmore » increased significantly with increasing Nb content, but the addition of Mo did not seem to influence the amount of eutectic constituent or the degree of backfilling. SEM/EDS analysis confirmed that the eutectic composition is constant and that increasing Nb above 4 wt% has little effect on expanding the solidification temperature range, but has a beneficial effect on mitigating solidification cracking by a crack healing effect. - Highlights: • Increasing fraction eutectic as a function of Nb, as predicted by ThermoCalc™, is consistent with image analysis results. • Nb, unlike Mo, had a significant effect on the fraction eutectic formed. • Both influence the composition of the eutectic. • Thermocalc™ predictions regarding Nb content in eutectic are consistent with EDS results, but are high for the Mo content. • Increased levels of niobium resulted in a higher degree of crack backfilling and leads to a lower cracking susceptibility. • Mo may influence the eutectic liquid along solidification grain boundaries, improving backfill and thus cracking resistance.« less
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Hot Extruded Polycrystalline Mg2Si with Embedded XS2 Nano-particles (X: Mo, W)
NASA Astrophysics Data System (ADS)
Bercegol, A.; Christophe, V.; Keshavarz, M. K.; Vasilevskiy, D.; Turenne, S.; Masut, R. A.
2017-05-01
Due to their abundant, inexpensive and non-toxic constituent elements, magnesium silicide and related alloys are attractive for large-scale thermoelectric (TE) applications in the 500-800 K temperature range, in particular for energy conversion. In this work, we propose a hot extrusion method favorable for large-scale production, where the starting materials (Mg2Si and XS2, X: W, Mo) are milled together in a sealed vial. The MoS2 nano-particles (0.5-2 at.%) act as solid lubricant during the extrusion process, thus facilitating material densification, as confirmed by density measurements based on Archimedes' method. Scanning electron microscopy images of bulk extruded specimens show a wide distribution of grain size, covering the range from 0.1 μm to 10 μm, and energy dispersive spectroscopy shows oxygen preferentially distributed at the grain boundaries. X-ray diffraction analysis shows that the major phase is the expected cubic structure of Mg2Si. The TE properties of these extruded alloys have been measured by the Harman method between 300 K and 700 K. Resistivity values at 700 K vary between 370 μΩ m and 530 μΩ m. The ZT value reaches a maximum of 0.26 for a sample with 2 at.% MoS2. Heat conductivity is reduced for extruded samples containing MoS2, which most likely behave as scattering centers for phonons. The reason why the WS2 particles do not bring any enhancement, for either densification or heat transfer reduction, might be linked to their tendency to agglomerate. These results open the way for further investigation to optimize the processing parameters for this family of TE alloys.
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Oxidation, carburization and/or sulfidation resistant iron aluminide alloy
Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton
2003-08-19
The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or Zro.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B. .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.
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NASA Astrophysics Data System (ADS)
Dzhumaev, P.; Yakushin, V.; Kalin, B.; Polsky, V.; Yurlova, M.
2016-04-01
This paper presents investigation results of the influence of high temperature pulsed plasma flows (HTPPF) treatment on the corrosion resistance of low-alloy steel 0.2C-Cr-Mn- Ni-Mo cladded by the rapidly quenched nickel-based alloy. A technique that allows obtaining a defect-free clad layer with a good adhesion to the substrate was developed. It is shown that the preliminary treatment of steel samples by nitrogen plasma flows significantly increases their corrosion resistance in the conditions of intergranular corrosion test in a water solution of sulfuric acid. A change of the corrosion mechanism of the clad layer from intergranular to uniform corrosion was observed as a result of sub-microcrystalline structure formation and homogeneous distribution of alloying elements in the plasma treated surface layer thus leading to the significant increase of the corrosion resistance.
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The Composition and Temperature Effects on the Ultra High Strength Stainless Steel Design
NASA Astrophysics Data System (ADS)
Xu, W.; Del Castillo, P. E. J. Rivera Díaz; van der Zwaag, S.
Alloy composition and heat treatment are of paramount importance to determining alloy properties. Their control is of great importance for new alloy design and industrial fabrication control. A base alloy utilizing MX carbide is designed through a theory guided computational approach coupling a genetic algorithm with optimization criteria based on thermodynamic, kinetic and mechanical principles. The combined effects of 11 alloying elements (Al, C, Co, Cr, Cu, Mo, Nb, Ni, Si, Ti and V) are investigated in terms of the composition optimization criteria: the martensite start (Ms) temperature, the suppression of undesirable phases, the Cr concentration in the matrix and the potency of the precipitation strengthening contribution. The results show the concentration sensitivities of each component and also point out new potential composition domains for further strength increase. The aging temperature effect is studied and the aging temperature industrially followed is recovered.
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Xie, Hongmei; Jiang, Bin; Hu, Xingyu; Peng, Cheng; Guo, Hongli; Pan, Fusheng
2017-01-01
The tribological performances of the SiO2/MoS2 hybrids as lubricant additives were explored by a reciprocating ball-on-flat tribometer for AZ31 magnesium alloy/AISI 52100 bearing steel pairs. The results demonstrated that the introduction of SiO2/MoS2 hybrids into the base oil exhibited a significant reduction in the friction coefficient and wear volume as well as an increase in load bearing capacity, which was better than the testing results of the SiO2 or MoS2 nanolubricants. Specifically, the addition of 0.1 wt % nano-SiO2 mixed with 1.0 wt % nano-MoS2 into the base oil reduced the friction coefficient by 21.8% and the wear volume by 8.6% compared to the 1.0 wt % MoS2 nanolubricants. The excellent lubrication behaviors of the SiO2/MoS2 hybrid nanolubricants can be explained by the micro-cooperation of different nanoparticles with disparate morphology and lubrication mechanisms. PMID:28644394
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NASA Astrophysics Data System (ADS)
Lee, Young-Joo; Shin, Hae-A.-Seul; Nam, Dae-Hyun; Yeon, Han-Wool; Nam, Boae; Woo, Kyoohee; Joo, Young-Chang
2015-01-01
The mechanical fatigue of Cu films and lines on flexible substrates was investigated, and an improvement in the structures through the use of a MoTi alloy under-layer was proposed. Fatigue reliability was decreased by 3-fold in lines compared with films in the tensile condition and by 6-fold in the compressive condition. Crack formation was observed to be more detrimental for lines than for films. With a MoTi under-layer, the fatigue limit was increased by 2 times that of a structure without MoTi in the tensile condition and by 15 times in the compressive bending condition. The suppression of delamination through the use of a MoTi under-layer improved the fatigue reliability under compressive bending.
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Effects of substitution of Mo for Nb on less-common properties of Finemet alloys
NASA Astrophysics Data System (ADS)
Butvin, P.; Butvinová, B.; Silveyra, J. M.; Chromčíková, M.; Janičkovič, D.; Sitek, J.; Švec, P.; Vlasák, G.
2010-10-01
Particular properties of Fe-Nb/Mo-Cu-B-Si rapidly quenched ribbons were examined. Apart from minor variation, no significant difference due to the Mo for Nb substitution was observed in alloy density and its annealing-induced changes. The same holds for the anisotropic thermal expansion of as-cast ribbon when annealed and for induced anisotropy when annealed under stress. The Mo-substituted ribbons show only slightly higher crystallinity and lower coercivity if annealed in inert gas ambience than in vacuum. Some diversity in surface to interior heterogeneity of the differently annealed ribbons can still be distinguished. Preserving a minor percentage of Nb together with Mo does not seem substantiated to obtain favorable soft magnetic properties of ribbons annealed in inert gas.
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NASA Astrophysics Data System (ADS)
Sitek, R.; Bolek, T.; Mizera, J.
2018-04-01
The paper presents investigation of microstructure and corrosion resistance of the multi-component surface layers built of intermetallic phases of the Ti-Al system and an outer Al2O3 ceramic sub-layer. The layers were produced on a two phase (α + β) Ti6Al2Mo2Cr titanium alloy using the PACVD method with the participation of trimethylaluminum vapors. The layers are characterized by a high surface hardness and good corrosion, better than that of these materials in the starting state. In order to find the correlation between their structure and properties, the layers were subjected to examinations using optical microscopy, X-ray diffraction analysis (XRD), surface analysis by XPS, scanning electron microscopy (SEM), and analyses of the chemical composition (EDS). The properties examined included: the corrosion resistance and the hydrogen absorptiveness. Moreover growth of the Al2O3 ceramic layer and its influence on the residual stress distribution was simulated using finite element method [FEM]. The results showed that the produced layer has amorphous-nano-crystalline structure, improved corrosion resistance and reduces the permeability of hydrogen as compared with the base material of Ti6Al2Mo2Cr -titanium alloy.
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NASA Astrophysics Data System (ADS)
Yin, Guoli; Zhu, Dancheng; Lv, Danhui; Hashemi, Arsalan; Fei, Zhen; Lin, Fang; Krasheninnikov, Arkady V.; Zhang, Ze; Komsa, Hannu-Pekka; Jin, Chuanhong
2018-04-01
Herein we report the successful doping of tellurium (Te) into molybdenum disulfide (MoS2) monolayers to form MoS2x Te2(1-x) alloy with variable compositions via a hydrogen-assisted post-growth chemical vapor deposition process. It is confirmed that H2 plays an indispensable role in the Te substitution into as-grown MoS2 monolayers. Atomic-resolution transmission electron microscopy allows us to determine the lattice sites and the concentration of introduced Te atoms. At a relatively low concentration, tellurium is only substituted in the sulfur sublattice to form monolayer MoS2(1-x)Te2x alloy, while with increasing Te concentration (up to ˜27.6% achieved in this study), local regions with enriched tellurium, large structural distortions, and obvious sulfur deficiency are observed. Statistical analysis of the Te distribution indicates the random substitution. Density functional theory calculations are used to investigate the stability of the alloy structures and their electronic properties. Comparison with experimental results indicate that the samples are unstrained and the Te atoms are predominantly substituted in the top S sublattice. Importantly, such ultimately thin Janus structure of MoS2(1-x)Te2x exhibits properties that are distinct from their constituents. We believe our results will inspire further exploration of the versatile properties of asymmetric 2D TMD alloys.
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Direct Metal Deposition of Refractory High Entropy Alloy MoNbTaW
NASA Astrophysics Data System (ADS)
Dobbelstein, Henrik; Thiele, Magnus; Gurevich, Evgeny L.; George, Easo P.; Ostendorf, Andreas
Alloying of refractory high entropy alloys (HEAs) such as MoNbTaW is usually done by vacuum arc melting (VAM) or powder metallurgy (PM) due to the high melting points of the elements. Machining to produce the final shape of parts is often needed after the PM process. Casting processes, which are often used for aerospace components (turbine blades, vanes), are not possible. Direct metal deposition (DMD) is an additive manufacturing technique used for the refurbishment of superalloy components, but generating these components from the bottom up is also of current research interest. MoNbTaW possesses high yield strength at high temperatures and could be an alternative to state-of-the-art materials. In this study, DMD of an equimolar mixture of elemental powders was performed with a pulsed Nd:YAG laser. Single wall structures were built, deposition strategies developed and the microstructure of MoNbTaW was analyzed by back scattered electrons (BSE) and energy dispersive X-ray (EDX) spectroscopy in a scanning electron microscope. DMD enables the generation of composition gradients by using dynamic powder mixing instead of pre-alloyed powders. However, the simultaneous handling of several elemental or pre-alloyed powders brings new challenges to the deposition process. The influence of thermal properties, melting point and vapor pressure on the deposition process and chemical composition will be discussed.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hakan Ozaltun; Pavel Medvedev
The effects of the foil flatness on stress-strain behavior of monolithic fuel mini-plates during fabrication and irradiation were studied. Monolithic plate-type fuels are a new fuel form being developed for research and test reactors to achieve higher uranium densities. This concept facilitates the use of low-enriched uranium fuel in the reactor. These fuel elements are comprised of a high density, low enrichment, U–Mo alloy based fuel foil encapsulated in a cladding material made of Aluminum. To evaluate the effects of the foil flatness on the stress-strain behavior of the plates during fabrication, irradiation and shutdown stages, a representative plate frommore » RERTR-12 experiments (Plate L1P756) was considered. Both fabrication and irradiation processes of the plate were simulated by using actual irradiation parameters. The simulations were repeated for various foil curvatures to observe the effects of the foil flatness on the peak stress and strain magnitudes of the fuel elements. Results of fabrication simulations revealed that the flatness of the foil does not have a considerable impact on the post fabrication stress-strain fields. Furthermore, the irradiation simulations indicated that any post-fabrication stresses in the foil would be relieved relatively fast in the reactor. While, the perfectly flat foil provided the slightly better mechanical performance, overall difference between the flat-foil case and curved-foil case was not significant. Even though the peak stresses are less affected, the foil curvature has several implications on the strain magnitudes in the cladding. It was observed that with an increasing foil curvature, there is a slight increase in the cladding strains.« less
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Electrochemical hydrogen storage alloys and batteries fabricated from Mg containing base alloys
Ovshinsky, Stanford R.; Fetcenko, Michael A.
1996-01-01
An electrochemical hydrogen storage material comprising: (Base Alloy).sub.a M.sub.b where, Base Alloy is an alloy of Mg and Ni in a ratio of from about 1:2 to about 2:1, preferably 1:1; M represents at least one modifier element chosen from the group consisting of Co, Mn, Al, Fe, Cu, Mo, W, Cr, V, Ti, Zr, Sn, Th, Si, Zn, Li, Cd, Na, Pb, La, Mm, and Ca; b is greater than 0.5, preferably 2.5, atomic percent and less than 30 atomic percent; and a+b=100 atomic percent. Preferably, the at least one modifier is chosen from the group consisting of Co, Mn, Al, Fe, and Cu and the total mass of the at least one modifier element is less than 25 atomic percent of the final composition. Most preferably, the total mass of said at least one modifier element is less than 20 atomic percent of the final composition.
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Bulk Fe-based metallic glass with extremely soft ferromagnetic properties
DOE Office of Scientific and Technical Information (OSTI.GOV)
Shen, T. D.; Harms, U. S.; Schwarz, R. B.
2001-01-01
The authors have investigated the DC and AC magnetic properties of a bulk glassy Fe{sub 65.5}Cr{sub 4}Mo{sub 4}Ga{sub 4}P{sub 12}B{sub 5.5}C{sub 5} alloy. In the annealed state the alloy has coercivity H{sub C} and maximum DC permeability {mu}{sub m} of approximately 0.4 A/m (5 mOe) and 2.8 x 10{sup 5}, comparable to those found in annealed zero-magnetostriction Co-based alloys. The low H{sub C} found in the bulk glassy alloy is attributed to the low ratio of surface-roughness to sample thickness, and low residual internal-stress. The total power loss in the annealed bulk glass is about one order of magnitude lowermore » than that of rapidly quenched Fe-based glassy ribbons. This is attributed to a low anomalous eddy-current loss.« less
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NASA Astrophysics Data System (ADS)
Krishnan, Gopi; Verheijen, Marcel A.; Ten Brink, Gert H.; Palasantzas, George; Kooi, Bart J.
