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Sample records for mo-si-b intermetallic coatings

  1. FeAl and Mo-Si-B Intermetallic Coatings Prepared by Thermal Spraying

    SciTech Connect

    Totemeier, T.C.; Wright, R.N.; Swank, W.D.

    2003-04-22

    FeAl and Mo-Si-B intermetallic coatings for elevated temperature environmental resistance were prepared using high-velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques. For both coating types, the effect of coating parameters (spray particle velocity and temperature) on the microstructure and physical properties of the coatings was assessed. Fe-24Al (wt.%) coatings were prepared using HVOF thermal spraying at spray particle velocities varying from 540 m/s to 700 m/s. Mo-13.4Si-2.6B coatings were prepared using APS at particle velocities of 180 and 350 m/s. Residual stresses in the HVOF FeAl coatings were compressive, while stresses in the APS Mo-Si-B coatings were tensile. In both cases, residual stresses became more compressive with increasing spray particle velocity due to increased peening imparted by the spray particles. The hardness and elastic moduli of FeAl coatings also increased with increasing particle velocity, again due to an increased peening effect. For Mo-Si-B coatings, plasma spraying at 180 m/s resulted in significant oxidation of the spray particles and conversion of the T1 phase into amorphous silica and {alpha}-Mo. The T1 phase was retained after spraying at 350 m/s.

  2. FeAI and Mo-Si-B Intermetallic Coatings Prepared by Thermal Spraying

    SciTech Connect

    Terry C. Totemeier; Richard N. Wright; W. David Swank

    2004-12-01

    FeAl and Mo–Si–B intermetallic coatings for elevated temperature environmental resistance were prepared using high-velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques. For both coating types, the effect of coating parameters (spray particle velocity and temperature) on the microstructure and physical properties of the coatings was assessed. Fe–24Al (wt%) coatings were prepared using HVOF thermal spraying at spray particle velocities varying from 540 to 700 m/s. Mo–13.4Si–2.6B coatings were prepared using APS at particle velocities of 180 and 350 m/s. Residual stresses in the HVOF FeAl coatings were compressive, while stresses in the APS Mo–Si–B coatings were tensile. In both cases, residual stresses became more compressive with increasing spray particle velocity due to increased peening imparted by the spray particles. The hardness and elastic moduli of FeAl coatings also increased with increasing particle velocity. For Mo–Si–B coatings, plasma spraying at 180 m/s resulted in significant oxidation of the spray particles and conversion of the T1 phase into amorphous silica and a-Mo. The T1 phase was retained after spraying at 350 m/s.

  3. Mo-Si-B-Based Coatings for Ceramic Base Substrates

    NASA Technical Reports Server (NTRS)

    Perepezko, John Harry (Inventor); Sakidja, Ridwan (Inventor); Ritt, Patrick (Inventor)

    2015-01-01

    Alumina-containing coatings based on molybdenum (Mo), silicon (Si), and boron (B) ("MoSiB coatings") that form protective, oxidation-resistant scales on ceramic substrate at high temperatures are provided. The protective scales comprise an aluminoborosilicate glass, and may additionally contain molybdenum. Two-stage deposition methods for forming the coatings are also provided.

  4. Extended Functionality of Environmentally-Resistant Mo-Si-B-Based Coatings

    NASA Astrophysics Data System (ADS)

    Perepezko, J. H.; Sakidja, R.

    2013-02-01

    Multiphase Mo-Si-B alloys with compositions which yield the ternary intermetallic Mo5SiB2 (T2) phase as a key microstructure constituent together with the Mo and Mo3Si phases, offer an attractive balance of high melting temperature, oxidation resistance, and mechanical properties. The investigation of reaction kinetics involving the T2 phase enables the analysis of oxidation in terms of diffusion pathways and the design of effective coatings. From this basis, kinetic biasing is used together with pack cementation to develop Mo-Si-B-based multilayered coatings with an aluminoborosilica surface and in situ diffusion barriers with self-healing characteristics for enhanced oxidation resistance. While a combustion environment contains water vapor that can accelerate an attack of silica-based coatings, the Mo-Si-B-based coatings provide oxidation resistance in water vapor up to at least 1,500°C. An exposure to hot ionized gas species generated in an arc jet confirms the robust coating performance in extreme environments. To extend the application beyond Mo-based systems, a two-stage process has been implemented to provide effective oxidation resistance for refractory metal cermets, SiC and ZrB2 ultra-high-temperature composites.

  5. Novel Processing of mo-si-b Intermetallics for improved efficiency of power systems

    SciTech Connect

    M.J. Kramer; O. Degirmen; A.J. Thom; M. Akinc

    2004-09-30

    Multiphase composite alloys based on the Mo-Si-B system are candidate materials for ultra-high temperature applications. In non load-bearing applications such as thermal barrier coatings or heat exchangers in fossil fuel burners, these materials may be ideally suited. Alloys based on the Mo{sub 5}Si{sub 3}B{sub x} phase (Tl phase) possess excellent oxidation resistance to at least 1600 C in synthetic air atmospheres. However, the ability of Tl-based alloys to resist aggressive combustion environments has not yet been determined. The present work seeks to investigate the resistance of these Mo-Si-B alloys to simulated combustion atmospheres. Material was pre-alloyed by combustion synthesis, and samples for testing were prepared by classic powder metallurgical processing techniques. Precursor material synthesized by self-heating-synthesis was sintered to densities exceeding 98% in an argon atmosphere at 1800 C. The approximate phase assemblage of the material was 57% Tl, 29% MoB, 14% MoSi{sub 2} (wt%). The alloy was oxidized from 1000-1100 C in flowing air containing water vapor at 18 Torr. At 1000 C the material achieved a steady state mass loss, and at 1100 C the material undergoes a steady state mass gain. The oxidation rate of these alloys in this temperature regime was accelerated by the presence of water vapor compared to oxidation in dry air. The results of microstructural analysis of the tested alloys will be discussed. Techniques and preliminary results for fabricating near-net-shaped parts will also be presented.

  6. Polymer-Derived Ceramics as Innovative Oxidation Barrier Coatings for Mo-Si-B Alloys

    NASA Astrophysics Data System (ADS)

    Hasemann, Georg; Baumann, Torben; Dieck, Sebastian; Rannabauer, Stefan; Krüger, Manja

    2015-04-01

    A preceramic polymer precursor, perhydropolysilazane, is used to investigate its function as a new type of oxidation barrier coating on Mo-Si-B alloys. After dip-coating and pyrolysis at 1073 K (800 °C), dense and well-adhering SiON ceramic coatings could be achieved, which were investigated by SEM and cyclic oxidation tests at 1073 K and 1373 K (800 °C and 1100 °C). The coating is promising in reducing the mass loss during the initial stage of oxidation exposure at 1373 K (1100 °C) significantly.

  7. PROCESSING, MICROSTRUCTURE AND CREEP BEHAVIOR OF MO-SI-B-BASED INTERMETALLIC ALLOYS FOR VERY HIGH TEMPERATURE STRUCTURAL APPLICATIONS

    SciTech Connect

    Vijay K. Vasudevan

    2005-02-08

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. During this year, the microstructure, bend strength and compressive creep behavior of a Mo-3Si-1B (in wt.%) alloy were studied. The microstructure of this alloy was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. The elastic limit strength of the alloy remained quite high until 1200 C with a value of 800MPa, but dropped rapidly thereafter to a value of 220 MPa at 1400 C. Results of compressive creep tests at 1200 C showed that the creep rates were quite high and varied nearly linearly with stress between 250 and 500 MPa, which suggests that diffusional mechanisms dominate the creep process. Microstructural observations of post-crept samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. These results and presented and discussed.

  8. Synthesis and analysis of Mo-Si-B based coatings for high temperature oxidation protection of ceramic materials

    NASA Astrophysics Data System (ADS)

    Ritt, Patrick J.

    The use of Ni-based superalloys in turbine engines has all but been exhausted, with operating temperatures nearing the melting point of these materials. The use of ceramics in turbine engines, particularly ceramic matrix composites such as SiC/C and SiC/SiC, is of interest due to their low density and attractive mechanical properties at elevated temperatures. The same materials are also in consideration for leading edges on hypersonic vehicles. However, SiC-based composites degrade in high temperature environments with low partial pressures of oxygen due to active oxidation, as well as high temperature environments containing water or sand. The need for a protective external coating for SiC-based composites in service is obvious. To date, no coating investigated for SiC/C or SiC/SiC has been proven to be resistant to oxidation and corrosion at intermediate and high temperatures, as well as in environments deficient in oxygen. The Mo-Si-B coating shows great promise in this area, having been proven resistant to attack from oxidation at extreme temperatures, from water vapor and from calcia-magnesia-aluminosilicate (CMAS). The adaptation of the Mo-Si-B coating for ceramic materials is presented in detail here. Evaluation of the coating under a range of oxidation conditions as well as simulated re-entry conditions confirms the efficacy of the Mo-Si-B based coating as protection from catastrophic failure. The key to the oxidation and corrosion resistance is a robust external aluminoborosilica glass layer that forms and flows quickly to cover the substrate, even under the extreme simulated re-entry conditions. Suppression of active oxidation of SiC, which may occur during atmospheric re-entry and hypersonic flight trajectories, has also been examined. In order to adapt the Mo-Si-B based coating to low partial pressures of oxygen and elevated temperatures, controlled amounts of Al were added to the Mo-Si-B based coating. The resulting coating decreased the inward

  9. Processing, Microstructure and Creep Behavior of Mo-Si-B-Based Intermetallic Alloys for Very High Temperature Structural Applications

    SciTech Connect

    Vijay Vasudevan

    2008-03-31

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. In the first part of this project, the compression creep behavior of a Mo-8.9Si-7.71B (in at.%) alloy, at 1100 and 1200 C was studied, whereas in the second part of the project, the constant strain rate compression behavior at 1200, 1300 and 1400 C of a nominally Mo-20Si-10B (in at.%) alloy, processed such as to yield five different {alpha}-Mo volume fractions ranging from 5 to 46%, was studied. In order to determine the deformation and damage mechanisms and rationalize the creep/high temperature deformation data and parameters, the microstructure of both undeformed and deformed samples was characterized in detail using x-ray diffraction, scanning electron microscopy (SEM) with back scattered electron imaging (BSE) and energy dispersive x-ray spectroscopy (EDS), electron back scattered diffraction (EBSD)/orientation electron microscopy in the SEM and transmission electron microscopy (TEM). The microstructure of both alloys was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. The values of stress exponents and activation energies, and their dependence on microstructure were determined. The data suggested the operation of both dislocation as well as diffusional mechanisms, depending on alloy, test temperature, stress level and microstructure. Microstructural observations of post-crept/deformed samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. TEM observations revealed the presence of recrystallized {alpha}-Mo grains and sub-grain boundaries composed of dislocation arrays within the grains (in Mo-8.9Si-7.71B) or fine sub-grains with a high density of b = 1/2<111> dislocations (in Mo-20Si-10B), which

  10. PROCESSING, MICROSTRUCTURE AND CREEP BEHAVIOR OF Mo-Si-B-BASED INTERMETALLIC ALLOYS FOR VERY HIGH TEMPERATURE STRUCTURAL APPLICATIONS

    SciTech Connect

    Vijay K. Vasudevan

    2005-12-21

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. During this year, the compressive creep behavior of a Mo-3Si-1B (in wt.%) alloy at 1100 and 1200 C were studied and related to the deformation mechanisms through electron microscopy observations of microstructural changes and deformation structures. The microstructure of this alloy was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. Results of compressive creep tests at 1200 and 1100 C showed that the creep rates were quite high at stress levels between 250 and 500 MPa, Two minima in the creep strain rate versus strain data were noted, one at small strain values and the second at much larger strains. A stress exponent of 4.26 was obtained upon plotting the strain rate corresponding to the first minima versus stress, which suggests that dislocation climb and glide dominate the creep process in the early stages. On the other hand, the large strain, minimum creep rate versus stress data gave a stress exponent of {approx}1.18, which indicates diffusional mechanisms and recrystallization dominate the later stages of the creep process. At 1100 C, a stress exponent of 2.26 was obtained, which suggests that both diffusional and dislocation mechanisms contribute to the creep strain. Based on the minimum creep rate data at 1100 C and 1200 C, the activation energy for creep was determined to be 525 kJ/mole, which is somewhat higher than that reported for self diffusion in {alpha}-Mo. Microstructural observations of post-crept samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. In addition, TEM observations revealed the presence of recrystallized grains and sub-grain boundaries composed of dislocation arrays

  11. An ultra-high temperature Mo-Si-B based coating for oxidation protection of NbSS/Nb5Si3 composites

    NASA Astrophysics Data System (ADS)

    Su, Linfen; Lu-Steffes, Otto; Zhang, Hu; Perepezko, John H.

    2015-05-01

    A Mo-Si-B based coating was prepared on an NbSS/Nb5Si3 composite by a two-step process consisting of the initial deposition of Mo followed by pack cementation co-deposition of Si and B. After a conditioning treatment, an aluminoborosilica layer fully covered the sample. Following oxidation at 1300 °C for 24 h, the coated sample demonstrated a weight loss of about 0.55 mg/cm2 and the uncoated sample exhibited catastrophic oxidation with a weight gain of 87.6 mg/cm2. These results demonstrate that the Mo-Si-B based coating can enable the use of the NbSS/Nb5Si3 composites at temperature up to 1300 °C in an oxidizing environment.

  12. Development of a multi-variate calibration approach for quantitative analysis of oxidation resistant Mo-Si-B coatings using laser ablation inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Cakara, Anja; Bonta, Maximilian; Riedl, Helmut; Mayrhofer, Paul H.; Limbeck, Andreas

    2016-06-01

    Nowadays, for the production of oxidation protection coatings in ultrahigh temperature environments, alloys of Mo-Si-B are employed. The properties of the material, mainly the oxidation resistance, are strongly influenced by the Si to B ratio; thus reliable analytical methods are needed to assure exact determination of the material composition for the respective applications. For analysis of such coatings, laser ablation inductively coupled mass spectrometry (LA-ICP-MS) has been reported as a versatile method with no specific requirements on the nature of the sample. However, matrix effects represent the main limitation of laser-based solid sampling techniques and usually the use of matrix-matched standards for quantitative analysis is required. In this work, LA-ICP-MS analysis of samples with known composition and varying Mo, Si and B content was carried out. Between known analyte concentrations and derived LA-ICP-MS signal intensities no linear correlation could be found. In order to allow quantitative analysis independent of matrix effects, a multiple linear regression model was developed. Besides the three target analytes also the signals of possible argides (40Ar36Ar and 98Mo40Ar) as well as detected impurities of the Mo-Si-B coatings (108Pd) were considered. Applicability of the model to unknown samples was confirmed using external validation. Relative deviations from the values determined using conventional liquid analysis after sample digestion between 5 and 10% for the main components Mo and Si were observed.

  13. Processing of Mo-Si-B intermetallics by extrusion and oxidation properties of the extruded Tl-MoSi{sub 2}-MoB System

    SciTech Connect

    Summers, Eric

    1999-11-08

    An extrusion process was developed that is able to consistently produce large quantities of Mo-Si-B rods without the presence of defects. Binder removal from the extruded rods was studied in detail and it was determined that heating rates on the order of 0.02{degree}/minute (1.2{degree}/hour) are necessary to remove the binder without the formation of defects. This low heating rate resulted in debinding times in excess of 70 hours (approximately 3 days). Wicking was investigated as a means to decrease the time necessary for binder removal. Using 0.05{micro}m alumina powder as a wicking agent, binder removal times were reduced to 10 hours with heating rates up to 1{degree}/minute employed without defect formation. Once the extrusion process was complete the oxidation properties of the Tl-MoSi{sub 2}-MoB extruded phase assemblage was investigated. It was determined that this composition exhibits catastrophic oxidation or pesting in the temperature range of 660--760 C, resulting in the material turning to dust. Outside of this temperature range the composition is oxidatively stable. Continuous mass measurements were taken at 1,300, 1,450, and 1,600 C to determine the oxidation rate constants of this material. Parabolic rate constants of 6.9 x 10{sup {minus}3}, 1.3 x 10{sup {minus}3}, and 9.1 x 10{sup {minus}3} mg{sup 2}/cm{sup 4}/hr were determined for 1,300, 1,450, and 1,600 C respectively.

  14. Superplasticity of a multiphase refractory Mo-Si-B alloy

    SciTech Connect

    Jehanno, P.; Heilmaier, M.; Saage, H.; Heyse, Hartmut; Boening, Mike Boening; Kestler, Heinrich; Schneibel, Joachim H

    2006-01-01

    Mo-Si-B alloys consisting of a Mo solid solution and the intermetallic phases Mo{sub 3}Si and Mo{sub 5}SiB{sub 2} were synthesized by mechanical alloying followed by sintering and hot isostatic pressing to field an ultra-fine (triplex) microstructure with all three phases being in the sub-micron range. at temperatures as low as 1300C the material exhibits superplasticity, with tensile strain to failures of 200-400% at strain rates as high as 10{sup -3}s{sup -1}.

  15. Mo-Si-B Alloy Development

    SciTech Connect

    Schneibel, Joachim H; Brady, Michael P; Meyer III, Harry M; Horton Jr, Joe A; Kruzic, JJ; Ritchie, R O

    2005-01-01

    Mo-Si-B silicides consisting of the phases {alpha}-Mo (Mo solid solution), Mo{sub 3}Si, and Mo{sub 5}SiB{sub 2} have melting points on the order of 2000 C and have potential as ultra-high temperature structural materials. Mo-Si-B alloys can be processed such that the {alpha}-Mo is present in the form of isolated particles in a silicide matrix, or as a continuous matrix 'cementing' individual silicide particles together. The latter microstructure is similar to that of WC-Co hard metals. This paper focuses on the relationship between the topology as well as scale of the microstructure of Mo-Mo{sub 3}Si-Mo{sub 5}SiB{sub 2} alloys, and their creep strength and fracture toughness. For example, the creep strength of Mo-Si-B alloys is improved by reducing the {alpha}-Mo volume fraction and by making the {alpha}-Mo phase discontinuous. The fracture toughness is improved by increasing the {alpha}-Mo volume fraction and by making the {alpha}-Mo phase continuous. Room temperature stress intensity factors as high as 21 MPa m{sup 1/2} were obtained. The room temperature fracture toughness of Mo-Si-B alloys can also be improved by microalloying with Zr. The room temperature ductility of Mo itself can be improved by adding MgAl{sub 2}O{sub 4} spinel particles suggesting yet another way to improve the ductile phase toughening of Mo-Si-B alloys.

  16. Mo-Si-B Alloy Development

    SciTech Connect

    Schneibel, J.H.; Kruzie, J.J.; Ritchie, R.O.

    2003-04-24

    Mo-Si-B silicides consisting of the phases {alpha}-Mo (Mo solid solution), Mo{sub 3}Si, and Mo{sub 5}SiB{sub 2} have melting points on the order of 2000 C and have potential as ultra-high temperature structural materials. Mo-Si-B alloys can be processed such that the {alpha}-Mo is present in the form of isolated particles in a silicide matrix, or as a continuous matrix ''cementing'' individual silicide particles together. The latter microstructure is similar to that of WC-Co hard metals. This paper focuses on the relationship between the topology as well as scale of the microstructure of Mo-Mo{sub 3}Si-Mo{sub 5}SiB{sub 2} alloys, and their creep strength and fracture toughness. For example, the creep strength of Mo-Si-B alloys is improved by reducing the {alpha}-Mo volume fraction and by making the {alpha}-Mo phase discontinuous. The fracture toughness is improved by increasing the {alpha}-Mo volume fraction and by making the {alpha}-Mo phase continuous. Room temperature stress intensity factors as high as 21 MPa m{sup 1/2} were obtained. The room temperature fracture toughness of Mo-Si-B alloys can also be improved by microalloying with Zr. The room temperature ductility of Mo itself can be improved by adding MgAl{sub 2}O{sub 4} spinel particles suggesting yet another way to improve the ductile phase toughening of Mo-Si-B alloys.

  17. High-Temperature Creep and Oxidation Behavior of Mo-Si-B Alloys with High Ti Contents

    NASA Astrophysics Data System (ADS)

    Schliephake, Daniel; Azim, Maria; von Klinski-Wetzel, Katharina; Gorr, Bronislava; Christ, Hans-Jürgen; Bei, Hongbin; George, Easo P.; Heilmaier, Martin

    2013-08-01

    Multiphase alloys in the Mo-Si-B system are potential high-temperature structural materials due to their good oxidation and creep resistance. Since they suffer from relatively high densities, the current study focuses on the influence of density-reducing Ti additions on creep and oxidation behavior at temperatures above 1273 K (1000 °C). Two alloys with compositions of Mo-12.5Si-8.5B-27.5Ti and Mo-9Si-8B-29Ti (in at. pct) were synthesized by arc melting and then homogenized by annealing in vacuum for 150 hours at 1873 K (1600 °C). Both alloys show similar creep behavior at stresses of 100 to 300 MPa and temperatures of 1473 K and 1573 K (1200 °C and 1300 °C), although they possess different intermetallic volume fractions. They exhibit superior creep resistance and lower density than a state-of-the-art Ni-base superalloy (single-crystalline CMSX-4) as well as other Mo-Si-B alloys. Solid solution strengthening due to Ti was confirmed by Vickers hardness measurements and is believed to be the reason for the significant increase in creep resistance compared to Mo-Si-B alloys without Ti, but with comparable microstructural length scales. The addition of Ti degrades oxidation resistance relative to a Mo-9Si-8B reference alloy due to the formation of a relatively porous duplex layer with titania matrix enabling easy inward diffusion of oxygen.

  18. Role of Microstructure in Promoting Fracture and Fatigue Resistance in Mo-Si-B Alloys

    SciTech Connect

    Schneibel, Joachim H

    2005-04-01

    An investigation of how microstructural features affect the fracture and fatigue properties of a promising class of high temperature Mo-Si-B based alloys is presented. Fracture toughness and fatigue-crack growth properties are measured at 25 and 1300 C for five Mo-Mo{sub 3}Si-Mo{sub 5}SiB{sub 2} containing alloys produced by powder metallurgy with {alpha}-Mo matrices. Results are compared with previous studies on intermetallic-matrix microstructures in alloys with similar compositions. It is found that increasing the {alpha}-Mo phase volume fraction (17-49%) or ductility (by increasing the temperature) benefits the fracture resistance; in addition, {alpha}-Mo matrix materials show significant improvements over intermetallic-matrix alloys. Fatigue thresholds were also increased with increasing {alpha}-Mo phase content, until a transition to more ductile fatigue behavior occurred with large amounts of {alpha}-Mo phase (49%) and ductility (i.e., at 1300 C). The beneficial role of such microstructural variables are attributed to the promotion of the observed toughening mechanisms of crack trapping and bridging by the relatively ductile {alpha}-Mo phase.

  19. Mechanically alloyed Mo-Si-B alloys with a continuous a-Mo matrix and improved mechanical properties

    SciTech Connect

    Krueger, M.; Franz, S.; Heilmaier, M.; Schneibel, Joachim H; Jehanno, P.; Boening, Mike Boening; Kestler, Heinrich

    2008-01-01

    Mechanical alloying (MA) followed by cold isostatic pressing (CIPing), sintering and hot isostatic pressing (HIPing) was used to prepare Mo-base silicide alloys consisting of a Mo(Si) solid solution and the intermetallic phases Mo{sub 3}Si and Mo{sub 5}SiB{sub 2}. The microstructural development during milling of both binary Mo-Si and Mo-B and ternary Mo-Si-B powder mixtures was evaluated. While obtaining a supersaturated solid solution requires rather long milling times, domain size (which correlates with the grain size) is reduced to below 100 {angstrom} after about 10 h of milling. After heat treatment and consolidation the microstructure reveals a continuous {alpha}-Mo matrix with embedded, uniformly distributed intermetallic particles. The establishment of such a microstructure is beneficial for the mechanical properties since, as compared to a discontinuous {alpha}-Mo matrix, it decreases the brittle-to-ductile transition temperature (BDTT) by about 150 K.

  20. Oxidation Behavior of Mo-Si-B Alloys in Wet Air

    SciTech Connect

    M. Kramer; A. Thom; O. Degirmen; V. Behrani; M. Akinc

    2002-04-22

    Multiphase composite alloys based on the Mo-Si-B system are candidate materials for ultra-high temperature applications. In non load-bearing uses such as thermal barrier coatings or heat exchangers in fossil fuel burners, these materials may be ideally suited. The present work investigated the effect of water vapor on the oxidation behavior of Mo-Si-B phase assemblages. Three alloys were studied: Alloy 1 = Mo{sub 5}Si{sub 3}B{sub x} (T1)- MoSi{sub 2}- MoB, Alloy 2 = T1- Mo{sub 5}SiB{sub 2} (T2)- Mo{sub 3}Si, and Alloy 3 = Mo- T2- Mo{sub 3}Si. Tests were conducted at 1000 and 1100C in controlled atmospheres of dry air and wet air nominally containing 18, 55, and 150 Torr H{sub 2}O. The initial mass loss of each alloy was approximately independent of the test temperature and moisture content of the atmosphere. The magnitude of these initial losses varied according to the Mo content of the alloys. All alloys formed a continuous, external silica scale that protected against further mass change after volatilization of the initially formed MoO{sub 3}. All alloys experienced a small steady state mass change, but the calculated rates cannot be quantitatively compared due to statistical uncertainty in the individual mass measurements. Of particular interest is that Alloy 3, which contains a significant volume fraction of Mo metal, formed a protective scale. All alloys formed varying amounts of subscale Mo and MoO{sub 2}. This implies that oxygen transport through the external silica scale has been significantly reduced. For all alloys, water vapor accelerated the growth of a multiphase interlayer at the silica scale/unoxidized alloy interface. This interlayer is likely composed of fine Mo and MoO{sub 2} that is dispersed within a thin silica matrix. Alloy 3 was particularly sensitive to water accelerated growth of this interlayer. At 1100 C, the scale thickness after 300 hours increased from about 20 mm in dry air to nearly 100 mm in wet air.

  1. Cold Sprayed Intermetallic Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Leshchinsky, Evgeny

    Conventional thermal barrier coating (TBC) systems consist of a duplex structure with a metallic bond coat and a ceramic heat-isolative topcoat. Several recent research activities are concentrated on the development of improved multilayer bond coat and TBC materials. This study represents an investigation performed for the aluminum based bond coats, especially those with reduced thermal conductivities. Using alternative TBC materials, such as metal alloys and intermetallics, their processing methods can be further optimized to achieve the best thermal physical parameters. One example is the ten-layer system in which cold sprayed aluminum based intermetallics are synthesized. These systems demonstrated improved heat insulation and thermal fatigue capabilities compared to conventional TBC. The microstructures and properties of the laminar coatings were characterized by SEM, EDS, XRD; micromechanical and durability tests were performed to define the structure and coating formation mechanisms. Application prospects for HCCI engines are discussed. Fuel energy can be utilized more efficiently with the concept of low heat rejection engines with applied TBC.

  2. Phase field simulation of a directional solidification of a ternary eutectic Mo-Si-B Alloy

    NASA Astrophysics Data System (ADS)

    Kazemi, O.; Hasemann, G.; Krüger, M.; Halle, T.

    2016-03-01

    We present a eutectic Phase-Field Model for a Mo-Si-B alloy at ternary eutectic composition (Mo-17.5Si-8B), under a constant thermal gradient. The process parameters like cooling rate and thermal gradient were obtained directly from the experimental procedure of zone melting. The equilibrium interface geometries and interface mobility were calculated using an isotropic model. The phase equilibria and the other thermodynamic parameters are obtained by linearizing the Mo-Si-B ternary phase diagram. We have investigated the effect of process parameters on the lamellar growth pattern and lamella pattern stability with respect to the Jackson-Hunt minimum undercooling spacing theory. In order to examine the generated results by the model, they were validated with experimental observed microstructures and measurements and showed to be in a good agreement with the experimental observations.

  3. Oxidation Behavior and Chlorination Treatment to Improve Oxidation Resistance of Nb-Mo-Si-B Alloys

    SciTech Connect

    Vikas Behrani

    2004-12-19

    This thesis is written in an alternate format. The thesis is composed of a general introduction, two original manuscripts, and a general conclusion. References cited within each chapter are given at the end of each chapter. The general introduction starts with the driving force behind this research, and gives an overview of previous work on boron doped molybdenum silicides, Nb/Nb{sub 5}Si{sub 3} composites, boron modified niobium silicides and molybdenum niobium silicides. Chapter 2 focuses on the oxidation behavior of Nb-Mo-Si-B alloys. Chapter 3 contains studies on a novel chlorination technique to improve the oxidation resistance of Nb-Mo-Si-B alloys. Chapter 4 summarizes the important results in this study.

  4. Chlorination treatment to improve the oxidation resistance of Nb-Mo-Si-B alloys

    NASA Astrophysics Data System (ADS)

    Behrani, Vikas; Thom, Andrew J.; Kramer, Matthew J.; Akinc, Mufit

    2005-03-01

    Recent studies have shown that the quaternary Nb-Mo-Si-B system is not oxidation resistant. The difference in oxidation resistance between Mo-Si-B and Nb-Mo-Si-B may be interpreted in terms of the volatility of the metal oxide that forms. MoO3 evaporates from the surface scale at about 650 °C, leaving a porous borosilicate glassy scale. Nb2O5 persists as a rapidly growing condensed phase that overwhelms the ability of the borosilicate glass to form a protective layer. In the present work, a novel chlorination process was employed to selectively remove Nb2O5 from the scale of the quaternary alloy as volatile NbCl5. A Nb-Mo-Si-B alloy was studied with a nominal composition of 63(Nb,Mo)-30Si-7B (at. pct) with Nb/Mo = 1:1. The alloy consisted of a three-phase microstructure of (Nb,Mo)5Si3B x (T1)-(Nb,Mo)5(Si,B)3 (T2)-(Nb,Mo)5Si3B x (D88). The oxidation behavior of these alloys in air was studied both before and after chlorination. Results showed that Nb2O5 can be selectively removed from the scale to leave a borosilicate-rich scale, which then forms a dense scale after heat treatment at 1100 °C in argon. The oxidation rate of the chlorinated alloy was about one-third that of the unchlorinated alloy under identical conditions. Alloy oxidation during heating to the test temperature was studied, and a plausible mechanism for the formation of porosity in the oxide scale has been offered.

  5. Temperature dependent mechanical properties of Mo-Si-B compounds via ab initio molecular dynamics

    NASA Astrophysics Data System (ADS)

    Dharmawardhana, C. C.; Sakidja, R.; Aryal, S.; Ching, W. Y.

    2013-07-01

    A new method was proposed to obtain high temperature mechanical properties with a combination of ab initio molecular dynamics and stress-strain analyses. It was applied to compounds in the Mo-Si-B ternary system, namely, T1 (Mo5Si3) and T2 (Mo5SiB2) phases. The calculated coefficient of thermal expansion, thermal expansion anisotropy, and elastic constants agree well with those from the available experiments. The method enables us to theoretically access these properties up to 2000 K.

  6. Creep Resistance and Oxidation Behavior of Novel Mo-Si-B-Ti Alloys

    NASA Astrophysics Data System (ADS)

    Azim, M. A.; Schliephake, D.; Hochmuth, C.; Gorr, B.; Christ, H.-J.; Glatzel, U.; Heilmaier, M.

    2015-11-01

    Mo-Si-B-alloys are promising materials for high-temperature applications because of their high melting point, excellent phase stability, large alloying capabilities, and reasonable mechanical as well as oxidative properties. A continuing alloy development is, however, required because of the catastrophic oxidation taking place at intermediate temperatures and the rather high density. The addition of Ti stabilizes a new ternary phase field including the Mo5Si3 (T1) phase instead of the Mo3Si (A15) phase. Alloys comprising the phases Moss, T1 and Mo5SiB2 (T2) show very high creep resistance, improved oxidation behavior and significantly reduced density. The new T1 phase seems to play a crucial role in the improved oxidation resistance of these new materials, since this phase exhibits excellent oxidation behavior at intermediate and high temperatures. The 4-component alloys possess superior creep behavior compared to Mo-Si-B alloys with the same microstructural phase arrangement and size or to the single crystal Ni-base superalloy CMSX-4. The main reason was found to be the formation of Ti-rich silicide precipitates during processing.

  7. Phase stability and alloying behavior in the Mo-Si-B system

    NASA Astrophysics Data System (ADS)

    Sakidja, R.; Perepezko, J. H.

    2005-03-01

    The effect of transition metal (TM) substitution for Mo has been examined in terms of the phase stability and multiphase microstructures in the Mo-Si-B ternary system. The metal-rich portion of the ternary Mo-Si-B system at equilibrium is comprised of thermally stable bcc Mo(ss) phase, a ternary-based Mo5SiB2 (T2) phase, and a binary-based metal-rich silicide (Mo3Si [A15]). The structures that are developed by following systematic alloying with a wide range of TMs, which are substitutional in both Mo(ss) and T2 phases (group IVB, VB, and VIB metals), have been analyzed to elucidate the roles of the substitution on the stability of the three phase fields of Mo(ss) + T2 + Mo3Si. In particular, the borosilicide ternary-based T2 phase shows an extended solid solution with a wide range of TMs. The extended solubility in the T2 phase essentially mimics the alloying behavior of the TM-based bcc phase. The critical factor for the phase stability appears to be the existence of a unique feature of bcc-like TM clusters within the T2 lattice structure. The combined criteria of atomic size factor and the valence electron concentration per atom (e/a) have been used to elucidate the observed alloying behavior.

  8. Mo-Si-B alloys for ultrahigh-temperature structural applications.

    PubMed

    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. PMID:22711489

  9. High-Temperature Compressive Properties of TiC-Added Mo-Si-B Alloys

    NASA Astrophysics Data System (ADS)

    Yoshimi, Kyosuke; Nakamura, Junya; Kanekon, Daiki; Yamamoto, Shiho; Maruyama, Kouichi; Katsui, Hirokazu; Goto, Takashi

    2014-09-01

    High-temperature compressive properties of two TiC-added Mo-Si-B alloys with nominal compositions of Mo-5Si-10B-7.5TiC (70Mo alloy) and Mo-6.7Si-13.3B-7.5TiC (65Mo alloy) (at.%) were investigated. The alloys were composed of four constituent phases: Mo solid solution (Moss), Mo5SiB2, (Mo,Ti)C, and (Mo,Ti)2C. The primary phases of the 70Mo and 65Mo alloys were Moss and T2, respectively. The compressive deformability of the 65Mo alloy was significantly limited even at 1600°C because of the elongated, coarse primary T2 phase, whereas the 70Mo alloy had good compressive deformability and a high strength in the test-temperature range of 1000-1600°C; the peak stresses were 1800 MPa at 1000°C, 1230 MPa at 1200°C, and 350 MPa at 1600°C. At and above 1200°C, the peak stress values were more than double those of Mo-6.7Si-7.9B, Ti-Zr-Mo, and Mo-Hf-C alloys. The plastic strain in the 70Mo alloy at temperatures lower than the ductile-brittle transition temperature of T2 was generated by plastic deformation of not only Moss but also of (Mo,Ti)C and (Mo,Ti)2C. This work indicates that (Mo,Ti)C and (Mo,Ti)2C play an important role in determining the high-temperature strength and deformation properties of TiC-added Mo-Si-B alloys.

  10. Characterization of electrical resistivity as a function of temperature in the Mo-Si-B system

    SciTech Connect

    Beckman, Sarah E.

    1999-12-10

    Measurements of electrical resistivity as a function of temperature from 25 to 1,500 C were conducted on polycrystalline samples in the Mo-Si-B system. Single phase, or nearly single phase, samples were prepared for the following phases: Mo{sub 3}Si, Mo{sub 5}SiB{sub 2}, Mo{sub 5}Si{sub 3}B{sub x}, MoB, MoSi{sub 2}, and Mo{sub 5}Si{sub 3}. Thesis materials all exhibit resistivity values within a narrow range(4--22 x 10{sup {minus}7}{Omega}-m), and the low magnitude suggests these materials are semi-metals or low density of states metals. With the exception of MoSi{sub 2}, all single phase materials in this study were also found to have low temperature coefficient of resistivity(TCR) values. These values ranged from 2.10 x 10{sup {minus}10} to 4.74 x 10{sup {minus}10}{Omega}-m/{degree} C, and MoSi{sub 2} had a TCR of 13.77 x 10{sup {minus}10}{Omega}-m/{degree} C. The results from the single phase sample measurements were employed in a natural log rule-of-mixtures model to relate the individual phase resistivity values to those of multiphase composites. Three Mo-Si-B phase regions were analyzed: the binary Mo{sub 5}Si{sub 3}-MoSi{sub 2} system, the ternary phase field Mo{sub 5}Si{sub 3}B{sub x}MoB-MoSi{sub 2}, and the Mo{sub 3}Si-Mo{sub 5}SiB{sub 2}-Mo{sub 5} Si{sub 3}B{sub x} ternary region. The experimental data for samples in each of these regions agreed with the natural log model and illustrated that this model can predict the electrical resistivity as a function of temperature of multi-phase, sintered samples within an error of one standard deviation.

  11. Development of intermetallic coatings for fusion power applications

    SciTech Connect

    Park, J.H.; Domenico, T.; Dragel, G.; Clark, R.

    1994-03-01

    In the design of liquid-metal cooling systems, corrosion resistance of structural materials and magnetohydrodynamic (MHD) force and its subsequent influence on thermal hydraulics and corrosion are major concerns. The objective of this study is to develop stable corrosion-resistant electrical insulator coatings at the liquid-metal/structural-material interface, with emphasis on electrically insulating coatings that prevent adverse MHD-generated currents from passing through the structural walls. Vanadium and V-base alloys are potential materials for structural applications in a fusion reactor. Insulator coatings inside the tubing are required when the system is cooled by liquid metals. Various intermetallic films were produced on V, V-t, and V-20 Ti, V-5Cr-t and V-15Cr-t, and Ti, and Types 304 and 316 stainless steel. The intermetallic layers were developed by exposure of the materials to liquid lithium of 3--5 at.% and containing dissolved metallic solutes at temperatures of 416--880{degrees}C. Subsequently, electrical insulator coatings were produced by reaction of the reactive layers with dissolved nitrogen in liquid lithium or by air oxidation under controlled conditions at 600--1000{degrees}C. These reactions converted the intermetallic layers to electrically insulating oxide/nitride or oxy-nitride layers. This coating method could be applied to a commercial product. The liquid metal can be used over and over because only the solutes are consumed within the liquid metal. The technique can be applied to various shapes because the coating is formed by liquid-phase reaction. This paper will discuss initial results on the nature of the coatings and their in-situ electrical resistivity characteristics in liquid lithium at high temperatures.

  12. Effects of Wet Air and Synthetic Combustion Gas Atmospheres on the Oxidation Behavior of Mo-Si-B Alloys

    SciTech Connect

    Kramer, M.J.; Thom, A.J.; Mandal, P.; Behrani, V.; Akinc, M.

    2003-04-24

    Continuing our work on understanding the oxidation behavior of multiphase composite alloys based on the Mo-Si-B system, we investigated three alloys in the Mo-Si-B system, designated as A1, A2, and A3. The nominal phase assemblages of these alloys are: A1 = Mo{sub 5}Si{sub 3}B{sub x} (T1)-MoSi{sub 2}-MoB, A2 = T1-Mo{sub 5}SiB{sub 2} (T2)-Mo{sub 3}Si, and A3 = Mo-T2-Mo{sub 3}Si. Our previous work showed that for exposures to 1100 C, all alloys formed a protective oxide scale in dry air. Exposures to wet air containing about 150 Torr water promoted the formation of a multiphase layer near the scale/alloy interface composed of Mo and MoO{sub 2}. Interrupted mass loss measurements indicated a near zero mass change. In the present study, isothermal mass measurements were conducted in order to quantitatively determine the oxidation rate constants at 1000 C in both dry and wet air. These measurements are critical for understanding the nature of scale development during the initial exposure, as well as the nature of scale stability during the long-term exposure. Isothermal measurements were also conducted at 1600 C in dry air to make an initial determination of alloy stability with respect to Vision 21 goals. We also conducted alloy oxidation testing in a synthetic oxidizing combustion atmosphere. Alloys were exposed up to 300 hours at 1100 C to a gas mixture having an approximate gas composition of N{sub 2} - 13 CO{sub 2} - 10 H{sub 2}O - 4 O{sub 2}. This gas composition simulates oxidizing flue gas, but does not contain a sulfidizing agent that would also be present in flue gas. The oxidized samples were carefully analyzed by SEM/EDS. This analysis will be discussed to provide an understanding of the role of water vapor and the synthetic combustion atmosphere on the oxidative stability of Mo-Si-B alloys.

  13. Phase Equilibria, Microstructure, and High-Temperature Strength of TiC-Added Mo-Si-B Alloys

    NASA Astrophysics Data System (ADS)

    Miyamoto, Shimpei; Yoshimi, Kyosuke; Ha, Seong-Ho; Kaneko, Takahiro; Nakamura, Junya; Sato, Tetsuya; Maruyama, Kouichi; Tu, Rong; Goto, Takashi

    2013-05-01

    TiC was added to Mo-Si-B alloys using a conventional Ar arc-melting technique, and the phase equilibria, microstructure evolution, and high-temperature strength at 1673 K (1400 °C) were investigated. The primary phase changed to Mo solid solution (Moss), Mo5SiB2 (T2), or TiC depending on the composition. Following the primary phase solidification, a Moss + TiC, Moss + T2, or Moss + T2 + TiC + Mo2C eutectic reaction took place as the secondary solidification step. In some alloys, Moss + T2 + TiC and Moss + T2 + Mo2C eutectic reactions were present as higher-order solidification steps. After annealing at 2073 K (1800 °C) for 24 hours, Moss, T2, TiC, and Mo2C coexisted stably with microstructural coarsening. The coarsening rate was much faster in an alloy with no TiC dispersion, suggesting that TiC has a strong pinning effect on the grain boundary and interface migration. Compression tests conducted at 1673 K (1400 °C) revealed strength properties of almost all the alloys that were better than those of the Mo-Hf-C alloy (MHC). Alloy densities were 9 g/cm3 or less, which is lighter than pure Mo and MHC (≥10 g/cm3) and competitive with Ni-base superalloys. TiC-added Mo-Si-B alloys are promising candidates for ultrahigh-temperature materials beyond Ni-base superalloys.

  14. Thermal stability of sputtered intermetallic Al-Au coatings

    SciTech Connect

    Moser, M.; Mayrhofer, P. H.; Ross, I. M.; Rainforth, W. M.

    2007-09-15

    Recently, the authors have shown that single-phase Al{sub 2}Au coatings, prepared by unbalanced magnetron sputtering, exhibit a dense columnar structure and highest hardness and indentation moduli of 8 and 144 GPa, respectively, within the Al-Au films investigated. This study focuses on the thermal stability of Al{sub 2}Au with respect to films containing more Al and Au having Al/Au at. % ratios of 4.32 and 1.85, respectively. Single-phase Al{sub 2}Au has the highest onset temperature for recovery of 475 deg. C and recrystallization of 575 deg. C. Upon annealing Au- and Al-rich films, their stresses deviate from the linear thermoelastic behavior at temperatures (T) above 200 and 450 deg. C, respectively, due to pores and metallic phases present. Metastable Au within the as-deposited Au-rich film is consumed by the growing intermetallic AlAu and AlAu{sub 2} phases at T{>=}450 deg. C, which themselves melt at {approx}625 deg. C. Due to nanometer scale segregations of Al, encapsulated by Al{sub 2}Au in Al-rich coatings, their melting point is reduced by {approx}85 deg. C to 575 deg. C. Dynamic thermal analyses up to 1100 deg. C in synthetic air reveal the single-phase Al{sub 2}Au films with a superior thermal stability and only negligible oxidation. At 750 deg. C, the mass gain is {approx}1.5 mg/cm{sup 2} after 50 h isothermal exposure. Based on the investigations, the authors can conclude that single-phase intermetallic Al{sub 2}Au films have a high potential for oxidation protection of sensitive materials.

  15. Modification of Surface Layers by Surfacing Intermetallic Coatings with Variable Properties

    NASA Astrophysics Data System (ADS)

    Makeev, D. N.; Zakharov, O. V.; Vinogradov, A. N.; Kochetkov, A. V.

    2016-02-01

    The paper considers the possibility of forming coating layers for parts within wide limits of microhardness. The technology uses surfacing of intermetallic coatings provided by a unique experimental setup. Theoretical and experimental dependence of the coating layer microhardness on the filler concentration using the changes in the speed of the filler wire feed and current intensity were determined.

  16. Microstructural Simulation of Three-Point Bending Test with Mo-Si-B Alloy at High Temperature: Sources of Strain Field Localization

    NASA Astrophysics Data System (ADS)

    Chollacoop, Nuwong; Alur, Amruthavalli P.; Kumar, K. Sharvan

    Deformation behavior in three-point bending test of Mo-Si-B alloy was investigated by recourse to finite element analysis (FEA) with microstructure incorporated. This Mo-Si-B alloy consists of hard, brittle T2 (Mo5SiB2) phase embedded in soft matrix of Mo solid solution. The sample contains pre-crack configuration at the middle in order to study the effect of the second phase (T2 particles) onto a crack tip during the bending test. Various optical micrographs were scanned, digitized and meshed for FEA. It was found that strain localization from the second phase at the crack tip was interfered with that from the loading pin in three-point bending test. Such interference could be reduced by replacement with end moment loading, in order to identify sole strain localization effect from the second phase at the crack tip.

  17. Oxidation Control of Atmospheric Plasma Sprayed FeAl Intermetallic Coatings Using Dry-Ice Blasting

    NASA Astrophysics Data System (ADS)

    Song, Bo; Dong, Shujuan; Coddet, Pierre; Hansz, Bernard; Grosdidier, Thierry; Liao, Hanlin; Coddet, Christian

    2013-03-01

    The performance of atmospheric plasma sprayed FeAl coatings has been remarkably limited because of oxidation and phase transformation during the high-temperature process of preparation. In the present work, FeAl intermetallic coatings were prepared by atmospheric plasma spraying combined with dry-ice blasting. The microstructure, oxidation, porosity, and surface roughness of FeAl intermetallic coatings were investigated. The results show that a denser FeAl coating with a lower content of oxide and lower degree of phase transformation can be achieved because of the cryogenic, the cleaning, and the mechanical effects of dry-ice blasting. The surface roughness value decreased, and the adhesive strength of FeAl coating increased after the application of dry-ice blasting during the atmospheric plasma spraying process. Moreover, the microhardness of the FeAl coating increased by 72%, due to the lower porosity and higher dislocation density.

  18. Novel Nanocrystalline Intermetallic Coatings for Metal Alloys in Coal-fired Environments

    SciTech Connect

    Z. Zak Fang; H. Y. Sohn

    2009-08-31

    Intermetallic coatings (iron aluminide and nickel aluminide) were prepared by a novel reaction process. In the process, the aluminide coating is formed by an in-situ reaction between the aluminum powder fed through a plasma transferred arc (PTA) torch and the metal substrate (steel or Ni-base alloy). Subjected to the high temperature within an argon plasma zone, aluminum powder and the surface of the substrate melt and react to form the aluminide coatings. The prepared coatings were found to be aluminide phases that are porosity-free and metallurgically bonded to the substrate. The coatings also exhibit excellent high-temperature corrosion resistance under the conditions which simulate the steam-side and fire-side environments in coal-fired boilers. It is expected that the principle demonstrated in this process can be applied to the preparation of other intermetallic and alloy coatings.

  19. Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, Robert A. (Inventor); Doychak, Joseph (Inventor)

    1994-01-01

    A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

  20. Preparation and properties of the Ni-Al/Fe-Al intermetallics composite coating produced by plasma cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Min; Liu, Bang-Wu; Sun, Dong-Bai

    2011-12-01

    A novel approach to produce an intermetallic composite coating was put forward. The microstructure, microhardness, and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) analysis, microhardness test, and ball-on-disc wear experiment. XRD results indicate that some new phases FeAl, Fe0.23Ni0.77Al, and Ni3Al exit in the composite coating with the Al2O3 addition. SEM results show that the coating is bonded with carbon steel metallurgically and exhibits typical rapid directional solidification structures. The Cr7C3 carbide and intermetallic compounds co-reinforced composite coating has a high average hardness and exhibits an excellent wear resistance under dry-sliding wear test compared with the Cr7C3 carbide-reinforced composite coating. The formation mechanism of the intermetallic compounds was also investigated.

  1. Wear Behavior and Mechanism of Fe-Al Intermetallic Coating Prepared by Hot-Dip Aluminizing and Diffusion

    NASA Astrophysics Data System (ADS)

    Zhang, Q. Y.; Zhou, Y.; Liu, J. Q.; Chen, K. M.; Mo, J. G.; Cui, X. H.; Wang, S. Q.

    2016-05-01

    A Fe-Al intermetallic compound coating was prepared on AISI H13 steel by hot-dip aluminizing and subsequent high-temperature diffusion. Dry sliding wear tests of the Fe-Al intermetallic coating were performed at 298 K to 873 K (25 °C to 600 °C). The wear behavior of the Fe-Al intermetallic coating was noticed to vary markedly with the temperature and load. At 298 K (25 °C), the wear rate rapidly increased with an increase of the load. As the temperature was elevated, the wear rate dramatically decreased except for the cases under 300 N at 473 K and 673 K (200 °C and 400 °C). The Fe-Al intermetallic coating possessed an excellent elevated-temperature wear performance, especially at 673 K to 873 K (400 °C to 600 °C), but worse room-temperature one, which were noticed to be attributed to the existence and inexistence of thin tribo-oxide layers, respectively. Such a thin tribo-oxide layer was considered to provide a protection for the intermetallic compound. When the tribo-oxide layer did not form at room temperature or the formed one was massively delaminated above the critical load at elevated temperatures, Fe-Al intermetallic coating possessed poor wear resistance.

  2. Fabrication of intermetallic coatings for electrical insulation and corrosion resistance on high-temperature alloys

    SciTech Connect

    Park, J.-H.; Cho, W.D.

    1996-11-01

    Several intermetallic films were applied to high-temperature alloys (V alloys and 304, 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain growth at 1000 C for the V-5Cr-5Ti alloy was investigated to determine stability of the alloy substrate during coating formation by CVD or metallic vapor processes at 800-850 C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and XRD analysis; they were also tested for electrical resistivity and corrosion resistance. Results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.

  3. Intermetallic-ceramic coatings for metals protection against erosion-corrosion at high temperatures

    SciTech Connect

    Wang, B.Q.; Verstak, A.; Beliaev, A.

    1999-07-01

    A series of erosion-corrosion (E-C) tests was carried out on the NiAl-Al{sub 2}O{sub 3} intermetallic-ceramic coatings deposited with high-velocity oxygen-fuel method (HVOF). The tests attempted to simulate the erosion conditions at the heat exchanger tubes in coal-fired boilers. The E-C behavior of these coatings was investigated and compared with other thermal sprayed coatings. It was found that in comparison to other coatings, eroded by the bed ash at 300 C, the HVOF NiAl-40Al{sub 2}0{sub 3} coating exhibited the lowest thickness loss at a 90{degree} impact angle, and was the second best at a 30{degree} impact angle. Eroded by the fly ash under test temperatures 450--600 C, the HVOF NiAl-40Al{sub 2}O{sub 3} coating demonstrated the highest erosion-corrosion resistance at all impact angles of testing. At temperatures below 200 C, the E-C wastage of the HVOF NiAl-40Al{sub 2}O{sub 3} coating had essentially no dependence on temperature. From 200 C to 600 C the coating thickness loss increased and from 600 to 800 C the thickness loss decreased with temperature. The HVOF NiAl-40Al{sub 2}O{sub 3} coating eroded by cracking and chipping brittle mechanism.

  4. Development of Cu alloy anode and separator coated with Al-Ni intermetallic compound

    SciTech Connect

    Toyokura, K.; Hoshino, K.; Yamamoto, M.

    1996-12-31

    Anode made of Cu alloy and separator coated with Al-Ni intermetallic compound have been developed for VCFC. Anode of Ni alloy is usually used. However, the alternative of cost lower than Ni alloy anode should be needed, because Ni is expensive. Cu is attractive as an anode material for VCFC because it is inexpensive and electrochemically noble. However, the creep resistance of Cu is not sufficient, compared with Ni alloy. In this study, strengthening due to oxide-dispersed microstructure has been developed in Cu-Ni-Al alloy with the two-step sintering process. A wet-seal technique has been widely applied for gas-sealing and supporting of electrolyte in MCFC. Since the wet-seal area is exposed to a severe corrosive environment, corrosion resistance of material for wet sealing is related with the cell performance. Al-Ni plating with post-heat treating for stainless steel has been investigated. Stainless steel substrate was plated with Al after being coated with Ni, then heat-treated at 750 {degrees}C for 1 hour in Ar gas atmosphere. Due to the treatment, Al-Ni intermetallic compound ( mainly Al3Ni2 ) layer is formed on stainless steel surface. The long-term immersion test was carried out till 14,500 hours in 62 mol% Li{sub 2}CO{sub 3}-38 mol% K{sub 2}CO{sub 3} at 650 {degrees}C under air-30%CO{sub 2} atmosphere, for the purpose of evaluating the corrosion resistance and thermal stability of Al-Ni intermetallic compound layer in actual generating with VCFC.

  5. Fabrication of intermetallic coatings for electrical and corrosion resistance on high-temperature alloys

    SciTech Connect

    Park, J.H.; Cho, W.D.

    1994-10-01

    Several intermetallic films were fabricated to high-temperature alloys (V-alloys and 304 and 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain-growth behavior at 1000{degrees}C for the V-5Cr-5Ti was investigated to determine the stability of alloy substrate during coating formation by chemical vapor deposition (CVD) or metallic vapor processes at 800-850{degrees}C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and X-ray diffraction analysis and tested for electrical resistivity and corrosion resistance. The results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.

  6. Deposition of Functional Coatings Based on Intermetallic Systems TiAl on the Steel Surface by Vacuum Arc Plasma

    NASA Astrophysics Data System (ADS)

    Budilov, V.; Vardanyan, E.; Ramazanov, K.

    2015-11-01

    Laws governing the formation of intermetallic phase by sequential deposition of nano-sized layers coatings from vacuum arc plasma were studied. Mathematical modeling process of deposition by vacuum arc plasma was performed. In order to identify the structural and phase composition of coatings and to explain their physical and chemical behaviour XRD studies were carried out. Production tests of the hardened punching tools were performed.

  7. CaO insulator and Be intermetallic coatings on V-base alloys for liquid-lithium fusion blanket applications

    SciTech Connect

    Park, J.H.; Kassner, T.F.

    1996-04-01

    The objective of this study is to develop (a) stable CaO insulator coatings at the Liquid-Li/structural-material interface, with emphasis on electrically insulating coating that prevent adverse MHD-generated currents from passing through the V-alloy wall, and (b) stable Be-V intermetallic coating for first-wall components that face the plasma. Electrically insulating and corrosion-resistant coatings are required at the liquid-Li/structural interface in fusion first-wall/blanket application. The electrical resistance of CaO coatings produced on oxygen-enriched surface layers of V-5%Cr-5%Ti by exposing the alloy to liquid Li that contained 0.5-85 wt% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. Crack-free Be{sub 2}V intermetallic coatings were also produced by exposing V-alloys to liquid Li that contained Be as a solute. These techniques can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coatings are formed by liquid-phase reactions.

  8. Heat treatment induced intermetallic phase transition of arc-sprayed coating prepared by the wires combination of aluminum-cathode and steel-anode

    NASA Astrophysics Data System (ADS)

    Chen, Yongxiong; Liang, Xiubing; Wei, Shicheng; Liu, Yan; Xu, Binshi

    2009-07-01

    A method to prepare intermetallic composite coatings employing the cost-efficient electric arc spraying twin wires assistant with suitable heat treatment was developed. In this study, a Fe-Al composite coating was produced by spraying twin wires, i.e. a carbon steel wire as the anode and an aluminum wire as the cathode. The inter-deposited Fe-Al coating was transformed in-situ to Fe-Al intermetallic composite coating after a post annealing treatment. The effect of annealing treatment conditions on phase composition, microstructure and mechanical properties of the coating was investigated by using XRD, SEM, EDS and OM as well as microhardness tester. The results show that the desirable intermetallic phases such as Fe 2Al 5, FeAl and Fe 3Al are obtained under the annealing condition. The main oxide in the coating is FeO which can partially transform to Fe 3O 4 up to the annealing condition.

  9. Characterization of High-Temperature Abrasive Wear of Cold-Sprayed FeAl Intermetallic Compound Coating

    NASA Astrophysics Data System (ADS)

    Li, Chang-Jiu; Wang, Hong-Tao; Yang, Guan-Jun; Bao, Chong-Gao

    2011-01-01

    FeAl intermetallic compound coating was prepared by cold spraying using a mechanically alloyed Fe(Al) alloy powder followed by post-spray annealing at 950 °C. The high-temperature abrasive wear test was carried out for the FeAl coating at a temperature range from room temperature to 800 °C. The high-temperature abrasive wear of a heat-resistant stainless steel 2520 was performed for comparison. It was observed that the abrasive wear weight loss of FeAl coating was proportional to wear cycles in terms of sample revolutions at the tested temperatures. It was found that with the increase of the test temperature higher than 400 °C, the wear rate of cold-sprayed FeAl coating decreased with the increase of test temperature, while the wear rate of the heat-resistant steel increased significantly. The results indicate that the high-temperature abrasive wear resistance of the cold-sprayed FeAl intermetallic coating increased with the increase of the wear temperature in a temperature range from 400 to 800 °C. The wear resistance of cold-sprayed FeAl coating was higher than that of heat-resistant 2520 stainless steel under 800 °C by a factor of 3.

  10. Nanocomposite Fe-Al Intermetallic Coating Obtained by Gas Detonation Spraying of Milled Self-Decomposing Powder

    NASA Astrophysics Data System (ADS)

    Senderowski, Cezary

    2014-10-01

    The nanocomposite structure of Fe-Al intermetallic coating, created in situ during gas detonation spraying (GDS) of as-milled self-decomposing powder and containing disordered 8 nm FeAl nanocrystals, was analyzed using scanning electron microscopy (SEM) with energy-dispersive x-ray (EDX) spectroscopy, transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and x-ray diffraction methods. It is found that the Fe-Al coating is characterized by a sublayer morphology consisting of flattened and partially melted splats containing a wide Al range from about 26 to 52 at.%, as well as Al2O3 oxides, created in situ at the internal interfaces of splats during the GDS process. The complex oxide films, identified as amorphous Al2O3, which are formed in the nanocrystalline Fe-Al matrix of the GDS coating behave like a composite reinforcement in the intermetallic Fe-Al coating. The combined presence of nanosized subgrains in the Fe-Al matrix and the Al2O3 nanoceramic dispersoids significantly increases the microhardness of the coating.

  11. Electrodeposited nickel(3) aluminide base intermetallic coatings and their resistance to high temperature degradation in hydrocarbon cracking environments

    NASA Astrophysics Data System (ADS)

    Liu, Haifeng

    This research was aimed at developing novel Ni-A1 base intermetallic coatings to protect commercial Fe-Ni-Cr tube alloys from severe corrosive degradation at high temperatures. These alloys are widely used in petrochemical, chemical, and energy conversion industries. The coating process and coating evaluation were the two main aspects of this investigation. A two-step coating processing has been successfully developed to in situ apply pure and CeO2-modified Ni3Al intermetallic coatings onto Fe-Ni-Cr substrates. The process consists of the electrodeposition of Ni-Al and Ni-Al-CeO2 composite coatings from a Watt's nickel bath containing Al and CeO2 particles via a cost-effective electroplating technique and an annealing treatment of the as-plated coatings. It was found that the deposition of Al particles obeyed a Guglielmi model, and that REO particles interfered significantly with the deposition of Al particles. The long-term resistance of pure and CeO2-modified Ni 3A1 coatings to cyclic oxidation, carburization, coke formation, and metal dusting was evaluated in flowing dry air, 2 % CH4-H 2, and CO-H2-H2O respectively. Due to the high porosity, pure and CeO2-dispersed Ni3Al coatings exhibited poor resistance to cyclic oxidation at 850°C. CeO2 improved the spallation resistance of the Ni3Al base coatings during cyclic oxidation at 1050°C. CeO2-dispersed Ni3Al coatings showed better carburization resistance, particularly at 1050°C. Ni 3A1-based coatings. Those CeO2-dispersed were susceptible to coke formation and metal dusting at 650°C. Pre-oxidation improved the resistance of Ni3Al-based coatings to coke formation and metal dusting at 650°C, but the effectiveness depended on the integrity of the induced alumina scale. Special attention was paid to several aspects of coating degradation. These aspects included microstructure changes, degradation mechanisms, coating/substrate interdiffusion, effect of corrosive atmosphere, and effect of CeO2 on coating

  12. Corrosion behaviour and biocompatibility of a novel Ni-free intermetallic coating growth on austenitic steel by hot dipping in an Al-12.6%Si alloy.

    PubMed

    Arenas, M A; Frutos, E; Saldaña, L; Conde, A; Labajos-Broncano, L; González-Martín, M L; González-Carrasco, J L; Vilaboa, N

    2011-04-01

    Commercial 316 LVM austenitic stainless steel samples have been coated by immersion in a bath of molten Al-12.6%Si alloy for 120 s. The coating consists of the Al(12)(Fe,Cr)(3)Si(2) intermetallic. In vitro corrosion behaviour has been evaluated in the Ringer's solution by means of potentiodynamic curves and electrochemical impedance spectroscopy. The results reveal that the coated specimens exhibit lower susceptibility to localised corrosion with respect to the substrate. XPS analysis suggests that the ennoblement of the pitting potential is due to the formation of a chromium oxyhydroxide containing passive layer. The intermetallic coating shows a good biocompatibility, as demonstrated by culturing human mesenchymal stem cells isolated from bone marrow which attached, grew and differentiated to the osteoblastic lineage to a similar extent on coated and bare steels. In summary, this study proposes a method that generates Ni-free coatings of the stainless steel with useful properties for biomedical applications. PMID:21437641

  13. Characterization of the elastic-plastic behavior of intermetallic coatings growth on medical stainless steel by instrumented ultramicroindentation.