2013-05-01
Nowadays bimetallic nanoparticles (NPs) have emerged as key materials for important modern applications in nanoplasmonics, catalysis, biodiagnostics, and nanomagnetics. Consequently the control of bimetallic structural motifs with specific shapes provides increasing functionality and selectivity for related applications. However, producing bimetallic NPs with well controlled structural motifs still remains a formidable challenge. Hence, we present here a general methodology for gas phase synthesis of bimetallic NPs with distinctively different structural motifs ranging at a single particle level from a fully mixed alloy to core-shell, to onion (multi-shell), and finally to a Janus/dumbbell, with the same overall particle composition. These concepts are illustrated for Mo-Cu NPs, where the precise control of the bimetallic NPs with various degrees of chemical ordering, including different shapes from spherical to cube, is achieved by tailoring the energy and thermal environment that the NPs experience during their production. The initial state of NP growth, either in the liquid or in the solid state phase, has important implications for the different structural motifs and shapes of synthesized NPs. Finally we demonstrate that we are able to tune the alloying regime, for the otherwise bulk immiscible Mo-Cu, by achieving an increase of the critical size, below which alloying occurs, closely up to an order of magnitude. It is discovered that the critical size of the NP alloy is not only affected by controlled tuning of the alloying temperature but also by the particle shape.Nowadays bimetallic nanoparticles (NPs) have emerged as key materials for important modern applications in nanoplasmonics, catalysis, biodiagnostics, and nanomagnetics. Consequently the control of bimetallic structural motifs with specific shapes provides increasing functionality and selectivity for related applications. However, producing bimetallic NPs with well controlled structural motifs still remains a formidable challenge. Hence, we present here a general methodology for gas phase synthesis of bimetallic NPs with distinctively different structural motifs ranging at a single particle level from a fully mixed alloy to core-shell, to onion (multi-shell), and finally to a Janus/dumbbell, with the same overall particle composition. These concepts are illustrated for Mo-Cu NPs, where the precise control of the bimetallic NPs with various degrees of chemical ordering, including different shapes from spherical to cube, is achieved by tailoring the energy and thermal environment that the NPs experience during their production. The initial state of NP growth, either in the liquid or in the solid state phase, has important implications for the different structural motifs and shapes of synthesized NPs. Finally we demonstrate that we are able to tune the alloying regime, for the otherwise bulk immiscible Mo-Cu, by achieving an increase of the critical size, below which alloying occurs, closely up to an order of magnitude. It is discovered that the critical size of the NP alloy is not only affected by controlled tuning of the alloying temperature but also by the particle shape. Electronic supplementary information (ESI) available: Experimental details including schematics of the gas phase synthesis set up, target arrangement, synthesis condition for various structures, and TEM images of alloy, core-shell and Mo-Cu-Mo onion nanoparticles. See DOI: 10.1039/c3nr00565h
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Surface segregation in HAYNES 230 alloy
NASA Astrophysics Data System (ADS)
Pop, D.; Wolski, K.
2006-12-01
The surface segregation in the Ni-based alloy HAYNES 230 was studied by Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy between 400 and 1100 °C. The qualitative variations of the surface contents of S, P, W, Mo, N, Si, and Mn were determined as a function of annealing temperature and time. It was found that at 925 °C the maximum coverage of sulphur at the alloy surface is in the range 0.06-0.15 monolayers. Chromium evaporation from the HAYNES 230 surface under UHV conditions is clearly evidenced for annealing at 1100 °C.
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[Study on corrosion resistance of three non-noble porcelain alloys].
Wu, Zhikai; Xu, Sheng; Li, Wei; Teng, Jin; Li, Ning
2011-10-01
To study the electrochemical corrosion behavior of Co-Cr, Ni-Cr and Ni-Cr-Be based porcelain alloys in NaCl solution. Five samples of each alloy were made respectively, electric polarization curve of each alloy was obtained using potentiodynamic polarization technique. Self-corrosion potential (E(corr)), self-corrosion current density (I(corr), passive region and transpassivation potential were tested. Microstructure and constituent was examined using scanning electron microscopy and energy dispersive spectroscopy. Co-Cr alloy possessed the most desirable corrosion resistance because of its integrated, homogeneous and compact passive film. The poor compactness of Ni-Cr alloy's passive film decreased its corrosion resistance. Ni-Cr-Be alloy exhibited the worst corrosion resistance due to the Cr and Mo depleted Ni-Be eutectic phases in the alloy. Taking biological security into consideration, it is necessary to avoid the application of porcelain alloys with Be element. Co-Cr alloy with better biocompatibility possesses much broader prospect in the field of dental restoration.
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Prediction of A2 to B2 Phase Transition in the High Entropy Alloy Mo-Nb-Ta-W
NASA Astrophysics Data System (ADS)
Huhn, William; Widom, Michael
2014-03-01
In this talk we show that an effective Hamiltonian fit with first principles calculations predicts an order/disorder transition occurs in the high entropy alloy Mo-Nb-Ta-W. Using the Alloy Theoretic Automated Toolset, we find T=0K enthalpies of formation for all binaries containing Mo, Nb, Ta, and W, and in particular we find the stable structures for binaries at equiatomic concentrations are close in energy to the associated B2 structure, suggesting that at intermediate temperatures a B2 phase is stabilized in Mo-Nb-Ta-W. Our ``hybrid Monte Carlo/molecular dynamics'' results for the Mo-Nb-Ta-W system are analyzed to identify certain preferred chemical bonding types. A mean field free energy model incorporating nearest neighbor bonds will be presented, allowing us to predict the mechanism of the order/disorder transition. We find the temperature evolution of the system is driven by strong Mo-Ta bonding. Comparison of the free energy model and our MC/MD results suggest the existence of additional low-temperature phase transitions in the system likely ending with phase segregation into binary phases. We would like to thank DOD-DTRA for funding this research under contract number DTRA-11-1-0064.
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Processing and Mechanical Properties of NiAl-Based In-Situ Composites. Ph.D. Thesis Final Report
NASA Technical Reports Server (NTRS)
Johnson, David Ray
1994-01-01
In-situ composites based on the NiAl-Cr eutectic system were successfully produced by containerless processing and evaluated. The NiAl-Cr alloys had a fibrous microstructure while the NiAl-(Cr,Mo) alloys containing 1 at. percent or more molybdenum exhibited a lamellar structure. The NiAl-28Cr-6Mo eutectic displays promising high temperature strength while still maintaining a reasonable room temperature fracture toughness when compared to other NiAl-based materials. The Laves phase NiAlTa was used to strengthen NiAl and very promising creep strengths were found for the directionally solidified NiAl-NiAlTa eutectic. The eutectic composition was found to be near NiAl-15.5Ta (at. percent) and well aligned microstructures were produced at this composition. An off-eutectic composition of NiAl-14.5Ta was also processed, consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of these two phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Polyphase in-situ composites were generated by directional solidification of ternary eutectics. The systems investigated were the Ni-Al-Ta-X (X=Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and both the eutectic composition and temperature were determined. Of these ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr,Al)NiTa-Cr eutectic was intermediate between those of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.
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Relative susceptibility of titanium alloys to hot-salt stress-corrosion
NASA Technical Reports Server (NTRS)
Gray, H. R.
1971-01-01
Susceptibility of titanium alloys to hot-salt stress-corrosion cracking increased as follows: Ti-2Al-11Sn-5Zr-0.2Si(679), Ti-6Al-2Sn-4Zr-2Mo(6242), Ti-6Al-4V(64), Ti-6Al-4V-3Co(643), Ti-8Al-1Mo-1V(811), and Ti-13V-11Cr-3A1(13-11-3). The Ti-5Al-6Sn-2Zr-1Mo-0.25Si(5621S) alloy was both the least and most susceptible depending on heat treatment. Such rankings can be drastically altered by heat-to-heat and processing variations. Residual compressive stresses and cyclic exposures also reduce susceptibility to stress-corrosion. Simulated turbine-engine compressor environmental variables such as air velocity, pressure, dewpoint, salt concentration, and salt deposition temperature have only minor effects. Detection of substantial concentrations of hydrogen in all corroded alloys confirmed the existence of a hydrogen embrittlement mechanism.
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Development of Co-based bulk metallic glasses as potential biomaterials.
Zhou, Zeyan; Wei, Qin; Li, Qiang; Jiang, Bingliang; Chen, You; Sun, Yanfei
2016-12-01
A new series of Co80-x-yCrxMoyP14B6 (x=5 y=5; x=5 y=10; x=10 y=10, all values in at.%) bulk metallic glasses (BMGs) with a maximum diameter of 1.5mm has been developed for using them as potential bio-implant materials by a combination of fluxing treatment and J-quenching technique. The performance of the present Co-based BMGs in biomedical implant applications was investigated as compared to the CoCrMo biomedical alloy (ASTM F75) and 316L stainless steel (316L SS). The corrosion behavior of the samples was investigated in both Hank's solution (pH=7.4) and artificial saliva solution (pH=6.3) at 37°C employing electrochemical measurements. The results indicate that the Co-based BMGs exhibit much higher corrosion resistance in the simulated body solutions than that of 316L SS. Compared with the corrosion resistance of ASTM F75, that of Co70Cr5Mo5P14B6 and Co65Cr5Mo10P14B6 BMGs is found to be lower and that of Co60Cr10Mo10P14B6 BMG is higher. The concentrations of Co, Cr, and Mo ions released into the simulated body solutions from our Co-based BMGs after potentiodynamic polarization are significantly lower than that released from ASTM F75. The biocompatibility of the specimens was evaluated using an in vitro test of NIH3T3 cell culture in the specimen extraction media for 1, 3, 5, and 7days, revealing the non-cytotoxicity of the Co-based BMGs towards NIH3T3 cells. Moreover, examinations on the cell adhesion and growth on the surface of the specimens indicate that the Co-based BMGs exhibit better cell viability compared to ASTM F75 and 316L SS biomedical alloys. Copyright © 2016 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Haseeb, A. S. M. A.; Arafat, M. M.; Tay, S. L.; Leong, Y. M.
2017-10-01
Tin (Sn)-based solders have established themselves as the main alternative to the traditional lead (Pb)-based solders in many applications. However, the reliability of the Sn-based solders continues to be a concern. In order to make Sn-based solders microstructurally more stable and hence more reliable, researchers are showing great interest in investigating the effects of the incorporation of different nanoparticles into them. This paper gives an overview of the influence of metallic nanoparticles on the characteristics of interfacial intermetallic compounds (IMCs) in Sn-based solder joints on copper substrates during reflow and thermal aging. Nanocomposite solders were prepared by mechanically blending nanoparticles of nickel (Ni), cobalt (Co), zinc (Zn), molybdenum (Mo), manganese (Mn) and titanium (Ti) with Sn-3.8Ag-0.7Cu and Sn-3.5Ag solder pastes. The composite solders were then reflowed and their wetting characteristics and interfacial microstructural evolution were investigated. Through the paste mixing route, Ni, Co, Zn and Mo nanoparticles alter the morphology and thickness of the IMCs in beneficial ways for the performance of solder joints. The thickness of Cu3Sn IMC is decreased with the addition of Ni, Co and Zn nanoparticles. The thickness of total IMC layer is decreased with the addition of Zn and Mo nanoparticles in the solder. The metallic nanoparticles can be divided into two groups. Ni, Co, and Zn nanoparticles undergo reactive dissolution during solder reflow, causing in situ alloying and therefore offering an alternative route of alloy additions to solders. Mo nanoparticles remain intact during reflow and impart their influence as discrete particles. Mechanisms of interactions between different types of metallic nanoparticles and solder are discussed.
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Interfacial and Alloying Effects on Activation of Ethanol from First-Principles
An, Wei; Men, Yong; Wang, Jinguo; ...
2017-02-24
Here, we present a first-principles density-functional theory study of ethanol activation at oxide/Rh(111) interface and the alloying effect on mitigating carbon deposition, which are essential to direct ethanol fuel cell (DEFC) anode reaction and steam reforming of ethanol (SRE) reaction. Our calculated results show that charge can transfer from Rh(111) substrate to MO x chain (e.g., MoO 3 and MnO 2), or from MO x chain (e.g., MgO, SnO 2, ZrO 2, and TiO 2) to Rh(111) substrate. The OH-binding strength is increased exponentially with M δ+ charge ranging from 1.4 to 2.2, which renders MnO 2/Rh(111) and MgO/Rh(111) interfacesmore » weaker OH-binding, and thereby enhanced oxidizing functionality of OH* for promoting ethanol oxidation reaction (EOR) at DEFC anode. For efficient C–C bond breaking, a large number of Rh ensemble sizes are critically needed at the interface of MO x/Rh(111). We found that Rh 1Au 3 near surface alloy has the weakest C* and CO* binding, followed by Rh 1Cu 3 and Rh 1Pd 3 near surface alloys, while Rh 1Ir 3 and Rh 1Ru 3 surface alloys have C* and CO* binding strength similar to that of pure Rh metal. The general implication of this study is that by engineering alloyed structure of weakened C* and CO* binding complemented with metal oxides of weakened OH-binding, high-performance DEFC anode or SRE catalysts can be identified.« less
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Alloy design for intrinsically ductile refractory high-entropy alloys
NASA Astrophysics Data System (ADS)
Sheikh, Saad; Shafeie, Samrand; Hu, Qiang; Ahlström, Johan; Persson, Christer; Veselý, Jaroslav; Zýka, Jiří; Klement, Uta; Guo, Sheng
2016-10-01
Refractory high-entropy alloys (RHEAs), comprising group IV (Ti, Zr, Hf), V (V, Nb, Ta), and VI (Cr, Mo, W) refractory elements, can be potentially new generation high-temperature materials. However, most existing RHEAs lack room-temperature ductility, similar to conventional refractory metals and alloys. Here, we propose an alloy design strategy to intrinsically ductilize RHEAs based on the electron theory and more specifically to decrease the number of valence electrons through controlled alloying. A new ductile RHEA, Hf0.5Nb0.5Ta0.5Ti1.5Zr, was developed as a proof of concept, with a fracture stress of close to 1 GPa and an elongation of near 20%. The findings here will shed light on the development of ductile RHEAs for ultrahigh-temperature applications in aerospace and power-generation industries.
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Effects of thermal treatment on the co-rolled U-Mo fuel foils
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dennis D. Keiser, Jr.; Tammy L. Trowbridge; Cynthia R. Breckenridge
2014-11-01
A monolithic fuel type is being developed to convert US high performance research and test reactors such as Advanced Test Reactor (ATR) at Idaho National Laboratory from highly enriched uranium (HEU) to low-enriched uranium (LEU). The interaction between the cladding and the U-Mo fuel meat during fuel fabrication and irradiation is known to have negative impacts on fuel performance, such as mechanical integrity and dimensional stability. In order to eliminate/minimize the direct interaction between cladding and fuel meat, a thin zirconium diffusion barrier was introduced between the cladding and U-Mo fuel meat through a co-rolling process. A complex interface betweenmore » the zirconium and U-Mo was developed during the co-rolling process. A predictable interface between zirconium and U-Mo is critical to achieve good fuel performance since the interfaces can be the weakest link in the monolithic fuel system. A post co-rolling annealing treatment is expected to create a well-controlled interface between zirconium and U-Mo. A systematic study utilizing post co-rolling annealing treatment has been carried out. Based on microscopy results, the impacts of the annealing treatment on the interface between zirconium and U-Mo will be presented and an optima annealing treatment schedule will be suggested. The effects of the annealing treatment on the fuel performance will also be discussed.« less
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NASA Astrophysics Data System (ADS)
Rieth, M.; Dafferner, B.
1996-10-01
In the last few years a lot of different low activation CrWVTa steels have been developed world-wide. Without irradiation some of these alloys show clearly a better low temperature embrittlement behaviour than commercial CrNiMoV(Nb) alloys. Within the MANITU project a study was carried out to compare, prior to the irradiation program, the embrittlement behaviour of different alloys in the unirradiated condition performing instrumented Charpy impact bending tests with sub-size specimens. The low activation materials (LAM) considered were different OPTIFER alloys (Forschungszentrum Karlsruhe), F82H (JAERI), 9Cr2WVTa (ORNL), and GA3X (PNL). The modified commercial 10-11% CrNiMoVNb steels were MANET and OPTIMAR. A meaningful comparison between these alloys could be drawn, since the specimens of all materials were manufactured and tested under the same conditions.
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NASA Astrophysics Data System (ADS)
Jiao, Guohua; Liu, Bo; Li, Qiran
2015-08-01
Ultrathin RuMoC amorphous films prepared by magnetron co-sputtering with Ru and MoC targets in a sandwiched scheme Si/ p-SiOC:H/RuMoC/Cu were investigated as barrier in copper metallization. The evolution of final microstructure of RuMoC alloy films show sensitive correlation with the content of doped Mo and C elements and can be easily controlled by adjusting the sputtering power of the MoC target. There was no signal of interdiffusion between the Cu and SiOC:H layer in the sample of Cu/RuMoC/ p-SiOC:H/Si, even annealing up to 500 °C. Very weak signal of oxygen have been confirmed in the RuMoC barrier layer both as-deposited and after being annealed, and a good performance on preventing oxygen diffusion has been proved. Leakage current and resistivity evaluations also reveal the excellent thermal reliability of this Si/ p-SiOC:H/RuMoC/Cu film stack at the temperatures up to 500 °C, indicating its potential application in the advanced barrierless Cu metallization.
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Thermal cooling effects in the microstructure and properties of cast cobalt-base biomedical alloys
NASA Astrophysics Data System (ADS)
Vega Valer, Vladimir
Joint replacement prosthesis is widely used in the biomedical field to provide a solution for dysfunctional human body joints. The demand for orthopedic knee and hip implants motivate scientists and manufacturers to develop novel materials or to increase the life of service and efficiency of current materials. Cobalt-base alloys have been investigated by various researchers for biomedical implantations. When these alloys contain Chromium, Molybdenum, and Carbon, they exhibit good tribological and mechanical properties, as well as excellent biocompatibility and corrosion resistance. In this study, the microstructure of cast Co-Cr-Mo-C alloy is purposely modified by inducing rapid solidification through fusion welding processes and solution annealing heat treatment (quenched in water at room temperature. In particular the effect of high cooling rates on the athermal phase transformation FCC(gamma)↔HCP(epsilon) on the alloy hardness and corrosion resistance is investigated. The Co-alloy microstructures were characterized using metallography and microscopy techniques. It was found that the as cast sample typically dendritic with dendritic grain sizes of approximately 150 microm and containing Cr-rich coarse carbide precipitates along the interdendritic boundaries. Solution annealing gives rise to a refined microstructure with grain size of 30 microm, common among Co-Cr-Mo alloys after heat treating. Alternatively, an ultrafine grain structure (between 2 and 10 microm) was developed in the fusion zone for specimens melted using Laser and TIG welding methods. When laser surface modification treatments were implemented, the developed solidification microstructure shifted from dendritic to a fine cellular morphology, with possible nanoscale carbide precipitates along the cellular boundaries. In turn, the solidified regions exhibited high hardness values (461.5HV), which exceeds by almost 110 points from the alloy in the as-cast condition. The amount of developed athermal epsilon-martensite phase was determined using X-ray diffractrometry. It was found that the amount of epsilon-martensite increases significantly from 2% for the Laser surface processing to 13% in the as cast specimen, 24% in the annealed specimen, and 51% for the TIG surface processing. Moreover, the corrosion rate in Ringer solution was calculated by applying the Tafel extrapolation method on each alloy condition. The lowest corrosion rate (0.435 microm/year) was achieved in the Laser treated alloy and it is attributed to the lack of appreciable athermal epsilon-martensite. The highest corrosion rate (15.5 microm/year) was found to occur in the TIG treated alloy, which possesses the largest amount of epsilon-martensite. In turn, this suggests that surface modification through melting induces variable amounts of athermal epsilon-martensite in the as-cast Co-Cr-Mo-C alloys. Apparently, rapid solidification of melted surfaces in the Co-alloy is highly effective in modifying the induced amounts of HCP phase, and hence, the exhibited properties.
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NASA Astrophysics Data System (ADS)
Hibino, Yusuke; Ishihara, Seiya; Sawamoto, Naomi; Ohashi, Takumi; Matsuura, Kentarou; Machida, Hideaki; Ishikawa, Masato; Sudoh, Hiroshi; Wakabayashi, Hitoshi; Ogura, Atsushi
2018-06-01
Transition metal dichalcogenides are gathering increasing attention owing to their unique physical properties and wide variety of application possibilities. In our study, Mo1‑ x W x S2, an alloy of MoS2 and WS2, was fabricated by the co-sputtering deposition of MoS2 and W, followed by post-deposition sulfurization. The resulting film exhibited a W concentration of up to 23%, relative to the Mo and W added. The alloy exhibited the characteristic behaviors, when subjected to Raman spectroscopy and X-ray photoelectron spectroscopy. It was confirmed that the bandgap shifted as the W concentration increased. By evaluating the bandgap and valence band edge energy, it was confirmed that W incorporation tuned the band structure.
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Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability
NASA Astrophysics Data System (ADS)
Khong, J. C.; Daisenberger, D.; Burca, G.; Kockelmann, W.; Tremsin, A. S.; Mi, J.
2016-11-01
This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe48Cr15Mo14C15B6Gd2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications.
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Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability.
Khong, J C; Daisenberger, D; Burca, G; Kockelmann, W; Tremsin, A S; Mi, J
2016-11-16
This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe 48 Cr 15 Mo 14 C 15 B 6 Gd 2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications.
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Iron aluminide useful as electrical resistance heating elements
Sikka, V.K.; Deevi, S.C.; Fleischhauer, G.S.; Hajaligol, M.R.; Lilly, A.C. Jr.
1997-04-15
The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, {<=}1% Cr and either {>=}0.05% Zr or ZrO{sub 2} stringers extending perpendicular to an exposed surface of the heating element or {>=}0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, {<=}2% Ti, {<=}2% Mo, {<=}1% Zr, {<=}1% C, {<=}0.1% B, {<=}30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, {<=}1% rare earth metal, {<=}1% oxygen, {<=}3% Cu, balance Fe. 64 figs.
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Creep modeling for life evaluation and strengthening mechanism of tungsten alloyed 9-12% Cr steels
NASA Astrophysics Data System (ADS)
Park, Kyu-Seop; Bae, Dong-Sik; Lee, Sung-Keun; Lee, Goo-Hyun; Kim, Jung-Ho; Endo, Takao
2006-10-01
Recently, high strength tungsten (W) alloyed steels have been developed for use in power plants with higher steam conditions for environmental reasons as well as the improvement of thermal efficiency resulting in lower fuel costs. In order to establish a creep modeling of high strength martensitic steel and to understand the basic role of W in tungsten alloyed 9-12Cr steels, conventional martensitic steels (X20CrMoV121, X20CrMoWV121, and Mod9Cr-1Mo) and tungsten alloyed steels (NF616 and HCM12A) were employed for creep tests and creep behavior analyses by the Ω method. The proposed creep model, which takes into account both primary and tertiary creep, satisfactorily described the creep curves and accurately predicted creep life, as martensitic steel undergoes a relatively large amount of primary creep, up to nearly 30%, over its normal life. The tungsten alloyed steels exhibited a smaller minimum creep rate and a larger stress exponent compared to the conventional steels. In addition, in tungsten alloyed steel, the Ω value features strong stress dependence such that creep life is prolonged at lower stresses due to high Ω values. The importance of the Ω value from the standpoint of creep strengthening in primary and tertiary creep is discussed.
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In vitro bioactivity investigations of Ti-15Mo alloy after electrochemical surface modification.
Kazek-Kęsik, Alicja; Kuna, Karolina; Dec, Weronika; Widziołek, Magdalena; Tylko, Grzegorz; Osyczka, Anna M; Simka, Wojciech
2016-07-01
Titanium and its aluminum and vanadium-free alloys have especially great potential for medical applications. Electrochemical surface modification improves their surface bioactivity and stimulates osseointegration process. In this work, the effect of plasma electrolytic oxidation of the β-type alloy Ti-15Mo surface on its bioactivity is presented. Bioactivity of the modified alloy was investigated by immersion in simulated body fluid (SBF). Biocompatibility of the modified alloys were tested using human bone marrow stromal cells (hBMSC) and wild intestinal strains (DV/A, DV/B, DV/I/1) of Desulfovibrio desulfuricans bacteria. The particles of apatite were formed on the anodized samples. Human BMSC cells adhered well on all the examined surfaces and expressed ALP, collagen, and produced mineralized matrix as determined after 10 and 21 days of culture. When the samples were inoculated with D. desulfuricans bacteria, only single bacteria were visible on selected samples. There were no obvious changes in surface morphology among samples. Colonization and bacterial biofilm formation was observed on as-ground sample. In conclusion, the surface modification improved the Ti-15Mo alloy bioactivity and biocompatibility and protected surface against colonization of the bacteria. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 903-913, 2016. © 2015 Wiley Periodicals, Inc.
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Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.; ...
2018-01-01
The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.
The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less
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Evolution of Constitution, Structure, and Morphology in FeCo-Based Multicomponent Alloys
NASA Astrophysics Data System (ADS)
Li, R.; Stoica, M.; Liu, G.; Eckert, J.
2010-07-01
Constituent phases, melting behaviors, and microstructure of multicomponent (Fe0.5Co0.5) x (Mo0.1C0.2B0.5Si0.2)100- x alloys ( x = 95, 90, 85, 80, and 70) produced by copper mold casting were evaluated by various analysis techniques, i.e., X-ray diffractometry, scanning electronic microscopy with energy dispersive X-ray spectrometry, and differential scanning calorimetry. Metastable Fe3C- and Cr23C6-type phases were identified in the chill-cast alloys. A schematic illustration was proposed to explain the evolution of constituent phases and microstructure for the alloys with x = 95, 90, and 85 during the solidification process, which could be applicable to controlling microstructural formation of other multicomponent alloys with similar microstructures by artificially adjusting the composition.
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New alloys to conserve critical elements. [replacing chromium in steels
NASA Technical Reports Server (NTRS)
Stephens, J. R.
1978-01-01
Previous studies and surveys on availability of domestic reserves have shown that chromium is a most critical element within the U.S. metal industry. More precisely, the bulk of chromium is consumed in the production of stainless steels, specifically Type 304 stainless steel (304SS) which contains 18% Cr. The present paper deals with means of reducing chromium in commercial stainless steels by substituting more abundant or less expensive elements with the intent of maintaining the properties of 304SS. The discussion focuses on some of the oxidation and corrosion properties of new substitute stainless steels with only 12% Cr, which represents a potential saving of 33% of the chromium consumed in the production of 304SS. The alloying elements substituted for Cr in 304SS are selected according to their potential for protective oxide formation during high-temperature oxidation; these are Al, Si, Ti, Y, and misch metal which is 99.7% rare-earth metals containing 50 to 55% cerium. Other alloying elements to impart corrosion resistance are Mn, Mo, and V.
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Environmentally Resistant Mo-Si-B-Based Coatings
NASA Astrophysics Data System (ADS)
Perepezko, J. H.; Sossaman, T. A.; Taylor, M.
2017-06-01
High-temperature applications have demonstrated aluminide-coated nickel-base superalloys to be remarkably effective, but are reaching their service limit. Alternate materials such as refractory (e.g., W, Mo) silicide alloys and SiC composites are being considered to extend high temperature capability, but the silica surfaces on these materials require coatings for enhanced environmental resistance. This can be accomplished with a Mo-Si-B-based coating that is deposited by a spray deposition of Mo followed by a chemical vapor deposition of Si and B by pack cementation to develop an aluminoborosilica surface. Oxidation of the as-deposited (Si + B)-pack coatings proceeds with partial consumption of the initial MoSi2 forming amorphous silica. This Si depletion leads to formation of a B-saturated Mo5Si3 (T1) phase. Reactions between the Mo and the B rich phases develop an underlying Mo5SiB2 (T2) layer. The T1 phase saturated with B has robust oxidation resistance, and the Si depletion is prevented by the underlying diffusion barrier (T2). Further, due to the natural phase transformation characteristics of the Mo-Si-B system, cracks or scratches to the outer silica and T1 layers can be repaired from the Si and B reservoirs of T2 + MoB layer to yield a self-healing characteristic. Mo-Si-B-based coatings demonstrate robust performance up to at least 1700 °C not only to the rigors of elevated temperature oxidation, but also to CMAS attack, hot corrosion attack, water vapor and thermal cycling.
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Autonomous Filling of Grain-Boundary Cavities during Creep Loading in Fe-Mo Alloys
NASA Astrophysics Data System (ADS)
Zhang, S.; Fang, H.; Gramsma, M. E.; Kwakernaak, C.; Sloof, W. G.; Tichelaar, F. D.; Kuzmina, M.; Herbig, M.; Raabe, D.; Brück, E.; van der Zwaag, S.; van Dijk, N. H.
2016-10-01
We have investigated the autonomous repair of creep damage by site-selective precipitation in a binary Fe-Mo alloy (6.2 wt pct Mo) during constant-stress creep tests at temperatures of 813 K, 823 K, and 838 K (540 °C, 550 °C, and 565 °C). Scanning electron microscopy studies on the morphology of the creep-failed samples reveal irregularly formed deposits that show a close spatial correlation with the creep cavities, indicating the filling of creep cavities at grain boundaries by precipitation of the Fe2Mo Laves phase. Complementary transmission electron microscopy and atom probe tomography have been used to characterize the precipitation mechanism and the segregation at grain boundaries in detail.
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Development of Coatings for Tantalum Alloy Nozzle Vanes
NASA Technical Reports Server (NTRS)
Stetson, A. R.; Wimber, R. T.
1967-01-01
A group of silicide coatings developed for the T222 tantalum-base alloy have afforded over 600 hours of protection at 1600 and 2400 F during cyclic exposure in air. These coatings were applied in two steps. A modifier alloy was applied by slurry techniques and was sintered in vacuum prior to siliciding by pack cementation in argon. Application of the modifier alloy by pack cementation was found to be much less effective. The addition of titanium and vanadium to molybdenum and tungsten yielded beneficial modifier alloys, whereas the addition of chromium showed no improvement. After siliciding, the 15Ti- 35W-15V-35Mo modifier alloy exhibited the best performance; one sample survived 1064 hours of oxidation at 2400 F. This same coating was the only coating to reproducibly provide 600 hours of protection at both 1600 and 2400 F; in the second and third of three experiments, involving oxidation of three to five specimens at each temperature in each experiment, no failures were observed in 600 hours of testing. The slurry coatings were also shown to protect the Cb752 and D43 columbium-base alloys.
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NASA Astrophysics Data System (ADS)
Simoes, T. A.; Goode, A. E.; Porter, A. E.; Ryan, M. P.; Milne, S. J.; Brown, A. P.; Brydson, R. M. D.
2014-06-01
CoCrMo alloys are utilised as the main material in hip prostheses. The link between this type of hip prosthesis and chronic pain remains unclear. Studies suggest that wear debris generated in-vivo may be related to post-operative complications such as inflammation. These alloys can contain different amounts of carbon, which improves the mechanical properties of the alloy. However, the formation of carbides could become sites that initiate corrosion, releasing ions and/or particles into the human body. This study analysed the mechanical milling of alloys containing both high and low carbon levels in relevant biological media, as an alternative route to generate wear debris. The results show that low carbon alloys produce significantly more nanoparticles than high carbon alloys. During the milling process, strain induces an fcc to hcp phase transformation. Evidence for cobalt and molybdenum dissolution in the presence of serum was confirmed by ICP-MS and TEM EDX techniques.
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2008-09-01
this study was the α+β titanium alloy, Ti- 6 -2- 4 - 6 , in the duplex microstructural condition. Two variants of the microstructure, which differed...condition, at a given stress level and temperature in the turbine engine alloy, Ti-6Al-2Sn-4Zr-6Mo (Ti- 6 -2- 4 - 6 ). The experimental conditions were chosen to...LSG surface. Fig. 1: Microstructures of the Ti- 6 -2- 4 - 6 alloy considered in the study; (a) Microstructure A and (b) Microstructure
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NASA Astrophysics Data System (ADS)
Girina, O.; Fonstein, N.; Yakubovsky, O.; Panahi, D.; Bhattacharya, D.; Jansto, S.
The influence of Nb, Mo, Cr and B on phase transformations and mechanical properties are studied in a 0.15C-2.0Mn-0.3Si-0.020Ti dual phase steel separately and in combination. The formation and decomposition of austenite together with recrystallization of ferrite are evaluated by dilatometry and constructed CCT-diagrams in laboratory processed cold rolled material cooled after full austenitization and from intercritical temperature range. The effect of alloying elements on formation of austenite through their effect on initial hot rolled structure is taken into account. The interpretation of phase transformations during heating and cooling is supported by metallography. The effect of alloying elements on mechanical properties and structure are evaluated by annealing simulations. It has been shown that mechanical properties are strongly influenced by alloying additions such as Nb, Mo, Cr and B through their effect on ferrite formation during continuous cooling and corresponding enrichment of remaining austenite by carbon. Depending on combined effect of these alloying elements, different phase transformations can be promoted during cooling. This allows controlling of final microstructural constituents and mechanical properties.