    PubMed

    Frutos, E; Cuevas, A; González-Carrasco, J L; Martín, F

    2012-12-01

    The purpose of this work is to study the elastoplastic properties of novel intermetallic coatings grown by hot dipping on medical steel 316 LVM and their correlation with the scratch resistance by means of instrumented ultramicroindentation techniques. Elastoplastic properties are defined by the plasticity index (PI), which correlates the hardness and the Young's modulus, and the yield strength that delimits the elastic-plastic transition. To avoid overestimations of the PI due to the so-called indentation size effect, macroscopic hardness values were determined. The PI of the coating increases from 0.6 to 0.8 with increasing immersion time. These values are always lower than those of the bare substrate (0.9) but higher than those found for ceramics (∼0.5). The increase of the PI is accompanied by a decrease in the yield strength from 0.73 to 0.34 GPa, which highlights the relevance of the compressive residual stresses and their relaxation with increasing immersion time. The higher plasticity is shown by higher apparent friction coefficients (0.159), which are always lower than those of the bare steel (0.264). Therefore, these intermetallic coatings could be considered "hard but tough" coatings, suitable for enhancing the wear resistance of the medical steel, especially when using short periods of immersion. The study provides evidence that the load-depth curve of indentation contains abundant information and that its analysis can be used to determine various mechanical properties of coatings that could be important for load bearing components. PMID:23137617

  14. Effects of Al Content and Addition of Third Element on Fabrication of Ti-Al Intermetallic Coatings by Heat Treatment of Warm-Sprayed Precursors

    NASA Astrophysics Data System (ADS)

    Sienkiewicz, J.; Kuroda, S.; Minagawa, K.; Murakami, H.; Araki, H.; Kurzydłowski, K. J.

    2015-06-01

    Four powder mixtures of titanium and aluminum with 50:50, 40:60, 30:70, and 20:80 atomic ratios were used as feedstock for Warm Spray process to produce composite coatings. A two-stage heat treatment at 600 and 1000 °C was applied to the deposits in order to obtain titanium aluminide intermetallic phases. The microstructure, chemical, and phase composition of the as-deposited and heat-treated coatings were investigated using SEM, EDS, and XRD. It was found that the Al content affects on the thickness expansion of the heat-treated Ti-Al coatings significantly and also has a major influence on the porosity development, which is caused by the Kirkendall effect. The effects of adding a third element Si and heat treatment with pressure to produce denser Ti-Al intermetallic coating were also examined. The investigated hot-pressed coatings with addition of Si exhibited much denser microstructure and contained Ti-Al intermetallic phases with titanium silicide precipitates.

  15. Technical note - Plasma-sprayed ceramic thermal barrier coatings for smooth intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Doychak, J.

    1992-01-01

    A new approach for plasma spray deposition of ceramic thermal barrier coatings directly to smooth substrates is described. Ceramic thermal barrier coatings were directly applied to substrates that had been coated with low-pressure plasma sprayed NiCrAlY bond coats and then centerless ground to simulate a smooth oxidation-resistant substrate. As the high-temperature oxidation behavior of NiAl+Zr is superior to that of MCrALY alloy, the bond coat is not required for oxidation resistance.

  16. Characterization of Nanostructured NbSi2 Intermetallic Coatings Obtained by Plasma Spraying of Mechanically Alloyed Powders

    NASA Astrophysics Data System (ADS)

    Yazdani, Zohreh; Karimzadeh, Fathallah; Abbasi, Mohammad-Hasan

    2015-08-01

    Nanostructured NbSi2 powders plasma sprayed on to Ti-6Al-4V substrates were characterized in this research. After preparation of the nanostructured NbSi2 powders by mechanical alloying of an Nb-Si powder mixture, agglomeration was performed to obtain a particle size suitable for spraying. The agglomerated powders were then sprayed by atmospheric plasma spraying. Structural transformation of the powders and morphological and mechanical changes of the coatings were examined by use of x-ray diffraction analysis, scanning electron microscopy, energy dispersive spectroscopy, and microhardness testing. During milling, NbSi2 intermetallic with a grain size of approximately 15 nm was gradually formed. After plasma spraying, a coating of hardness 550 ± 8 HV with a uniform nanocrystalline structure, low oxide content, low porosity, and a good adhesion to the substrate was obtained. No phase change occurred after spraying and the NbSi2 compound remained nanostructured with a grain size of approximately 82 nm.

  17. Synthesis of advanced aluminide intermetallic coatings by low-energy Al-ion radiation

    PubMed Central

    Shen, Mingli; Gu, Yan; Zhao, Panpan; Zhu, Shenglong; Wang, Fuhui

    2016-01-01

    Metals that work at high temperatures (for instance, superalloys in gas-turbines) depend on thermally grown oxide (TGO, commonly alumina) to withstand corrosion attack. Nickel Aluminide (NiAl) as one superior alumina TGO former plays an important role in protective coatings for turbine blades in gas-turbine engines used for aircraft propulsion and power generation. Lowering TGO growth rate is essentially favored for offering sustainable protection, especially in thermal barrier coatings (TBC). However, it can only be achieved currently by a strategy of adding the third element (Pt or reactive elements) into NiAl during traditional diffusion- or deposition-based synthesis of the coating. Here we present a highly flexible Al-ion radiation-based synthesis of advanced NiAl coatings, achieving low TGO growth rate without relying on the third element addition. Our results expand the strategy for lowering TGO growth rate and demonstrate potentials for ion radiation in advancing materials synthesis. PMID:27194417

  18. Synthesis of advanced aluminide intermetallic coatings by low-energy Al-ion radiation

    NASA Astrophysics Data System (ADS)

    Shen, Mingli; Gu, Yan; Zhao, Panpan; Zhu, Shenglong; Wang, Fuhui

    2016-05-01

    Metals that work at high temperatures (for instance, superalloys in gas-turbines) depend on thermally grown oxide (TGO, commonly alumina) to withstand corrosion attack. Nickel Aluminide (NiAl) as one superior alumina TGO former plays an important role in protective coatings for turbine blades in gas-turbine engines used for aircraft propulsion and power generation. Lowering TGO growth rate is essentially favored for offering sustainable protection, especially in thermal barrier coatings (TBC). However, it can only be achieved currently by a strategy of adding the third element (Pt or reactive elements) into NiAl during traditional diffusion- or deposition-based synthesis of the coating. Here we present a highly flexible Al-ion radiation-based synthesis of advanced NiAl coatings, achieving low TGO growth rate without relying on the third element addition. Our results expand the strategy for lowering TGO growth rate and demonstrate potentials for ion radiation in advancing materials synthesis.

  19. Synthesis of advanced aluminide intermetallic coatings by low-energy Al-ion radiation.

    PubMed

    Shen, Mingli; Gu, Yan; Zhao, Panpan; Zhu, Shenglong; Wang, Fuhui

    2016-01-01

    Metals that work at high temperatures (for instance, superalloys in gas-turbines) depend on thermally grown oxide (TGO, commonly alumina) to withstand corrosion attack. Nickel Aluminide (NiAl) as one superior alumina TGO former plays an important role in protective coatings for turbine blades in gas-turbine engines used for aircraft propulsion and power generation. Lowering TGO growth rate is essentially favored for offering sustainable protection, especially in thermal barrier coatings (TBC). However, it can only be achieved currently by a strategy of adding the third element (Pt or reactive elements) into NiAl during traditional diffusion- or deposition-based synthesis of the coating. Here we present a highly flexible Al-ion radiation-based synthesis of advanced NiAl coatings, achieving low TGO growth rate without relying on the third element addition. Our results expand the strategy for lowering TGO growth rate and demonstrate potentials for ion radiation in advancing materials synthesis. PMID:27194417

  20. FeAl and NbAl3 Intermetallic-HVOF Coatings: Structure and Properties

    NASA Astrophysics Data System (ADS)

    Guilemany, J. M.; Cinca, N.; Dosta, S.; Cano, I. G.

    2009-12-01

    Transition metal aluminides in their coating form are currently being explored in terms of resistance to oxidation and mechanical behavior. This interest in transition metal aluminides is mainly due to the fact that their high Al content makes them attractive for high-temperature applications. This is also a reason to study their resistance to wear; they may be suitable for use in applications that produce a lot of wear in aggressive environments, thus replacing established coating materials. In this study, the microstructure, microhardness, and wear and oxidation performance of FeAl and NbAl3 coatings produced by high-velocity oxy-fuel spraying are evaluated with two main aims: (i) to compare these two coating systems—a commonly studied aluminide (FeAl) and, NbAl3, an aluminide whose deposition by thermal spraying has not been attempted to date—and (ii) to analyze the relationship between their microstructure, composition and properties, and so clarify their wear and oxidation mechanisms. In the present study, the higher hardness of niobium aluminide coatings did not correlate with a higher wear resistance and, finally, although pesting phenomena (disintegration in oxidizing environments) were already known of in bulk niobium aluminides, here their behavior in the coating form is examined. It was shown that such accelerated oxidation was inevitable with respect to the better resistance of FeAl, but further improvements are foreseen by addition of alloying elements in that alloy.

  1. Influence of Detonation Gun Spraying Conditions on the Quality of Fe-Al Intermetallic Protective Coatings in the Presence of NiAl and NiCr Interlayers

    NASA Astrophysics Data System (ADS)

    Senderowski, Cezary; Bojar, Zbigniew

    2009-09-01

    The paper presents results of detailed research of the application of detonation gun (D-gun) spraying process for deposition of Fe-Al intermetallic coatings in the presence of NiAl and NiCr interlayers. A number of D-gun experiments have been carried out with significant changes in spraying parameters which define the process energy levels (changes in volumes of the working and fuel gases, and the distance and frequency of spraying). These changes directly influenced the quality of the coatings. The initial results underlay the choice of the process parameters with the view to obtain the most advantageous of geometric and physical-mechanical properties of the coating material, interlayer and substrate. The metallurgical quality of the coatings was considered by taking into account grain morphology, the inhomogeneity of chemical content and phase structure, the cohesive porosity in the coating volume, and adhesive porosity in the substrate/interlayer/coating boundaries. The surface roughness level was also considered. It was found that the D-gun sprayed coatings are in all cases built with flat lamellar splats. The splats develop from powder particles which are D-gun transformed in their plasticity and geometry. A significant result of the optimization of D-gun spraying parameters is the lack of signs of melting of the material (even in microareas) while the geometry of the subsequently deposited grains is considerably changed and the adhesivity and cohesion of the layers proves to be high. This is considered as an undeniable proof of high plasticity of the D-gun formed Fe-Al intermetallic coating.

  2. Whisker formation in Sn and Pb-Sn coatings: Role of intermetallic growth, stress evolution, and plastic deformation processes

    SciTech Connect

    Chason, E.; Jadhav, N.; Kumar, K. S.; Chan, W. L.; Reinbold, L.

    2008-04-28

    We have simultaneously measured the evolution of intermetallic volume, stress, and whisker density in Sn and Pb-Sn alloy layers on Cu to study the fundamental mechanisms controlling whisker formation. For pure Sn, the stress becomes increasingly compressive and then saturates, corresponding to a plastically deformed region spreading away from the growing intermetallic particles. Whisker nucleation begins after the stress saturates. Pb-Sn layers have similar intermetallic growth kinetics but the resulting stress and whisker density are much less. Measurements after sputtering demonstrate the important role of the surface oxide in inhibiting stress relaxation.

  3. Dynamic nanomechanical properties of novel Si-rich intermetallic coatings growth on a medical 316 LVM steel by hot dipping in a hypereutectic Al-25Si alloy.

    PubMed

    Frutos, E; González-Carrasco, J L

    2015-06-01

    This aim of this study is to determine the elastoplastic properties of Ni-free Al3FeSi2 intermetallic coatings grown on medical stainless steel under different experimental conditions. Elastoplastic properties are defined by the plasticity index (PI), which correlates the hardness and the Young's modulus. Special emphasis is devoted to correlate the PI with the wear resistance under sliding contact, determined by scratch testing, and fracture toughness, determined by using a novel method based on successive impacts with small loads. With regard to the substrate, the developed coatings are harder and exhibit a lower Young's reduced modulus, irrespective of the experimental conditions. It has been shown that preheating of the samples prior to hot dipping and immersion influences the type and volume fraction of precipitates, which in turn also affect the nanomechanical properties. The higher the preheating temperature is, the greater the Young's reduced modulus is. For a given preheating condition, an increase of the immersion time yields a decrease in hardness. Although apparent friction coefficients of coated specimens are smaller than those obtained on AISI 316 LVM, they increase when using preheating or higher immersion times during processing, which correlates with the PI. The presence of precipitates produces an increase in fracture toughness, with values greater than those presented by samples processed on melted AlSi alloys with lower Si content (12 wt%). Therefore, these intermetallic coatings could be considered "hard but tough", suitable to enhance the wear resistance, especially when using short periods of immersion. PMID:25778350

  4. The structure and physical-mechanical properties of the heat-resistant Ni-Co-Cr-Al-Y intermetallic coating obtained using rebuilt plasma equipment

    NASA Astrophysics Data System (ADS)

    Tarasenko, Yu. P.; Tsareva, I. N.; Berdnik, O. B.; Fel, Ya. A.; Kuzmin, V. I.; Mikhalchenko, A. A.; Kartaev, E. V.

    2014-12-01

    Results of a study of the structure, physico-mechanical properties, and the resistance to heat of Ni-Co-Cr-Al-Y intermetallic coatings obtained by powder spraying on the standard UPU-3D plasma spray facility (plasmatron with self-establishing arc length) and on the rebuilt facility equipped with the enhanced-power PNK-50 plasmatron with sectionalized inter-electrode insert, are reported. Coatings of higher density ( ρ = 7.9 g/cm3) and higher microhardness (H μ = 770 kg-force/mm2) with lower porosity values ( P = 5.7 %, P c = 5.1 %, and P 0 = 0.6 %) and high resistance to heat ((M - M0)/M0 = 1.2) were obtained. The developed coating is intended for protection of the working surfaces of turbine engine blades in gas-turbine power plants.

  5. Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

    2010-11-01

    A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600°C and 800°C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

  6. Intermetallic nanoparticles

    SciTech Connect

    Singh, Dileep; Yusufoglu, Yusuf; Timofeeva, Elena; Routbort, Jules L.

    2015-11-20

    A process for preparing intermetallic nanoparticles of two or more metals is provided. In particular, the process includes the steps: a) dispersing nanoparticles of a first metal in a solvent to prepare a first metal solution, b) forming a reaction mixture with the first metal solution and a reducing agent, c) heating the reaction mixture to a reaction temperature; and d) adding a second metal solution containing a salt of a second metal to the reaction mixture. During this process, intermetallic nanoparticles, which contain a compound with the first and second metals are formed. The intermetallic nanoparticles with uniform size and a narrow size distribution is also provided. An electrochemical device such as a battery with the intermetallic nanoparticles is also provided.

  7. Intermetallic nanoparticles

    SciTech Connect

    Singh, Dileep; Yusufoglu, Yusuf; Timofeeva, Elena; Routbort, Jules

    2015-07-14

    A process for preparing intermetallic nanoparticles of two or more metals is provided. In particular, the process includes the steps: a) dispersing nanoparticles of a first metal in a solvent to prepare a first metal solution, b) forming a reaction mixture with the first metal solution and a reducing agent, c) heating the reaction mixture to a reaction temperature; and d) adding a second metal solution containing a salt of a second metal to the reaction mixture. During this process, intermetallic nanoparticles, which contain a compound with the first and second metals are formed. The intermetallic nanoparticles with uniform size and a narrow size distribution is also provided. An electrochemical device such as a battery with the intermetallic nanoparticles is also provided.

  8. Microstructure and Sliding Wear Behavior of Fe-Based Coatings Manufactured with HVOF and HVAF Thermal Spray Processes

    NASA Astrophysics Data System (ADS)

    Milanti, A.; Matikainen, V.; Bolelli, G.; Koivuluoto, H.; Lusvarghi, L.; Vuoristo, P.

    2016-04-01

    The microstructure and micromechanical behavior of thermally sprayed Fe-based coatings manufactured with high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes were investigated. Fe-Cr-Ni-Si-B-C and Fe-Cr-Ni-Mo-Si-B-C powders were used as the feedstock materials. The coatings showed a highly dense microstructure with near-zero oxidation. The microstructure of the feedstock powders was better retained when sprayed with HVAF process. Differential scanning calorimetry revealed two small exothermic peaks at about 600 °C for the HVOF-sprayed coatings, without any increase in weight in thermogravimetric analysis. It suggested the re-precipitation of carbides that were dissolved during spraying due to the higher particle temperature reported by spray diagnostics system during the HVOF process (≈1800 °C) compared to the HVAF one (≈1400 °C). Micro- and nano-indentations helped to show the difference in inter-lamellar cohesive strength and, in turn, in the particle deposition mechanism. Coatings sprayed with Fe-Cr-Ni-Mo-Si-B-C composition possessed higher sliding wear resistance than that of Fe-Cr-Ni-Si-B-C due to higher nano-hardness. More specifically, HVOF-sprayed Fe-Cr-Ni-Mo-Si-B-C coating showed the largest intra-lamellar hardness, the largest elasticity, and high quality of particle interfaces which resulted in lower sliding wear rate.

  9. Microstructure and Sliding Wear Behavior of Fe-Based Coatings Manufactured with HVOF and HVAF Thermal Spray Processes

    NASA Astrophysics Data System (ADS)

    Milanti, A.; Matikainen, V.; Bolelli, G.; Koivuluoto, H.; Lusvarghi, L.; Vuoristo, P.

    2016-06-01

    The microstructure and micromechanical behavior of thermally sprayed Fe-based coatings manufactured with high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes were investigated. Fe-Cr-Ni-Si-B-C and Fe-Cr-Ni-Mo-Si-B-C powders were used as the feedstock materials. The coatings showed a highly dense microstructure with near-zero oxidation. The microstructure of the feedstock powders was better retained when sprayed with HVAF process. Differential scanning calorimetry revealed two small exothermic peaks at about 600 °C for the HVOF-sprayed coatings, without any increase in weight in thermogravimetric analysis. It suggested the re-precipitation of carbides that were dissolved during spraying due to the higher particle temperature reported by spray diagnostics system during the HVOF process (≈1800 °C) compared to the HVAF one (≈1400 °C). Micro- and nano-indentations helped to show the difference in inter-lamellar cohesive strength and, in turn, in the particle deposition mechanism. Coatings sprayed with Fe-Cr-Ni-Mo-Si-B-C composition possessed higher sliding wear resistance than that of Fe-Cr-Ni-Si-B-C due to higher nano-hardness. More specifically, HVOF-sprayed Fe-Cr-Ni-Mo-Si-B-C coating showed the largest intra-lamellar hardness, the largest elasticity, and high quality of particle interfaces which resulted in lower sliding wear rate.

  10. Processing and properties of molybdenum silicide intermetallics containing boron

    SciTech Connect

    Schneibel, J.H.; Liu, C.T.; Heatherly, L. Jr.; Carmichael, C.A.

    1998-11-01

    The processing and mechanical properties of Mo-Si-B intermetallic alloys with compositions Mo-26.7Si-7.3B and Mo-12Si-8.5B (at.%) were investigated. The first alloy consisted of the phases Mo{sub 3}Si, Mo{sub 5}Si{sub 3} (T1) and Mo{sub 5}SiB{sub 2} (T2). Attempts to extrude castings of this alloy at 1700 or 1800 C were not successful. Hot isostatic pressing of elemental powders was more promising and room temperature flexure strengths on the order of 200 MPa were reached. The second alloy with the composition Mo-12Si-8.5B could be readily cast and consisted of {alpha}-Mo inclusion in a brittle matrix of Mo{sub 3}Si and T2. A heat treatment of 1 day at 1600C in vacuum improved the room temperature strength and fracture toughness. Values on the order of 500 MPa and 10 MPa m{sup 1/2}, respectively, were obtained. Consistent with ductile phase toughening, limited plastic deformation as well as debonding of the {alpha}-Mo inclusions were seen on fracture surfaces.

  11. In-situ identification of iron--zinc intermetallics in galvannealed steel coatings and iron oxides on exposed steel

    NASA Astrophysics Data System (ADS)

    Cook, Desmond C.

    1998-12-01

    Identification of all the compounds present in various coatings on steels is particularly difficult. Non-destructive, in-situ analysis is necessary if the fraction of each compound as well as its probable layering within the coating, is to be determined. Mössbauer spectroscopy is one valuable probe capable of uniquely identifying all iron compounds which form as coatings on steel and other iron alloy surfaces. To investigate a complete coating several criteria need to be considered. Removing the coating inevitably leaves a small and perhaps important component intact on the substrate. Therefore investigating the coating as it remains intact on the steel is important if complete identification of the iron compounds is to be made. This also preserves crystalline texture or preferred growth orientation within the coating to which the Mössbauer effect is sensitive. Mössbauer spectroscopy is a non-destructive technique which allows the integrity of the coating to be maintained during analysis. The combined transmission and scattering Mössbauer geometries generally result in accurate analysis of the coating composition. For the scattering geometry added information on compound layering is obtained if separate Mössbauer spectra are recorded using the re-emitted gamma rays as well as the conversion electrons and subsequently emitted X-rays. In-situ scattering Mössbauer spectroscopy has been used to characterize the iron--zinc alloys which form in the coatings of commercially produced corrosion resistant galvannealed sheet steel, a product of great interest to automotive producers. The results show that different amounts of four iron--zinc phases are present depending on the production conditions of the coating. The different phases are also distinctly layered. Mössbauer analyses of corrosion coatings formed on the surface of steels which have been exposed to different environments has also been undertaken. Materials include structural steels exposed for up to 25

  12. The structure and composition of chromate conversion coatings formed on aluminum-copper alloy AA2024-T3 and thin film analogs of constituent intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Vasquez, Marvin Jaime

    2002-01-01

    A comprehensive suite of spectroscopy have been used to study the composition and structure of Chromate Conversion Coatings (CCC) formed on Aluminum Copper (Al-Cu) alloy AA2024-T3 and constituent Intermetallic Compounds (IMCs). Based on previous work the CCC formed over the IMCs is expected to be thinner and therefore different in structure and composition than the CCC formed on the matrix. The formation of the CCC over the different IMCs is expected to be dependent on the chemistry and the interaction of the IMCs with accelerators such as ferricyanide. Surface chemical and structural data determined by X-ray Photoelectron Spectroscopy (XPS), Synchrotron Infrared Microspectroscopy, X-ray Absorption Near Edge Spectroscopy (XANES), Extended X-ray Absorption Fine Structure (EXAFS), Secondary Ion Mass Spectrometry (SIMS), and Secondary Electron Microscopy/Energy Dispersive Analysis of X-rays (SEM/EDAX) have been developed to refine an existing model for the CCC formed on the AA2024-T3 surface, an Al-Cu aircraft alloy, by considering the composition and structure of the CCC formed on constituent intermetallic compounds (IMCs). The limited corrosion behavior of AA2024-T3 aluminum alloy is generally attributed to the presence of a variety of constituent IMC. These IMC particles are of the order of 1--20 mum which makes their direct analysis exceedingly difficult and has lead to a limited understanding of their surface chemical properties relative to CCC formation. To overcome this limitation, it was necessary to develop for the first time large area samples composed of compositionally homogenous thin films of the various IMCs found on the AA2024-T3 surface, which were galvanically attached to thin films of Al-4.2wt%Cu (representative of the AA2024-T3 matrix). This was performed in a two-step process: Disks of IMC compositions were formed by Reactive Arc Melting (RAM), followed by ultra-fast laser ablation of the RAM IMCs resulting in the formation of homogenous thin films

  13. Al-21Ti-23Cr high-temperature protective coating on TiAl intermetallic compounds by RF magnetron sputtering

    SciTech Connect

    Park, J.Y.; Lee, H.N.; Wee, D.M.; Park, S.W.; Oh, M.H.

    1997-12-31

    Ti-48Al specimens were coated with Al-21Ti-23Cr film at 200 W, 0.8 Pa and 573 K by RF magnetron sputtering. The oxidation behavior of the coated specimens was investigated through isothermal and cyclic oxidation tests, and the tensile deformation properties of the coated specimens were also investigated before and after oxidation. The isothermal and cyclic oxidation curves showed that the Al-21Ti-23Cr film was very effective in decreasing the oxidation rate of Ti-48Al. This excellent oxidation resistance is attributable to the formation of a protective Al{sub 2}O{sub 3} layer on the surface of the Al-21Ti-23Cr film. It was found from the results of the tensile test that the protective Al{sub 2}O{sub 3} layer on the surface of the Al-21Ti-23Cr film enabled the Ti-48Al to maintain its tensile properties in an oxidizing environment.

  14. Intermetallic Compounds

    NASA Astrophysics Data System (ADS)

    Takagiwa, Y.; Matsuura, Y.; Kimura, K.

    2014-06-01

    We have focused on the binary narrow-bandgap intermetallic compounds FeGa3 and RuGa3 as thermoelectric materials. Their crystal structure is FeGa3-type (tetragonal, P42/ mnm) with 16 atoms per unit cell. Despite their simple crystal structure, their room temperature thermal conductivity is in the range 4-5-W-m-1-K-1. Both compounds have narrow-bandgaps of approximately 0.3-eV near the Fermi level. Because their Seebeck coefficients are quite large negative values in the range 350-<-| S 373K|-<-550- μV-K-1 for undoped samples, it should be possible to obtain highly efficient thermoelectric materials both by adjusting the carrier concentration and by reducing the thermal conductivity. Here, we report the effects of doping on the thermoelectric properties of FeGa3 and RuGa3 as n and p-type materials. The dimensionless figure of merit, ZT, was significantly improved by substitution of Sn for Ga in FeGa3 (electron-doping) and by substitution of Zn for Ga in RuGa3 (hole-doping), mainly as a result of optimization of the electronic part, S 2 σ.

  15. Reaction synthesis of intermetallics

    SciTech Connect

    Deevi, S.C.; Sikka, V.K.

    1994-12-31

    Exothermicity associated with the synthesis of aluminides was utilized to obtain nickel, iron, and cobalt aluminides. Combustion synthesis, extrusion, and hot pressing were utilized to obtain intermetallics and their composites. Extrusion conditions, reduction ratios, and hot-pressing conditions of the intermetallics and their composites are discussed.

  16. Magnesium silicide intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Li, Gh.; Gill, H. S.; Varin, R. A.

    1993-11-01

    Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

  17. Dislocation sources in ordered intermetallics

    SciTech Connect

    Yoo, M.H.; Appel, F.; Wagner, R.; Mecking, H.

    1996-09-01

    An overview on the current understanding of dislocation sources and multiplication mechanisms is made for ordered intermetallic alloys of the L1{sub 2}, B2, and D0{sub 19} structures. In L1{sub 2} alloys, a large disparity of edge/screw segments in their relative mobility reduces the efficiency of a Frank-Read Type multiplication mechanism. In Fe-40%Al of the B2 structure, a variety of dislocation sources are available for <111> slip, including ones resulting from condensation of thermal vacancies. In NiAl with the relatively high APB energy, <100> dislocations may result from the dislocation decomposition reactions, the prismatic punching out from inclusion particles, and/or steps and coated layers of the surface. Internal interfaces often provide sites for dislocation multiplication, e.g., grain boundaries, sub-boundaries in Ni{sub 3}Ga, NiAl and Ti{sub 3}Al, and antiphase domain boundaries in Ti{sub 3}Al. As for the crack tip as a dislocation source, extended SISFs trailed by super-Shockley partials emanating form the cracks in Ni{sub 3}Al and Co{sub 3}Ti are discussed in view of a possible toughening mechanism.

  18. Recent advances in ordered intermetallics

    SciTech Connect

    Liu, C.T.

    1992-12-31

    This paper briefly summarizes recent advances in intermetallic research and development. Ordered intermetallics based on aluminides and silicides possess attractive properties for structural applications at elevated temperatures in hostile environments; however, brittle fracture and poor fracture resistance limit their use as engineering materials in many cases. In recent years, considerable efforts have been devoted to the study of the brittle fracture behavior of intermetallic alloys; as a result, both intrinsic and extrinsic factors governing brittle fracture have been identified. Recent advances in first-principles calculations and atomistic simulations further help us in understanding atomic bonding, dislocation configuration, and alloying effects in intermetallics. The basic understanding has led to the development of nickel, iron, and titanium aluminide alloys with improved mechanical and metallurgical properties for structural use. Industrial interest in ductile intermetallic alloys is high, and several examples of industrial involvement are mentioned.

  19. Recent advances in ordered intermetallics

    SciTech Connect

    Liu, C.T.

    1994-12-31

    Ordered intermetallic alloys based on aluminides and silicides offer many advantages for structural use at high temperatures in hostile environments. Attractive properties include excellent oxidation and corrosion resistance, light weight, and superior strength at high temperatures. The major concern for structural use of intermetallics was their low ductility and poor fracture resistance at ambient temperatures. For the past 10 years, considerable effort was devoted to R&D of ordered intermetallic alloys, and progress has been made on understanding intrinsic and extrinsic factors controlling brittle fracture in intermetallic alloys based on aluminides and silicides. Parallel effort on alloy design has led to the development of a number of ductile and strong intermetallic alloys based on Ni{sub 3}Al, NiAl, Fe{sub 3}Al, FeAl, Ti{sub 3}Al, and TiAl systems for structural applications.

  20. High temperature intermetallic binders for HVOF carbides

    SciTech Connect

    Shaw, K.G.; Gruninger, M.F.; Jarosinski, W.J.

    1994-12-31

    Gas turbines technology has a long history of employing the desirable high temperature physical attributes of ceramic-metallic (cermet) materials. The most commonly used coatings incorporate combinations of WC-Co and Cr{sub 3}C{sub 2}-NiCr, which have also been successfully utilized in other non-turbine coating applications. Increased turbine operating temperatures and other high temperature service conditions have made apparent the attractive notion of increasing the temperature capability and corrosion resistance of these coatings. In this study the intermetallic binder NiAl has been used to replace the cobalt and NiCr constituents of conventional WC and Cr{sub 3}C{sub 2} cermet powders. The composite carbide thermal spray powders were fabricated for use in the HVOF coating process. The structure of HVOF deposited NiAl-carbide coatings are compared directly to the more familiar WC-Co and Cr{sub 3}C{sub 2}-NiCr coatings using X-ray diffraction, back-scattered electron imaging (BEI) and electron dispersive spectroscopy (EDS). Hardness variations with temperature are reported and compared between the NiAl and Co/NiCr binders.

  1. Microstructure and Properties of HVOF-Sprayed Ni-50Cr Coatings

    SciTech Connect

    Joel A. Simpson; Terry C. Totemeier; Richard N. Wright

    2006-06-01

    Thermal spray coatings represent a potential cost-effective means of protecting structural components in advanced fossil energy systems. Previous work at the INL has focused on relationships between thermal spray processing conditions, structure, and properties in alumina- and silica-forming coatings, namely Fe3Al, FeAl, and Mo-Si-B alloys. This paper describes the preparation and characterization of chromia-forming Ni-50%Cr coatings, an alloy similar to the INCOCLAD 671 cladding, which has shown excellent performance in the Niles Plant service tests. The structure and properties of Ni-50Cr coatings are similar to other HVOF-sprayed metallic coatings: a typical lamellar microstructure is observed with essentially no porosity and little oxide. The microhardness and compressive residual stress both increase with increased spray particle velocity. Corrosion tests were performed on a variety of free-standing coatings (removed from the substrate, wrought Fe3Al alloy, and Grade 91 steel in a simulated coal combustion gas (N2-10%CO-5%CO2-2%H2O-0.12%H2S) and gas-slag environments (same gas, with iron sulfide powder in contact with the coating surface). The coatings tested included Fe3Al, FeAl, and Ni-50Cr alloys sprayed at different velocities. In these tests the iron aluminides in wrought and coating form showed the best performance, with Ni-50Cr coatings slightly worse; the Grade 91 steel was severely attacked.

  2. Intermetallic Layers in Soldered Joints

    Energy Science and Technology Software Center (ESTSC)

    1998-12-10

    ILAG solves the one-dimensional partial differential equations describing the multiphase, multicomponent, solid-state diffusion-controlled growth of intermetallic layers in soldered joints. This software provides an analysis capability for materials researchers to examine intermetallic growth mechanisms in a wide variety of defense and commercial applications involving both traditional and advanced materials. ILAG calculates the interface positions of the layers, as well as the spatial distribution of constituent mass fractions, and outputs the results at user-prescribed simulation times.

  3. Property evaluation of thermal sprayed metallic coating by acoustic emission analysis

    SciTech Connect

    Ishida, Asako; Mizutani, Yoshihiro; Takemoto, Mikio; Ono, Kanji

    2000-03-01

    The authors analyzed acoustic emission signals from plasma sprayed sheets by first obtaining the Young's modulus, Poisson's ratio, and density. The sheets of a high Cr-Ni alloy (55Cr-41Ni-Mo, Si, B) were made by low pressure plasma spraying (LPPS) and heat treated. Utilizing laser induced surface acoustic waves (SAWs), the group velocity dispersion data of Rayleigh waves was obtained and matched to that computed by Adler's matrix transfer method. They monitored the acoustic emissions (Lamb waves) produced by microfractures in free standing as sprayed coating subjected to bending. Fast cleavage type microfracture with source rise time of around 2 {micro}s occurred as precursors to the final brittle fracture. The velocity and time-frequency amplitude spectrograms (wavelet contour maps) of the Lamb waves were utilized for the source location and fracture kinetic analyses.

  4. Intermetallics for structural applications

    SciTech Connect

    Sikka, V.K.; Deevi, S.C.

    1995-09-01

    Intermetallics are introduced as possible structural materials. The attributes and useful temperature limits of eight of the most likely candidates have been described. In addition, detailed descriptions are given for chemical compositions, corrosion properties, mechanical properties, melting and processing, and applications of Ni{sub 3}Al and Fe{sub 3}Al-based alloys. Mechanical properties of Ni{sub 3}Al-based alloys are compared with commercially used HU alloys in the cast condition and Haynes 214 in the wrought condition. The mechanical properties of Fe{sub 3}Al-based alloys are compared with an oxide-dispersion-strengthened (ODS) Inco alloy MA-956. Comparisons have shown that Ni{sub 3}Al-based alloys offer the best combination of oxidation and carburization resistance and are significantly stronger than the commercially used HU alloy for many of the furnace-fixture applications. However, the Fe{sub 3}Al-based alloys, which offer the best sulfidation resistance of the commercially available alloys, are significantly weaker in creep than the ODS MA-956 alloy. Even with the current strength level, Fe{sub 3}Al-based alloys are superior as porous, sintered metal filters for hot-gas cleanup in coal gasification systems. Oxide-dispersion strengthening of the Fe{sub 3}Al-based alloys is currently under way to improve their creep strength.

  5. Coatings.

    ERIC Educational Resources Information Center

    Anderson, Dennis G.

    1989-01-01

    This review covers analytical techniques applicable to the examination of coatings, raw materials, and substrates upon which coatings are placed. Techniques include chemical and electrochemical methods, chromatography, spectroscopy, thermal analysis, microscopy, and miscellaneous techniques. (MVL)

  6. Third Intermetallic Matrix Composites Symposium, volume 350

    SciTech Connect

    Graves, J.A.; Bowman, R.R.; Lewandowski, J.J.

    1994-04-01

    Partial contents include: issues in potential IMC application for aerospace structures; powder metallurgy processing of intermetallic matrix composites; microstructure and properties of intermetallic matrix composites produced by reaction synthesis; combustion synthesis of niobium aluminide matrix composites; ambient temperature synthesis of bulk intermetallics; wear behavior of SHS intermetallic matrix composites; fracture characteristics of metal-intermetallic laminates produced by SHS reactions; and vapor phase synthesis of Ti aluminides and the interfacial bonding effect on the mechanical property of micro-composites reinforced by pyrolized SiC fibers.

  7. Low-Temperature Synthesis Routes to Intermetallic Superconductors

    SciTech Connect

    Schaak, Raymond E

    2008-01-08

    of many of the products, the superconductors and their nanocrystalline precursors are potentially amenable to inexpensive and large-scale solution-based processing into wires, coatings, films, and templated or patterned structures with nanoscale and microscale features. Also, because of the new synthetic variables that play a key role in the low-temperature formation of intermetallics, the possibility exists to discover new superconductors.

  8. Microstructure of a plasma-sprayed Mo-Si-B alloy

    NASA Astrophysics Data System (ADS)

    Kramer, M. J.; Okumus, S. C.; Besser, M. F.; Ünal, Ö.; Akinc, M.

    2000-03-01

    Powders of Mo52Si38B10 were plasma sprayed under inert conditions onto stainless steel substrates to determine if high density free standing forms could be synthesized by this process. Thermal spray conditions were varied to minimize porosity and oxygen impurities while minimizing evaporative metal losses. The assprayed and sintered microstructures were characterized using scanning and transmission electron microscopy and quantitative x-ray diffraction (XRD). The as-sprayed microstructure consisted of elongated splats tens of microns in length and only one to three microns in thickness. The splats contained submicrometer grains of primarily MoB and Mo5Si3B x (T1) and minor amounts of MoSi2 and a glassy grain boundary phase. The interior of the splats typically consisted of a fine eutectic of MoB and T1. Small pieces were cut out of the cross section of the sample and pressureless sintered for 2, 6, and 10 h at 1800 °C in flowing Ar. After sintering for 2 h at 1800 °C, the samples exhibited a coarser but equiaxed microstructure (1 to 5 µm grain size) containing 78 vol.% T1, 16 vol.% MoB, and 6 vol.% MoSi2 as determined by XRD. Approximately 8 at.% of the Si formed silica. The high-temperature anneal removed all vestiges of the layered structure observed in the as-sprayed samples.

  9. Phase Stability and Deformation Behavior of Mo-Si-B System and effect of alloying

    NASA Astrophysics Data System (ADS)

    Kontsevoi, Oleg Y.; Freeman, Arthur J.

    2012-02-01

    Molybdenum silicides are promising materials for ultra-high temperature applications above 1300 C. One of the main drawbacks is their brittleness at low temperatures, which may be improved by additions. We employ first principles calculations with the highly precise FLAPW method to investigate the effect of alloying with 3d, 4d and 5d transition metals on phase stability, cleavage and shear characteristics of the 3-component system Mo -- Mo3Si -- Mo5SiB2. We determined site preference, phase partitioning of alloying elements, and their effect on shear behavior and preferred deformation modes. We show that in Mo3Si alloying with 3d transition metals results in a significant reduction of energy barriers to shear deformation (softening effect), while 4d and 5d additions increase shear barriers (hardening effect). In Mo5SiB2, 3d transition metals (except for Ti) act as weak softeners, while 4d and 5d show mixed behavior -- hardening for early elements and softening for late ones. The softening potency of additions increases with atomic number, but exhibits non-monotonic behavior as a result of a competition between size and electronic effects. The results are discussed in conjunction with possible pathways to ductility enhancement through alloying.

  10. Fracture and fatigue resistance of Mo-Si-B alloys for ultrahigh-temperature structural applications

    SciTech Connect

    Kruzic, J.J.; Schneibel, J.H.; Ritchie, R.O.

    2003-08-29

    Fracture and fatigue-crack growth properties are examined for a series of Mo-Mo3Si-Mo5SiB2 containing alloys, which utilize a continuous a-Mo matrix to achieve unprecedented room-temperature fracture resistance (>20 MPaAm). Mechanistically, these properties are explained in terms of toughening by crack trapping and crack bridging by the more ductile a-Mo phase.

  11. Intermetallic-Based High-Temperature Materials

    SciTech Connect

    Sikka, V.K.

    1999-04-25

    The intermetallic-based alloys for high-temperature applications are introduced. General characteristics of intermetallics are followed by identification of nickel and iron aluminides as the most practical alloys for commercial applications. An overview of the alloy compositions, melting processes, and mechanical properties for nickel and iron aluminizes are presented. The current applications and commercial producers of nickel and iron aluminizes are given. A brief description of the future prospects of intermetallic-based alloys is also given.

  12. Method for making devices having intermetallic structures and intermetallic devices made thereby

    DOEpatents

    Paul, Brian Kevin; Wilson, Richard Dean; Alman, David Eli

    2004-01-06

    A method and system for making a monolithic intermetallic structure are presented. The structure is made from lamina blanks which comprise multiple layers of metals which are patternable, or intermetallic lamina blanks that are patternable. Lamina blanks are patterned, stacked and registered, and processed to form a monolithic intermetallic structure. The advantages of a patterned monolithic intermetallic structure include physical characteristics such as melting temperature, thermal conductivity, and corrosion resistance. Applications are broad, and include among others, use as a microreactor, heat recycling device, and apparatus for producing superheated steam. Monolithic intermetallic structures may contain one or more catalysts within the internal features.

  13. Suppressors made from intermetallic materials

    DOEpatents

    Klett, James W; Muth, Thomas R; Cler, Dan L

    2014-11-04

    Disclosed are several examples of apparatuses for suppressing the blast and flash produced as a projectile is expelled by gases from a firearm. In some examples, gases are diverted away from the central chamber to an expansion chamber by baffles. The gases are absorbed by the expansion chamber and desorbed slowly, thus decreasing pressure and increasing residence time of the gases. In other examples, the gases impinge against a plurality of rods before expanding through passages between the rods to decrease the pressure and increase the residence time of the gases. These and other exemplary suppressors are made from an intermetallic material composition for enhanced strength and oxidation resistance at high operational temperatures.

  14. Microstructure and wear behavior of γ/Al 4C 3/TiC/CaF 2 composite coating on γ-TiAl intermetallic alloy prepared by Nd:YAG laser cladding

    NASA Astrophysics Data System (ADS)

    Liu, Xiu-Bo; Shi, Shi-Hong; Guo, Jian; Fu, Ge-Yan; Wang, Ming-Di

    2009-03-01

    As a further step in obtaining high performance elevated temperature self-lubrication anti-wear composite coatings on TiAl alloy, a novel Ni-P electroless plating method was adopted to encapsulate the as-received CaF 2 in the preparation of precursor NiCr-Cr 3C 2-CaF 2 mixed powders with an aim to decrease its mass loss and increase its compatibility with the metal matrix during a Nd:YAG laser cladding. The microstructure of the coating was examined using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) and the friction and wear behavior of the composite coatings sliding against the hardened 0.45% C steel ring was evaluated using a block-on-ring wear tester at room temperature. It was found that the coating had a unique microstructure consisting of primary dendrites TiC and block Al 4C 3 carbides reinforcement as well as fine isolated spherical CaF 2 solid lubrication particles uniformly dispersed in the NiCrAlTi ( γ) matrix. The good friction-reducing and anti-wear abilities of the laser clad composite coating was suggested to the Ni-P electroless plating and the attendant reduction of mass loss of CaF 2 and the increasing of it's wettability with the NiCrAlTi ( γ) matrix during the laser cladding process.

  15. Structure Defect Property Relationships in Binary Intermetallics

    NASA Astrophysics Data System (ADS)

    Medasani, Bharat; Ding, Hong; Chen, Wei; Persson, Kristin; Canning, Andrew; Haranczyk, Maciej; Asta, Mark

    2015-03-01

    Ordered intermetallics are light weight materials with technologically useful high temperature properties such as creep resistance. Knowledge of constitutional and thermal defects is required to understand these properties. Vacancies and antisites are the dominant defects in the intermetallics and their concentrations and formation enthalpies could be computed by using first principles density functional theory and thermodynamic formalisms such as dilute solution method. Previously many properties of the intermetallics such as melting temperatures and formation enthalpies were statistically analyzed for large number of intermetallics using structure maps and data mining approaches. We undertook a similar exercise to establish the dependence of the defect properties in binary intermetallics on the underlying structural and chemical composition. For more than 200 binary intermetallics comprising of AB, AB2 and AB3 structures, we computed the concentrations and formation enthalpies of vacancies and antisites in a small range of stoichiometries deviating from ideal stoichiometry. The calculated defect properties were datamined to gain predictive capabilities of defect properties as well as to classify the intermetallics for their suitability in high-T applications. Supported by the US DOE under Contract No. DEAC02-05CH11231 under the Materials Project Center grant (Award No. EDCBEE).

  16. Environmental Effects in Advanced Intermetallics

    SciTech Connect

    Liu, C.T.

    1998-11-24

    This paper provides a comprehensive review of environmental embrittlement in iron and nickel aluminizes. The embrittlement involves the interaction of these intermetallics with moisture in air and generation of atomic hydrogen, resulting in hydrogen-induced embrittlement at ambient temperatures. Environmental embrittlement promotes brittle grain-boundary fracture in Ni{sub 3}Al alloys but brittle cleavage fracture in Fe{sub 3}Al-FeAl alloys. The embrittlement strongly depends on strain rate, with tensile-ductility increase with increasing strain rate. It has been demonstrated that environmental embrittlement can be alleviated by alloying additions, surface modifications, and control of grain size and shape. Boron tends to segregate strongly to grain boundaries and is most effective in suppressing environmental embrittlement in Ni{sub 3}Al alloys. The mechanistic understanding of alloy effects and environmental embrittlement has led to the development of nickel and iron aluminide alloys with improved properties for structural use at elevated temperatures in hostile environments.

  17. Method of making sintered ductile intermetallic-bonded ceramic composites

    DOEpatents

    Plucknett, Kevin; Tiegs, Terry N.; Becher, Paul F.

    1999-01-01

    A method of making an intermetallic-bonded ceramic composite involves combining a particulate brittle intermetallic precursor with a particulate reactant metal and a particulate ceramic to form a mixture and heating the mixture in a non-oxidizing atmosphere at a sufficient temperature and for a sufficient time to react the brittle intermetallic precursor and the reactant metal to form a ductile intermetallic and sinter the mixture to form a ductile intermetallic-bonded ceramic composite.

  18. Method of making sintered ductile intermetallic-bonded ceramic composites

    DOEpatents

    Plucknett, K.; Tiegs, T.N.; Becher, P.F.

    1999-05-18

    A method of making an intermetallic-bonded ceramic composite involves combining a particulate brittle intermetallic precursor with a particulate reactant metal and a particulate ceramic to form a mixture and heating the mixture in a non-oxidizing atmosphere at a sufficient temperature and for a sufficient time to react the brittle intermetallic precursor and the reactant metal to form a ductile intermetallic and sinter the mixture to form a ductile intermetallic-bonded ceramic composite. 2 figs.

  19. New twisted intermetallic compound superconductor: A concept

    NASA Technical Reports Server (NTRS)

    Coles, W. D.; Brown, G. V.; Laurence, J. C.

    1972-01-01

    Method for processing Nb3Sn and other intermetallic compound superconductors produces a twisted, stabilized wire or tube which can be used to wind electromagnetics, armatures, rotors, and field windings for motors and generators as well as other magnetic devices.

  20. SURFACE MODIFICATION OF ZIRCALOY-4 SUBSTRATES WITH NICKEL ZIRCONIUM INTERMETALLICS

    SciTech Connect

    Luscher, Walter G.; Gilbert, Edgar R.; Pitman, Stan G.; Love, Edward F.

    2013-02-01

    Surfaces of Zircaloy-4 (Zr-4) substrates were modified with nickel-zirconium (NiZr) intermetallics to tailor oxidation performance for specialized applications. Surface modification was achieved by electroplating Zr-4 substrates with nickel (Ni) and then performing thermal treatments to fully react the Ni plating with the substrates, which resulted in a coating of NiZr intermetallics on the substrate surfaces. Both plating thickness and thermal treatment were evaluated to determine the effects of these fabrication parameters on oxidation performance and to identify an optimal surface modification process. Isothermal oxidation tests were performed on surface-modified materials at 290°, 330°, and 370°C under a constant partial pressure of oxidant (i.e., 1 kPa D2O in dry Ar at 101 kPa) for 64 days. Test results revealed an enhanced, transient oxidation rate that decreased asymptotically toward the rate of the Zr-4 substrate. Oxidation kinetics were analyzed from isothermal weight gain data, which were correlated with microstructure, hydrogen pickup, strength, and hardness.

  1. Advanced ordered intermetallic alloy deployment

    SciTech Connect

    Liu, C.T.; Maziasz, P.J.; Easton, D.S.

    1997-04-01

    The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositions and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.

  2. Overview of the development of FeAl intermetallic alloys

    SciTech Connect

    Maziasz, P.J.; Liu, C.T.; Goodwin, G.M.

    1995-09-01

    B2-phase FeAl ordered intermetallic alloys based on an Fe-36 at.% Al composition are being developed to optimize a combination of properties that includes high-temperature strength, room-temperature ductility, and weldability. Microalloying with boron and proper processing are very important for FeAl properties optimization. These alloys also have the good to outstanding resistance to oxidation, sulfidation, and corrosion in molten salts or chlorides at elevated temperatures, characteristic of FeAl with 30--40 at.% Al. Ingot- and powder-metallurgy (IM and PM, respectively) processing both produce good properties, including strength above 400 MPa up to about 750 C. Technology development to produce FeAl components for industry testing is in progress. In parallel, weld-overlay cladding and powder coating technologies are also being developed to take immediate advantage of the high-temperature corrosion/oxidation and erosion/wear resistance of FeAl.

  3. Chemical effect on diffusion in intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Ting

    With the trend of big data and the Internet of things, we live in a world full of personal electronic devices and small electronic devices. In order to make the devices more powerful, advanced electronic packaging such as wafer level packaging or 3D IC packaging play an important role. Furthermore, ?-bumps, which connect silicon dies together with dimension less than 10 ?m, are crucial parts in advanced packaging. Owing to the dimension of ?-bumps, they transform into intermetallic compound from tin based solder after the liquid state bonding process. Moreover, many new reliability issues will occur in electronic packaging when the bonding materials change; in this case, we no longer have tin based solder joint, instead, we have intermetallic compound ?-bumps. Most of the potential reliability issues in intermetallic compounds are caused by the chemical reactions driven by atomic diffusion in the material; thus, to know the diffusivities of atoms inside a material is significant and can help us to further analyze the reliability issues. However, we are lacking these kinds of data in intermetallic compound because there are some problems if used traditional Darken's analysis. Therefore, we considered Wagner diffusivity in our system to solve the problems and applied the concept of chemical effect on diffusion by taking the advantage that large amount of energy will release when compounds formed. Moreover, by inventing the holes markers made by Focus ion beam (FIB), we can conduct the diffusion experiment and obtain the tracer diffusivities of atoms inside the intermetallic compound. We applied the technique on Ni3Sn4 and Cu3Sn, which are two of the most common materials in electronic packaging, and the tracer diffusivities are measured under several different temperatures; moreover, microstructure of the intermetallic compounds are investigated to ensure the diffusion environment. Additionally, the detail diffusion mechanism was also discussed in aspect of diffusion

  4. Growth behavior and corrosion resistance of 5% Al-Zn coating

    SciTech Connect

    Lin, K.L.; Ho, J.K.; Lee, J.T. . Dept. of Materials Engineering)

    1993-09-01

    Effects of reaction time and temperature on growth behavior and corrosion performance of batch type 5% aluminum-zinc (Al-Zn) coating were investigated. A fast growth in coating thickness and intermetallic layer occurred within temperatures of 480 C. to 520 C. The coatings grew to a maximum thickness after 520 C. Corrosion performance was enhanced greatly by formation of an intermetallic layer. The best performance was produced at 500 C.

  5. Reduced workfunction intermetallic seed layers allow growth of porous n-GaN and low resistivity, ohmic electron transport.

    PubMed

    Bilousov, Oleksandr V; Carvajal, Joan J; Drouin, Dominique; Mateos, Xavier; Díaz, Francesc; Aguiló, Magdalena; O'Dwyer, Colm

    2012-12-01

    Porous GaN crystals have been successfully grown and electrically contacted simultaneously on Pt- and Au-coated silicon substrates as porous crystals and as porous layers. By the direct reaction of metallic Ga and NH(3) gas through chemical vapor deposition, intermetallic metal-Ga alloys form at the GaN-metal interface, allowing vapor-solid-solid seeding and subsequent growth of porous GaN. Current-voltage and capacitance-voltage measurements confirm that the intermetallic seed layers prevent interface oxidation and give a high-quality reduced workfunction contact that allows exceptionally low contact resistivities. Additionally, the simultaneous formation of a lower workfunction intermetallic permits ohmic electron transport to n-type GaN grown using high workfunction metals that best catalyze the formation of porous GaN layers and may be employed to seed and ohmically contact a range of III-N compounds and alloys for broadband absorption and emission. PMID:23167596

  6. Surfaces of Intermetallics: Quasicrystals and Beyond

    SciTech Connect

    Yuen, Chad

    2012-01-01

    The goal of this work is to characterize surfaces of intermetallics, including quasicrystals. In this work, surface characterization is primarily focused on composition and structure using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) performed under ultrahigh vacuum (UHV) conditions.

  7. High-temperature ordered intermetallic alloys VII

    SciTech Connect

    Koch, C.C.; Liu, C.T.; Stoloff, N.S.; Wanner, A.

    1997-12-31

    This volume is divided into the following sections: (1) processing; (2) titanium aluminides; (3) creep and fatigue of titanium aluminides; (4) iron aluminides; (5) nickel aluminides; (6) refractory metal-based and other intermetallics; and (7) composites. Separate abstracts were prepared for most papers in this volume.

  8. Synthesis, Characterization and Properties of Nanoparticles of Intermetallic Compounds

    SciTech Connect

    DiSalvo, Francis J.

    2015-03-12

    The research program from 2010 to the end of the grant focused on understanding the factors important to the synthesis of single phase intermetallic nano-particles (NPs), their size, crystalline order, surface properties and electrochemical activity. The synthetic method developed is a co-reduction of mixtures of single metal precursors by strong, soluble reducing agents in a non-protic solvent, tetrahydrofuran (THF). With some exceptions, the particles obtained by room temperature reduction are random alloys that need to be annealed at modest temperatures (200 to 600 °C) in order to develop an ordered structure. To avoid significant particle size growth and agglomeration, the particles must be protected by surface coatings. We developed a novel method of coating the metal nanoparticles with KCl, a by-product of the reduction reaction if the proper reducing agents are employed. In that case, a composite product containing individual metal nanoparticles in a KCl matrix is obtained. The composite can be heated to at least 600 °C without significant agglomeration or growth in particle size. Washing the annealed product in the presence of catalyst supports in ethylene glycol removes the KCl and deposits the particles on the support. Six publications present the method and its application to producing and studying new catalyst/support combinations for fuel cell applications. Three publications concern the use of related methods to explore new lithium-sulfur battery concepts.

  9. Forging of FeAl intermetallic compounds

    SciTech Connect

    Flores, O.; Juarez, J.; Campillo, B.; Martinez, L.; Schneibel, J.H.

    1994-09-01

    Much activity has been concentrated on the development of intermetallic compounds with the aim of improving tensile ductility, fracture toughness and high notch sensitivity in order to develop an attractive combination of properties for high and low temperature applications. This paper reports experience in processing and forging of FeAl intermetallic of B2 type. During the experiments two different temperatures were employed, and the specimens were forged after annealing in air, 10{sup {minus}2} torr vacuum and argon. From the results it was learned that annealing FeAl in argon atmosphere prior to forging resulted in better deformation behavior than for the other two environments. For the higher forging temperature used in the experiments (700C), the as-cast microstructure becomes partially recrystallized.

  10. Plasma spray forming metals, intermetallics, and composites

    NASA Astrophysics Data System (ADS)

    Sampath, Sanjay; Herman, Herbert

    1993-07-01

    Plasma spray processing is a droplet deposition method that combines the steps of melting, rapid solidification, and consolidation into a single step. The versatility of the technology enables the processing of freestanding bulk, near-net shapes of a wide range of alloys, intermetallics, ceramics, and composites, while still retaining the benefits of rapid solidification processing. In particular, it is possible to produce dense forms through vacuum plasma spraying.

  11. Oxygen stabilized zirconium vanadium intermetallic compound

    DOEpatents

    Mendelsohn, Marshall H.; Gruen, Dieter M.

    1982-01-01

    An oxygen stabilized intermetallic compound having the formula Zr.sub.x OV.sub.y where x=0.7 to 2.0 and y=0.18 to 0.33. The compound is capable of reversibly sorbing hydrogen at temperatures from -196.degree. C. to 450.degree. C. at pressures down to 10.sup.-6 Torr. The compound is also capable of selectively sorbing hydrogen from gaseous mixtures in the presence of CO and CO.sub.2.

  12. Arc Casting Intermetallic Alloy (Materials Preparation Center)

    SciTech Connect

    2010-01-01

    Arc casting of intermetallic (La-Ni-Sn) AB5 alloy used for metal hydride hydrogen storage. Upon solidification the Sn is partially rejected and increases in concentration in the remaining liquid. Upon completing solidification there is a great deal of internal stress in the ingot. As the ingot cools further the stress is relieved. This material was cast at the Ames Laboratorys Materials Preparation Center http://www.mpc.ameslab.gov

  13. Brushing up on the history of intermetallics in dentistry

    NASA Astrophysics Data System (ADS)

    Waterstrat, Richard M.

    1990-03-01

    Employing a silver-tin-mercury intermetallic to repair cavities may seem a little unusual, but intermetallics are quite common in dentistry, ranging from gold crowns to braces. Although the human mouth can be unfriendly territory for a brittle intermetallic alloy, dental amalgam has been around since 659 A.D., and its technology has been developed to the point where a filling can be expected to last 30 years or more.

  14. SYNTHESIS AND CHARACTERIZATION OF NEW INTERMETALLIC COMPOUNDS

    SciTech Connect

    Professor Monica Sorescu

    2003-05-07

    This six-month work is focused mainly on the properties of novel magnetic intermetallics. In the first project, we synthesized several 2:17 intermetallic compounds, namely Nd{sub 2}Fe{sub 15}Si{sub 2}, Nd{sub 2}Fe{sub 15}Al{sub 2}2, Nd{sub 2}Fe{sub 15}SiAl and Nd{sub 2}Fe{sub 15}SiMn, as well as several 1:12 intermetallic compounds, such as NdFe{sub 10}Si{sub 2}, NdFe{sub 10}Al{sub 2}, NdFe{sub 10}SiAl and NdFe{sub 10}MnAl. In the second project, seven compositions of Nd{sub x}Fe{sub 100-x-y}B{sub y} ribbons were prepared by a melt spinning method with Nd and B content increasing from 7.3 and 3.6 to 11 and 6, respectively. The alloys were annealed under optimized conditions to obtain a composite material consisting of the hard magnetic Nd{sub 2}Fe{sub 14}B and soft magnetic {alpha}-Fe phases, typical of a spring magnet structure. In the third project, intermetallic compounds of the type Zr{sub 1}Cr{sub 1}Fe{sub 1}T{sub 0.8} with T=Al, Co and Fe were subjected to hydrogenation. In the fourth project, we performed three crucial experiments. In the first experiment, we subjected a mixture of Fe{sub 3}O{sub 4} and Fe(80-20 wt%) to mechanochemical activation by high-energy ball milling, for time periods ranging from 0.5 to 14 hours. In the second experiment, we ball-milled Fe{sub 3}O{sub 4}:Co{sup 2+} (x=0.1) for time intervals between 2.5 and 17.5 hours. Finally, we exposed a mixture of Fe{sub 3}O{sub 4} and Co(80-20 wt%) to mechanochemical activation for time periods ranging from 0.5 to 10 hours. In all cases, the structural and magnetic properties of the systems involved were elucidated by X-ray diffraction (XRD), Moessbauer spectroscopy and hysteresis loop measurements. The four projects resulted in four papers, which are currently being considered for publication in Intermetallics, IEEE Transactions on Magnetics, Journal of Materials Science Letters and Journal of Materials Science. The contributions reveal for the first time in literature the effect of

  15. Identification and Characterization of the Iron - Intermetallics Formed in Galvanneal Steel.

    NASA Astrophysics Data System (ADS)

    Grant, Richard Frederick George

    1995-01-01

    electrons which are emitted from the galvanneal coatings following the resonant absorption of a gamma -ray. The detector probes the full coating depth allowing the complete coating composition to be determined. Finally, the database of the crystallographic and hyperfine parameters of the iron-zinc intermetallics along with the new detector were used to study several commercially produced galvanneal coatings. The detailed analysis of the coatings has enabled the positive identification of the phases as layers within the coatings. Phase fractions and relative iron concentrations were determined for each coating. Furthermore, the Mossbauer spectral areas showed a linear correlation with the weight of iron in the coatings. Lastly, the effect of aluminum impurity in the galvanneal bath on phase formation was investigated.

  16. Nonstoichiometry of Al-Zr intermetallic phases

    SciTech Connect

    Radmilovic, V.; Thomas, G.

    1994-06-01

    Nonstoichiometry of metastable cubic {beta}{prime} and equilibrium tetragonal {beta} Al-Zr intermetallic phases of the nominal composition Al{sub 3}Zr in Al-rich alloys has been extensively studied. It is proposed that the ``dark contrast`` of {beta}{prime} core in {beta}{prime}/{sigma}{prime} complex precipitates, in Al-Li-Zr based alloys, is caused by incorporation of Al and Li atoms into the {beta}{prime} phase on Zr sublattice sites, forming nonstoichiometric Al-Zr intermetallic phases, rather than by Li partitioning only. {beta}{prime} particles contain very small amounts of Zr, approximately 5 at.%, much less than the stoichiometric 25 at.% in the Al{sub 3}Zr metastable phase. These particles are, according to simulation of high resolution images, of the Al{sub 3}(Al{sub 0.4}Li{sub 0.4}Zr{sub 0.2}) type. Nonstoichiometric particles of average composition Al{sub 4}Zr and Al{sub 6}Zr are observed also in the binary Al-Zr alloy, even after annealing for several hours at 600{degree}C.