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Melli, Virginia; Rondelli, Gianni; Sandrini, Enrico; Altomare, Lina; Bolelli, Giovanni; Bonferroni, Benedetta; Lusvarghi, Luca; Cigada, Alberto; De Nardo, Luigi
2013-10-01
Industrial manufacturing of prosthesis components could take significant advantage by the introduction of new, cost-effective manufacturing technologies with near net-shape capabilities, which have been developed during the last years to fulfill the needs of different technological sectors. Among them, metal injection molding (MIM) appears particularly promising for the production of orthopedic arthroplasty components with significant cost saving. These new manufacturing technologies, which have been developed, however, strongly affect the chemicophysical structure of processed materials and their resulting properties. In order to investigate this relationship, here we evaluated the effects on electrochemical properties, ion release, and in vitro response of medical grade CoCrMo alloy processed via MIM compared to conventional processes. MIM of the CoCrMo alloy resulted in coarser polygonal grains, with largely varying sizes; however, these microstructural differences between MIM and forged/cast CoCrMo alloys showed a negligible effect on electrochemical properties. Passive current densities values observed were 0.49 µA cm(-2) for MIM specimens and 0.51 µA cm(-2) for forged CoCrMo specimens, with slightly lower transpassive potential in the MIM case; open circuit potential and Rp stationary values showed no significant differences. Moreover, in vitro biocompatibility tests resulted in cell viability levels not significantly different for MIM and conventionally processed alloys. Although preliminary, these results support the potential of MIM technology for the production of CoCrMo components of implantable devices. Copyright © 2013 Wiley Periodicals, Inc.
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Royhman, Dmitry; Radhakrishnan, Rashmi; Yuan, Judy Chia-Chun; Mathew, Mathew T; Mercuri, Louis G; Sukotjo, Cortino
2014-10-01
To investigate the corrosion behaviour of commonly used TMJ implants alloys (CoCrMo and Ti6Al4V) under simulated physiological conditions. Corrosion behaviour was evaluated using standard electrochemical corrosion techniques and galvanic corrosion techniques as per ASTM standards. Standard electrochemical tests (E(corr), I(corr), R(p) and C(f)) were conducted in bovine calf serum (BCS), as a function of alloys type and different pHs. Galvanic corrosion tests were conducted in BCS at a pH of 7.6. Alloy surfaces were characterized using white-light interferometry (WLI) and scanning electron microscopy (SEM). The potentiodynamic test results exhibited the enhanced passive layer growth and a better corrosion resistance of Ti6Al4V compared to CoCrMo. Electrochemical impedance spectroscopy measurements demonstrated the influence of protein as a function of pH on corrosion mechanisms/kinetics. Galvanic coupling was not a major contributor to corrosion. SEM and WLI images demonstrated a significantly higher in surface roughness in CoCrMo after corrosion. The results of this study suggest that Ti6Al4V shows superior corrosion behaviour to CoCrMo due to its strong passive layer, simulated joint fluid components can affect the electrochemical nature of the metal/electrolyte interface as a function of pH, and the galvanic effect of coupling CoCrMo and Ti6Al4V in a single joint is weak. Published by Elsevier Ltd.
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Hedberg, Yolanda; Odnevall Wallinder, Inger
2014-05-01
The objective of this study was to investigate the extent of released Co, Cr(III), Cr(VI), and Mo from a biomedical high-carbon CoCrMo alloy exposed in phosphate-buffered saline (PBS), without and with the addition of 10 µM H2 O2 (PBS + H2 O2 ), and 10 g L(-1) bovine serum albumin (PBS + BSA) for time periods up to 28 days. Comparative studies were made on AISI 316L for the longest time period. No Cr(VI) release was observed for any of the alloys in either PBS or PBS + H2 O2 at open-circuit potential (no applied potential). However, at applied potentials (0.7 V vs. Ag/AgCl), Cr was primarily released as Cr(VI). Co was preferentially released from the CoCrMo alloy at no applied potential. As a consequence, Cr was enriched in the utmost surface oxide reducing the extent of metal release over time. This passivation effect was accelerated in PBS + H2 O2 . As previously reported for 316L, BSA may also enhance metal release from CoCrMo. However, this was not possible to verify due to the precipitation of metal-protein complexes with reduced metal concentrations in solution as a consequence. This was particularly important for Co-BSA complexes after sufficient time and resulted in an underestimation of metals in solution. Copyright © 2013 Wiley Periodicals, Inc.
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METHOD OF MAKING ALLOYS OF SECOND RARE EARTH SERIES METALS
Baker, R.D.; Hayward, B.R.
1963-01-01
>This invention relates to a process for alloying the second rare earth series metals with Mo, Nb, or Zr. A halide of the rare earth metal is mixed with about 1 to 20 at.% of an oxide of Mo, Nb, or Zr. Iodine and an alkali or alkaline earth metal are added, and the resulting mixture is heated in an inert atmosphere to 350 deg C. (AEC)
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[Use of powder metallurgy for development of implants of Co-Cr-Mo alloy powder].
Dabrowski, J R
2001-04-01
This paper discusses the application of powder metallurgy for the development of porous implantation materials. Powders obtained from Co-Cr-Mo alloy with different carbon content by water spraying and grinding, have been investigated. Cold pressing and rotary re-pressing methods were used for compressing the powder. It was found that the sintered materials obtained from water spraying have the most advantageous properties.
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Wang, Zhenguo; Li, Yan; Huang, Weijiu; Chen, Xiaoli; He, Haoran
2016-10-01
The micro-abrasion-corrosion behaviour of the biomedical Ti-25Nb-3Mo-3Zr-2Sn alloy in Hank׳s solution with protein has been investigated using electrochemical measurements, tribological tests and scanning electron microscope (SEM) observations. The potentiodynamic polarization tests showed that the corrosion potential (Ecorr) exhibits the maximum value at the abrasive concentration of 0.05gcm(-3) despite of the load level. The tribological results indicated that the total material loss of the Ti-25Nb-3Mo-3Zr-2Sn alloy during micro-abrasion increased with the increasing abrasive concentration at a certain applied load. When the abrasive concentration is no more than 0.15gcm(-3), the total material loss increases with increasing load, while the total material loss exhibits the maximum value at a moderate load in case of higher abrasive concentration levels. This was ascribed to the three-body or two-body micro-abrasion-corrosion at different abrasive concentration levels. The wastage map, abrasion mode map and synergy map associated with the applied load and the abrasive concentration were constructed to evaluate the micro-abrasion-corrosion behaviour of the Ti-25Nb-3Mo-3Zr-2Sn alloy in potential biomedical applications. Copyright © 2016 Elsevier Ltd. All rights reserved.
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Durable pd-based alloy and hydrogen generation membrane thereof
Benn, Raymond C.; Opalka, Susanne M.; Vanderspurt, Thomas Henry
2010-02-02
A durable Pd-based alloy is used for a H.sub.2-selective membrane in a hydrogen generator, as in the fuel processor of a fuel cell plant. The Pd-based alloy includes Cu as a binary element, and further includes "X", where "X" comprises at least one metal from group "M" that is BCC and acts to stabilize the .beta. BCC phase for stability during operating temperatures. The metal from group "M" is selected from the group consisting of Fe, Cr, Nb, Ta, V, Mo, and W, with Nb and Ta being most preferred. "X" may further comprise at least one metal from a group "N" that is non-BCC, preferably FCC, that enhances other properties of the membrane, such as ductility. The metal from group "N" is selected from the group consisting of Ag, Au, Re, Ru, Rh, Y, Ce, Ni, Ir, Pt, Co, La and In. The at. % of Pd in the binary Pd--Cu alloy ranges from about 35 at. % to about 55 at. %, and the at. % of "X" in the higher order alloy, based on said binary alloy, is in the range of about 1 at. % to about 15 at. %. The metals are selected according to a novel process.
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Thermal Conductivity of Metals and Alloys at Low Temperatures. A Review of the Literature
1954-09-01
between OnF and Ag , Ni. anda .. er.ta.. ducovruml s f (96) .. J m Sa . Oye-rveehg odciiy.. W.1 Powe28). sample .. &...... - .3a. IM. C.. Dp..... .Je...R. KikuchiBERYLIUM (932). Cominrl See figure 2, under "Metallic Elements".. E.J. Lewi 6.0 Ag ............. k= 1.16at27WC...9 Al 2 Zn, 0.1 .71 1.32 ........................ Aged . Mo. U ~5.Cu, 0.5 Si, 0.8 Fe, 0.5 Mn, 1.23 ......................... Quenched. MIA.B
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Compositional Effects on Nickel-Base Superalloy Single Crystal Microstructures
NASA Technical Reports Server (NTRS)
MacKay, Rebecca A.; Gabb, Timothy P.; Garg,Anita; Rogers, Richard B.; Nathal, Michael V.
2012-01-01
Fourteen nickel-base superalloy single crystals containing 0 to 5 wt% chromium (Cr), 0 to 11 wt% cobalt (Co), 6 to 12 wt% molybdenum (Mo), 0 to 4 wt% rhenium (Re), and fixed amounts of aluminum (Al) and tantalum (Ta) were examined to determine the effect of bulk composition on basic microstructural parameters, including gamma' solvus, gamma' volume fraction, volume fraction of topologically close-packed (TCP) phases, phase chemistries, and gamma - gamma'. lattice mismatch. Regression models were developed to describe the influence of bulk alloy composition on the microstructural parameters and were compared to predictions by a commercially available software tool that used computational thermodynamics. Co produced the largest change in gamma' solvus over the wide compositional range used in this study, and Mo produced the largest effect on the gamma lattice parameter and the gamma - gamma' lattice mismatch over its compositional range, although Re had a very potent influence on all microstructural parameters investigated. Changing the Cr, Co, Mo, and Re contents in the bulk alloy had a significant impact on their concentrations in the gamma matrix and, to a smaller extent, in the gamma' phase. The gamma phase chemistries exhibited strong temperature dependencies that were influenced by the gamma and gamma' volume fractions. A computational thermodynamic modeling tool significantly underpredicted gamma' solvus temperatures and grossly overpredicted the amount of TCP phase at 982 C. Furthermore, the predictions by the software tool for the gamma - gamma' lattice mismatch were typically of the wrong sign and magnitude, but predictions could be improved if TCP formation was suspended within the software program. However, the statistical regression models provided excellent estimations of the microstructural parameters based on bulk alloy composition, thereby demonstrating their usefulness.
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Magnetic Properties of Hard Magnetic Alloy Fe - 28% Cr - 13.4% Co - 2% Mo - 0.5% Si
NASA Astrophysics Data System (ADS)
Vompe, T. A.; Milyaev, I. M.; Yusupov, V. S.
2017-01-01
The method of regression analysis is used to obtain equations describing the dependences of magnetic hysteresis properties of magnetically hard powder alloy Fe - 28% Cr - 13.4% Co - 2% Mo - 0.5% Si on regimes of thermomagnetic treatment (the temperatures of the start of the treatment and the rates of cooling in magnetic field). The determined treatment modes make it possible to obtain in an alloy with a coercive force H c up to 40 kA/m, a residual induction B r up to 1.2 T, and a maximum energy product ( BH)max up to 25 kJ/m3. The alloy may find application in the production of rotors of synchronous hysteresis-reluctance motors.
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Study of Ni-Mo electrodeposition in direct and pulse-reverse current
NASA Astrophysics Data System (ADS)
Stryuchkova, Yu M.; Rybin, N. B.; Suvorov, D. V.; Gololobov, G. P.; Tolstoguzov, A. B.; Tarabrin, D. Yu; Serpova, M. A.; Korotchenko, V. A.; Slivkin, E. V.
2017-05-01
Process of electrochemical deposition of the coating based on a binary nickel-molybdenum alloy onto a nickel substrate under pulse mode with current reverse within the range of current density change from 2 to 9 A/dm2 has been researched. Coating structure and its surface morphology have been studied. Method of X-ray energy dispersive spectroscopy has determined a percentage ratio of alloy components in the coating. Mode to obtain the densest and smoothest deposits has been identified under considered terms.
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Heat treatment giving a stable high temperature micro-structure in cast austenitic stainless steel
Anton, Donald L.; Lemkey, Franklin D.
1988-01-01
A novel micro-structure developed in a cast austenitic stainless steel alloy and a heat treatment thereof are disclosed. The alloy is based on a multicomponent Fe-Cr-Mn-Mo-Si-Nb-C system consisting of an austenitic iron solid solution (.gamma.) matrix reinforced by finely dispersed carbide phases and a heat treatment to produce the micro-structure. The heat treatment includes a prebraze heat treatment followed by a three stage braze cycle heat treatment.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
D. D. Keiser, Jr.; A. B. Robinson; M. R. Finlay
2007-09-01
Evaluation of the PIE results of the monolithic plates that were irradiated as part of the RERTR-6 experiment has continued. Specifically, comparisons have been made between the microstructures of the fuel plates before and after irradiation. Using the results from the rigorous characterization that was performed on the as-fabricated plates using scanning electron microscopy, it is possible to improve understanding of how monolithic fuel plates perform when they are irradiated. This paper will discuss the changes that occur, if any, in the microstructure of a monolithic fuel plate that is fabricated using techniques like what were employed for fabricating RERTR-6more » fuel plates. In addition, the performance of fuel/cladding interaction layers that were present in the fuel plates due to the fabrication process will be discussed, particularly in the context of swelling of these layers and how these layers exhibit different behaviors depending on whether the fuel alloy in the fuel plate is U-7Mo or U-10Mo.« less
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NASA Astrophysics Data System (ADS)
Romankov, S.; Park, Y. C.; Shchetinin, I. V.
2017-11-01
Cobalt (Co), molybdenum (Mo), and nickel (Ni) components were simultaneously introduced onto titanium (Ti) surfaces from a composed target using ball collisions. Tungsten carbide (WC) balls were selected for processing as the source of a cemented carbide reinforcement phase. During processing, ball collisions continuously introduced components from the target and the grinding media onto the Ti surface and induced mechanical intermixing of the elements, resulting in formation of a complex nanocomposite structure onto the Ti surface. The as-fabricated microstructure consisted of uniformly dispersed WC particles embedded within an integrated metallic matrix composed of an amorphous phase with nanocrystalline grains. The phase composition of the alloyed layers, atomic reactions, and the matrix grain sizes depended on the combination of components introduced onto the Ti surface during milling. The as-fabricated layer exhibited a very high hardness compared to industrial metallic alloys and tool steel materials. This approach could be used for the manufacture of both cemented carbides and amorphous matrix composite layers.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Pavlina, Erik J., E-mail: e.pavlina@deakin.edu.au; Van Tyne, C.J.; Speer, J.G.
2015-04-15
The effects of combined silicon and molybdenum alloying additions on microalloy precipitate formation in austenite after single- and double-step deformations below the austenite no-recrystallization temperature were examined in high-strength low-alloy (HSLA) steels microalloyed with titanium and niobium. The precipitation sequence in austenite was evaluated following an interrupted thermomechanical processing simulation using transmission electron microscopy. Large (~ 105 nm), cuboidal titanium-rich nitride precipitates showed no evolution in size during reheating and simulated thermomechanical processing. The average size and size distribution of these precipitates were also not affected by the combined silicon and molybdenum additions or by deformation. Relatively fine (< 20more » nm), irregular-shaped niobium-rich carbonitride precipitates formed in austenite during isothermal holding at 1173 K. Based upon analysis that incorporated precipitate growth and coarsening models, the combined silicon and molybdenum additions were considered to increase the diffusivity of niobium in austenite by over 30% and result in coarser precipitates at 1173 K compared to the lower alloyed steel. Deformation decreased the size of the niobium-rich carbonitride precipitates that formed in austenite. - Highlights: • We examine combined Si and Mo additions on microalloy precipitation in austenite. • Precipitate size tends to decrease with increasing deformation steps. • Combined Si and Mo alloying additions increase the diffusivity of Nb in austenite.« less
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Quan, Guo-zheng; Yu, Chun-tang; Liu, Ying-ying; Xia, Yu-feng
2014-01-01
The stress-strain data of 20MnNiMo alloy were collected from a series of hot compressions on Gleeble-1500 thermal-mechanical simulator in the temperature range of 1173 ∼ 1473 K and strain rate range of 0.01 ∼ 10 s(-1). Based on the experimental data, the improved Arrhenius-type constitutive model and the artificial neural network (ANN) model were established to predict the high temperature flow stress of as-cast 20MnNiMo alloy. The accuracy and reliability of the improved Arrhenius-type model and the trained ANN model were further evaluated in terms of the correlation coefficient (R), the average absolute relative error (AARE), and the relative error (η). For the former, R and AARE were found to be 0.9954 and 5.26%, respectively, while, for the latter, 0.9997 and 1.02%, respectively. The relative errors (η) of the improved Arrhenius-type model and the ANN model were, respectively, in the range of -39.99% ∼ 35.05% and -3.77% ∼ 16.74%. As for the former, only 16.3% of the test data set possesses η-values within ± 1%, while, as for the latter, more than 79% possesses. The results indicate that the ANN model presents a higher predictable ability than the improved Arrhenius-type constitutive model.
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Piercing mandrel strengthening by surfacing with nickel aluminide-based alloy
NASA Astrophysics Data System (ADS)
Zorin, I. V.; Dubtsov, Yu N.; Sokolov, G. N.; Artem'ev, A. A.; Lysak, V. I.; Elsukov, S. N.
2017-02-01
Electrode composite wire (CW) was used for argon-arc surfacing of a thermal-resisting nickel aluminide-based alloy (Ni-Al-Cr-W-Mo-Ta system) on the butt-end surface of the non-water-cooled piercing mandrel. It was shown that multipassing surfacing forms a defect-free deposited metal based on the γ’-Ni3Al phase of various structural origins. Using high-temperature sclerometry and thermal fatigue testing methods, the metal deposited with CW containing ultrafine particle of 0.3-0.4 % wt. WC carbide features increased resistance to thermal and force effects at temperatures up to 1200 °C.
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NASA Astrophysics Data System (ADS)
Perez, E.; Yao, B.; Keiser, D. D., Jr.; Sohn, Y. H.
2010-07-01
For higher U-loading in low-enriched U-10 wt.%Mo fuels, monolithic fuel plate clad in AA6061 is being developed as a part of Reduced Enrichment for Research and Test Reactor (RERTR) program. This paper reports the first characterization results from a monolithic U-10 wt.%Mo fuel plate with a Zr diffusion barrier that was fabricated as part of a plate fabrication campaign for irradiation testing in the Advanced Test Reactor (ATR). Both scanning and transmission electron microscopy (SEM and TEM) were employed for analysis. At the interface between the Zr barrier and U-10 wt.%Mo, going from Zr to U(Mo), UZr 2, γ-UZr, Zr solid-solution and Mo 2Zr phases were observed. The interface between AA6061 cladding and Zr barrier plate consisted of four layers, going from Al to Zr, (Al, Si) 2Zr, (Al, Si)Zr 3 (Al, Si) 3Zr, and AlSi 4Zr 5. Irradiation behavior of these intermetallic phases is discussed based on their constituents. Characterization of as-fabricated phase constituents and microstructure would help understand the irradiation behavior of these fuel plates, interpret post-irradiation examination, and optimize the processing parameters of monolithic fuel system.
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METHOD AND ALLOY FOR BONDING TO ZIRCONIUM
McCuaig, F.D.; Misch, R.D.
1960-04-19
A brazing alloy can be used for bonding zirconium and its alloys to other metals, ceramics, and cermets, and consists of 6 to 9 wt.% Ni, 6 to 9 wn~.% Cr, Mo, or W, 0 to 7.5 wt.% Fe, and the balance Zr.
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Effect of friction on anodic polarization properties of metallic biomaterials.
Okazaki, Yoshimitsu
2002-05-01
The effect of friction on the anodic polarization properties of metallic biomaterials in a physiological saline solution was investigated. The current density during friction becomes higher than during the static condition. The fluctuation range of the current density caused by the destruction and formation of passive film was observed. For SUS316L stainless steel and Co-Cr-Mo casting alloy, the fluctuation range was observed in the passivity zone. Otherwise, for Ti alloys, the fluctuation range was observed in both the activity and passivity zones. The decrease of the corrosion potential for Ti alloys due to friction was much larger than that of SUS316L stainless steel and Co-Cr-Mo casting alloy. From this result, it was considered that in a the frictional environment, the stressing zone turned anodic and its periphery cathodic, and corrosion tended to progress more than in the static environment. The effect of wear on the anodic polarization curves also changed depending on the frictional load, potential zone and the pH of the solution. A rapid increase in current density due to corrosion starting from the frictional area was found in the Ti-6Al-4V and Ti-15Mo-5Zr-3Al alloys containing Al. However, for the new Ti-15Zr-4Nb-4Ta alloy, this rapid increase was not seen in the high-potential region. The effect of the lateral reciprocal speed was also negligible for the new Ti alloy. It was found that the new Ti-15Zr-4Nb-4Ta alloy exhibited excellent corrosion resistance under friction.
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High strength Sn-Mo-Nb-Zr alloy tubes and method of making same
Cheadle, Brian A.
1977-01-01
Tubes for use in nuclear reactors fabricated from a quaternary alloy comprising 2.5-4.0 wt% Sn, 0.5-1.5 wt% Mo, 0.5-1.5 wt% Nb, balance essentially Zr. The tubes are fabricated by a process of hot extrusion, heat treatment, cold working to size and age hardening, so as to produce a microstructure comprising elongated .alpha. grains with an acicular transformed .beta. grain boundary phase.
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NASA Astrophysics Data System (ADS)
Mann, B. S.
2013-12-01
This article deals with water droplet and cavitation erosion behavior of diode laser-treated X10CrNiMoV1222 stainless steel and Ti6Al4V alloy. After laser surface treatment, the water droplet and cavitation erosion resistance (WDER and CER) of these materials improved significantly. The main reason for the improvement is the increased surface hardness and formation of fine-grained microstructures after laser surface treatment. It is observed that there is a similarity in both the phenomena. The WDER and CER can be correlated with a single mechanical property based on modified ultimate resilience (MUR) provided the laser-treated layers are free from microcracks and interface defects. The CER and WDER behavior of HPDL-treated X10CrNiMoV1222 stainless steel and Ti6Al4V alloy samples using different test equipment as per ASTM G32-2003 and ASTM G73-1978, their correlation with MUR, and their damage mechanism compared on the basis of XRD analyses, optical and scanning electron micrographs are discussed and reported in this article.
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Fracture toughness measurements of three titanium alloy extrusions
DOE Office of Scientific and Technical Information (OSTI.GOV)
DeSisto, T.S.
1973-07-01
Plane strain static K/sub Ic/ and dynamic Kid measurements were obtained on 3-in. dia. titanium alloy extrusions which received a 5.9: 1 reduction followed by air cooling. The alloys investigated were Ti-6Al--6V--2Sn, Ti--8Mo-- 8V--2Fe--3Al, and Ti-- 11.5Mo-6Zr-4.5Sn (Beta III). Compact tension specimens were used to obtain K/sub Ic/ measurements and precracked standard Charpy V- notched specimens were used to obtain Kid measurements. The highest K/sub Ic/ and K /sub Id/ values were obtained from the Beta III extrusion while the lowest K/sub Ic/ and K/sub Id/ values were obtained for the Ti-8Mo--8V--2Fe -- 3Al extrusion. Good agreement was found tomore » exist between K/sub Ic/ values obtained from precracked Charpy V-notch specimens and compact tension specimens. (auth)« less
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Iron aluminide useful as electrical resistance heating elements
Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton
1997-01-01
The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.
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Iron aluminide useful as electrical resistance heating elements
Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton
1999-01-01
The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.
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Iron aluminide useful as electrical resistance heating elements
Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton
2001-01-01
The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.
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Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability
Khong, J. C.; Daisenberger, D.; Burca, G.; Kockelmann, W.; Tremsin, A. S.; Mi, J.
2016-01-01
This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe48Cr15Mo14C15B6Gd2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications. PMID:27848991
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Microstructural characteristics of σ phase and P phase in Ru-containing single crystal superalloys
DOE Office of Scientific and Technical Information (OSTI.GOV)
Huo, Jiajie, E-mail: jiajiehuo0618@163.com
Microstructural instability caused by topologically close-packed (TCP) phase precipitation restricts the useful compositional range of advanced Ni-base single crystal superalloys in industrial applications. Limited systematic investigations of TCP formers (Cr and Mo) additions on microstructural evolution of both the σ phase and the P phase in Ru-containing single crystal superalloys have been reported. In this study, the microstructural characteristics of σ phase and P phase were investigated in three Ru-containing superalloys with different levels of Cr and Mo additions at 950 °C and 1100 °C by using phase extraction, X-ray diffraction, scanning electron microscope and high resolution transmission electron microscopy.more » The experimental results indicated that the high level additions of Cr and Mo promoted the formation of σ phase and P phase, respectively. The amount of σ phase was much higher than that of P phase after long term exposure at 950 °C and 1100 °C. The sheet-like σ phase existed in the alloy with higher Cr addition after thermal exposure at 950 °C and 1100 °C for 1000 h, while the needle-like P phase precipitated in high Mo content alloy after thermal exposure at 1100 °C for 1000 h and the intergrowth of σ phase and P phase was observed after thermal exposure at 950 °C for 500 h. Both the σ phase and P phase were enriched in Re, W, Cr and Mo, but the σ phase contained more Re and Cr while the P phase contained more Mo and Ni, and Ru was found in both phases. The nucleation of σ phase was much easier than P phase due to the more ledge steps in the interfacial structure between σ phase and matrix, as well as the higher partitioning ratios of Re, Cr and Mo. This study is helpful to understand the microstructural evolution of σ phase and P phase, and to optimize the alloy design in Ru-containing superalloys. - Highlights: •Microstructures of σ phase and P phase were characterized in detail. •Cr and Mo influenced the precipitation of σ phase and P phase, respectively. •Partitioning ratios and interfacial relationship decided precipitation behaviors.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wood, Elizabeth Sooby; Parker, Stephen Scott; Nelson, Andrew Thomas
The Fuel Cycle Research and Development program’s Advanced Fuels Campaign is currently supporting a range of experimental efforts aimed at the development and qualification of ‘accident tolerant’ nuclear fuel forms. One route to enhance the accident tolerance of nuclear fuel is to replace the zirconium alloy cladding, which is prone to rapid oxidation in steam at elevated temperatures, with a more oxidation-resistant cladding. Several cladding replacement solutions have been envisaged. The cladding can be completely replaced with a more oxidation resistant alloy, a layered approach can be used to optimize the strength, creep resistance, and oxidation tolerance of various materials,more » or the existing zirconium alloy cladding can be coated with a more oxidation-resistant material. Molybdenum is one candidate cladding material favored due to its high temperature creep resistance. However, it performs poorly under autoclave testing and suffers degradation under high temperature steam oxidation exposure. Development of composite cladding architectures consisting of a molybdenum core shielded by a molybdenum disilicide (MoSi 2) coating is hypothesized to improve the performance of a Mo-based cladding system. MoSi 2 was identified based on its high temperature oxidation resistance in O 2 atmospheres (e.g. air and “wet air”). However, its behavior in H 2O is less known. This report presents thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and x-ray diffraction (XRD) results for MoSi 2 exposed to 670-1498 K water vapor. Synthetic air (80-20%, Ar-O 2) exposures were also performed, and those results are presented here for a comparative analysis. It was determined that MoSi 2 displays drastically different oxidation behavior in water vapor than in dry air. In the 670-1498 K temperature range, four distinct behaviors are observed. Parabolic oxidation is exhibited in only 670-773 K water vapor, a temperature range in which the material pests in dry O 2 environments. From 877-1084 K in water vapor, MoSi 2 undergoes rapid mass gain resulting in oxidation throughout the bulk of the sample at 980 K and 1084 K. The resulting material displays swelling and warping after the 980-1084 K exposures. A pre-passivation heat treatment performed at 1395 K was found capable of producing a coarse SiO 2 layer that limited pesting at lower temperatures in water vapor over the time periods investigated.« less
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In situ phase transformation of Laves phase from Chi-phase in Mo-containing Fe–Cr–Ni alloys
Tan, L.; Yang, Y.
2015-11-01
For an in situ phase transformation of the Chi (χ) phase to the Laves phase we observed in a Fe–Cr–Ni–Mo model alloy. The morphology, composition, and crystal structure of the χ and Laves phases, and their orientation relationship with the matrix austenite phase were investigated. The resulted Laves phase has larger lattice mismatch with the matrix phase than the χ phase, leading to the increase of local strain fields and the formation of dislocations. Moreover, this finding is helpful to understand the precipitation behavior of the intermetallic phases in the Mo-containing austenitic stainless steels.
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Effects of stress ratio on the temperature-dependent high-cycle fatigue properties of alloy steels
NASA Astrophysics Data System (ADS)
Lü, Zhi-yang; Wan, Ao-shuang; Xiong, Jun-jiang; Li, Kuang; Liu, Jian-zhong
2016-12-01
This paper addresses the effects of stress ratio on the temperature-dependent high-cycle fatigue (HCF) properties of alloy steels 2CrMo and 9CrCo, which suffer from substantial vibrational loading at small stress amplitude, high stress ratio, and high frequency in the high-temperature environments in which they function as blade and rotor spindle materials in advanced gas or steam turbine engines. Fatigue tests were performed on alloy steels 2CrMo and 9CrCo subjected to constant-amplitude loading at four stress ratios and at four and three temperatures, respectively, to determine their temperature-dependent HCF properties. The interaction mechanisms between high temperature and stress ratio were deduced and compared with each other on the basis of the results of fractographic analysis. A phenomenological model was developed to evaluate the effects of stress ratio on the temperature-dependent HCF properties of alloy steels 2CrMo and 9CrCo. Good correlation was achieved between the predictions and actual experiments, demonstrating the practical and effective use of the proposed method.
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NASA Technical Reports Server (NTRS)
Gill, A.
1983-01-01
Titanium and Ti-8Al-1Mo-1V alloy were nitrided with an ion-beam source of nitrogen or argon and nitrogen at a total pressure of 2 x 10 to the minus 4th power to 10 x 10 to the minus 4th power torr. The treated surface was characterized by surface profilometry, X-ray diffractometry, Auger electron spectroscopy and microhardness measurements. The tetragonal Ti2N phase formed in pure titanium and Ti-8Al-1Mo-1V alloy with traces of AlN in the alloy. Two opposite processes competed during the ion-beam-nitriding process: (1) formation of nitrides in the surface layer and (2) sputtering of the nitrided layers by the ion beam. The highest surface hardnesses, about 500 kg/sq mm in titanium and 800 kg/sq mm in Ti-8Al-1Mo-1V, were obtained by ion nitriding with an ion beam of pure nitrogen at 4.2 x 10 to the minus 4th power torr at a beam voltage of 1000 V.
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Post-irradiation examination of uranium 7 wt% molybdenum atomized dispersion fuel
NASA Astrophysics Data System (ADS)
Leenaers, A.; Van den Berghe, S.; Koonen, E.; Jarousse, C.; Huet, F.; Trotabas, M.; Boyard, M.; Guillot, S.; Sannen, L.; Verwerft, M.