  17. Oxidation of high-temperature intermetallics; Proceedings of the Workshop, Cleveland, OH, Sept. 22, 23, 1988

    NASA Technical Reports Server (NTRS)

    Grobstein, Toni (Editor); Doychak, Joseph (Editor)

    1989-01-01

    The present conference on the high-temperature oxidation behavior of aerospace structures-applicable intermetallic compounds discusses the influence of reactive-element additions on the oxidation of Ni3Al base alloys, the effect of Ni3Al oxidation below 850 C on fracture behavior, the oxidation of FeAl + Hf, Zr, and B, the synergistic effect of Al and Si on the oxidation resistance of Fe alloys, and pack cementation coatings of Cr-Al on Fe, Ni, and Co alloys. Also discussed are the formation of alumina on Nb- and Ti-base alloys, the oxidation behavior of titanium aluminide alloys, silicide coatings for refractory metals, the oxidation of chromium disilicide, and the oxidation behavior of nickel beryllides.

  18. Abrasion Resistant Coating and Method of making the same

    SciTech Connect

    Sordelet, Daniel J.; Besser, Matthew F.

    1999-06-25

    An abrasion resistant coating is created by adding a ductile phase to a brittle matrix phase during spray coating where an Al-Cu-Fe quasicrystalline phase (brittle matrix) and an FeAl intermetallic (ductile phase) are combined. This composite coating produces a coating mostly of quasicrystal phase and an inter-splat layer of the FeAl phase to help reduce porosity and cracking within the coating. Coatings are prepared by plasma spraying unblended and blended quasicrystal and intermetallic powders. The blended powders contain 1, 5, 10 and 20 volume percent of the intermetallic powders. The unblended powders are either 100 volume percent quasicrystalline or 100 volume percent intermetallic; these unblended powders were studied for comparison to the others. Sufficient ductile phase should be added to the brittle matrix to transform abrasive wear mode from brittle fracture to plastic deformation, while at the same time the hardness of the composite should not be reduced below that of the original brittle phase material.

  19. Abrasion resistant coating and method of making the same

    DOEpatents

    Sordelet, Daniel J.; Besser, Matthew F.

    2001-06-05

    An abrasion resistant coating is created by adding a ductile phase to a brittle matrix phase during spray coating where an Al--Cu--Fe quasicrystalline phase (brittle matrix) and an FeAl intermetallic (ductile phase) are combined. This composite coating produces a coating mostly of quasicrystal phase and an inter-splat layer of the FeAl phase to help reduce porosity and cracking within the coating. Coatings are prepared by plasma spraying unblended and blended quasicrystal and intermetallic powders. The blended powders contain 1, 5, 10 and 20 volume percent of the intermetallic powders. The unblended powders are either 100 volume percent quasicrystalline or 100 volume percent intermetallic; these unblended powders were studied for comparison to the others. Sufficient ductile phase should be added to the brittle matrix to transform abrasive wear mode from brittle fracture to plastic deformation, while at the same time the hardness of the composite should not be reduced below that of the original brittle phase material.

  20. Containerless automated processing of intermetallic compounds and composites

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Joslin, S. M.; Reviere, R. D.; Oliver, B. F.; Noebe, R. D.

    1993-01-01

    An automated containerless processing system has been developed to directionally solidify high temperature materials, intermetallic compounds, and intermetallic/metallic composites. The system incorporates a wide range of ultra-high purity chemical processing conditions. The utilization of image processing for automated control negates the need for temperature measurements for process control. The list of recent systems that have been processed includes Cr, Mo, Mn, Nb, Ni, Ti, V, and Zr containing aluminides. Possible uses of the system, process control approaches, and properties and structures of recently processed intermetallics are reviewed.

  1. Titanium aluminide intermetallic alloys with improved wear resistance

    DOEpatents

    Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

    2014-07-08

    The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

  2. Thermomechanical processing of plasma sprayed intermetallic sheets

    DOEpatents

    Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

    2001-01-01

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having 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 iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  3. Roles of Titanium-Intermetallic Compound Layer

    NASA Astrophysics Data System (ADS)

    Lee, Chii-Chang

    Four different configurations have been tested: Al-Cu, Ti/Al-Cu, Al-Cu/Ti, and Ti/Al-Cu/Ti to evaluate the possible contributions of Ti-intermetallic compound layer(s) to enhancement of the lifetime to failure. Basically, the proposed mechanisms can be classified into two groups: shunting effect and effects limited to changes in Al-Cu conducting layer(s). A resistance monitoring technique was adopted to supplement lifetime measurement to separate these two effects. By correlating the first resistance jump (spike) to the happening of a complete open across Al-Cu layer, it was found that the shunting effect contributes to enhancement of the lifetime by 4 times in Ti/Al-Cu, 2 times in Al-Cu/Ti, and 2 times in Ti/Al-Cu/Ti. A Ti underlayer was found to contribute mainly the shunting effect. However, from drift velocity measurements and failure mode analysis, it is possible to deduce that a Ti overlayer contributes not only the shunting effect but also another effect that acts to diminish the grain boundary mass transport rate by a factor of about 76. It is believed that the latter effect is a consequence of the high compressive yield stength conferred by the Ti-intermetallic compound overlayer to the Al-Cu layer. Finally, an important non-destructive technique, based on the characteristic x-rays generated by energetic electrons, to characterize the mass divergences in multilayer interconnects, was developed in this research, called SMEISIS, representing Simultaneous Multiple Elements Intensity Scanning of Interconnecting Stripes. This technique was proved to be capable of revealing detail about the shapes, nature, and location of mass divergence that cannot be revealed by thermal wave image technique and that requires time consuming multiple sectioning in TEM and SEM methods.

  4. Multishell Intermetallic Onions by Symmetrical Configuration of Ordered Domains

    NASA Astrophysics Data System (ADS)

    Yu, R.; Chen, W.; Cheng, Z. Y.; Li, Y. D.; Zhu, J.

    2010-11-01

    Ordered domains are utilized to construct new nanostructures, i.e., multishell intermetallic onions, which are formed by symmetrical configuration of ordered domains. Through density-functional theory calculations, we have shown that the energy penalties for introducing antiphase boundaries into the nanoparticles are small in some alloy systems compared to typical surface energies, making it feasible to prepare intermetallic onions by tuning surface energies. The unique surface atomic arrangements would provide opportunities for developing novel materials like efficient catalysts.

  5. Section 2: Phase transformation studies in mechanically alloyed Fe-Nz and Fe-Zn-Si intermetallics

    SciTech Connect

    Jordan, A.; Uwakweh, O.N.C.; Maziasz, P.J.

    1997-04-01

    The initial stage of this study, which was completed in FY 1995, entailed an extensive analysis characterizing the structural evolution of the Fe-Zn intermetallic system. The primary interest in these Fe-Zn phases stems from the fact that they form an excellent coating for the corrosion protection of steel (i.e., automobile body panels). The Fe-Zn coating generally forms up to four intermetallic phases depending on the particular industrial application used, (i.e., galvanization, galvannealing, etc.). Since the different coating applications are non-equilibrium in nature, it becomes necessary to employ a non-equilibrium method for producing homogeneous alloys in the solid-state to reflect the structural changes occurring in a true coating. This was accomplished through the use of a high energy/non-equilibrium technique known as ball-milling which allowed the authors to monitor the evolution process of the alloys as they transformed from a metastable to stable equilibrium state. In FY 1996, this study was expanded to evaluate the presence of Si in the Fe-Zn system and its influence in the overall coating. The addition of silicon in steel gives rise to an increased coating. However, the mechanisms leading to the coating anomaly are still not fully understood. For this reason, mechanical alloying through ball-milling of pure elemental powders was used to study the structural changes occurring in the sandelin region (i.e., 0.12 wt % Si). Through the identification of invariant reactions (i.e., eutectic, etc.) the authors were able to explore the sandelin phenomenon and also determine the various fields or boundaries associated with the Fe-Zn-Si ternary system.

  6. First Principles Study of Al-Li Intermetallic Compounds

    NASA Astrophysics Data System (ADS)

    Yu, Hai-li; Duan, Xiao-hui; Ma, Yong-jun; Zeng, Min

    2012-12-01

    The structural properties, heats of formation, elastic properties, and electronic structures of four compositions of binary Al-Li intermetallics, Al3Li, AlLi, Al2Li3, and Al4Li9, are analyzed in detail by using density functional theory. The calculated formation heats indicate a strong chemical interaction between Al and Li for all the Al-Li intermetallics. In particular, in the Li-rich Al-Li compounds, the thermodynamic stability of intermetallics linearly decreases with increasing concentration of Li. According to the computational single crystal elastic constants, all the four Al-Li intermetallic compounds considered here are mechanically stable. The polycrystalline elastic modulus and Poisson's ratio have been deduced by using Voigt, Reuss, and Hill approximations, and the calculated ratios of bulk modulus to shear modulus indicate that the four compositions of binary Al-Li intermetallics are brittle materials. With the increase of Li concentration, the bulk modulus of Al-Li intermetallics decreases in a linear manner.

  7. First-principles studies of Al-Ni intermetallic compounds

    SciTech Connect

    Shi Dongmin; Wen Bin; Melnik, Roderick; Yao Shan; Li Tingju

    2009-10-15

    The structural properties, heats of formation, elastic properties, and electronic structures of Al-Ni intermetallic compounds are analyzed here in detail by using density functional theory. Higher calculated absolute values of heats of formation indicate a very strong chemical interaction between Al and Ni for all Al-Ni intermetallic compounds. According to the computational single crystal elastic constants, all the Al-Ni intermetallic compounds considered here are mechanically stable. The polycrystalline elastic modulus and Poisson's ratio have been deduced by using Voigt, Reuss, and Hill (VRH) approximations, and the calculated ratio of shear modulus to bulk modulus indicated that AlNi, Al{sub 3}Ni, AlNi{sub 3} and Al{sub 3}Ni{sub 5} compounds are ductile materials, but Al{sub 4}Ni{sub 3} and Al{sub 3}Ni{sub 2} are brittle materials. With increasing Ni concentration, the bulk modulus of Al-Ni intermetallic compounds increases in a linear manner. The electronic energy band structures confirm that all Al-Ni intermetallic compounds are conductors. - Graphical abstract: Calculated bulk modulus compared to experimental and other theoretical values for the Al-Ni intermetallic compounds.

  8. Microstructure characterization of hypereutectoid aluminium bronze composite coating

    NASA Astrophysics Data System (ADS)

    Kucita, P.; Wang, S. C.; Li, W. S.; Cook, R. B.; Starink, M. J.

    2015-10-01

    Hypereutectoid aluminium bronze coating was deposited onto an E.N. 10503 steel substrate using plasma transferred arc welding (PTA). Microstructure characterisation of the coating and a section near the steel substrate joint was carried out using SEM, EBSD, EDS in conjunction with XRD and depth-sensing nano-indentation. The constituent phases in the coating were identified as: martensitic Cu3Al β1' phase, solid solution of Al in Cu α phase and the intermetallic Fe3Al κ1 phase. The region near the steel substrate was characterised by high hardness, large grains and presence of Cu precipitates. No cracks were observed in this region. The coating has high hardness of 4.9GPa and Young's modulus of 121.7GPa. This is attributed to homogeneous distribution of sub microns size Fe3Al intermetallic phase. The implications of the coating to the engineering application of sheet metal forming are discussed.

  9. Coating Microstructure-Property-Performance Issues

    SciTech Connect

    Terry C. Totemeier; Richard N. Wright

    2005-05-01

    Results of studies on the relationships between spray parameters and performance of thermally-sprayed intermetallic coatings for high-temperature oxidation and corrosion resistance are presented. Coating performance is being assessed by corrosion testing of free-standing coatings, thermal cycling of coating substrates, and coating ductility measurement. Coating corrosion resistance was measured in a simulated coal combustion gas environment (N2-CO-CO2-H2O-H2S) at temperatures from 500 to 800°C using thermo-gravimetric analysis (TGA). TGA testing was also performed on a typical ferritic-martensitic steel, austenitic stainless steel, and a wrought Fe3Al-based alloy for direct comparison to coating behavior. FeAl and Fe3Al coatings showed corrosion rates slightly greater than that of wrought Fe3Al, but markedly lower than the steels at all temperatures. The corrosion rates of the coatings were relatively independent of temperature. Thermal cycling was performed on coated 316SS and nickel alloy 600 substrates from room temperature to 800°C to assess the relative effects of coating microstructure, residual stress, and thermal expansion mismatch on coating cracking by thermal fatigue. Measurement of coating ductility was made by acoustic emission monitoring of coated 316SS tensile specimens during loading.

  10. Effects of molten aluminum on H13 dies and coatings

    NASA Astrophysics Data System (ADS)

    Yu, M.; Shivpuri, R.; Rapp, R. A.

    1995-04-01

    The effects of molten aluminum casting alloy A390 on a commercially heat treated H13 die steel and two wear-resistant coatings, Cr23C6 and TiN, were investigated by an accelerated corrosion test. The H13 steel suffered severe corrosion due to the rapid formation of intermetallic compounds. The formation of multilayer intermetallic compounds and the simultaneous dissociation of the intermetallic compound τ6 (Al4FeSi) were attributed to the fast dissolution of H13 steels into the melt. This dissolution of the H13 steel was accelerated dramatically by turbulence and an increase in melt temperature. Significant improvement in corrosion resistance was achieved for the H13 steel coated by Cr23C6 via a pack cementation process.

  11. Driving magnetostructural transitions in layered intermetallic compounds.

    PubMed

    Wang, J L; Caron, L; Campbell, S J; Kennedy, S J; Hofmann, M; Cheng, Z X; Din, M F Md; Studer, A J; Brück, E; Dou, S X

    2013-05-24

    We report the dramatic effect of applied pressure and magnetic field on the layered intermetallic compound Pr(0.5)Y(0.5)Mn(2)Ge(2). In the absence of pressure or magnetic field this compound displays interplanar ferromagnetism at room temperature and undergoes an isostructural first order magnetic transition (FOMT) to an antiferromagnetic state below 158 K, followed by another FOMT at 50 K due to the reemergence of ferromagnetism as praseodymium orders (T(C)(Pr)). The application of a magnetic field drives these two transitions towards each other, whereas the application of pressure drives them apart. Pressure also produces a giant magnetocaloric effect such that a threefold increase of the entropy change associated with the lower FOMT (at T(C)(Pr)) is seen under a pressure of 7.5 kbar. First principles calculations, using density functional theory, show that this remarkable magnetic behavior derives from the strong magnetoelastic coupling of the manganese layers in this compound. PMID:23745927

  12. Ground state searches in fcc intermetallics

    SciTech Connect

    Wolverton, C.; de Fontaine, D. ); Ceder, G. ); Dreysse, H. . Lab. de Physique du Solide)

    1991-12-01

    A cluster expansion is used to predict the fcc ground states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. The intermetallic structures are not assumed, but derived regorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearized-muffin-tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration.

  13. Thermal stress effects in intermetallic matrix composites

    NASA Technical Reports Server (NTRS)

    Wright, P. K.; Sensmeier, M. D.; Kupperman, D. S.; Wadley, H. N. G.

    1993-01-01

    Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

  14. Bulk and defect properties of ordered intermetallics

    SciTech Connect

    Fu, C.L.; Yoo, M.H.

    1993-12-31

    First-principles calculations based on the local-density-functional theory have been used to investigate the factors governing strength of ordered intermetallic alloys. Unlike Ni{sub 3}Al, calculated elastic constants and shear fault energies indicate anomalous yield strength behavior is not likely to occur in Ni{sub 3}Si. This suggests the inadequacy of cross-slip-pinning model to explain the strength anomaly in the L1{sub 2} structure. For strongly ordered NiAl, the defect structure is dominated by two types of defects -- monovacancies on the Ni sites and substitutional antisite defects on the Al sites. By contrast, for Ni{sub 3}Al, absence of structural vacancies and deviations from stoichiometry are accommodated by substitutional antisite defects on both sublattices. Intrinsic strengthening mechanisms in TiAl are discussed in terms of calculated elastic constants and shear fault energies. Because of reduced fault energies at the {gamma}/{alpha}{sub 2} interface, slip and twinning contribute significantly to high shear deformation of the lamellar structure.

  15. SCB ignition of pyrotechnics, thermites and intermetallics

    SciTech Connect

    Bickes, R.W. Jr.; Grubelich, M.C.

    1996-09-01

    We investigated ignition of pyrotechnics, metal-fuel/metal-oxide compositions (thermites), and exothermic alloy compositions (intermetallics) using a semiconductor bridge (SCB). It was shown that these materials could be ignited at low energy levels with an appropriately designed SCB, proper loading density, and good thermal isolation. Materials tested included Al/CuO, B/BaCrO{sub 4}, TiH{sub 1.65}/KClO{sub 4}, Ti/KClO{sub 4}, Zr/BaCrO{sub 4}, Zr/CuO, Zr/Fe{sub 2}O{sub 3}, Zr/KClO{sub 4}, and 100-mesh Al/Pd. Firing set was a capacitor discharge unit with charge capacitors ranging from 3 to 20,000 {mu}F at charge voltages 5-50 V. Devices functioned a few miliseconds after onset of current pulse at input energies as low as 3 mJ. We also report on a thermite torch design.

  16. First-principles studies of Ni-Ta intermetallic compounds

    SciTech Connect

    Zhou Yi; Wen Bin; Ma Yunqing; Melnik, Roderick; Liu Xingjun

    2012-03-15

    The structural properties, heats of formation, elastic properties, and electronic structures of Ni-Ta intermetallic compounds are investigated in detail based on density functional theory. Our results indicate that all Ni-Ta intermetallic compounds calculated here are mechanically stable except for P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2}. Furthermore, we found that Pmmn-Ni{sub 3}Ta is the ground state stable phase of Ni{sub 3}Ta polymorphs. The polycrystalline elastic modulus has been deduced by using the Voigt-Reuss-Hill approximation. All Ni-Ta intermetallic compounds in our study, except for NiTa, are ductile materials by corresponding G/K values and poisson's ratio. The calculated heats of formation demonstrated that Ni{sub 2}Ta are thermodynamically unstable. Our results also indicated that all Ni-Ta intermetallic compounds analyzed here are conductors. The density of state demonstrated the structure stability increases with the Ta concentration. - Graphical abstract: Mechanical properties and formation heats of Ni-Ta intermetallic compounds are discussed in detail in this paper. Highlights: Black-Right-Pointing-Pointer Ni-Ta intermetallic compounds are investigated by first principle calculations. Black-Right-Pointing-Pointer P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2} are mechanically unstable phases. Black-Right-Pointing-Pointer Pmmn-Ni{sub 3}Ta is ground stable phase of Ni{sub 3}Ta polymorphs. Black-Right-Pointing-Pointer All Ni-Ta intermetallic compounds are conducting materials.

  17. Phase stability in processing of high temperature intermetallic alloys

    SciTech Connect

    Perepezko, J.H.; Nunes, C.A.; Yi, S.H.; Thoma, D.J.

    1997-12-31

    In the development of high temperature intermetallics involving various aluminides, silicides and Laves phases, it has become evident that it is essential to consider the strong influence of materials processing throughout all stages. The underlying basis for alloy synthesis, processing and the assessment of thermal stability is established by the relevant phase equilibria, the characteristic diffusivities and the possible solidification reaction pathways. In almost all cases the microstructures of the most useful metallic alloys are multiphase assemblies in which the relative phase fractions, compositions and morphologies play key roles in optimizing the performance under high temperature conditions. The microstructure designs are usually tailored for strength, toughness, creep resistance and environmental stability and involve a balance of features derived from mixtures of a ductile phase and intermetallic phases. There is a clear experience that the level of materials processing can only be as sophisticated as the level of knowledge of the phase equilibria and the underlying kinetics. In many of the contemporary intermetallic alloys the phase stability must be considered in terms of multicomponent equilibria and non-stoichiometric intermetallic compositions. Recent developments in several important intermetallic alloy classes illustrate the guidance into alloy design and processing options provided by systematic studies of phase stability. 58 refs., 7 figs.

  18. Laser Assisted Additively Manufactured Transition Metal Coating on Aluminum

    NASA Astrophysics Data System (ADS)

    Vora, Hitesh D.; Rajamure, Ravi Shanker; Roy, Anurag; Srinivasan, S. G.; Sundararajan, G.; Banerjee, Rajarshi; Dahotre, Narendra B.

    2016-07-01

    Various physical and chemical properties of surface and subsurface regions of Al can be improved by the formation of transition metal intermetallic phases (Al x TM y ) via coating of the transition metal (TM). The lower equilibrium solid solubility of TM in Al (<1 at.%) is a steep barrier to the formation of solid solutions using conventional alloying methods. In contrast, as demonstrated in the present work, surface engineering via a laser-aided additive manufacturing approach can effectively synthesize TM intermetallic coatings on the surface of Al. The focus of the present work included the development of process control to achieve thermodynamic and kinetic conditions necessary for desirable physical, microstructural and compositional attributes. A multiphysics finite element model was developed to predict the temperature profile, cooling rate, melt depth, dilution of W in Al matrix and corresponding micro-hardness in the coating, and the interface between the coating and the base material and the base material.

  19. Laser Assisted Additively Manufactured Transition Metal Coating on Aluminum

    NASA Astrophysics Data System (ADS)

    Vora, Hitesh D.; Rajamure, Ravi Shanker; Roy, Anurag; Srinivasan, S. G.; Sundararajan, G.; Banerjee, Rajarshi; Dahotre, Narendra B.

    2016-05-01

    Various physical and chemical properties of surface and subsurface regions of Al can be improved by the formation of transition metal intermetallic phases (Al x TM y ) via coating of the transition metal (TM). The lower equilibrium solid solubility of TM in Al (<1 at.%) is a steep barrier to the formation of solid solutions using conventional alloying methods. In contrast, as demonstrated in the present work, surface engineering via a laser-aided additive manufacturing approach can effectively synthesize TM intermetallic coatings on the surface of Al. The focus of the present work included the development of process control to achieve thermodynamic and kinetic conditions necessary for desirable physical, microstructural and compositional attributes. A multiphysics finite element model was developed to predict the temperature profile, cooling rate, melt depth, dilution of W in Al matrix and corresponding micro-hardness in the coating, and the interface between the coating and the base material and the base material.

  20. Microwave assisted combustion synthesis of non-equilibrium intermetallic compounds.

    PubMed

    Veronesi, Paolo; Rosa, Roberto; Colombini, Elena; Leonelli, Cristina; Poli, Giorgio; Casagrande, Angelo

    2010-01-01

    A simplified model of the microwave-assisted combustion synthesis of Ni and Al metal powders to form the NiAl intermetallic on titanium and steel substrates is presented. The simulation couples an electro-thermal model with a chemical model, accounting for local heat generation due to the highly exothermic nature of the reactions between the powders. Numerical results, validated by experimental values, show that the capability of microwaves to convey energy, and not heat, can be used to alter the temperature profiles during and after the combustion synthesis, leading to unique intermetallic microstructures. This phenomenon is ascribed to the extended existence of high temperature liquid intermetallic phases, which react with the metallic substrates at the interface. Moreover, microwave heating selectivity allows to maintain the bulk of the substrate metallic materials to a much lower temperature, compared to combustion synthesis in conventionally heated furnaces, thus reducing possible unwanted transformations like phase change or oxidation. PMID:21721328

  1. Explosive reaction pressing of intermetallic compounds from stoichiometric powder mixtures

    SciTech Connect

    Kochsiek, D.; Pruemmer, R.; Brunold, A.

    1995-09-01

    Intermetallic NiAl, TiAl, and TiAl{sub 3} were synthesized by shock compression experiments from stoichiometric powder mixtures of nickel and aluminium as well as of titanium and aluminium. Good consolidation and complete intermetallic reaction were achieved by the direct method of explosive compaction. For each powder mixture, a certain individual threshold pressure has to be exceeded in order to initiate intermetallic reaction. The reacting compounds melted completely with subsequent rapid solidification during the passage of the shock wave. The new material shows high hardness. Pores are formed by gaseous reaction products in the NiAl and TiAl{sub 3} compacts. The TiAl structure is fully-dense and dendritic.

  2. Intermetallic alloy welding wires and method for fabricating the same

    DOEpatents

    Santella, M.L.; Sikka, V.K.

    1996-06-11

    Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined. 4 figs.

  3. Intermetallic alloy welding wires and method for fabricating the same

    DOEpatents

    Santella, Michael L.; Sikka, Vinod K.

    1996-01-01

    Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined.

  4. Stress distribution in a continuously cast intermetallic strip

    NASA Astrophysics Data System (ADS)

    Roy, George; Wronski, Zbignew; Sahoo, Mahi; Kiff, Dave

    Results of a study on the determination of the residual stress state in a nickel aluminide intermetallic strip by the hole drilling method (HDM) are presented. Special correlation functions that relate the relaxed surface strain and the original stresses before drilling were developed. It is shown that the HDM may be used to determine residual stresses in anisotropic materials such as intermetallic strips. The results indicate that a complex stress field develops through the thickness and across the width of the strip. However, a suitable thermomechanical treatment may be applied to redistribute the stresses before aluminide strips can be used to make engineering components.

  5. Quaternary borocarbides: New class of intermetallic superconductors

    NASA Technical Reports Server (NTRS)

    Nagarajan, R.; Gupta, L. C.; Dhar, S. K.; Mazumdar, Chandan; Hossain, Zakir; Godart, C.; Levy-Clement, C.; Padalia, B. D.; Vijayaraghavan, R.

    1995-01-01

    Our recent discovery of superconductivity (SC) in the four-element multiphase Y-Ni-B-C system at an elevated temperature (TC approximately 12 K) has opened up great possibilities of identifying new superconducting materials and generating new physics. Superconductivity with Tc (greater than 20 K) higher than that known so far in bulk intermetallics has been observed in multiphase Y-Pd-B-C and Th-Pd-B-C systems and a family of single phase materials RENi2B2C (RE= Y, rare earth) have been found. Our investigations show YNi2B2C to be a strong coupling hard type-II SC. HC2(T) exhibits an unconventional temperature dependence. Specific heat and magnetization studies reveal coexistence of SC and magnetism in RNi2B2C (R = Ho, Er, Tm) with magnetic ordering temperatures (Tc approximately 8 K, 10.5 K, 11 K and Tm approximately 5 K, approximately 7K, approximately 4 K respectively) that are remarkably higher than those in known magnetic superconductors . Mu-SR studies suggest the possibility of Ni atoms carrying a moment in TmNi2B2C. Resistivity results suggests a double re-entrant transition (SC-normal-SC) in HoNi2B2C. RENi2B2C (RE = Ce, Nd, Gd) do not show SC down to 4.2 K. The Nd- and Gd-compounds order magnetically at approximately 4.5 K and approximately 19.5 K, respectively. Two SC transitions are observed in Y-Pd-B-C (Tc approximately 22 K, approximately 10 K) and in Th-Pd-B-C (Tc approximately 20 K, approximately 14 K) systems, which indicate that there are at least two structures which support SC in these borocarbides. In our multiphase ThNi2B2C we observe SC at approximately 6 K. No SC was seen in multiphase UNi2B2C, UPd2B2C, UOs2Ge2C and UPd5B3C(0.35) down to 4.2 K. Tc in YNi2B2C is depressed by substitutions (Gd, Th and U at Y-sites and Fe, Co at Ni-sites).

  6. Quaternary borocarbides: New class of intermetallic superconductors

    NASA Astrophysics Data System (ADS)

    Nagarajan, R.; Gupta, L. C.; Dhar, S. K.; Mazumdar, Chandan; Hossain, Zakir; Godart, C.; Levy-Clement, C.; Padalia, B. D.; Vijayaraghavan, R.

    1995-04-01

    Our recent discovery of superconductivity (SC) in the four-element multiphase Y-Ni-B-C system at an elevated temperature (TC approximately 12 K) has opened up great possibilities of identifying new superconducting materials and generating new physics. Superconductivity with Tc (greater than 20 K) higher than that known so far in bulk intermetallics has been observed in multiphase Y-Pd-B-C and Th-Pd-B-C systems and a family of single phase materials RENi2B2C (RE= Y, rare earth) have been found. Our investigations show YNi2B2C to be a strong coupling hard type-II SC. HC2(T) exhibits an unconventional temperature dependence. Specific heat and magnetization studies reveal coexistence of SC and magnetism in RNi2B2C (R = Ho, Er, Tm) with magnetic ordering temperatures (Tc approximately 8 K, 10.5 K, 11 K and Tm approximately 5 K, approximately 7K, approximately 4 K respectively) that are remarkably higher than those in known magnetic superconductors . Mu-SR studies suggest the possibility of Ni atoms carrying a moment in TmNi2B2C. Resistivity results suggests a double re-entrant transition (SC-normal-SC) in HoNi2B2C. RENi2B2C (RE = Ce, Nd, Gd) do not show SC down to 4.2 K. The Nd- and Gd-compounds order magnetically at approximately 4.5 K and approximately 19.5 K, respectively. Two SC transitions are observed in Y-Pd-B-C (Tc approximately 22 K, approximately 10 K) and in Th-Pd-B-C (Tc approximately 20 K, approximately 14 K) systems, which indicate that there are at least two structures which support SC in these borocarbides. In our multiphase ThNi2B2C we observe SC at approximately 6 K. No SC was seen in multiphase UNi2B2C, UPd2B2C, UOs2Ge2C and UPd5B3C(0.35) down to 4.2 K. Tc in YNi2B2C is depressed by substitutions (Gd, Th and U at Y-sites and Fe, Co at Ni-sites).

  7. Erosion behavior of Fe-Al intermetallic alloys

    SciTech Connect

    Kim, Y.S.; Song, J.H.; Chang, Y.W.

    1997-04-01

    The Fe-rich Fe-Al intermetallics have generated some interest, especially during the last decade, due to their excellent resistance for oxidation and sulfidation, high specific strength, and low material cost. The aluminide is therefore considered as one of the promising candidates for high-temperature structural materials in a corrosive atmosphere. Research effort has been focused mainly on process, development, and enhancement of room-temperature ductility together with the characterization of physical properties such as mechanical properties, oxidation, corrosion, and abrasive wear behavior. However, there have been only a few works reported to date in regard to the erosion characteristics of the alloy, one of the most important material property of this ordered intermetallic alloy for the use in a fossil-fuel plant. In this study, the solid-particle erosion behavior of the Fe-Al intermetallic alloys containing the various aluminum contents ranging from 25 to 30 at.% has been investigated to clarify the effect of aluminum content and different ordered structures, viz. DO{sub 3} and B2, on the erosion behavior. An attempt has been made to correlate the erosion behavior of these intermetallics to their mechanical properties by carrying out tensile tests together with SEM observation of the eroded surfaces.