2004-10-01
Two low-enriched uranium fuel plates consisting of U-7wt%Mo atomized powder dispersed in an aluminum matrix, have been irradiated in the FUTURE irradiation rig of the BR2 reactor at SCK•CEN. The plates were submitted to a heat flux of maximum 353 W/cm 2 while the surface cladding temperature is kept below 130 °C. After 40 full power days, visual examination and profilometry of the fuel plates revealed an increase of the plate thickness. In view of this observation, the irradiation campaign was prematurely stopped and the fuel plates were retrieved from the reactor, having at their end-of-life a maximum burn-up of 32.8% 235U (6.5% FIMA). The microstructure of one of the fuel plates has been characterized in an extensive post-irradiation campaign. The U(Mo) fuel particles have been found to interact with the Al matrix, resulting in an interaction layer which can be identified as (U,Mo)Al 3 and (U,Mo)Al 4. Based on the composition of the interaction layer it is shown that the observed physical parameters like thickness of the interaction layer between the Al matrix and the U(Mo) fuel particles compare well to the values calculated by the MAIA code, an U(Mo) behavior modeling code developed by the Commissariat à l'énergie atomique (CEA).
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Annealing tests of in-pile irradiated oxide coated U-Mo/Al-Si dispersed nuclear fuel
NASA Astrophysics Data System (ADS)
Zweifel, T.; Valot, Ch.; Pontillon, Y.; Lamontagne, J.; Vermersch, A.; Barrallier, L.; Blay, T.; Petry, W.; Palancher, H.
2014-09-01
U-Mo/Al based nuclear fuels have been worldwide considered as a promising high density fuel for the conversion of high flux research reactors from highly enriched uranium to lower enrichment. In this paper, we present the annealing test up to 1800 °C of in-pile irradiated U-Mo/Al-Si fuel plate samples. More than 70% of the fission gases (FGs) are released during two major FG release peaks around 500 °C and 670 °C. Additional characterisations of the samples by XRD, EPMA and SEM suggest that up to 500 °C FGs are released from IDL/matrix interfaces. The second peak at 670 °C representing the main release of FGs originates from the interaction between U-Mo and matrix in the vicinity of the cladding.
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Solubility of Nitrogen in Superaustenitic Stainless Steels During Air Induction Melting
NASA Astrophysics Data System (ADS)
Chandrasekar, A.; Anburaj, J.; Narayanan, R.; Balusamy, V.; Mohamed Nazirudeen, S. S.
2013-04-01
The amount of nitrogen contained in super austenitic stainless steels (SASS) influences their properties significantly. The effect of maximum amount of nitrogen in the highly alloyed Cr and Ni SASS containing further additions of Mo and Mn is studied. The calculated nitrogen contents of the experimental alloys are compared with the actual nitrogen contents obtained in the alloys produced using induction melting furnace. The actual nitrogen content of the alloys is always lower than the calculated value, and this discrepancy is due to the presence of positive interaction parameters of Ni, Cu, and Si in the alloy. However, the yield of nitrogen in the liquid SASS is improved significantly with additions of Mn and Mo contents. The construction of multicomponent phase diagrams for SASS is demonstrated using Thermo-Calc software. SASS containing more nitrogen exhibited a very high strength without loss of toughness.
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Effect of rhenium on the structure and properties of the weld metal of a molybdenum alloy
NASA Technical Reports Server (NTRS)
Dyachenko, V. V.; Morozov, B. P.; Tylkina, M. A.; Savitskiy, Y. M.; Nikishanov, V. V.
1984-01-01
The structure and properties of welds made in molybdenum alloy VM-1 as a function of rhenium concentrations in the weld metal were studied. Rhenium was introduced into the weld using rhenium wire and tape or wires of Mo-47Re and Mo-52Re alloys. The properties of the weld metal were studied by means of metallographic techniques, electron microscopy, X-ray analysis, and autoradiography. The plasticity of the weld metal sharply was found to increase with increasing concentration of rhenium up to 50%. During welding, a decarburization process was observed which was more pronounced at higher concentrations of rhenium.
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Chao, P.J.
1974-01-01
A method is given for protecting Si--Ge and Si-- Mo alloys for use in thermocouples. The alloys are coated with silicon to inhibit the evaporation of the alloys at high tempenatures in a vacuum. Specific means and methods are provided. (5 fig) (Official Gazette)
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NASA Astrophysics Data System (ADS)
Karuppasamy, S.; Sivan, V.; Natarajan, S.; Kumaresh Babu, S. P.; Duraiselvam, M.; Dhanuskodi, R.
2018-05-01
High cost imported components of seamless steel tube manufacturing plants wear frequently and need replacement to ensure the quality of the product. Hard chrome plating, which is time consuming and hazardous, is conventionally used to restore the original dimension of the worn-out surface of the machine components. High Velocity Oxy-Fuel (HVOF) thermal spray coatings with NiCrBSi super alloy powder and Cr3C2 NiCr75/25 alloy powder applied on a 50CrMo4 (DIN-1.7228) chromium molybdenum alloy steel, the material of the wear prone machine component, were evaluated for use as an alternative for hard chrome plating in this present work. The coating characteristics are evaluated using abrasive wear test, sliding wear test and microscopic analysis, hardness test, etc. The study results revealed that the HVOF based NiCrBSi and Cr3C2NiCr75/25 coatings have hardness in the range of 800-900 HV0.3, sliding wear rate in the range of 50-60 µm and surface finish around 5 microns. Cr3C2 NiCr75/25 coating is observed to be a better option out of the two coatings evaluated for the selected application.
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Study of structural phase transitions in quinary TiNi(MoFeAg)-based alloys
NASA Astrophysics Data System (ADS)
Gunther, Victor; Marchenko, Ekaterina; Chekalkin, Timofey; Baigonakova, Gulsharat; Kang, Ji-hoon; Kim, Ji-soon; Klopotov, Anatoliy
2017-10-01
The structural phase transitions of quinary Ti50Ni49.5-X Mo0.3Fe0.2Ag X (X = 0, 0.1, 0.2, 0.5, 1.0, and 1.5 at%) alloys prepared by vacuum-induction melting were studied by means of the four-point-probe, x-ray diffraction (XRD), and optical microscopy methods after thermal cycling. The two-stage B2 ↔ R ↔ B19‧ reversible martensitic transformation (MT) took place in all the investigated samples. It is found that the substitution of Ag for Ni in the studied alloy when C Ag = 0-0.5 at%, reduces the T R, M s, and M f characteristic points by 20-30 K, whereas they increase by 15-35 K when the Ag content was varied from 1.0 to 1.5 at% and the B2 ↔ R ↔ B19‧ MT was realized in the high-temperature area. XRD patterns of the studied alloys recorded at the ambient temperature detected the pure Ag phase as well as Ti2Ni precipitate with a small volume fraction (up to 5%) alongside with structural lines of B2, R, and B19‧ phases.
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Influence of the casting processing route on the corrosion behavior of dental alloys.
Galo, Rodrigo; Rocha, Luis Augusto; Faria, Adriana Claudia; Silveira, Renata Rodrigues; Ribeiro, Ricardo Faria; de Mattos, Maria da Gloria Chiarello
2014-12-01
Casting in the presence of oxygen may result in an improvement of the corrosion performance of most alloys. However, the effect of corrosion on the casting without oxygen for dental materials remains unknown. The aim of this study was to investigate the influence of the casting technique and atmosphere (argon or oxygen) on the corrosion behavior response of six different dental casting alloys. The corrosion behavior was evaluated by electrochemical measurements performed in artificial saliva for the different alloys cast in two different conditions: arc melting in argon and oxygen-gas flame centrifugal casting. A slight decrease in open-circuit potential for most alloys was observed during immersion, meaning that the corrosion tendency of the materials increases due to the contact with the solution. Exceptions were the Co-based alloys prepared by plasma, and the Co-Cr-Mo and Ni-Cr-4Ti alloys processed by oxidized flame, in which an increase in potential was observed. The amount of metallic ions released into the artificial saliva solution during immersion was similar for all specimens. Considering the pitting potential, a parameter of high importance when considering the fluctuating conditions of the oral environment, Co-based alloys show the best performance in comparison with the Ni-based alloys, independent of the processing route. Copyright © 2014 Elsevier B.V. All rights reserved.
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Effects of chemical composition on the corrosion of dental alloys.
Galo, Rodrigo; Ribeiro, Ricardo Faria; Rodrigues, Renata Cristina Silveira; Rocha, Luís Augusto; de Mattos, Maria da Glória Chiarello
2012-01-01
The aim of this study was to determine the effect of the oral environment on the corrosion of dental alloys with different compositions, using electrochemical methods. The corrosion rates were obtained from the current-potential curves and electrochemical impedance spectroscopy (EIS). The effect of artificial saliva on the corrosion of dental alloys was dependent on alloy composition. Dissolution of the ions occurred in all tested dental alloys and the results were strongly dependent on the general alloy composition. Regarding the alloys containing nickel, the Ni-Cr and Ni-Cr-Ti alloys released 0.62 mg/L of Ni on average, while the Co-Cr dental alloy released ions between 0.01 and 0.03 mg/L of Co and Cr, respectively.The open-circuit potential stabilized at a higher level with lower deviation (standard deviation: Ni-Cr-6Ti = 32 mV/SCE and Co-Cr = 54 mV/SCE). The potenciodynamic curves of the dental alloys showed that the Ni-based dental alloy with >70 wt% of Ni had a similar curve and the Co-Cr dental alloy showed a low current density and hence a high resistance to corrosion compared with the Ni-based dental alloys. Some changes in microstructure were observed and this fact influenced the corrosion behavior for the alloys. The lower corrosion resistance also led to greater release of nickel ions to the medium. The quantity of Co ions released from the Co-Cr-Mo alloy was relatively small in the solutions. In addition, the quantity of Cr ions released into the artificial saliva from the Co-Cr alloy was lower than Cr release from the Ni-based dental alloys.
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Effect of Heat Treatment on the Properties of CoCrMo Alloy Manufactured by Selective Laser Melting
NASA Astrophysics Data System (ADS)
Guoqing, Zhang; Junxin, Li; Xiaoyu, Zhou; Jin, Li; Anmin, Wang
2018-04-01
To obtain medical implants with better mechanical properties, it is necessary to conduct studies on the heat treatment process of the selective laser melting (SLM) manufacturing parts. The differential scanning calorimetry method was used to study the heat treatment process of the phase transition of SLM CoCrMo alloy parts. The tensile properties were tested with a tensile test machine, the quantity of carbide precipitated after heat treatment was measured by energy-dispersive x-ray spectroscopy, and the tensile fracture morphology of the parts was investigated using SEM. The obtained results were: Mechanical properties in terms of elongation and tensile strength of CoCrMo alloy manufactured by SLM that had been heat-treated at 1200 °C for 2 h followed by cooling with water were not only higher than the national standard but also higher than the experimental results of the same batch of castings. The mechanism of fracture of parts manufactured by SLM without heat treatment was brittle fracture, whereas parts which had been heat-treated at 1200 °C for 2 h combined with water cooling and at 1200 °C for 1 h with furnace cooling suffered ductile fracture. This study provides the basis for defining the applications for which CoCrMo alloys manufactured by SLM are suitable within the field of medical implants.
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Effect of Heat Treatment on the Properties of CoCrMo Alloy Manufactured by Selective Laser Melting
NASA Astrophysics Data System (ADS)
Guoqing, Zhang; Junxin, Li; Xiaoyu, Zhou; Jin, Li; Anmin, Wang
2018-05-01
To obtain medical implants with better mechanical properties, it is necessary to conduct studies on the heat treatment process of the selective laser melting (SLM) manufacturing parts. The differential scanning calorimetry method was used to study the heat treatment process of the phase transition of SLM CoCrMo alloy parts. The tensile properties were tested with a tensile test machine, the quantity of carbide precipitated after heat treatment was measured by energy-dispersive x-ray spectroscopy, and the tensile fracture morphology of the parts was investigated using SEM. The obtained results were: Mechanical properties in terms of elongation and tensile strength of CoCrMo alloy manufactured by SLM that had been heat-treated at 1200 °C for 2 h followed by cooling with water were not only higher than the national standard but also higher than the experimental results of the same batch of castings. The mechanism of fracture of parts manufactured by SLM without heat treatment was brittle fracture, whereas parts which had been heat-treated at 1200 °C for 2 h combined with water cooling and at 1200 °C for 1 h with furnace cooling suffered ductile fracture. This study provides the basis for defining the applications for which CoCrMo alloys manufactured by SLM are suitable within the field of medical implants.
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Design of high-strength refractory complex solid-solution alloys
Singh, Prashant; Sharma, Aayush; Smirnov, A. V.; ...
2018-03-28
Nickel-based superalloys and near-equiatomic high-entropy alloys containing molybdenum are known for higher temperature strength and corrosion resistance. Yet, complex solid-solution alloys offer a huge design space to tune for optimal properties at slightly reduced entropy. For refractory Mo-W-Ta-Ti-Zr, we showcase KKR electronic structure methods via the coherent-potential approximation to identify alloys over five-dimensional design space with improved mechanical properties and necessary global (formation enthalpy) and local (short-range order) stability. Deformation is modeled with classical molecular dynamic simulations, validated from our first-principle data. We predict complex solid-solution alloys of improved stability with greatly enhanced modulus of elasticity (3× at 300 K)more » over near-equiatomic cases, as validated experimentally, and with higher moduli above 500 K over commercial alloys (2.3× at 2000 K). We also show that optimal complex solid-solution alloys are not described well by classical potentials due to critical electronic effects.« less
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Design of high-strength refractory complex solid-solution alloys
DOE Office of Scientific and Technical Information (OSTI.GOV)
Singh, Prashant; Sharma, Aayush; Smirnov, A. V.
Nickel-based superalloys and near-equiatomic high-entropy alloys containing molybdenum are known for higher temperature strength and corrosion resistance. Yet, complex solid-solution alloys offer a huge design space to tune for optimal properties at slightly reduced entropy. For refractory Mo-W-Ta-Ti-Zr, we showcase KKR electronic structure methods via the coherent-potential approximation to identify alloys over five-dimensional design space with improved mechanical properties and necessary global (formation enthalpy) and local (short-range order) stability. Deformation is modeled with classical molecular dynamic simulations, validated from our first-principle data. We predict complex solid-solution alloys of improved stability with greatly enhanced modulus of elasticity (3× at 300 K)more » over near-equiatomic cases, as validated experimentally, and with higher moduli above 500 K over commercial alloys (2.3× at 2000 K). We also show that optimal complex solid-solution alloys are not described well by classical potentials due to critical electronic effects.« less
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Effects of adding metals to MoS2 in a ytterbium doped Q-switched fiber laser
NASA Astrophysics Data System (ADS)
Khaleque, Abdul; Liu, Liming
2018-03-01
Molybdenum disulfide (MoS2) is widely used in lubricants, metallic alloys and in electronic and optical components. It is also used as saturable absorbers (SAs) in lasers (e.g. fiber lasers): a simple deposition of MoS2 on the fiber end can create a saturable absorber without the necessity of extensive alignment of the optical beam. In this article, we study the effects of adding different metals (Cr, Au, and Al) to MoS2 in a ytterbium (Yb)-doped Q-switched fiber laser. Experimental results show that the addition of a thin layer of gold and aluminium can reduce pulse durations to about 5.8 μs and 8.5 μs, respectively, compared with pure MoS2 with pulse duration of 12 μs. Experimental analysis of the combined metal and MoS2 based composite SAs can be useful in fiber laser applications where it may also find applications in medical, three dimensional (3D) active imaging and dental applications.
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Vanadium Oxide Thin Films Alloyed with Ti, Zr, Nb, and Mo for Uncooled Infrared Imaging Applications
NASA Astrophysics Data System (ADS)
Ozcelik, Adem; Cabarcos, Orlando; Allara, David L.; Horn, Mark W.
2013-05-01
Microbolometer-grade vanadium oxide (VO x ) thin films with 1.3 < x < 2.0 were prepared by pulsed direct-current (DC) sputtering using substrate bias in a controlled oxygen and argon environment. These films were systematically alloyed with Ti, Nb, Mo, and Zr using a second gun and radiofrequency (RF) reactive co-sputtering to probe the effects of the transition metals on the film charge transport characteristics. The results reveal that the temperature coefficient of resistance (TCR) and resistivity are unexpectedly similar for alloyed and unalloyed films up to alloy compositions in the ˜20 at.% range. Analysis of the film structures for the case of the 17% Nb-alloyed film by glancing-angle x-ray diffraction and transmission electron microscopy shows that the microstructure remains even with the addition of high concentrations of alloy metal, demonstrating the robust character of the VO x films to maintain favorable electrical transport properties for bolometer applications. Postdeposition thermal annealing of the alloyed VO x films further reveals improvement of electrical properties compared with unalloyed films, indicating a direction for further improvements in the materials.