  8. PAC Studies on Zr-Based Intermetallic Compounds

    NASA Astrophysics Data System (ADS)

    Damonte, L. C.; Mendoza-Zélis, L. A.

    2004-11-01

    The Zr2Al, Zr3Al2 and Zr6NiAl2 intermetallic compounds were characterized by means of time differential perturbed angular correlation (TDPAC) and X-ray diffraction. Our interest in these Zr(Hf) aluminides comes from crystallization studies of Zr(Hf)-based bulk metallic glasses which have a wide supercooled liquid region.

  9. Electrocatalytic activity of ordered intermetallic phases for fuel cell applications.

    PubMed

    Casado-Rivera, Emerilis; Volpe, David J; Alden, Laif; Lind, Cora; Downie, Craig; Vázquez-Alvarez, Terannie; Angelo, Antonio C D; DiSalvo, Francis J; Abruña, Héctor D

    2004-03-31

    The electrocatalytic activities of a wide range of ordered intermetallic phases toward a variety of potential fuels have been studied, and results have been compared to those of a pure polycrystalline platinum (Pt(pc)) electrode. A significant number of the ordered intermetallic phases exhibited enhanced electrocatalytic activity when compared to that of Pt, in terms of both oxidation onset potential and current density. The PtBi, PtIn, and PtPb ordered intermetallic phases appeared to be the most promising electrocatalysts tested thus far for fuel cell applications. PtPb, in particular, showed an onset potential that was 100 mV less positive and a peak current density approximately 40 times higher than those observed for Pt in the case of methanol oxidation. The ability to control the geometric and electronic structures of the electrocatalytic material by using ordered intermetallic phases has been shown to be a promising direction of inquiry in the search for superior electrocatalysts for fuel cell applications. PMID:15038758

  10. Intermetallic Phase Formation in Explosively Welded Al/Cu Bimetals

    NASA Astrophysics Data System (ADS)

    Amani, H.; Soltanieh, M.

    2016-05-01

    Diffusion couples of aluminum and copper were fabricated by explosive welding process. The interface evolution caused by annealing at different temperatures and time durations was investigated by means of optical microscopy, scanning electron microscopy equipped with energy dispersive spectroscopy, and x-ray diffraction. Annealing in the temperature range of 573 K to 773 K (300 °C to 500 °C) up to 408 hours showed that four types of intermetallic layers have been formed at the interface, namely Al2Cu, AlCu, Al3Cu4, and Al4Cu9. Moreover, it was observed that iron trace in aluminum caused the formation of Fe-bearing intermetallics in Al, which is near the interface of the Al-Cu intermetallic layers. Finally, the activation energies for the growth of Al2Cu, AlCu + Al3Cu4, Al4Cu9, and the total intermetallic layer were calculated to be about 83.3, 112.8, 121.6, and 109.4 kJ/mol, respectively. Considering common welding methods (i.e., explosive welding, cold rolling, and friction welding), although there is a great difference in welding mechanism, it is found that the total activation energy is approximately the same.

  11. Unique intermetallic compounds prepared by shock wave synthesis

    NASA Technical Reports Server (NTRS)

    Otto, G.; Reece, O. Y.; Roy, U.

    1971-01-01

    Technique compresses fine ground metallic powder mixture beyond crystal fusion point. Absence of vapor pressure voids and elimination of incongruous effects permit application of technique to large scale fabrication of intermetallic compounds with specific characteristics, e.g., semiconduction, superconduction, or magnetic properties.

  12. Intermetallic Phase Formation in Explosively Welded Al/Cu Bimetals

    NASA Astrophysics Data System (ADS)

    Amani, H.; Soltanieh, M.

    2016-08-01

    Diffusion couples of aluminum and copper were fabricated by explosive welding process. The interface evolution caused by annealing at different temperatures and time durations was investigated by means of optical microscopy, scanning electron microscopy equipped with energy dispersive spectroscopy, and x-ray diffraction. Annealing in the temperature range of 573 K to 773 K (300 °C to 500 °C) up to 408 hours showed that four types of intermetallic layers have been formed at the interface, namely Al2Cu, AlCu, Al3Cu4, and Al4Cu9. Moreover, it was observed that iron trace in aluminum caused the formation of Fe-bearing intermetallics in Al, which is near the interface of the Al-Cu intermetallic layers. Finally, the activation energies for the growth of Al2Cu, AlCu + Al3Cu4, Al4Cu9, and the total intermetallic layer were calculated to be about 83.3, 112.8, 121.6, and 109.4 kJ/mol, respectively. Considering common welding methods ( i.e., explosive welding, cold rolling, and friction welding), although there is a great difference in welding mechanism, it is found that the total activation energy is approximately the same.

  13. Advanced reinforcement systems for intermetallic applications

    SciTech Connect

    Merrick, H.F.; Labib, M.L.

    1993-03-01

    A 2-D axisymmetric model was employed to determine the magnitude of the radial, axial, and hoop stresses caused by the thermal expansion difference between fiber and matrix and which result from the fabrication temperature cycle. Finite element analysis was conducted for single fiber model systems based on SCS-6/Ti3Al+Nb and Al2O3/NiAl. The stress distribution due to the imposition of a graded intermediate layer for each system was determined and included variables of layer thickness and gradation in interlayer chemistry in order to vary the expansion gradient between fiber and matrix. Thermal cycling tests were conducted on sputter coated SCS-6 fibers selectively coated with Ti3Al+Nb, with and without an intermediate layer. Cracking of the Ti3Al+Nb layers was prevented by an interlayer based on Ti-TiN-Ti. The interlayer thickness appeared critical to its efficiency. Similarly, for the case of Al2O3/NiAl, an intermediate layer consisting of a Ni bond coat on the sapphire fiber followed by a graded Al2O3-NiAl layer did not crack when given a thermal excursion to 1100 C and then cooled to room temperature. Acoustic emission tests on single fiber specimens were unsuccessful in detecting load drops associated with the successive fracture of the fiber. For the SCS-6/Ti3Al system this was the result of several factors which included the matrix/fiber ratio and poor bonding of the matrix and fiber. In the case of the Al2O3/NiAl system brittle failure of the NiAl matrix precluded fiber breakdown during tensile loading.

  14. Advanced reinforcement systems for intermetallic applications

    NASA Technical Reports Server (NTRS)

    Merrick, Howard F.; Labib, Mohammed L.

    1993-01-01

    A 2-D axisymmetric model was employed to determine the magnitude of the radial, axial, and hoop stresses caused by the thermal expansion difference between fiber and matrix and which result from the fabrication temperature cycle. Finite element analysis was conducted for single fiber model systems based on SCS-6/Ti3Al+Nb and Al2O3/NiAl. The stress distribution due to the imposition of a graded intermediate layer for each system was determined and included variables of layer thickness and gradation in interlayer chemistry in order to vary the expansion gradient between fiber and matrix. Thermal cycling tests were conducted on sputter coated SCS-6 fibers selectively coated with Ti3Al+Nb, with and without an intermediate layer. Cracking of the Ti3Al+Nb layers was prevented by an interlayer based on Ti-TiN-Ti. The interlayer thickness appeared critical to its efficiency. Similarly, for the case of Al2O3/NiAl, an intermediate layer consisting of a Ni bond coat on the sapphire fiber followed by a graded Al2O3-NiAl layer did not crack when given a thermal excursion to 1100 C and then cooled to room temperature. Acoustic emission tests on single fiber specimens were unsuccessful in detecting load drops associated with the successive fracture of the fiber. For the SCS-6/Ti3Al system this was the result of several factors which included the matrix/fiber ratio and poor bonding of the matrix and fiber. In the case of the Al2O3/NiAl system brittle failure of the NiAl matrix precluded fiber breakdown during tensile loading.

  15. Characterization of industrially produced galvannealed coating using cross-sectional specimen in TEM

    SciTech Connect

    Chakraborty, A.; Saha, R.; Ray, R.K.

    2009-08-15

    Galvannealed coated sheet steels are extensively used in the automotive industry due to their inherent advantages, as compared to other zinc based coating, such as excellent spot weldability, good corrosion resistance and better paintability. Despite the above advantages, galvannealed coating suffers from poor formability due to the presence of hard and brittle Fe-Zn intermetallic phases. The formability of the coating depends on the amount and orientation of different Fe-Zn intermetallic phases. The present study deals with the characterization of an industrially produced galvannealed coating using cross-sectional specimen in a Transmission Electron Microscope. From the selected area diffraction patterns obtained in Transmission Electron Microscope, the orientations of the delta phase were calculated.

  16. Alloying of cold-sprayed Al Ni composite coatings by post-annealing

    NASA Astrophysics Data System (ADS)

    Lee, Ha Yong; Jung, Se Hun; Lee, Soo Yong; Ko, Kyung Hyun

    2007-01-01

    A new cold spray coating technique for thick Al coating with finely dispersed Al-Ni intermetallic compounds was tested. For easy powder preparation and high yield, rather than using of Al/compound mixture feed stock, the spraying of pure Al and Ni powders mixture followed by post-annealing was suggested. The powder composition of Al and Ni was 75:25, and 90:10 (wt.%) to expect full consumption of pure Ni into intermetallic compounds. After Al-Ni composite coatings, the Ni particles were finely dispersed and embedded in the Al matrix with a good coating yield. Above 450 °C of post-annealing temperature, the Al 3Ni and Al 3Ni 2 phases were observed in the cold-sprayed Al-Ni coatings. The Ni particles in the Al matrix were fully consumed via compounding reaction with Al at 550 °C of the annealing temperature.

  17. Multi-component intermetallic electrodes for lithium batteries

    DOEpatents

    Thackeray, Michael M; Trahey, Lynn; Vaughey, John T

    2015-03-10

    Multi-component intermetallic negative electrodes prepared by electrochemical deposition for non-aqueous lithium cells and batteries are disclosed. More specifically, the invention relates to composite intermetallic electrodes comprising two or more compounds containing metallic or metaloid elements, at least one element of which can react with lithium to form binary, ternary, quaternary or higher order compounds, these compounds being in combination with one or more other metals that are essentially inactive toward lithium and act predominantly, but not necessarily exclusively, to the electronic conductivity of, and as current collection agent for, the electrode. The invention relates more specifically to negative electrode materials that provide an operating potential between 0.05 and 2.0 V vs. metallic lithium.

  18. Discontinuously reinforced intermetallic matrix composites via XD synthesis. [exothermal dispersion

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Whittenberger, J. D.

    1992-01-01

    A review is given of recent results obtained for discontinuously reinforced intermetallic matrix composites produced using the XD process. Intermetallic matrices investigated include NiAl, multiphase NiAl + Ni2AlTi, CoAl, near-gamma titanium aluminides, and Ll2 trialuminides containing minor amounts of second phase. Such mechanical properties as low and high temperature strength, compressive and tensile creep, elastic modulus, ambient ductility, and fracture toughness are discussed as functions of reinforcement size, shape, and volume fraction. Microstructures before and after deformation are examined and correlated with measured properties. An observation of interest in many of the systems examined is 'dispersion weakening' at high temperatures and high strain rates. This behavior is not specific to the XD process; rather similar observations have been reported in other discontinuous composites. Proposed mechanisms for this behavior are presented.

  19. Theoretical energy release of thermites, intermetallics, and combustible metals

    SciTech Connect

    Fischer, S.H.; Grubelich, M.C.

    1998-06-01

    Thermite (metal oxide) mixtures, intermetallic reactants, and metal fuels have long been used in pyrotechnic applications. Advantages of these systems typically include high energy density, impact insensitivity, high combustion temperature, and a wide range of gas production. They generally exhibit high temperature stability, and possess insensitive ignition properties. In this paper, the authors review the applications, benefits, and characteristics of thermite mixtures, intermetallic reactants, and metal fuels. Calculated values for reactant density, heat of reaction (per unit mass and per unit volume), and reaction temperature (without and with consideration of phase changes and the variation of specific heat values) are tabulated. These data are ranked in several ways, according to density, heat of reaction, reaction temperature, and gas production.

  20. Fracture toughness of Cu-Sn intermetallic thin films

    NASA Astrophysics Data System (ADS)

    Balakrisnan, B.; Chum, C. C.; Li, M.; Chen, Z.; Cahyadi, T.

    2003-03-01

    Intermetallic compounds (IMCs) are formed as a result of interaction between solder and metallization to form joints in electronic packaging. These joints provide mechanical and electrical contacts between components. The knowledge of fracture strength of the IMCs will facilitate predicting the overall joint property, as it is more disposed to failure at the joint compared to the solder because of its brittle characteristics. The salient feature of this paper is the measurement of the fracture toughness and the critical energy-release rate of Cu3Sn and Cu6Sn5 intermetallic thin films, which is the result of the interaction between Sn from the solder and Cu from the metallization. To achieve the objective, a controlled buckling test was used. A buckling test in the current work refers to one that displays large transverse displacement caused by axial compressive loading on a slender beam. The stress and strain along the beam can be easily calculated by the applied displacement. Fracture-toughness values of Cu3Sn and Cu6Sn5 are 2.85 MPa √m ± 0.17 MPa √m and 2.36 MPa √m ± 0.15 MPa √m, respectively. Corresponding critical energy-release rate values are 65.5 J/m2 ± 8.0 J/m2 and 55.9 J/m2 ± 7.3 J/m2, respectively. The values obtained were much higher than the ones measured in bulk intermetallic samples but correlated well with those values obtained from conventional fracture-toughness specimens when fracture was confined within the intermetallic layers. Hence, the controlled buckling test is a promising fast and effective way to elucidate mechanical properties of thin films.

  1. Magnetism and superconductivity of uranium and intermetallic compounds

    SciTech Connect

    Cooley, J. C.; Gay, E. C.; Hanrahan, R. J.; Hults, W. L.; Lashley, J. C.; Manley, M. E.; McPheeters, C. C.; Schmiedeshoff, G. M.; Thoma, D. J.; Touton, S.; Smith, J. L.

    2001-01-01

    Heat capacity, resistivity, and phonon density of states have been measured on uranium and reported already. Many of the results are on single crystals of purity that has been unavailable before. Some intermetallic compounds have been measured that are in the class of so-called heavy-fermion materials. We present here the latest results along with a discussion of the occurrence of superconductivity or magnetism in these materials.

  2. An intermetallic forming steel under radiation for nuclear applications

    NASA Astrophysics Data System (ADS)

    Hofer, C.; Stergar, E.; Maloy, S. A.; Wang, Y. Q.; Hosemann, P.

    2015-03-01

    In this work we investigated the formation and stability of intermetallics formed in a maraging steel PH 13-8 Mo under proton radiation up to 2 dpa utilizing nanoindentation, microcompression testing and atom probe tomography. A comprehensive discussion analyzing the findings utilizing rate theory is introduced, comparing the aging process to radiation induced diffusion. New findings of radiation induced segregation of undersize solute atoms (Si) towards the precipitates are considered.

  3. Cluster expansion of fcc Pd-V intermetallics

    SciTech Connect

    de Fontaine, D.; Wolverton, C.; Ceder, G. ); Dreysse, H. . Lab. de Physique du Solide)

    1991-06-01

    A cluster expansion is used to compute fcc ground states from first principles for the Pd-V system. Intermetallic structures are not assumed but derived rigorously by minimizing the configurational energy subject to linear constraints. A large number of concentration-independent interactions are calculated by the method of direct configurational averaging. Agreement with the fcc-based portion of the experimentally-determined Pd-V phase diagram is quite satisfactory. 25 refs., 2 figs.

  4. Superplastic ceramics and intermetallics and their potential applications

    SciTech Connect

    Wadsworth, J.; Nieh, T.G.

    1994-11-01

    Recent advances in the basic understanding of superplasticity and superplastic forming of ceramics and intermetallics are reviewed. Fine-grained superplastic ceramics, including yttria-stabilized tetragonal zirconia polycrystal, Y- or MgO-doped Al{sub 2}O{sub 3} Hydroxyapatite, {beta}-spodumene glass ceramics, Al{sub 2}0{sub 3}-YTZP two-phase composites, SiC-Si{sub 3}N{sub 4} and Fe-Fe{sub 3}C composites, are discussed. Superplasticity in the nickel-base (e.g., Ni{sub 3}Al and Ni{sub 3}Si) and titanium-base intermetallics (TiAl and T1{sub 3}Al), is described. Deformation mechanisms as well as microstructural requirements and effects such as grain size, grain growth, and grain-boundary phases, on the superplastic deformation behavior am addressed. Factors that control the superplastic tensile elongation of ceramics are discussed. Superplastic forming, and particularly biaxial gas-pressure forming, of several ceramics and intermetallics are presented with comments on the likelihood of commercial application.

  5. Magnetic field controlled FZ single crystal growth of intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Hermann, R.; Behr, G.; Gerbeth, G.; Priede, J.; Uhlemann, H.-J.; Fischer, F.; Schultz, L.

    2005-02-01

    Intermetallic rare-earth-transition-metal compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of bulk single crystals is very often unsuccessful due to an unfavorable solid-liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds. This control is provided by a tailored design of the electromagnetic field and the resulting electromagnetically driven convection. Numerical simulations for the determination of the electromagnetic field configuration induced by the RF heater coil and the solution of the coupled heat and hydrodynamic equations were done for the model substance Ni with and without additional magnetic field. As a result, an innovative magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards/outwards flows to flows almost at rest. The selection of parameters necessary for the desired fluid flow is determined from numerical simulation. The basis for the calculations are the process-related fluid flow conditions which are determined by the mode of heating, heat radiation at the free surface and material parameters. This treatment of the problem leads to the customised magnetic field for the special intermetallic compound. The application of the new magnetic system leads to a distinct improvement of the solid-liquid interface validated on experiments with the model substance Nickel.

  6. Influence of Electron Beam Treatment Regimes on the Structure and Properties of Intermetallic Clads Obtained on Titanium Substrates

    NASA Astrophysics Data System (ADS)

    Lazurenko, D. V.; Bataev, I. A.; Lenivtseva, O. G.; Maliutina, Iu N.; Mats, O. E.; Samoylenko, V. V.; Polyakov, I. A.

    2016-04-01

    Intermetallic clads were obtained on the basis of the titanium workpieces. The cladding was carried out using a non-vacuum electron beam treatment technique. A powder mixture which contained 16.97 Al - 28.27 Ti - 41.07 CaF2 - 13.69 LiF (wt. %) was used for cladding. Two regimes with the beam current of 16 mA and 18 mA were used. The beam current influenced significantly the structure and phase composition of clads. In case of the electron beam treatment with a beam current of 16 mA a lamellar structure consisted of a mixture of AlTi3 and A1Ti was fabricated. An increase of the beam current to 18 mA led to the formation of an AlTi3 acicular structure. Microhardness and wear resistance of the intermetallic coating was significantly higher in comparison with cp-Ti. The maximum microhardness of clads was 480 HV. A wear rate of clads was 10 times lower than that of cp-Ti.

  7. Remaining Fatigue Life Assessment of Plasma Sprayed Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Robin, Philippe; Gitzhofer, François; Fauchais, Pierre; Boulos, Maher

    2010-09-01

    Ceramic functional coatings are frequently applied to structural materials, covering a wide range of thermomechanical and electrochemical applications. The main limiting feature is their reliability when subjected to cyclic transient thermal stresses. The study described in this article is a continuation of earlier research study focused on acoustic emission (AE) monitoring of the thermomechanical aging effects in ceramic coatings. Here, emphasis is placed on the usefulness of combining AE short-term monitoring with finite element modeling (FEM) to predict the performance of such coatings when subjected to cyclic thermal loads. The FEM study presented in this article is based on a three-dimensional, time-dependent approach, of the stress fields that developed within the coatings during the post-deposition cooling step and the thermal cycling. Experiments were conducted using yttrium-stabilized zirconia (YSZ) and Alumina (Al2O3) ceramic coatings combined with a NiCr-based intermetallic bond coat.

  8. Microstructural Evolution of the 55 Wt Pct Al-Zn Coating During Press Hardening

    NASA Astrophysics Data System (ADS)

    Lee, Chang Wook; De Cooman, Bruno Charles

    2014-09-01

    Press hardening is increasingly being used to produce ultra-high strength steel parts for passenger cars. Al-Si, Zn, and Zn-alloy coatings have been used to provide corrosion protection to press hardening steel grades. The use of coatings has drawbacks such as coating delamination or liquid metal-induced embrittlement. In the present work, the microstructural evolution of Al-Zn coating during press hardening was studied. The 55 wt pct Al-Zn coating can in principle provide both Al barrier protection and Zn cathodic protection to press hardened steel. During the heat treatment associated with the press hardening, the 55 wt pct Al-Zn alloy coating is converted to an intermetallic surface layer of Fe2Al5 and a FeAl intermetallic diffusion layer. The Zn is separated from both intermetallic compounds and accumulates at grain boundaries and at the surface. This Zn separation process is beneficial in terms of providing cathodic protection to Al-Zn coated press hardening steel.

  9. Innovative processing to produce advanced intermetallic materials. Phase 1 final report

    SciTech Connect

    Loutfy, R.O.

    1989-09-01

    The program demonstrates the technical feasibility of synthesizing submicron titanium aluminide in a thermal rf plasma. Micron and submicron spherical titanium aluminide particles are produced in argon, hydrogen, and argon/hydrogen plasmas from the reaction of TiCl4(g), and Al(g). The ratio of Ti and Al is varied to produce the compounds Ti3Al, TiAl, and TiAl3. Microalloying with boron and macroalloying with niobium is demonstrated. Ti3Al whiskers can be produced, as well as other intermetallics of niobium aluminide, nickel aluminide, and molybdenum disilicide in the plasma synthesis process. Since submicron particles are produced, they have a high surface area and are sensitive to oxidation if not treated with a fugitive protective coating or utilized in a nonoxidizing atmosphere. Ti3Al particles are consolidated and utilized as a matrix for TiC and AlN composites. The submicron AlTi3 has significantly higher strength at room temperature than reported for commercial Ti3Al-11Nb alloy and useable strength is maintained up to 1000 C. The elongation is about the same as for commercial material because of possible oxide contamination in powder handling. However, dimpling and nacking is evident in the fracture surface, which suggests true room temperature ductility. Titanium aluminides have the potential to replace superalloys and become the dominant material for aerospace engines, air frames and skins for hypersonic vehicles.

  10. Intermetallic Nickel-Titanium Alloys for Oil-Lubricated Bearing Applications

    NASA Technical Reports Server (NTRS)

    DellaCorte, C.; Pepper, S. V.; Noebe, R.; Hull, D. R.; Glennon, G.

    2009-01-01

    An intermetallic nickel-titanium alloy, NITINOL 60 (60NiTi), containing 60 wt% nickel and 40 wt% titanium, is shown to be a promising candidate material for oil-lubricated rolling and sliding contact applications such as bearings and gears. NiTi alloys are well known and normally exploited for their shape memory behavior. When properly processed, however, NITINOL 60 exhibits excellent dimensional stability and useful structural properties. Processed via high temperature, high-pressure powder metallurgy techniques or other means, NITINOL 60 offers a broad combination of physical properties that make it unique among bearing materials. NITINOL 60 is hard, electrically conductive, highly corrosion resistant, less dense than steel, readily machined prior to final heat treatment, nongalling and nonmagnetic. No other bearing alloy, metallic or ceramic encompasses all of these attributes. Further, NITINOL 60 has shown remarkable tribological performance when compared to other aerospace bearing alloys under oil-lubricated conditions. Spiral orbit tribometer (SOT) tests were conducted in vacuum using NITINOL 60 balls loaded between rotating 440C stainless steel disks, lubricated with synthetic hydrocarbon oil. Under conditions considered representative of precision bearings, the performance (life and friction) equaled or exceeded that observed with silicon nitride or titanium carbide coated 440C bearing balls. Based upon this preliminary data, it appears that NITINOL 60, despite its high titanium content, is a promising candidate alloy for advanced mechanical systems requiring superior and intrinsic corrosion resistance, electrical conductivity and nonmagnetic behavior under lubricated contacting conditions.

  11. Model-based predictions of solid state intermetallic compound layer growth in hybrid microelectronic circuits

    SciTech Connect

    Vianco, P.T.; Erickson, K.L.; Hopkins, P.L.

    1997-12-31

    A mathematical model was developed to quantitatively describe the intermetallic compound (IMC) layer growth that takes place between a Sn-based solder and a noble metal thick film conductor material used in hybrid microcircuit (HMC) assemblies. The model combined the reaction kinetics of the solder/substrate interaction, as determined from ancillary isothermal aging experiments, with a 2-D finite element mesh that took account of the porous morphology of the thick film coating. The effect of the porous morphology on the IMC layer growth when compared to the traditional 1-D computations was significant. The previous 1-D calculations under-predicted the nominal IMC layer thickness relative to the 2-D case. The 2-D model showed greater substrate consumption by IMC growth and lesser solder consumption that was determined with the 1-D computation. The new 2-D model allows the design engineer to better predict circuit aging and hence, the reliability of HMC hardware that is placed in the field.

  12. Distribution of aluminum in hot-dip galvanized coatings

    SciTech Connect

    Furdanowicz, V.; Shastry, C.R.

    1999-12-01

    Hot-dip galvanized panels of low-carbon (LC) and interstitial-free (IF) steels were produced in a laboratory simulator with an average coating mass of 60 g/m{sup 2}. Three pot aluminum levels were used, viz. 0.10% (by wt), 0.15%, and 0.18%. Metallography, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize coating and base steel microstructures. Wet chemical analysis and scanning transmission electron microscopy (STEM) were employed for compositional analyses. The aluminum content of the melt was found to be the predominant factor influencing the distribution of Al in the coating. At 0.18% melt aluminum, Al is partitioned between the aluminide inhibition layer at the coating-steel interface ({approximately}80%) and the zinc overlay ({approximately}20%). At 0.15%, it is partitioned among the aluminide layer ({approximately}75% to 80%), zinc-iron (FeZn{sub 13}, {zeta}) intermetallic layer ({approximately}5% to 15%), and the coating overlay ({approximately}10%). At 0.10%, the aluminum is divided almost equally between the overlay and the zinc-iron intermetallics. At the two lower aluminum levels is the distribution marginally influenced by the steel grade. The {zeta} was found to not preferentially nucleate at the ferrite grain boundaries. When both the aluminide and {zeta} occurred at the coating-steel interface, the {zeta} particles appeared near discontinuities and thinner regions in the aluminide layer. The coating, relative to the melt, is enriched in aluminum because of its concentration in the aluminide and in the zinc-iron intermetallics. This enrichment increases with melt aluminum through an increase in the aluminum content of the aluminide layer and not of its thickness.

  13. Exo-Melt{trademark} process for intermetallic powders

    SciTech Connect

    Sikka, V.K.; Deevi, S.C.

    1996-06-01

    The methods of powder production for intermetallics are reviewed. An innovative method known as Exo-Melt{trademark} is described for producing molten aluminides for gas- and water-atomization processes that require a molten metal stream. The Exo-Melt{trademark} process is based on the effective utilization of the heats of formation of aluminides from their constituent elements. The Exo-Melt{trademark} process principles are discussed along with a description of a furnace-loading sequence that uses the principles for practical applications. The benefits of the Exo-Melt{trademark} process are compared with the problems associated with the conventional melting process.

  14. Oxygen-stabilized zirconium-vanadium intermetallic compound

    DOEpatents

    Mendelsohn, M.H.; Gruen, D.M.

    1981-10-06

    An oxygen stabilized intermetallic compound having the formula Zr/sub x/OV/sub y/ where x = 0.7 to 2.0 and y = 0.18 to 0.33 is described. The compound is capable of reversibly sorbing hydrogen at temperatures from - 196/sup 0/C to 450/sup 0/C at pressures down to 10/sup -6/ Torr. The compound is also capable of selectively sorbing hydrogen from gaseous mixtures in the presence of CO and CO/sub 2/.

  15. Chemistry and Properties of Complex Intermetallics from Metallic Fluxes

    SciTech Connect

    Kanatzidis, Mercouri G.

    2015-03-28

    This project investigated the reaction chemistry and synthesis of new intermetallic materials with complex compositions and structures using metallic fluxes as solvents. It was found that the metallic fluxes offer several key advantages in facilitating the formation and crystal growth of new materials. The fluxes mostly explored were liquid aluminum, gallium and indium. The main purpose of this project was to exploit the potential of metallic fluxes as high temperature solvent for materials discovery in the broad class of intermetallics. This work opened new paths to compound formation. We discovered many new Si (or Ge)-based compounds with novel structures, bonding and physicochemical properties. We created new insights about the reaction chemistry that is responsible for stabilizing the new materials. We also studied the structural and compositional relationships to understand their properties. We investigated the use of Group-13 metals Al, Ga and In as solvents and have generated a wide variety of new results including several new ternary and quaternary materials with fascinating structures and properties as well as new insights as to how these systems are stabilized in the fluxes. The project focused on reactions of metals from the rare earth element family in combination with transition metals with Si and Ge. For example molten gallium has serves both as a reactive and non-reactive solvent in the preparation and crystallization of intermetallics in the system RE/M/Ga/Ge(Si). Molten indium behaves similarly in that it too is an excellent reaction medium, but it gives compounds that are different from those obtained from gallium. Some of the new phase identified in the aluminide class are complex phases and may be present in many advanced Al-matrix alloys. Such phases play a key role in determining (either beneficially or detrimentally) the mechanical properties of advanced Al-matrix alloys. This project enhanced our basic knowledge of the solid state chemistry

  16. Study of Intermetallic Nanostructures for Light-Water Reactors

    SciTech Connect

    Jensen, Niels Grobech; Asta, Mark D.; Hosemann, Peter; Maloy, Stuart

    2015-09-30

    High temperature mechanical measurements were conducted to study the effect of the dynamic precipitation process of PH 13-8 Mo maraging steel. Yield stress, ultimate tensile strength, total elongation, hardness, strain rate sensitivity and activation volume were evaluated as a function of the temperature. The dynamic changes in the mechanical properties at different temperatures were evaluated and a balance between precipitation hardening and annealed softening is discussed. A comparison between hardness and yield stress and ultimate tensile strength over a temperature range from 300 to 600 °C is made. The behavior of the strain rate sensitivity was correlated with the intermetallic precipitates formed during the experiments.

  17. A survey of combustible metals, thermites, and intermetallics for pyrotechnic applications

    SciTech Connect

    Fischer, S.H.; Grubelich, M.C.

    1996-08-01

    Thermite mixtures, intermetallic reactants, and metal fuels have long been used in pyrotechnics. Advantages include high energy density, impact insensitivity, high combustion temperature, and a wide range of gas production. They generally exhibit high temperature stability and possess insensitive ignition properties. This paper reviews the applications, benefits, and characteristics of thermite mixtures, intermetallic reactants, and metal fuels. 50 refs, tables.

  18. Structural and Tribological Properties of Nanostructured Supersonic Cold Sprayed Ni-20 wt.% Sn Coatings

    NASA Astrophysics Data System (ADS)

    Georgiou, E. P.; Dosta, S.; Fernández, J.; Matteazzi, P.; Kowalski, K.; Kusinski, J.; Piticescu, R. R.; Celis, J.-P.

    2016-05-01

    80-μm-thick nanostructured coatings consisting of a Ni solid solution, Ni3Sn, Ni3Sn2, and metastable NiSn intermetallic phases were deposited via supersonic cold spraying onto inconel 718 alloy substrates. These coatings have complex nanostructured metallurgical phases as revealed by transition electron microscopy, scanning electron microscopy, and x-ray diffraction techniques. Their mechanical properties were determined by nanoindentation measurements. Furthermore, the wear behavior of these nanostructured sprayed coatings was compared to the one of the industrial bulk or sprayed coated benchmark materials. It was found that the nanostructured coatings exhibit higher wear resistance than the industrial benchmarks, thanks to an appropriate balance of hard intermetallic phases and soft Ni matrix, as well as to their nanostructuring. Their frictional characteristics under reciprocating sliding are mainly determined by the formation of an oxide-based tribo-layer, which was analyzed by x-ray photoelectron spectroscopy. The role of intermetallic phases in these coatings on the friction and wear is also discussed.

  19. Structural and Tribological Properties of Nanostructured Supersonic Cold Sprayed Ni-20 wt.% Sn Coatings

    NASA Astrophysics Data System (ADS)

    Georgiou, E. P.; Dosta, S.; Fernández, J.; Matteazzi, P.; Kowalski, K.; Kusinski, J.; Piticescu, R. R.; Celis, J.-P.

    2016-06-01

    80-μm-thick nanostructured coatings consisting of a Ni solid solution, Ni3Sn, Ni3Sn2, and metastable NiSn intermetallic phases were deposited via supersonic cold spraying onto inconel 718 alloy substrates. These coatings have complex nanostructured metallurgical phases as revealed by transition electron microscopy, scanning electron microscopy, and x-ray diffraction techniques. Their mechanical properties were determined by nanoindentation measurements. Furthermore, the wear behavior of these nanostructured sprayed coatings was compared to the one of the industrial bulk or sprayed coated benchmark materials. It was found that the nanostructured coatings exhibit higher wear resistance than the industrial benchmarks, thanks to an appropriate balance of hard intermetallic phases and soft Ni matrix, as well as to their nanostructuring. Their frictional characteristics under reciprocating sliding are mainly determined by the formation of an oxide-based tribo-layer, which was analyzed by x-ray photoelectron spectroscopy. The role of intermetallic phases in these coatings on the friction and wear is also discussed.

  20. Theoretical Energy Release of Thermites, Intermetallics, and Combustible Metals

    SciTech Connect

    Fischer, S.H.; Grubelich, M.C.

    1999-05-14

    Thermite mixtures, intermetallic reactants, and metal fuels have long been used in pyrotechnic applications. Advantages of these systems typically include high energy density, high combustion temperature, and a wide range of gas production. They generally exhibit high temperature stability and possess insensitive ignition properties. For the specific applications of humanitarian demining and disposal of unexploded ordnance, these pyrotechnic formulations offer additional benefits. The combination of high thermal input with low brisance can be used to neutralize the energetic materials in mines and other ordnance without the "explosive" high-blast-pressure events that can cause extensive collateral damage to personnel, facilities, and the environment. In this paper, we review the applications, benefits, and characteristics of thermite mixtures, intermetallic reactants, and metal fuels. Calculated values for reactant density, heat of reaction (per unit mass and per unit volume), and reaction temperature (without and with consideration of phase changes and the variation of specific heat values) are tabulated. These data are ranked in several ways, according to density, heat of reaction, reaction temperature, and gas production.

  1. In situ examination of moving crack tips in ordered intermetallics.

    SciTech Connect

    Heuer, J.; Lam, N. Q.; Okamoto, P. R.; Stubbins, J. F.

    1999-01-25

    Recent studies have shown that high stress concentrations at moving crack tips in the intermetallic compound NiTi can induce a crystalline-to-amorphous (C-A) transformation of the crack tip region. This stress-induced C-A transformation has a temperature dependence and crystallization behavior similar to those of ion irradiation-induced C-A transformation of NiTi. The present study examines if these similarities between stress- and irradiation-induced amorphization hold true for two other intermetallic compounds, CuTi and Ni{sub 3}Ti. In situ straining was performed in an intermediate-voltage transmission electron microscope. The presence or absence of an amorphous phase was determined by dark field imaging and selected area diffraction of crack tip regions. Crack tips in both CuTi and Ni{sub 3}Ti were found to remain crystalline upon fracture. The observed absence of stress-induced amorphization in Ni{sub 3}Ti is consistent with its known absence during irradiation, but the absence in CuTi differs from its known irradiation-induced amorphization behavior. Reasons for the similarity and difference are discussed.

  2. Intermetallic and titanium matrix composite materials for hypersonic applications

    SciTech Connect

    Berton, B.; Surdon, G.; Colin, C. |

    1995-09-01

    As part of the French Program of Research and Technology for Advanced Hypersonic Propulsion (PREPHA) which was launched in 1992 between Aerospatiale, Dassault Aviation, ONERA, SNECMA and SEP, an important work is specially devoted to the development of titanium and intermetallic composite materials for large airframe structures. At Dassault Aviation, starting from a long experience in Superplastic Forming - Diffusion Bonding (SPF-DB) of titanium parts, the effort is brought on the manufacturing and characterization of composites made from Timet beta 21S or IMI 834 foils and Textron SCS6 fiber fabrics. At `Aersopatiale Espace & Defence`, associated since a long time about intermetallic composite materials with university research laboratories, the principal effort is brought on plasma technology to develop the gamma titanium aluminide TiAl matrix composite reinforced by protected silicon carbide fibers (BP SM 1240 or TEXTRON SCS6). The objective, is to achieve, after 3 years of time, to elaborate a medium size integrally stiffened panel (300 x 600 sq mm).

  3. Formation and nitridation of vanadium-aluminum intermetallic compounds.

    PubMed

    Lewalter, H; Bock, W; Kolbesen, B O

    2002-10-01

    V(5)Al(8) and V(3)Al intermetallics have been formed by interdiffusion, by annealing of sputtered V/Al-multilayers at 700 degrees C in vacuo; sapphire (102) was used as substrate. The V/Al intermetallics were nitridated in NH(3) at 900 degrees C for 1 min by RTP (rapid thermal processing). The samples were investigated with XRD (X-ray diffraction), SNMS (secondary neutral mass spectrometry), and AFM (atomic force microscopy). A 5-10 nm thick AlN film (001 textured) was formed by nitridation of V(5)Al(8) (110 textured) and 2-3% nitrogen was incorporated in the V(5)Al(8) bulk. Nitridation of V(3)Al resulted in the formation of VN and AlN. Direct nitridation of V/Al-multilayers showed that near the surface nitridation is faster than intermixing of the V and Al layers. The capability of VN as diffusion barrier for Al could also be shown. PMID:12397502

  4. Spark plasma sintering of titanium aluminide intermetallics and its composites

    NASA Astrophysics Data System (ADS)

    Aldoshan, Abdelhakim Ahmed

    Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (< 10 min) with a lower temperature and leads to highly dense products. Reactive synthesis of titanium aluminide intermetallics is carried out using SPS. Reactive sintering takes place between liquid aluminum and solid titanium. In this work, reactive sintering through SPS was used to fabricate fully densified gamma-TiAl and titanium aluminide composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

  5. Surfaces of complex intermetallic compounds: insights from density functional calculations.

    PubMed

    Hafner, Jürgen; Krajčí, Marian

    2014-11-18

    CONSPECTUS: Complex intermetallic compounds are a class of ordered alloys consisting of quasicrystals and other ordered compounds with large unit cells; many of them are approximant phases to quasicrystals. Quasicrystals are the limiting case where the unit cell becomes infinitely large; approximants are series of periodic structures converging to the quasicrystal. While the unique properties of quasicrystals have inspired many investigations of their surfaces, relatively little attention has been devoted to the surface properties of the approximants. In general, complex intermetallic compounds display rather irregular, often strongly corrugated surfaces, making the determination of their atomic structure a very complex and challenging task. During recent years, scanning tunneling microscopy (STM) has been used to study the surfaces of several complex intermetallic compounds. If atomic resolution can be achieved, STM permits visualization of the local atomistic surface structure. However, the interpretation of the STM images is often ambiguous and sometimes even impossible without a realistic model of the structure of the surface and the distribution of the electronic density above the surface. Here we demonstrate that ab initio density functional theory (DFT) can be used to determine the energetics and the geometric and electronic structures of the stable surfaces of complex intermetallic compounds. Calculations for surfaces with different chemical compositions can be performed in the grand canonical ensemble. Simulated cleavage experiments permit us to determine the formation of the cleavage planes requiring the lowest energy. The investigation of the adsorption of molecular species permits a comparison with temperature-programmed thermal desorption experiments. Calculated surface electronic densities of state can be compared with the results of photoelectron spectroscopy. Simulations of detailed STM images can be directly confronted with the experimental results

  6. Structural and Electronic Investigations of Complex Intermetallic Compounds

    SciTech Connect

    Ko, Hyunjin

    2008-01-01

    In solid state chemistry, numerous investigations have been attempted to address the relationships between chemical structure and physical properties. Such questions include: (1) How can we understand the driving forces of the atomic arrangements in complex solids that exhibit interesting chemical and physical properties? (2) How do different elements distribute themselves in a solid-state structure? (3) Can we develop a chemical understanding to predict the effects of valence electron concentration on the structures and magnetic ordering of systems by both experimental and theoretical means? Although these issues are relevant to various compound classes, intermetallic compounds are especially interesting and well suited for a joint experimental and theoretical effort. For intermetallic compounds, the questions listed above are difficult to answer since many of the constituent atoms simply do not crystallize in the same manner as in their separate, elemental structures. Also, theoretical studies suggest that the energy differences between various structural alternatives are small. For example, Al and Ga both belong in the same group on the Periodic Table of Elements and share many similar chemical properties. Al crystallizes in the fcc lattice with 4 atoms per unit cell and Ga crystallizes in an orthorhombic unit cell lattice with 8 atoms per unit cell, which are both fairly simple structures (Figure 1). However, when combined with Mn, which itself has a very complex cubic crystal structure with 58 atoms per unit cell, the resulting intermetallic compounds crystallize in a completely different fashion. At the 1:1 stoichiometry, MnAl forms a very simple tetragonal lattice with two atoms per primitive unit cell, while MnGa crystallizes in a complicated rhombohedral unit cell with 26 atoms within the primitive unit cell. The mechanisms influencing the arrangements of atoms in numerous crystal structures have been studied theoretically by calculating electronic

  7. Morphological and microstructural studies on aluminizing coating of carbon steel

    SciTech Connect

    Samsu, Zaifol; Othman, Norinsan Kamil; Daud, Abd Razak; Hussein, Hishammuddin

    2013-11-27

    Hot dip aluminizing is one of the most effective methods of surface protection for steels and is gradually gaining popularity. The morphology and microstructure of an inter-metallic layer form on the surface of low carbon steel by hot dip aluminization treatment had been studied in detail. This effect has been investigated using optical and scanning electron microscopy, and X-ray diffraction. The result shows that the reaction between the steel and the molten aluminium leads to the formation of Fe–Al inter-metallic compounds on the steel surface. X-ray diffraction and electron microscopic studies showed that a two layer coating was formed consisting of an external Al layer and a (Fe{sub 2}Al{sub 5}) inter metallic on top of the substrate after hot dip aluminizing process. The inter-metallic layer is ‘thick’ and exhibits a finger-like growth into the steel. Microhardness testing shown that the intermetallic layer has high hardness followed by steel substrate and the lowest hardness was Al layer.

  8. Aluminide coatings

    DOEpatents

    Henager, Jr; Charles, H [Kennewick, WA; Shin, Yongsoon [Richland, WA; Samuels, William D [Richland, WA

    2009-08-18

    Disclosed herein are aluminide coatings. In one embodiment coatings are used as a barrier coating to protect a metal substrate, such as a steel or a superalloy, from various chemical environments, including oxidizing, reducing and/or sulfidizing conditions. In addition, the disclosed coatings can be used, for example, to prevent the substantial diffusion of various elements, such as chromium, at elevated service temperatures. Related methods for preparing protective coatings on metal substrates are also described.

  9. COATED ALLOYS

    DOEpatents

    Harman, C.G.; O'Bannon, L.S.

    1958-07-15

    A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

  10. Influence of heat treatment on tribological properties of electroless Ni-P and Ni-P-Al 2O 3 coatings on Al-Si casting alloy

    NASA Astrophysics Data System (ADS)

    Novák, M.; Vojtěch, D.; Vítů, T.

    2010-02-01

    Evolution of tribological properties of electroless Ni-P and Ni-P-Al 2O 3 coating on an Al-10Si-0.3Mg casting alloy during heat treatment is investigated in this work. The pre-treated substrate was plated using a bath containing nickel hypophosphite, nickel lactate and lactic acid. For preparation of fiber-reinforced coating Al 2O 3 Saffil fibers pre-treated in demineralised water were used. The coated samples were heat treated at 400-550 °C/1-8 h. Tribological properties were studied using the pin-on-disc method. It is found that the best coating performance is obtained using optimal heat treatment regime (400 °C/1 h). Annealing at higher temperatures (450 °C and above) leads to the formation of intermetallic compounds that reduce the coating wear resistance. The reason is that the intermetallic phases adversely affect the coating adherence to the substrate. The analysis of wear tracks proves that abrasion is major wear mechanism, however due to the formed intermetallic sub-layers, partial coating delamination may occur during the pin-on-disc test on the samples annealed at 450 °C and above. It was found that fiber reinforcement reduces this scaling and increases wear resistance of coatings as compared to the non-reinforced Ni-P coatings.

  11. Role of Ag in the formation of interfacial intermetallic phases in Sn-Zn soldering

    NASA Astrophysics Data System (ADS)

    Song, Jenn-Ming; Liu, Pei-Chi; Shih, Chia-Ling; Lin, Kwang-Lung

    2005-09-01

    This study explored the effect of Ag as the substrate or alloying element of solders on the interfacial reaction in Sn-Zn soldering. Results show that instead of Ag-Sn compounds, ζ-AgZn and γ-Ag5Zn8 form at the Sn-Zn/Ag interface. The addition of Ag in Sn-Zn solders leads to the precipitation of ɛ-AgZn3 from the liquid solder on preformed interfacial intermetallics. The morphology of this additional AgZn3 is closely related to the solidification process of Ag-Zn intermetallics and the under intermetallic layer.

  12. Fundamentals of mechanical behavior in structural intermetallics: A synthesis of atomistic and continuum modeling

    SciTech Connect

    Yoo, M.H.; Fu, C.L.

    1993-08-01

    After a brief account of the recent advances in computational research on mechanical behavior of structural intermetallics, currently unresolved problems and critical issues are addressed and the knowledge base for potential answers to these problems is discussed. As large-scale problems (e.g., dislocation core structures, grain boundaries, and crack tips) are treated by atomistic simulations, future development of relevant interatomic potentials should be made consistent with the results of first-principles calculations. The bulk and defect properties calculated for intermetallic compounds, both known and as yet untested, can furnish insights to alloy designers in search of new high-temperature structural intermetallics.

  13. Formation of intermetallics at the interface of explosively welded Ni-Al multilayered composites during annealing

    NASA Astrophysics Data System (ADS)

    Ogneva, T. S.; Lazurenko, D. V.; Bataev, I. A.; Mali, V. I.; Esikov, M. A.; Bataev, A. A.

    2016-04-01

    The Ni-Al multilayer composite was fabricated using explosive welding. The zones of mixing of Ni and Al are observed at the composite interfaces after the welding. The composition of these zones is inhomogeneous. Continuous homogeneous intermetallic layers are formed at the interface after heat treatment at 620 °C during 5 h These intermetallic layers consist of NiAl3 and Ni2Al3 phases. The presence of mixed zones significantly accelerates the growth rate of intermetallic phases at the initial stages of heating.

  14. 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.

  15. Influence of Chemical Composition of Mg Alloys on Surface Alloying by Diffusion Coating

    NASA Astrophysics Data System (ADS)

    Hirmke, J.; Zhang, M.-X.; St John, D. H.

    2012-05-01

    A recently developed technique of surface alloying by diffusion-coating has been used to produce coatings on Mg alloys with various Al and Zn contents. The experimental results show that both Al and Zn solutes in the alloy promote the diffusion of alloying elements through grain refinement of the substrate alloys and through reduction of diffusion active energy because of the reduction of melting temperature of the alloys. Therefore, the efficiency of surface alloying increases by diffusion coating. Thick, dense, uniform, and continuous layers of intermetallic compounds, which consist of a τ-phase layer and a β-phase layer, can be produced on the surface of various Mg alloys. The intermetallic compound layers not only have microhardness values that are 4 to 6 times higher than the substrate but also provide effective protection of the Mg alloys from corrosion in 5 pct NaCl solution at room temperature.

  16. Mechanical and Tribological Behavior of Ni(Al)-Reinforced Nanocomposite Plasma Spray Coatings

    NASA Astrophysics Data System (ADS)

    Movahedi, B.

    2014-02-01

    The mechanical and tribological behavior and microstructural evolutions of the Ni(Al)-reinforced nanocomposite plasma spray coatings were studied. At first, the feedstock Ni(Al)-15 wt.% (Al2O3-13% TiO2) nanocomposite powders were prepared using low-energy mechanical milling of the pure Ni and Al powders as well as Al2O3-13% TiO2 nanoparticle mixtures. The characteristics of the powder particles and the prepared coatings depending on their microstructures were examined in detail. The results showed that the feedstock powders after milling contained only α-Ni solid solution with no trace of the intermetallic phase. However, under the air plasma spraying conditions, the NiAl intermetallic phase in the α-Ni solid solution matrix appeared. The lack of nickel aluminide formation during low-energy ball milling is beneficial hence, the exothermic reaction can occur between Ni and Al during plasma spraying, improving the adhesive strength of the nanocomposite coatings. The results also indicated that the microhardness of the α-Ni phase was 3.91 ± 0.23 GPa and the NiAl intermetallic phase had a mean microhardness of 5.69 ± 0.12 GPa. The high microhardness of the nanocomposite coatings must be due to the presence of the reinforcing nanoparticles. Due to the improvement in mechanical properties, the Ni(Al) nanocomposite coatings showed significant modifications in wear resistance with low frictional coefficient.

  17. Plastic deformation of ordered intermetallic alloys: Fundamental aspects

    SciTech Connect

    Yoo, M.H.

    1994-10-01

    Fundamental aspects of plastic deformation in ordered intermetallic alloys are reviewed by directly comparing the temperature-dependent yield stresses of Ni{sub 3}Al and Ni{sub 3}Si (the L1{sub 2} structure), NiAl and FeAl (the B2 structure), and TiAl and Ti{sub 3}Al (non-cubic L1{sub 0} and D0{sub 19} structures, respectively). While the yield strength anomaly observed in Ni{sub 3}Al is consistent with the prevailing dislocation models, that found in stoichiometric Ni{sub 3}Si is not. The strong plastic anisotropy observed in NiAl stems from the high antiphase boundary energy, and that found in two-phase {gamma}-TiAl/{alpha}{sub 2}-Ti{sub 3}Al is due to the exceptionally high compressive yield strength along the c-axis of Ti{sub 3}Al.

  18. The oxidation of Ni-rich Ni-Al intermetallics

    NASA Technical Reports Server (NTRS)

    Doychak, J.; Smialek, J. L.; Barrett, C. A.

    1989-01-01

    The oxidation of Ni-Al intermetallic alloys in the beta-NiAl phase field and in the two phase beta-NiAl/gamma'-Ni3Al phase field has been studied between 1000 and 1400 C. The stoichiometric beta-NiAl alloy doped with Zr was superior to other alloy compositions under cyclic and isothermal oxidation. The isothermal growth rates did not increase monotonically as the alloy Al content was decreased. The characteristically ridged alpha-Al203 scale morphology, consisting of cells of thin, textured oxide with thick growth ridges at cell boundaries, forms on oxidized beta-NiAl alloys. The correlation of scale features with isothermal growth rates indicates a predominant grain boundary diffusion growth mechanism. The 1200 C cyclic oxidation resistance decreases near the lower end of the beta-NiAl phase field.

  19. The oxidation of Ni-rich Ni-Al intermetallics

    NASA Technical Reports Server (NTRS)

    Doychak, Joseph; Smialek, James L.; Barrett, Charles A.

    1988-01-01

    The oxidation of Ni-Al intermetallic alloys in the beta-NiAl phase field and in the two phase beta-NiAl/gamma'-Ni3Al phase field has been studied between 1000 and 1400 C. The stoichiometric beta-NiAl alloy doped with Zr was superior to other alloy compositions under cyclic and isothermal oxidation. The isothermal growth rates did not increase monotonically as the alloy Al content was decreased. The characteristically ridged alpha-Al2O3 scale morphology, consisting of cells of thin, textured oxide with thick growth ridges at cell boundaries, forms on oxidized beta-NiAl alloys. The correlation of scale features with isothermal growth rates indicates a predominant grain boundary diffusion growth mechanism. The 1200 C cyclic oxidation resistance decreases near the lower end of the beta-NiAl phase field.

  20. Effects of elastic anisotropy on mechanical behavior of intermetallic compounds

    SciTech Connect

    Yoo, M.H.

    1991-01-01

    Fundamental aspects of the deformation and fracture behavior of ordered intermetallic compounds are examined within the framework of linear anisotropic elasticity theory of dislocations and cracks. The orientation dependence and the tension/compression asymmetry of yield stress are explained in terms of the anisotropic coupling effect of non-glide stresses to the glide strain. The anomalous yield behavior is related to the disparity (edge/screw) of dislocation mobility and the critical stress required for the dislocation multiplication mechanism of Frank-Read type. The slip-twin conjugate relationship, extensive faulting, and pseudo-twinning (martensitic transformation) at a crack tip can be enhanced also by the anisotropic coupling effect, which may lead to transformation toughening of shear type.

  1. Modeling of Intermetallic Compounds Growth Between Dissimilar Metals

    NASA Astrophysics Data System (ADS)

    Wang, Li; Wang, Yin; Prangnell, Philip; Robson, Joseph

    2015-09-01

    A model has been developed to predict growth kinetics of the intermetallic phases (IMCs) formed in a reactive diffusion couple between two metals for the case where multiple IMC phases are observed. The model explicitly accounts for the effect of grain boundary diffusion through the IMC layer, and can thus be used to explore the effect of IMC grain size on the thickening of the reaction layer. The model has been applied to the industrially important case of aluminum to magnesium alloy diffusion couples in which several different IMC phases are possible. It is demonstrated that there is a transition from grain boundary-dominated diffusion to lattice-dominated diffusion at a critical grain size, which is different for each IMC phase. The varying contribution of grain boundary diffusion to the overall thickening kinetics with changing grain size helps explain the large scatter in thickening kinetics reported for diffusion couples produced under different conditions.

  2. Development of New Cryocooler Regenerator Materials-Ductile Intermetallic Compounds

    SciTech Connect

    K.A. Gschneidner; A.O. Pecharsky; V.K. Pecharsky

    2004-09-30

    The volumetric heat capacities of a number of binary and ternary Er- and Tm-based intermetallic compounds, which exhibited substantial ductilities, were measured from {approx}3 to {approx}350 K. They have the RM stoichiometry (where R = Er or Tm, and M is a main group or transition metal) and crystallize in the CsCl-type structure. The heat capacities of the Tm-based compounds are in general larger than the corresponding Er-based materials. Many of them have heat capacities which are significantly larger than those of the low temperature (<15 K) prototype cryocooler regenerator materials HoCu{sub 2}, Er{sub 3}Ni and ErNi. Utilization of the new materials as regenerators in the various cryocoolers should improve the performance of these refrigeration units for cooling below 15 K.

  3. Compton Profile Study of Intermetallic Ti{sub 3}Al

    SciTech Connect

    Vyas, V.; Sharma, G.; Mishra, M. C.; Sharma, B. K.; Joshi, K. B.

    2011-10-20

    The Compton scattering measurement on intermetallic alloy Ti{sub 3}Al is reported in this work. The measurement is made using 59.54 keV gamma-rays from Am{sup 241} source. Theoretical calculation of Compton profile is also performed employing CRYSTAL code within the framework of density functional theory to compare with the measurement. The theoretical profile of the alloy is also synthesized following the superposition model taking the published Compton profiles of elemental solids from the APW method. The experimental study of charge transfer in the alloys has also been done by performing the experimental Compton profile measurements on Ti and Al following the superposition model and charge transfer from Al to Ti is clearly seen on the alloy formation.

  4. Intermetallic strengthened alumina-forming austenitic steels for energy applications

    NASA Astrophysics Data System (ADS)

    Hu, Bin

    In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, materials required are strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and Ni3Al precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe 2Nb + L12-Ni3Al precipitates) without harmful effects on oxidation resistance. This research starts with microstructural and microchemical analyses of these intermetallic strengthened alumina-forming austenitic steels in a scanning electron microscope. The microchemistry of precipitates, as determined by energy-dispersive x-ray spectroscopy and transmission electron microscope, is also studied. Different thermo-mechanical treatments were carried out to these stainless steels in an attempt to further improve their mechanical properties. The microstructural and microchemical analyses were again performed after the thermo-mechanical processing. Synchrotron X-ray diffraction was used to measure the lattice parameters of these steels after different thermo-mechanical treatments. Tensile tests at both room and elevated temperatures were performed to study mechanical behaviors of this novel alloy system; the deformation mechanisms were studied by strain rate jump tests at elevated temperatures. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these alumina-forming austenitic steels after creep tests. Experiments were carried out to study the effects of boron and carbon additions in the aged alumina-forming austenitic steels.

  5. The role of ALCHEMI in understanding the properties of ordered intermetallic alloys

    SciTech Connect

    Anderson, I.M.

    1998-11-01

    After one and one-half decades of development, ALCHEMI is approaching the status of an established analytical technique. Many of the problems that have plagued ALCHEMI, especially for the analysis of ordered intermetallic alloys, are now well understood, and accurate site-distributions can be extracted from a variety of intermetallic alloys. This paper begins with an overview of the factors that can lead to large systematic errors or gross misinterpretations of ALCHEMI data, with illustrations from a variety of ordered intermetallic alloys. The paper concludes with a discussion of ALCHEMI in the broader context of understanding the properties of ordered intermetallic alloys. The results of systematic studies are used to illustrate the role of ALCHEMI in determining the competing effects of thermodynamic and kinetic factors during alloy processing and the correlation of alloy properties with the atomic site distributions on which the properties ultimately depend.

  6. Oxidation resistant slurry coating for carbon-based materials

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Rybicki, G. C. (Inventor)

    1985-01-01

    An oxidation resistant coating is produced on carbon-base materials, and the same processing step effects an infiltration of the substrate with silicon containing material. The process comprises making a slurry of nickel and silicon powders in a nitrocellulose lacquer, spraying onto the graphite or carbon-carbon substrate, and sintering in vacuum to form a fused coating that wets and covers the surface as well as penetrates into the pores of the substrate. Optimum wetting and infiltration occurs in the range of Ni-60 w/o Si to Ni-90 w/o Si with deposited thicknesses of 25-100 mg/sq. cm. Sintering temperatures of about 1200 C to about 1400 C are used, depending on the melting point of the specific coating composition. The sintered coating results in Ni-Si intermetallic phases and SiC, both of which are highly oxidation resistant.

  7. Nanocrystalline Pd alloy films coated by electroless deposition.

    PubMed

    Strukov, G V; Strukova, G K; Batov, I E; Sakharov, M K; Kudrenko, E A; Mazilkin, A A

    2011-10-01

    The structures of palladium and palladium alloys thin films deposited from organic electrolytes onto metallic substrates by electroless plating method have been investigated. The coatings are dense, pore-free 0.005-1 microm thick films with high adhesive strength to the substrate surface. EDX, XRD, SEM and TEM methods were used to determine the composition and structure of alloy coatings of the following binary systems: Pd-Au, Pd-Ag, Pd-Ni, Pd-Pb, and ternary system Pd-Au-Ni. The coatings of Pd-Au, Pd-Ag and Pd-Ni have a solid solution structure, whereas Pd-Pb is intermetallic compound. It has been found that the deposited films consist of nanocrystalline grains with sizes in the range of 11-35 nm. Scanning and transmission electron microscopy investigations reveal the existence of clusters formed by nanocrystalline grains. The origin for the formation of nanocrystalline structures of coating films is discussed. PMID:22400291

  8. Coating Process

    NASA Technical Reports Server (NTRS)

    1983-01-01

    A black chrome coating, originally developed for spacecraft solar cells, led to the development of an efficient flat plate solar collector. The coating, called Chromonyx, helps the collector absorb more heat. Olympic Solar Corporation was formed to electroplate the collector. The coating technique allows 95% of the sun's energy to be utilized. The process is widely used.

  9. Modeling of crack tip dislocation emission in B2 intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Bartholomeusz, Michael F.; Wert, John A.

    1992-04-01

    A model has been previously proposed to describe the energy associated with emission of dissociated superlattice dislocations from crack tips in ordered intermetallic alloys. In the present paper, the model is applied to several B2 intermetallic alloys. The results of the analysis reveal a correlation between the range of slip system orientations for which emission of a dislocation from a crack tip is energetically favorable and the macroscopic fracture mode of the alloy.

  10. Intermetallics as Novel Supports for Pt Monolayer O2 Reduction Electrocatalysts: Potential for Significantly Improving Properties

    SciTech Connect

    Ghosh, T.; Vukmirovic, M.; DiSalvo, F.J.; Adzic, R.R.

    2010-01-27

    We report on a new class of core-shell electrocatalysts for the oxygen-reduction reaction. These electrocatalysts comprise a Pt monolayer shell and ordered intermetallic compounds cores and have enhanced activity and stability compared with conventional ones. These advantages are derived from combining the unique properties of Pt monolayer catalysts (high activity, low metal content) and of the intermetallic compounds (high stability and, possibly, low price). This method holds excellent potential for creating efficient fuel cell electrocatalysts.

  11. Metal Coatings

    NASA Technical Reports Server (NTRS)

    1994-01-01

    During the Apollo Program, General Magnaplate Corporation developed process techniques for bonding dry lubricant coatings to space metals. The coatings were not susceptible to outgassing and offered enhanced surface hardness and superior resistance to corrosion and wear. This development was necessary because conventional lubrication processes were inadequate for lightweight materials used in Apollo components. General Magnaplate built on the original technology and became a leader in development of high performance metallurgical surface enhancement coatings - "synergistic" coatings, - which are used in applications from pizza making to laser manufacture. Each of the coatings is designed to protect a specific metal or group of metals to solve problems encountered under operating conditions.