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The Tribological Difference between Biomedical Steels and CoCrMo-Alloys
Fischer, Alfons; Weiß, Sabine; Wimmer, Markus A.
2012-01-01
In orthopedic surgery different self-mating metal couples are used for sliding wear applications. Despite the fact that in mechanical engineering self-mating austenitic alloys often lead to adhesion and seizure in biomedical engineering the different grades of Co-base alloys show good clinical results e.g. as hip joints. The reason stems from the fact that they generate a so-called tribomaterial during articulation, which consists of a mixture of nanometer small metallic grains and organic substances from the interfacial medium, which act as boundary lubricant. Even though stainless steels also generate such a tribomaterial they were ruled out from the beginning already in the 1950 as “inappropriate”. On the basis of materials with a clinical track record this contribution shows that the cyclic creep characteristics within the shear zone underneath the tribomaterial are another important criterion for a sufficient wear behavior. By means of sliding wear and torsional fatigue tests followed by electron microscopy it is shown, that austenitic materials generate wear particles of either nano- or of microsize. The latter are produced by crack initiation and propagation within the shear fatigue zone which is related to the formation of subsurface dislocation cells and, therefore, by the fact that a Ni-containing CrNiMo solid solution allows for wavy-slip. In contrast to this a Ni-free CrMnMo solid solution with further additions of C and N only shows planar slip. This leads to the formation of nanosize wear particles and distinctly improves the wear behavior. Still the latter does not fully achieve that of CoCrMo, which also shows solely planar-slip behavior. This explains why for metallurgical reasons the Ni-containing 316L-type of steels had to fail in such boundary lubricated sliding wear tribosystems. PMID:22498283
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Creep of Refractory Fibers and Modeling of Metal and Ceramic Matrix Composite Creep Behavior
NASA Technical Reports Server (NTRS)
Tewari, S.N.
1995-01-01
Our concentration during this research was on the following subprograms. (1) Ultra high vacuum creep tests on 218, ST300 and WHfC tungsten and MoHfC molybdenum alloy wires, temperature range from 1100 K to 1500 K, creep time of 1 to 500 hours. (2) High temperature vacuum tensile tests on 218, ST300 and WHfC tungsten and MoHfC molybdenum alloy wires. (3) Air and vacuum tensile creep tests on polycrystalline and single crystal alumina fibers, such as alumina-mullite Nextel fiber, yttrium aluminum ganet (YAG) and Saphikon, temperature range from 1150 K to 1470 K, creep time of 2 to 200 hours. (4) Microstructural evaluation of crept fibers, TEM study on the crept metal wires, SEM study on the fracture surface of ceramic fibers. (5) Metal Matrix Composite creep models, based on the fiber creep properties and fiber-matrix interface zone formation.
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NASA Astrophysics Data System (ADS)
Max, B.; San Juan, J.; Nó, M. L.; Cloue, J. M.; Viguier, B.; Andrieu, E.
2018-06-01
In many Ni-based superalloys, dynamic strain aging (DSA) generates an inhomogeneous plastic deformation resulting in jerky flow known as the Portevin-Le Chatelier (PLC) effect. This phenomenon has a deleterious effect on the mechanical properties and, at high temperature, is related to the diffusion of substitutional solute atoms toward the core of dislocations. However, the question about the nature of the atomic species responsible for the PLC effect at high temperature still remains open. The goal of the present work is to answer this important question; to this purpose, three different 718-type and a 625 superalloy were studied through a nonconventional approach by mechanical spectroscopy. The internal friction (IF) spectra of all the studied alloys show a relaxation peak P 718 (at 885 K for 0.1 Hz) in the same temperature range, 700 K to 950 K, as the observed PLC effect. The activation parameters of this relaxation peak have been measured, E a( P 718) = 2.68 ± 0.05 eV, τ 0 = 2·10-15 ± 1 s as well as its broadening factor β = 1.1. Experiments on different alloys and the dependence of the relaxation strength on the amount of Mo attribute this relaxation to the stress-induced reorientation of Mo-Mo dipoles due to the short distance diffusion of one Mo atom by exchange with a vacancy. Then, it is concluded that Mo is the atomic species responsible for the high-temperature PLC effect in 718 superalloy.
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NASA Astrophysics Data System (ADS)
Max, B.; San Juan, J.; Nó, M. L.; Cloue, J. M.; Viguier, B.; Andrieu, E.
2018-03-01
In many Ni-based superalloys, dynamic strain aging (DSA) generates an inhomogeneous plastic deformation resulting in jerky flow known as the Portevin-Le Chatelier (PLC) effect. This phenomenon has a deleterious effect on the mechanical properties and, at high temperature, is related to the diffusion of substitutional solute atoms toward the core of dislocations. However, the question about the nature of the atomic species responsible for the PLC effect at high temperature still remains open. The goal of the present work is to answer this important question; to this purpose, three different 718-type and a 625 superalloy were studied through a nonconventional approach by mechanical spectroscopy. The internal friction (IF) spectra of all the studied alloys show a relaxation peak P 718 (at 885 K for 0.1 Hz) in the same temperature range, 700 K to 950 K, as the observed PLC effect. The activation parameters of this relaxation peak have been measured, E a(P 718) = 2.68 ± 0.05 eV, τ 0 = 2·10-15 ± 1 s as well as its broadening factor β = 1.1. Experiments on different alloys and the dependence of the relaxation strength on the amount of Mo attribute this relaxation to the stress-induced reorientation of Mo-Mo dipoles due to the short distance diffusion of one Mo atom by exchange with a vacancy. Then, it is concluded that Mo is the atomic species responsible for the high-temperature PLC effect in 718 superalloy.
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NASA Astrophysics Data System (ADS)
Pharkya, Pallavi
Alloy 22, a Ni-Cr-Mo-W alloy, and SAM1651, an Fe-Cr-Mo-B-Y-C bulk metallic glass are highly corrosion-resistant alloys. The high corrosion resistance of these alloys is due to the formation of tenacious oxide films on their surfaces. This study examines the reformation behavior of the passive films as a function of the corrosion resistance of the alloys and the corrosivity of the environment. The main tasks of this study were (i) to determine the chemical durability of passive films on these highly corrosion-resistant alloys in aggressive environments, (ii) to investigate the durability after mechanically damaging the passive films either locally or over the entire surface area and to study the reformation kinetics, (iii) to compare the durability of the passive films of the aforementioned highly corrosion resistant alloys with an alloy of intermediate corrosion resistance, AL6XN, and an alloy of less corrosion resistance, 316L SS, (iv) to examine the evolution of the electronic properties of the passive films on alloy 22 and SAM1651 under different environmental conditions such as concentrated chloride solution, acidic solution, temperature, potential and oxyanions, and (v) to develop an understanding of the relationship between the passive films' composition, electronic and electrochemical properties and the performance. A combination of techniques was utilized to meet the above mentioned objectives. Cyclic potentiodynamic polarization (CPP) was used to determine the electrochemical parameters such as freely corroding, breakdown and repassivation potentials. Electrochemical impedance spectroscopy (EIS) was used to determine the electronic properties such as impedance, thickness and capacitance of the passive films. Mott-Schottky (M-S) analysis was used to determine the type and the density of the defects in the passive films. The mechanical durability and reformation kinetics of the passive films was investigated using a scratch-repassivation method. The quality and the protectiveness of the reformed passive films after scribing were examined using EIS, M-S analysis, and AES. The results show that the passive films on alloy 22 and SAM1651 possess high chemical and mechanical durability. The reformed passive films acquired the same electronic and elemental properties as the passive films which were undamaged. The passive films on SAM1651 and alloy 22 showed better corrosion resistance and durability than did the passive films on AL6XN and 316L SS. The results also showed that the passive film behavior depends on the inherent corrosion resistance of an alloy and the corrosivity of the environment. The inherent corrosion resistance depends on the concentration of the passivity-providing elements such as Cr and Mo in the bulk composition of the alloy (and passive film), and the corrosivity of the environment which is influenced by chloride concentration, oxyanions, temperature, pH, and oxidizing potential.
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Phase Transformation Temperatures and Solute Redistribution in a Quaternary Zirconium Alloy
NASA Astrophysics Data System (ADS)
Cochrane, C.; Daymond, M. R.
2018-05-01
This study investigates the phase stability and redistribution of solute during heating and cooling of a quaternary zirconium alloy, Excel (Zr-3.2Sn-0.8Mo-0.8Nb). Time-of-flight neutron diffraction data are analyzed using a novel Vegard's law-based approach to determine the phase fractions and location of substitutional solute atoms in situ during heating from room temperature up to 1050 °C. It is seen that this alloy exhibits direct nucleation of the β Zr phase from martensite during tempering, and stable retention of the β Zr phase to high temperatures, unlike other two-phase zirconium alloys. The transformation strains resulting from the α \\leftrightarrow β transformation are shown to have a direct impact on the development of microstructure and crystallographic texture.
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Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo
NASA Technical Reports Server (NTRS)
Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.
2001-01-01
The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33 Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approximately 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.
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Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo
NASA Technical Reports Server (NTRS)
Whittenberger, J. D.; Raj, S. V.; Locci, I. E.
2001-01-01
The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approx. 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.
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Metallurgy and deformation of electron beam welded similar titanium alloys
NASA Astrophysics Data System (ADS)
Pasang, T.; Sabol, J. C.; Misiolek, W. Z.; Mitchell, R.; Short, A. B.; Littlefair, G.
2012-04-01
Butt welded joins were produced between commercially pure titanium and various titanium alloys using an electron beam welding technique. The materials used represent commercially pure grade, α-β alloy and β alloy. They were CP Ti, Ti-6Al-4V (Ti64) and Ti-5Al-5V-5Mo-3Cr (Ti5553), respectively. Grains were largest in the FZs of the different weldments, decreasing in size towards the heat affected zones (HAZs) and base metals. Hardness measurements taken across the traverse cross-sections of the weldments were constant from base metal-to-weld-to-base metal for CP Ti/CP Ti and Ti64/Ti64 welds, while the FZ of Ti5553/Ti5553 had a lower hardness compared with the base metal. During tensile testing the CP Ti/CP Ti weldments fractured at the base metal, whereas both the Ti64/Ti64 and Ti5553/Ti5553 broke at the weld zones. Fracture surface analysis suggested microvoid coalescence as the failure mechanism. The compositional analysis showed a relatively uniform distribution of solute elements from base metal-to-weld-to-base metal. CP Ti has always been known for its excellent weldability, Ti64 has good weldability and, preliminary results indicated that Ti5553 alloy is also weldable.
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Conti, Malcolm Caligari; Karl, Andreas; Wismayer, Pierre Schembri; Buhagiar, Joseph
2014-01-01
High failure rates of cobalt-chromium-molybdenum (Co-Cr-Mo) metal-on-metal hip prosthesis were reported by various authors, probably due to the alloy's limited hardness and tribological properties. This thus caused the popularity of the alloy in metal-on-metal hip replacements to decrease due to its poor wear properties when compared with other systems such as ceramic-on-ceramic. S-phase surface engineering has become an industry standard when citing surface hardening of austenitic stainless steels. This hardening process allows the austenitic stainless steel to retain its corrosion resistance, while at the same time also improving its hardness and wear resistance. By coupling S-phase surface engineering, using the proprietary Kolsterising® treatment from Bodycote Hardiff GmbH, that is currently being used mainly on stainless steel, with Co-Cr-Mo alloys, an improvement in hardness and tribological characteristics is predicted. The objective of this paper is to analyze the biocompatibility of a Kolsterised® Co-Cr-Mo alloy, and to characterize the material surface in order to show the advantages gained by using the Kolsterised® material relative to the original untreated alloy, and other materials. This work has been performed on 3 fronts including; Material characterization, “In-vitro” corrosion testing, and Biological testing conforming to BS EN ISO 10993–18:2009 - Biological evaluation of medical devices. Using these techniques, the Kolsterised® cobalt-chromium-molybdenum alloys were found to have good biocompatibility and an augmented corrosion resistance when compared with the untreated alloy. The Kolsterised® samples also showed a 150% increase in surface hardness over the untreated material thus predicting better wear properties. PMID:24451266
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Conti, Malcolm Caligari; Karl, Andreas; Wismayer, Pierre Schembri; Buhagiar, Joseph
2014-01-01
High failure rates of cobalt-chromium-molybdenum (Co-Cr-Mo) metal-on-metal hip prosthesis were reported by various authors, probably due to the alloy's limited hardness and tribological properties. This thus caused the popularity of the alloy in metal-on-metal hip replacements to decrease due to its poor wear properties when compared with other systems such as ceramic-on-ceramic. S-phase surface engineering has become an industry standard when citing surface hardening of austenitic stainless steels. This hardening process allows the austenitic stainless steel to retain its corrosion resistance, while at the same time also improving its hardness and wear resistance. By coupling S-phase surface engineering, using the proprietary Kolsterising(®) treatment from Bodycote Hardiff GmbH, that is currently being used mainly on stainless steel, with Co-Cr-Mo alloys, an improvement in hardness and tribological characteristics is predicted. The objective of this paper is to analyze the biocompatibility of a Kolsterised(®) Co-Cr-Mo alloy, and to characterize the material surface in order to show the advantages gained by using the Kolsterised(®) material relative to the original untreated alloy, and other materials. This work has been performed on 3 fronts including; Material characterization, "In-vitro" corrosion testing, and Biological testing conforming to BS EN ISO 10993-18:2009 - Biological evaluation of medical devices. Using these techniques, the Kolsterised(®) cobalt-chromium-molybdenum alloys were found to have good biocompatibility and an augmented corrosion resistance when compared with the untreated alloy. The Kolsterised(®) samples also showed a 150% increase in surface hardness over the untreated material thus predicting better wear properties.
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Binary titanium alloys as dental implant materials-a review.
Liu, Xiaotian; Chen, Shuyang; Tsoi, James K H; Matinlinna, Jukka Pekka
2017-10-01
Titanium (Ti) has been used for long in dentistry and medicine for implant purpose. During the years, not only the commercially pure Ti but also some alloys such as binary and tertiary Ti alloys were used. The aim of this review is to describe and compare the current literature on binary Ti alloys, including Ti-Zr, Ti-In, Ti-Ag, Ti-Cu, Ti-Au, Ti-Pd, Ti-Nb, Ti-Mn, Ti-Mo, Ti-Cr, Ti-Co, Ti-Sn, Ti-Ge and Ti-Ga, in particular to mechanical, chemical and biological parameters related to implant application. Literature was searched using the PubMed and Web of Science databases, as well as google without limiting the year, but with principle key terms such as ' Ti alloy', 'binary Ti ', 'Ti-X' (with X is the alloy element), 'dental implant' and 'medical implant'. Only laboratory studies that intentionally for implant or biomedical applications were included. According to available literatures, we might conclude that most of the binary Ti alloys with alloying <20% elements of Zr, In, Ag, Cu, Au, Pd, Nb, Mn, Cr, Mo, Sn and Co have high potential as implant materials, due to good mechanical performance without compromising the biocompatibility and biological behaviour compare to cp-Ti.
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Siderophile trace element diffusion in Fe-Ni alloys
NASA Astrophysics Data System (ADS)
Watson, Heather C.; Watson, E. Bruce
2003-09-01
Experiments were performed in a piston cylinder apparatus to characterize the diffusion behavior of the siderophile elements, Mo, Cu, Pd, Au, and Re in solid Fe-Ni alloy (90 wt.% Fe, 10 wt.% Ni). All experiments were conducted at 1 GPa and temperatures ranging from 1175 to 1400 °C. Activation energies of all elements fall between 270 kJ/mol (Cu) and 360 kJ/mol (Mo). Mo, Cu, Pd, and Au all show similar diffusivities at the same conditions, but the diffusivity of Re was consistently close to an order of magnitude lower. Initial experiments on other refractory elements (Os, Pt, and Ir) indicate that their diffusivities are close to or slightly lower than that of Re.
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2012-08-01
growth rates as well as the variability in the same, in the + titanium alloy, Ti-6Al-2Sn-4Zr-6Mo (Ti- 6 -2- 4 - 6 ) was studied at 260°C. A probabilistic...were obtained in a separate study on the effect of R on the small-crack growth regime in another + titanium alloy, Ti- 6 - 4 [32]. Given that crack...microstructure of Ti-6Al-2Sn-4Zr-6Mo (Ti- 6 -2- 4 - 6 ) at 260°C with particular emphasis on incorporating small-crack data into probabilistic life prediction
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Cation and Vacancy Disorder in U 1-yNd yO 2.00-X Alloys
Barabash, Rozaliya I.; Voit, Stewart L.; Aidhy, Dilpuneet S.; ...
2015-09-14
In this study, the intermixing and clustering of U/Nd, O, and vacancies were studied by both laboratory and synchrotron-based x-ray diffraction in U 1-yNd yO 2-X alloys. It was found that an increased holding time at the high experimental temperature during initial alloy preparation results in a lower disorder of the Nd distribution in the alloys. Adjustment of the oxygen concentration in the U 1-yNd yO 2-X alloys with different Nd concentrations was accompanied by the formation of vacancies on the oxygen sublattice and a nanocrystalline component. The lattice parameters in the U 1-yNd yO 2-X alloys were also foundmore » to deviate significantly from Vegard's law when the Nd concentration was high (53%) and decreased with increasing oxygen concentration. Such changes indicate the formation of large vacancy concentrations during oxygen adjustment at these high temperatures. Finally, the change in the vacancy concentration after the oxygen adjustment was estimated relative to Nd concentration and oxygen stoichiometry.« less
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1992-09-01
Optical macrograph of flat-etched sample 75B3-8 ........................ 30 Figure 4.15 Constitutional supercooling in alloy solidification ... alloying elements such as Mn, Mo, Ni and Cr are added to increase the strength and hardenability of the steel. However, substantial limitations on...0.9 Carbon Equivalent CE = C + Mn + Si + Ni + Cu + Cr + Mo + V 6 15 5 Figure 2.1 Graville Diagram (Blicharski et al, 1989, p.318) 3 B. ULTRA LOW
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Development of Nitride Coating Using Atomic Layer Deposition for Low-Enriched Uranium Fuel Powder
NASA Astrophysics Data System (ADS)
Bhattacharya, Sumit
High-performance research reactors require fuel that operates at high specific power and can withstand high fission density, but at relatively low temperatures. The design of the research reactor fuels is done for efficient heat emission, and consists of assemblies of thin-plates cladding made from aluminum alloy. The low-enriched fuels (LEU) were developed for replacing high-enriched fuels (HEU) for these reactors necessitates a significantly increased uranium density in the fuel to counterbalance the decrease in enrichment. One of the most promising new fuel candidate is U-Mo alloy, in a U-Mo/Al dispersion fuel form, due to its high uranium loading as well as excellent irradiation resistance performance, is being developed extensively to convert from HEU fuel to LEU fuel for high-performance research reactors. However, the formation of an interaction layer (IL) between U-Mo particles and the Al matrix, and the associated pore formation, under high heat flux and high burnup conditions, degrade the irradiation performance of the U-Mo/Al dispersion fuel. From the recent tests results accumulated from the surface engineering of low enriched uranium fuel (SELENIUM) and MIR reactor displayed that a surface barrier coating like physical vapor deposited (PVD) zirconium nitride (ZrN) can significantly reduce the interaction layer. The barrier coating performed well at low burn up but above a fluence rate of 5x 1021 ions/cm2 the swelling reappeared due to formation interaction layer. With this result in mind the objective of this research was to develop an ultrathin ZrN coating over particulate uranium-molybdenum nuclear fuel using a modified savannah 200 atomic layer deposition (ALD) system. This is done in support of the US Department of Energy's (DOE) effort to slow down the interaction at fluence rate and reach higher burn up for high power research reactor. The low-pressure Savannah 200 ALD system is modified to be designed as a batch powder coating system using the metal organic chemical precursors tetrakis dimethylamido zirconium (TDMAZr) and ammonia( NH3) for succesful deposition of ZrN coating. Nitrogen (N2) gas carried the chemicals to a hot wall reactor maintained at a temperature range of 235 to 245 °C. The ALD system design evolved over the course of this research as the process variables were steadily improved. The conditions found deemed for attaining best coating were at a temperature of 245 °C, with pulse time of 0.8 seconds for TDMAZr and 0.1 seconds for NH3 along with 15 seconds of purge time in-between each cycle. The ALD system was successful in making 1-micrometer (um) ZrN with low levels of chemical impurities over U-Mo powder batches. The deposited coatings were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron energy loss spectroscopy (EELS) and Transmission electron microscope (TEM). This document describes the establishment of the Savannah 200 ALD system, precursor surface reaction procedures and finally the nature of the coating achieved, including characterization of the coating at the different stages of deposition. It was found that an interlayer of alumina in between ZrN and the U-Mo surface was required to reduce the residual stress generated during the ALD procedure. The alumina not only removed the risk of cracking and spallation of the ZrN coating but also provided adequate strength for the barrier layer to withstand the fuel plate rolling conditions. The ZrN coating was nano crystalline in nature, with grain size varying from 5-10 nm, the deposited layer was found to be dense consisting of a layered structure. The coating could retain its crystallinity and maintain its phase when irradiated with 1 MeV single charged ion Kr to produce a damage of 10 displacement per atom (DPA) at intermediate voltage electron microscopy (IVEM).
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Surface Modifications with Laser Synthesized Mo Modified Coating
NASA Astrophysics Data System (ADS)
Sun, Lu; Chen, Hao; Liu, Bo
2013-01-01
Mg-Cu-Al was first used to improve the surface performance of TA15 titanium alloys by means of laser cladding technique. The synthesis of hard composite coating on TA15 titanium alloy by laser cladding of Mg-Cu-Al-B4C/Mo pre-placed powders was investigated by means of scanning electron microscope, energy dispersive spectrometer and high resolution transmission electron microscope. Experimental results indicated that such composite coating mainly consisted of TiB2, TiB, TiC, Ti3Al and AlCuMg. Compared with TA15 alloy substrate, an improvement of wear resistance was observed for this composite coating due to the actions of fine grain, amorphous and hard phase strengthening.
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NASA Astrophysics Data System (ADS)
Liu, Yu; Qin, Shengwei; Zhang, Jiazhi; Wang, Ying; Rong, Yonghua; Zuo, Xunwei; Chen, Nailu
2017-10-01
Based on the hardenability of three medium carbon steels, cylinders with the same 60-mm diameter and 240-mm length were designed for quenching in water to obtain microstructures, including a pearlite matrix (Chinese steel mark: 45), a bainite matrix (42CrMo), and a martensite matrix (40CrNiMo). Through the combination of normalized functions describing transformation plasticity (TP), the thermo-elasto-plastic constitutive equation was deduced. The results indicate that the finite element simulation (FES) of the internal stress distribution in the three kinds of hardenable steel cylinders based on the proposed exponent-modified (Ex-Modified) normalized function is more consistent with the X-ray diffraction (XRD) measurements than those based on the normalized functions proposed by Abrassart, Desalos, and Leblond, which is attributed to the fact that the Ex-Modified normalized function better describes the TP kinetics. In addition, there was no significant difference between the calculated and measured stress distributions, even though TP was taken into account for the 45 carbon steel; that is, TP can be ignored in FES. In contrast, in the 42CrMo and 40CrNiMo alloyed steels, the significant effect of TP on the residual stress distributions was demonstrated, meaning that TP must be included in the FES. The rationality of the preceding conclusions was analyzed. The complex quenching stress is a consequence of interactions between the thermal and phase transformation stresses. The separated calculations indicate that the three steels exhibit similar thermal stress distributions for the same water-quenching condition, but different phase transformation stresses between 45 carbon steel and alloyed steels, leading to different distributions of their axial and tangential stresses.
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Metal elution from Ni- and Fe-based alloy reactors under hydrothermal conditions.
Faisal, Muhammad; Quitain, Armando T; Urano, Shin-Ya; Daimon, Hiroyuki; Fujie, Koichi
2004-05-20
Elution of metals from Ni- and Fe-based alloy (i.e. Inconel 625 and SUS 316) under hydrothermal conditions was investigated. Results showed that metals could be eluted even in a short contact time. At subcritical conditions, a significant amount of Cr was extracted from SUS 316, while only traces of Ni, Fe, Mo, and Mn were eluted. In contrast, Ni was removed in significant amounts compared to Cr when Inconel 625 was tested. Several factors including temperature and contact time were found to affect elution behavior. The presence of air in the fluid even promoted elution under subcritical conditions.
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NASA Astrophysics Data System (ADS)
Dogan, A.; Arslan, H.; Dogan, T.
2015-06-01
Using different prediction methods, such as the General Solution Model of Kohler and Muggianu, the excess energy and activities of molybdenum for the sections of the phase diagram for the penternary Ni-Cr-Co-Al-Mo system with mole ratios xNi/ xMo = 1, xCr/ xMo = 1, xCo/ xMo = 1, and xAl/ xMo = r = 0.5 and 1, were thermodynamically investigated at a temperature of 2000 K, whereas the excess energy and activities of Bi for the section corresponding to the ternary Bi-Ga-Sb system with mole ratio xGa/ xSb = 1/9 were thermodynamically investigated at a temperature of 1073 K. In the case of r = 0.5 and 1 in the alloys Ni-Cr-Co-Al-Mo, a positive deviation in the activity coefficient was revealed, as molybdenum content increased. Moreover, in the calculations performed in Chou's GSM model, the obtained values for excess Gibbs energies are negative in the whole concentration range of bismuth at 1073 K and exhibit the minimum of about -2.2 kJ/mol at the mole ratio xGa/ xSb = 1/9 in the alloy Bi-Ga-Sb.
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Letter Report Documenting Progress of Second Generation ATF FeCrAl Alloy Fabrication
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yamamoto, Y.; Yang, Y.; Field, K. G.
2014-06-10
Development of the 2nd generation ATF FeCrAl alloy has been initiated, and a candidate alloy was selected for trial tube fabrication through hot-extrusion and gun-drilling processes. Four alloys based on Fe-13Cr-4.5Al-0.15Y in weight percent were newly cast with minor alloying additions of Mo, Si, Nb, and C to promote solid-solution and second-phase precipitate strengthening. The alloy compositions were selected with guidance from computational thermodynamic tools. The lab-scale heats of ~ 600g were arc-melted and drop-cast, homogenized, hot-forged and -rolled, and then annealed producing plate shape samples. An alloy with Mo and Nb additions (C35MN) processed at 800°C exhibits very finemore » sub-grain structure with the sub-grain size of 1-3μm which exhibited more than 25% better yield and tensile strengths together with decent ductility compared to the other FeCrAl alloys at room temperature. It was found that the Nb addition was key to improving thermal stability of the fine sub-grain structure. Optimally, grains of less than 30 microns are desired, with grains up to and order of magnitude in desired produced through Nb addition. Scale-up effort of the C35MN alloy was made in collaboration with a commercial cast company who has a capability of vacuum induction melting. A 39lb columnar ingot with ~81mm diameter and ~305mm height (with hot-top) was commercially cast, homogenized, hot-extruded, and annealed providing 10mm-diameter bar-shape samples with the fine sub-grain structure. This commercial heat proved consistent with materials produced at ORNL at the lab-scale. Tubes and end caps were machined from the bar sample and provided to another work package for the ATF-1 irradiation campaign in the milestone M3FT-14OR0202251.« less
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Thermal properties of U-7Mo/Al dispersion fuel
NASA Astrophysics Data System (ADS)
Cho, Tae Won; Kim, Yeon Soo; Park, Jong Man; Lee, Kyu Hong; Kim, Sunghwan; Lee, Chong-Tak; Yang, Jae Ho; Oh, Jang Soo; Won, Ju-Jin; Sohn, Dong-Seong
2017-12-01
The thermal diffusivity and heat capacity of U-7Mo/Al and U-7Mo/Al-5Si as functions of U-Mo fuel volume fraction and temperature were measured. The density of the sample was measured at room temperature and estimated using thermal expansion data at elevated temperatures. Using the measured data, the thermal conductivity was obtained as a function of U-Mo volume fraction and temperature. The thermal conductivity of U-7Mo/Al-5Si was found to be lower than that of U-7Mo/Al because of the Si addition to the Al. Due to a lower porosity and reduced interaction between U-Mo and Al in the sample, the thermal conductivity data reported in the present study were higher than those in the literature. The present data were found to be in agreement with the predictions of theoretical models.
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Lin, Chia-Wei; Ju, Chien-Ping; Chern Lin, Jiin-Huey
2005-06-01
The purpose of the present study is to compare the high-cycle fatigue behavior of newly developed Ti-7.5Mo alloy with that of c.p. Ti, Ti-13Nb-13Zr and Ti-6Al-4V alloys in their as-cast state. Experimental results indicate that Ti-6Al-4V and c.p. Ti have higher stress-controlled fatigue resistance but lower strain-controlled fatigue resistance than Ti-7.5Mo and Ti-13Nb-13Zr. Among four materials Ti-7.5Mo demonstrates the best strain-controlled fatigue performance. The fracture surfaces of the present materials are comprised of three morphologically distinct zones: crack initiation zone, crack propagation zone, and the final-stage overload zone. The fatigue cracks almost always initiate from casting-induced surface/subsurface pores. A river pattern is observed in the propagation zone. In the overload zone dimples are typically observed. Three factors most significantly affecting the fatigue performance of the present materials are the presence of the casting-induced surface/subsurface pores; the location of the pores; and the inherent mechanical properties of the materials.
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NPF MECHANICAL CELL NaK DISPOSAL AND FUME ABATEMENT
DOE Office of Scientific and Technical Information (OSTI.GOV)
Rey, G.
Some of the fuels originally scheduled for processing in the nonproduction fuel (NPF) processing program incorporated sodium or sodium- potassium alloy (NaK) as the bonding material between stainless-steel cladding and the uranium or uranium-molybdenum alloy core. Because of the special hazards involved in handling NaK, studies were made to determine safe methods for processing NaK-containing fuels. An underwater NaK dispensing system was installed, and tests were made to determine the characteristics of the NaK-water reaction. The equipment consisted of a dispenser, reaction pan, and off-gas scrubber. After initinl studies, a prototype test was made wherein U-Mo canned slugs containing NaKmore » reservoirs were hack sawed underwater. The studies demonstrated that the NaK reservoirs can be safely deactivated by hack sawing under a submerged hood in a shallow water bath. (W.L.H.)« less
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Yu, Chun-tang; Liu, Ying-ying; Xia, Yu-feng
2014-01-01
The stress-strain data of 20MnNiMo alloy were collected from a series of hot compressions on Gleeble-1500 thermal-mechanical simulator in the temperature range of 1173∼1473 K and strain rate range of 0.01∼10 s−1. Based on the experimental data, the improved Arrhenius-type constitutive model and the artificial neural network (ANN) model were established to predict the high temperature flow stress of as-cast 20MnNiMo alloy. The accuracy and reliability of the improved Arrhenius-type model and the trained ANN model were further evaluated in terms of the correlation coefficient (R), the average absolute relative error (AARE), and the relative error (η). For the former, R and AARE were found to be 0.9954 and 5.26%, respectively, while, for the latter, 0.9997 and 1.02%, respectively. The relative errors (η) of the improved Arrhenius-type model and the ANN model were, respectively, in the range of −39.99%∼35.05% and −3.77%∼16.74%. As for the former, only 16.3% of the test data set possesses η-values within ±1%, while, as for the latter, more than 79% possesses. The results indicate that the ANN model presents a higher predictable ability than the improved Arrhenius-type constitutive model. PMID:24688358