  12. Zintl and intermetallic phases grown from calcium/lithium flux

    NASA Astrophysics Data System (ADS)

    Blankenship, Trevor

    Metal flux synthes is a useful alternative method to high temperature solid state synthesis; it allows easy diffusion of reactants at lower temperatures, and presents favorable conditions for crystal growth. A mixed flux of calcium and lithium in a 1:1 ratio was explored in this work; this mixture melts at 300°C and is an excellent solvent for main group elements and CaH 2. Reactions of p-block elements in a 1:1 Ca/Li flux have produced several new intermetallic and Zintl phases. Electronegative elements from groups 14 and 15 are reduced to anions in this flux, yielding charge-balanced products. More electropositive metals from group 13 are not fully reduced; the resulting products are complex intermetallics. The reactions of tin or lead and carbon in Ca/Li flux produced the analogous phases Ca11Tt3C8 (Tt = Sn, Pb) in the monoclinic C21/c space group (a = 13.2117(8) A, b =10.7029(7) A, c = 14.2493(9) A, beta = 105.650(1)° for the Sn analog). These compounds are carbide Zintl phases that includes the rare combination of C3 4- and C22- units as well as Sn4- or Pb4- anions. Ca/Li flux reactions of CaH2 and arsenic have produced the Zintl phases LiCa3As 2H in orthorhombic Pnma (a = 11.4064(7), b = 4.2702(3), c = 11.8762(8) A), and Ca 13As6C0.46N1.155H6.045in tetragonal P4/mbm (a = 15.7493(15), c = 9.1062(9) A). The complex stoichiometry of the latter phase was caused by incorporation of light element contaminants and was studied by neutron diffraction, showing mixing of anionic sites to achieve charge balance. Ca/Li flux reactions with group 13 metals have resulted in several new intermetallic phases. Reactions of indium and CaH2 in the Ca/Li flux (with or without boron) formed Ca53In13B4-x H23+x(2.4 < x < 4.0) in cubic space group Im-3 (a = 16.3608(6) A) which features metallic indium atoms and ionic hydride sites. The electronic properties of this "subhydride" were confirmed by 1H and 115In NMR spectroscopy. Attempts to replace boron with carbon yielded Ca12InC13-x

  13. Deformation-Induced Amorphization of Copper-Titanium Intermetallics

    NASA Astrophysics Data System (ADS)

    Askenazy, Philip Douglas

    Two methods of inducing amorphization in Cu-Ti intermetallic compounds by mechanical means have been investigated. Ingots of compositions Cu_{35}Ti _{65} and Cu_ {33.3}Ti_{66.7} were rapidly quenched into ribbons. The microstructure consisted largely of microcrystals in an amorphous matrix, which were either quenched in or grown by annealing. The ribbons were cold-rolled, which reduced their effective thickness by a factor of about 8. The status of the intermetallic compound CuTi_2 was monitored by x-ray diffraction and transmission electron microscopy (TEM). The crystals were found to amorphize as rolling progressed. This behavior was not reproduced in polycrystalline samples that had no amorphous matrix present initially. The presence of the amorphous phase is thus necessary for amorphization of the crystal: it eliminates the need to nucleate the new glass, and it prevents the ribbon from disintegrating at high deformation stages. It may also change the deformation mechanism that occurs in the crystals, retarding the onset of amorphization. Diffuse scattering in close-packed directions is similar to that seen in electron irradiation experiments. It is postulated that the chemical disorder present in antiphase boundaries caused by deformation raises the free energy of the crystal higher than that of the amorphous phase. Ingots of the same compound were worn against each other in a custom-built wear apparatus. The design eliminates iron contamination of the wear sample and requires relatively small quantities of material. Alteration of the surface structure was monitored by plane-view and cross -sectional TEM. Larger subsurface crystals exhibit diffuse scattering, similar to that found in the rolled samples. A wide range of grain sizes was observed, due to the inhomogeneous nature of the wear process. An unusual phase was observed at the surface, consisting of a nanometer-scale mixture of aligned nanocrystalline regions and disordered areas. Some amorphous phase is

  14. Reaction synthesis of Ni-Al based particle composite coatings

    SciTech Connect

    SUSAN,DONALD F.; MISIOLEK,WOICECK Z.; MARDER,ARNOLD R.

    2000-02-11

    Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles. By optimizing the process parameters, coatings were deposited with 20 volume percent aluminum particles. Coating morphology and composition were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on coating phase formation was studied in the temperature range 415 to 1,000 C. Long-time exposure at low temperature results in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original Al particles. Upon heating to the 500--600 C range, the aluminum particles react with the nickel matrix to form NiAl islands within the Ni matrix. When exposed to higher temperatures (600--1,000 C), diffusional reaction between NiAl and nickel produces ({gamma})Ni{sub 3}Al. The final equilibrium microstructure consists of blocks of ({gamma}{prime})Ni{sub 3}Al in a {gamma}(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during intermetallic phase formation and microstructural development is discussed with reference to reaction synthesis of bulk nickel aluminides.

  15. Interfacial reaction of intermetallic compounds of ultrasonic-assisted brazed joints between dissimilar alloys of Ti6Al4V and Al4Cu1Mg.

    PubMed

    Ma, Zhipeng; Zhao, Weiwei; Yan, Jiuchun; Li, Dacheng

    2011-09-01

    Ultrasonic-assisted brazing of Al4Cu1Mg and Ti6Al4V using Zn-based filler metal (without and with Si) has been investigated. Before brazing, the Ti6Al4V samples were pre-treated by hot-dip aluminizing and ultrasonic dipping in a molten filler metal bath in order to control the formation of intermetallic compounds between the Ti6Al4V samples and the filler metal. The results show that the TiAl(3) phase was formed in the interface between the Ti6Al4V substrate and the aluminized coating. For the Zn-based filler metal without Si, the Ti6Al4V interfacial area of the brazed joint did not change under the effect of the ultrasonic wave, and only consisted of the TiAl(3) phase. For the Zn-based filler metal with Si, the TiAl(3) phase disappeared and a Ti(7)Al(5)Si(12) phase was formed at the interfacial area of the brazed joints under the effect of the ultrasonic wave. Due to the TiAl(3) phase completely changing to a Ti(7)Al(5)Si(12) phase, the morphology of the intermetallic compounds changed from a block-like shape into a lamellar-like structure. The highest shear strength of 138MPa was obtained from the brazed joint free of the block-like TiAl(3) phase. PMID:21489846

  16. Effect of La2O3 addition on interface chemistry between 4YSZ top layer and Ni based alloy bond coat in thermal barrier coating by EB PVD.

    PubMed

    Park, Chan-Young; Yang, Young-Hwan; Kim, Seong-Won; Lee, Sung-Min; Kim, Hyung-Tae; Jang, Byung-Koog; Lim, Dae-Soon; Oh, Yoon-Suk

    2014-11-01

    The effect of a 5 mol% La2O3 addition on the forming behavior and compositional variation at interface between a 4 mol% Yttria (Y2O3) stabilized ZrO2 (4YSZ) top coat and bond coat (NiCrAlY) as a thermal barrier coating (TBC) has been investigated. Top coats were deposited by electron beam physical vapor deposition (EB PVD) onto a super alloy (Ni-Cr-Co-Al) substrate without pre-oxidation of the bond coat. Top coats are found to consist of dense columnar grains with a thin interdiffusion layer between metallic bond coats. In the as-received 4YSZ coating, a thin interdiffusion zone at the interface between the top and bond coats was found to consist of a Ni-Zr intermetallic compound with a reduced quantity of Y, Al or O elements. On the other hand, in the case of an interdiffusion area of 5 mol% La2O3-added 4YSZ coating, it was found that the complicated composition and structure with La-added YSZ and Ni-Al rich compounds separately. The thermal conductivity of 5 mol% La2O3-added 4YSZ coating (- 1.6 W/m x k at 1100 degrees C) was lower than a 4YSZ coating (- 3.2 W/m x k at 1100 degrees C) alone. PMID:25958580

  17. Determination of site-occupancies in aluminide intermetallics by ALCHEMI

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Duncan, A.J.

    1995-04-01

    The site-distributions of Fe in four B2-ordered NiAl-based alloys with Fe concentrations of 10%, 2%, and 0.5% have been determined by ALCHEMI (atom-location by channeling-enhanced microanalysis). Site-distributions have been extracted with standard errors between {approximately} 1.5% (10% Fe concentration) and {approximately} 6% (0.5% Fe concentration). The results show that Fe has no strong site-preference in NiAl and tends to reside on the site of the stoichiometrically deficient host element. An improved ALCHEMI analysis procedure is outlined. The analysis explicitly addresses the phenomenon of ionization delocalization, which previously complicated the determination of site-distributions in aluminide intermetallics, leading to inaccurate and oftentimes nonphysical results. The improved ALCHEMI analysis also addresses the presence of anti-site defects. The data acquisition conditions have been optimized to minimize the sources of statistical and systematic error. This optimized procedure should be suitable for all analyses of B2-ordered alloys. Several analyses at different channeling orientations show that the extracted site-occupancies are robust as long as the data are acquired at orientations that are remote from any major pole of the crystal.

  18. Processing and properties of molybdenum silicide intermetallics containing boron

    SciTech Connect

    Schneibel, J.H.; Liu, C.T.; Heatherly, L.; Wright, J.L.; Carmichael, C.A.

    1997-08-01

    Molybdenum-silicon-boron intermetallics with the composition Mo-10.5 Si-1.1 B, wt% (Mo-26.7 Si-7.3 B, at. %) were fabricated by several processing techniques. Powder processing (PM) resulted in macrocrack-free material containing no or only few microcracks. The PM materials contained quasi-equilibrium pores and large concentrations of oxygen. Average room temperature flexure strengths of 270 MPa were obtained. At 1,200 C in air, flexure strengths as high as 600 MPa were observed. These high values are attributed to crack healing and incipient plasticity. Ingot metallurgy (IM) materials contained much less oxygen than their PM counterparts. Depending on the cooling rate during solidification, they developed either mostly macrocracks or mostly microcracks. Due to the high flaw densities, the room temperature flexure strengths were only of the order of 100 MPa. However, the flexure strengths at 1,200 C were up to 3 times higher than those at room temperature. Again, this is attributed to crack healing and incipient plasticity. The IM materials will require secondary processing to develop their full potential. A preliminary examination of secondary processing routes included isothermal forging and hot extrusion.

  19. Griffiths phase behaviour in a frustrated antiferromagnetic intermetallic compound

    PubMed Central

    Ghosh, Krishanu; Mazumdar, Chandan; Ranganathan, R.; Mukherjee, S.

    2015-01-01

    The rare coexistence of a Griffiths phase (GP) and a geometrically frustrated antiferromagnetism in the non-stoichiometric intermetallic compound GdFe0.17Sn2 (the paramagnetic Weiss temperature θp ~ −59 K) is reported in this work. The compound forms in the Cmcm space group with large structural anisotropy (b/c ~ 4). Interestingly, all the atoms in the unit cell possess the same point group symmetry (Wycoff position 4c), which is rather rare. The frustration parameter, f = |θp|/TN has been established as 3.6, with the Néel temperature TN and Griffiths temperature TG being 16.5 and 32 K, respectively. The TG has been determined from the heat capacity measurement and also from the magnetocaloric effect (MCE). It is also shown that substantial difference in GP region may exist between zero field and field cooled measurements - a fact hitherto not emphasized so far. PMID:26515256

  20. Thermal stress effects in intermetallic matrix composites. Final report

    SciTech Connect

    Wright, P.K.; Sensmeier, M.D.; Kupperman, D.S.; Wadley, H.N.G.

    1993-09-01

    Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

  1. A magnetization study of RCo 12B 6 intermetallics

    NASA Astrophysics Data System (ADS)

    Mittag, M.; Rosenberg, M.; Buschow, K. H. J.

    1989-11-01

    The magnetic properties of polycrystalline intermetallics RCo 12B 6 with R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm have been studied in the temperature range 3-300 K and in fields up to 2 T. All compounds order magnetically between Tc=134.3 K for CeCo 12B 6 and Tc=162 K for GdCo 12B 6. YCo 12B 6 has an average Co moment of 0.42μ B. Since the Co moment is constant for all samples the R moments can be easily obtained and they are in good agreement with free R 3+ ion values. Ce is quadripositive in CeCo 12B 6 and therefore nonmagnetic. All light rare-earth compounds are ferromagnetic, while all heavy rare-earth compounds are ferrimagnetic with compensation points between Tcomp=11.6 K ( TmCo12B6) and Tcomp=82.8 K ( TbCo12B6). In the paramagnetic state an effective magnetic moment of 1.94μ B per Co atom has been found. The mean-field approximation yields a 3d-3d exchange integral of {J CoCo}/{k B}=110 K . The 3d-4f exchange integral is much smaller and equal to about {J RCo}/{k B}=6 K .

  2. Intermetallic compound formation at Cu-Al wire bond interface

    SciTech Connect

    Bae, In-Tae; Young Jung, Dae; Chen, William T.; Du Yong

    2012-12-15

    Intermetallic compound (IMC) formation and evolution at Cu-Al wire bond interface were studied using focused ion beam /scanning electron microscopy, transmission electron microscopy (TEM)/energy dispersive x-ray spectroscopy (EDS), nano beam electron diffraction (NBED) and structure factor (SF) calculation. It was found that discrete IMC patches were formed at the Cu/Al interface in as-packaged state and they grew toward Al pad after high temperature storage (HTS) environment at 150 Degree-Sign C. TEM/EDS and NBED results combined with SF calculation revealed the evidence of metastable {theta} Prime -CuAl{sub 2} IMC phase (tetragonal, space group: I4m2, a = 0.404 nm, c= 0.580 nm) formed at Cu/Al interfaces in both of the as-packaged and the post-HTS samples. Two feasible mechanisms for the formation of the metastable {theta} Prime -CuAl{sub 2} phase are discussed based on (1) non-equilibrium cooling of wire bond that is attributed to highly short bonding process time and (2) the epitaxial relationships between Cu and {theta} Prime -CuAl{sub 2}, which can minimize lattice mismatch for {theta} Prime -CuAl{sub 2} to grow on Cu.

  3. Excitonic correlations in the intermetallic Fe2VAl

    NASA Astrophysics Data System (ADS)

    Weht, Ruben; Pickett, W. E.

    1998-09-01

    The intermetallic compound Fe2VAl looks nonmetallic in transport and strongly metallic in thermodynamic and photoemission data. It has in its band structure a highly differentiated set of valence and conduction bands leading to a semimetallic system with a very low density of carriers. The pseudogap itself is sensitive to the presence of Al states, but the resulting carriers have only minor Al character. The effects of generalized gradient corrections to the local density band structure are shown to be important, reducing the carrier density by a factor of 3. Spin-orbit coupling results in a redistribution of the holes among pockets at the Brillouin zone center. Doping of this nonmagnetic compound by 0.5 electrons per cell in a virtual crystal fashion results in a moment of 0.5μB and destroys the pseudogap. We assess the tendencies toward the formation of an excitonic condensate and toward an excitonic Wigner crystal and find both to be unlikely. We propose a model in which the observed properties result from excitonic correlations arising from two interpenetrating lattices of distinctive electrons (eg on V) and holes (t2g on Fe) of low density (one carrier of each sign per 350 formula units).

  4. Molecular assembly and organic film growth on complex intermetallic surfaces

    NASA Astrophysics Data System (ADS)

    Al-Mahboob, Abdullah; Sharma, Hem Raj; Sadowski, Jerzy T.; Ledieu, Julian; Fournée, Vincent; McGrath, Ronan

    We extensively studied the role of molecular symmetry and symmetry/structures of wide ranges of substrate-surfaces from non-periodic to periodic to quasi-crystalline in nucleation, growth and phase transition in films made of organic molecular materials. Recently, most interest in quasicrystals is due to the generalization of aperiodic ordering to several classes of systems. Compared to periodic materials, these provide a closer approximation to an isotropic first Brillouin zone, which is of great importance to the design of new functional materials. Here, we present results obtained from our ongoing study of interface mediated molecular assembly extended on complex intermetallic surfaces with specific examples of C60 and Zn-phthalocyanine on quasicrystalline and approximant surfaces. We employed in-situ real-time low-energy electron microscopy (LEEM) for investigation of the processes in assembly and film growth and post-growth STM study and DFT calculations to understand structural details and growth mechanism. Research were carried out in part at the Center for Functional Nanomaterials, Brookhaven National Lab, USA; partly at Institut Jean Lamour, Université de Lorraine, France; and partly at the Surface Science Research Centre, University of Liverpool, UK.

  5. Magnetic Anisotropy and Crystalline Electric Field in Quaternary Intermetallic Compounds

    NASA Astrophysics Data System (ADS)

    Lee, W. C.

    All isostructural compounds RNi2B2C (R =Er, Ho, Dy) show some magnetic transitions in magnetization isotherms at certain applied magnetic fields and temperatures above and below Neel and superconducting temperatures (TN, TC) where TN/TC varies from 0.57 to 1.66 for ErNi2B2C and DyNi2B2C. By using theoretical group analysis of D4h (I4/mmm) to the energy level scheme of crystalline electric field of magnetization isotherms anisotropy at various temperatures, we have obtained some possible ground state energy levels such as singlet Γ4 and first excited doublet state Γ5 in addition to another excited singlet Γ1 . Our crystalline electric field energy scheme analysis shows some qualitative agreement between theoretical calculation and experiments at high magnetic fields regime only, which means the interplay between antiferromagnetsm and superconductivity should be included. Magnetic Anisotropy and Crystalline Electric Field in Quaternary Intermetallic Compounds.

  6. Sealing Treatment of Aluminum Coating on S235 Steel with Thermal Diffusion of Zinc

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Zhang, Timing; Zhao, Weimin; Tang, Xiuyan

    2015-08-01

    The study introduced a thermal diffusion sealing treatment for arc-sprayed aluminum coating on S235 carbon steel. The sprayed aluminum-zinc duplex coating was heated to 420 °C, so that the low-melting-point zinc could diffuse into the pores of the aluminum coating. Optical microscope, microhardness, electron probe microanalysis, and x-ray diffraction were used to evaluate the sealing treatment. The calculated diffusion coefficient for zinc in the arc-sprayed aluminum coating was approximately 7.735 × 10-9 cm2/s. The diffused zinc could increase the compactness and microhardness of the aluminum coating. Nevertheless, adverse interface reactions could destroy the coating if the zinc made contact with the steel substrate. FeZn10 could form initially, and then the heat from the exothermic reactions between zinc and iron would initiate the reactions among iron, aluminum, and zinc. FeAl-Zn x , FeAl2-Zn x , and Fe2Al5-Zn x were generated following FeZn10. The defected structures were mainly composed of Fe2Al5-Zn x and FeZn10. All of these formed tough, brittle, intermetallics that have a negative effect on the coating performance. Thus, the contact between zinc and the steel substrate should be avoided, and the holding time should be restricted to 8.16 × 106 L 2 to prevent the generation of intermetallics.

  7. Morbus Coats

    PubMed Central

    Förl, B.; Schmack, I.; Grossniklaus, H.E.; Rohrschneider, K.

    2010-01-01

    Der fortgeschrittene Morbus Coats stellt im Kleinkindalter eine der schwierigsten Differenzialdiagnosen zum Retinoblastom dar. Wir beschreiben die klinischen und histologischen Befunde zweier Jungen im Alter von 9 und 21 Monaten mit einseitiger Leukokorie. Trotz umfassender Diagnostik mittels Narkoseuntersuchung, MRT und Ultraschall konnte ein Retinoblastom nicht sicher ausgeschlossen werden, und es erfolgte eine Enukleation. Histologisch wurde die Diagnose eines Morbus Coats gesichert. Da eine differenzialdiagnostische Abgrenzung zwischen Morbus Coats und Retinoblastom schwierig sein kann, halten wir in zweifelhaften Fällen auch angesichts der eingeschränkten Visusprognose und potenzieller Sekundärkomplikationen beim fortgeschrittenen Morbus Coats eine Enukleation für indiziert. PMID:18299842

  8. Thermal Stability of Intermetallic Phases in Fe-rich Fe-Cr-Ni-Mo Alloys

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-09-01

    Understanding the thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys is critical to alloy design and application of Mo-containing austenitic steels. Coupled with thermodynamic modeling, the thermal stability of intermetallic Chi and Laves phases in two Fe-Cr-Ni-Mo alloys was investigated at 1273 K, 1123 K, and 973 K (1000 °C, 850 °C, and 700 °C) for different annealing times. The morphologies, compositions, and crystal structures of the precipitates of the intermetallic phases were carefully examined by scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and transmission electron microscopy. Two key findings resulted from this study. First, the Chi phase is stable at high temperature, and with the decreasing temperature it transforms into the Laves phase that is stable at low temperature. Secondly, Cr, Mo, and Ni are soluble in both the Chi and Laves phases, with the solubility of Mo playing a major role in the relative stability of the intermetallic phases. The thermodynamic models that were developed were then applied to evaluating the effect of Mo on the thermal stability of intermetallic phases in type 316 and NF709 stainless steels.

  9. Modeling non-isothermal intermetallic layer growth in the 63Sn-37Pb/Cu system

    SciTech Connect

    Vianco, P.T.; Hopkins, P.L.; Erickson, K.L.; Frear, D.R.; Davidson, R.

    1996-12-31

    A model describing diffusion-controlled growth of multiple intermetallic layers and the displacement of the interfaces between layers was developed and implemented in a 1-D computer code based on method-of-lines. The code was applied to analysis of intermetallic layer growth in isothermal solder aging experiments performed with 100 Sn/Cu and 63Sn-37Pb/Cu solder-substrate systems. Analyses indicated that intermetallic layer growth was consistent with a bulk diffusion mechanism involving Cu and/or Sn. In this work, nonisothermal solder-aging experiments were done with the 63Sn- 37Pb/Cu system using two temperature histories (4 cycles/day between 223-443 K, and 72 cycles/day between 223-443 K). Isothermal experiments were also done at 443 K. Thickness of Cu{sub 3}Sn and Cu{sub 6}Sn{sub 5} intermetallic layers were determined vs time for each temperature history. An updated version of the model and code were used to predict the intermetallic layer growth. Arrhenius expressions for diffusion coefficients in both Cu3Sn and Cu6Sn5 layers were determined. Agreement between prediction and experiment was generally good. In some cases, predicted layer growth was less than experiment, but within error. This paper describes the nonisothermal experiments and a comparison of predicted and observed layer growth vs time.

  10. The Structure-Phase Compositions of Powder Ni - based Coatings after Modification by DC Plasma Jet Irradiation

    NASA Astrophysics Data System (ADS)

    Alontseva, D.; Ghassemieh, E.

    2015-10-01

    This paper presents the results of investigation of the structure-phase compositions of Ni-based coatings deposited by plasma jet on steel substrates after modification by direct current (DC) plasma jet irradiation. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Diffraction (XRD) are used in the current study. The phase structures and morphology of precipitation of strengthening phases from solid solution are defined. The irradiation of the coatings leads to the evolution of the structural-phase state of coatings: an increase in the volume fraction of hardening intermetallic phases, the formation of sufficiently homogeneous fine-grained structure in the irradiated coatings. There is a mutual penetration of the substrate main element Fe into the coating and base coating elements Ni into the substrate as a result of the coating treatment by a pulse DC plasma jet.

  11. Synthesis of cerium rich intermetallics using molten metal eutectics

    NASA Astrophysics Data System (ADS)

    Tucker, Patricia Christine

    Metal eutectic fluxes are useful for exploratory synthesis of new intermetallic phases. In this work the use of cerium/transition metal eutectics such as: Ce/Co, Ce/Ni, and Ce/Fe have yielded many new synthetically and magnetically complex phases. Structural units that were previously observed in phases grown in La/Ni eutectic reactions have also been observed in new structures and analogs grown from cerium/transition metal eutectics. These structural units include a main group element coordinated by 9 rare-earth atoms (such as the Al Ce9 clusters seen in Ce31.0(2)Fe11.8(5)Al6.5(6) B13C4), trigonal planar FeC3 units (also seen in Ce31.0(2)Fe11.8(5)Al6.5(6)B 13C4), iron clusters capped by light elements (Fe4C 6 frustrated tetrahedral in Ce21Fe8M7C 14, and larger Fe clusters in Ce33Fe14B25 C34). Variants of these building blocks were observed in Ce10Co2B7C16 with square Co units and chains of B and C connected to them, Fe2C8 units observed in Ce7Fe2C9, and FeC4 observed in Ce4FeGa0.85Al0.15C4 and Ce4FeAlC4. Two new phases were grown from Ce/Fe eutectic, Ce33Fe 14B25C34 and Ce33Fe13B 18C34 which exhibits very similar structures, but significantly different magnetic behavior. Structurally these two phases are similar. Both crystallize in the Im-3m space group, but differ by the centering of the Fe clusters. Ce33Fe14B25C34 contains Fe clusters centered by B atoms and Al doped on the Fe2 site. In Ce33Fe13B18C34, the Fe cluster is a perfect cuboctahedron. Ce33Fe14B25 C34 exhibits mixed valent behavior of cerium at 75K and no magnetic moment on iron, where-as Ce33Fe13B18C 34 exhibits tetravalent cerium and its iron clusters undergo a ferromagnetic transition at 180K. Another borocarbide, Ce10Co2B7C 16 was synthesized from Ce/Co eutectic flux. This structure features squares of Co surrounded by chains of C and B and a sea of cerium atoms. Temperature dependent magnetic susceptibility measurements at 1 Tesla were fit to a modified Curie-Weiss law and a moment per Ce was

  12. Magnetic and crystallographic structures in UTX intermetallic compounds

    SciTech Connect

    Robinson, R.A.; Lawson, A.C.; Sechovsky, V.; Havela, L.; Kergadallan, Y.; Nakotte, H.; de Boer, F.R.

    1993-08-01

    Uranium, along with other actinides and lanthanides, forms a large group of ternary intermetallic compounds of stoichiometry UTX (T = transition metal, X = p-electron metal). These compounds are formed in several structure types and the occurrence and stability of particular structures with respect to the transition metal content suggests reasonable systematics. The authors have also investigated the magnetic structures of selected UTX compounds and it is revealing to relate the crystallographic and magnetic structures, because of the relationship between the magnetic symmetry and that of the U-atom environment produced by the 5f-ligand hybridization, and the consequent anisotropic exchange. Those of ZrNiAl structure type are collinear, with moments along the hexagonal c-axis. In the orthorhombic NiSiTi structure type, the moments are confined to the b- c plane (perpendicular to the uranium chains) and the structures are often incommensurate. In the hexagonal CaIn{sub 2} (or GaGeLi) structure type, the magnetic structures form in an orthorhombic cell, and at least in the disordered centric group, again the moments lie perpendicular to the nearest-neighbor uranium spacing. This work presents a phenomenology of trends in UTX ternary compounds. It is shown that there is an apparent strong hybridization parallel to nearest neighbor U-U directions, with ferromagnetic coupling in the same directions. There may be a systematic relationship between the hybridization anisotropy and the magnetic anisotropy, in which the quantization axes are the same and the moments point along directions of relatively weak hybridization.

  13. Modeling of Substitutional Site Preference in Ordered Intermetallic Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Honecy, Frank

    1998-01-01

    We investigate the site substitution scheme of specific alloying elements in ordered compounds and the dependence of site occupancy on compound stoichiometry, alloy concentration. This basic knowledge, and the interactions with other alloying additions are necessary in order to predict and understand the effect of various alloying schemes on the physical properties of a material, its response to various temperature treatments, and the resulting mechanical properties. Many theoretical methods can provide useful but limited insight in this area, since most techniques suffer from constraints in the type of elements and the crystallographic structures that can be modeled. With this in mind, the Bozzolo-Ferrante-Smith (BFS) method for alloys was designed to overcome these limitations, with the intent of providing an useful tool for the theoretical prediction of fundamental properties and structure of complex systems. After a brief description of the BFS method, its use for the determination of site substitution schemes for individual as well as collective alloying additions to intermetallic systems is described, including results for the concentration dependence of the lattice parameter. Focusing on B2 NiAl, FeAl and CoAl alloys, the energetics of Si, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Hf, Ta and W alloying additions are surveyed. The effect of single additions as well as the result of two simultaneous additions, discussing the interaction between additions and their influence on site preference schemes is considered. Finally, the BFS analysis is extended to ternary L1(sub 2) (Heusler phase) alloys. A comparison between experimental and theoretical results for the limited number of cases for which experimental data is available is also included.

  14. Identification and control of grinding processes for intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Razavi, Hosein Ali

    2000-10-01

    An intermetallic compound (IMC) is a combination of two or more metals with a particular atomic formula by having either ionic and covalent bonds, or metallic bonds with specific crystal structures. They may be thought of as the intermediate between metals and ceramics. These new materials may combine the best of each class: the ductility, heat and electric conductivity of metals with the strength and oxidation resistance of ceramics. Previous study has proposed that the depth of plastic deformation can be used as a parameter to describe the influence of grinding conditions on other physical properties of subsurface layers. Accordingly, the indentation model has been developed to correlate the depth of plastic deformation with the normal component of grinding force. It has been reported that the under certain grinding conditions the depth of plastic deformation does not follow the indentation model. The primary objective of this research is to explain such deviations and to demonstrate that this model can be used to control and predict the depth of plastic deformation. Elements of this research include the development of an open architecture platform to study grinding process, a signal processing algorithm for gap elimination, introducing and implementation of model reference unfalsification and learning concept, development of a mathematical model for grinding gamma-TiAl, a comparison between conventional and superabrasive grinding, control and prediction of the depth of plastic deformation, and initiation of one of the first databases for grinding gamma-TiAl. This work not only serves as a step toward the use of IMCs in future technology but also serves as a step toward autonomous machining systems using intelligent control and advanced monitoring which is a feature of the future abrasive technology.

  15. New Interest in Intermetallic Compound ZnSb

    NASA Astrophysics Data System (ADS)

    Fedorov, M. I.; Prokof'eva, L. V.; Pshenay-Severin, D. A.; Shabaldin, A. A.; Konstantinov, P. P.

    2014-06-01

    The intermetallic compound ZnSb has been known since the 1830s. It has semiconductor properties, but its mechanical, thermal, and chemical properties are very close to those of a metallic alloy. When thermoelectrics based on (BiSb)2(TeSe)3 solid solutions were created, interest in ZnSb subsided. However, the current situation is different, as tellurium has become expensive and rare. Moreover, its compounds are too toxic, and it is too difficult to produce such materials and devices from these solid solutions. Recently, n-type material based on Mg2(SnSi) solid solution was proposed in the Laboratory of Physics for Thermoelements of the Ioffe Physical-Technical Institute. This material together with ZnSb may form a promising couple for creating various thermoelectric modules. In this paper, various properties (Hall and Seebeck coefficients, electrical and thermal conductivities) are reported in the temperature range from 80 K to 797 K. Different acceptor impurities have been tested. The Hall concentration at room temperature varied from 1.5 × 1018 cm-3 to 2.7 × 1019 cm-3. Some features have been discovered in the behavior of the thermoelectric parameters of double-doped ZnSb samples at temperatures above 500 K. Their nature points to a temperature-dependent increase of the Hall concentration. The existence of two temperature ranges with additional doping is revealed by Hall coefficient and electrical conductivity measurements in the range from 80 K to 797 K. The experimental data are discussed based on a model of the energy spectrum with impurity and native defect states localized in the energy gap. It is shown that the dimensionless thermoelectric figure of merit of ZnSb: Cd, Ag, Sn is not less than 1.0 at 600 K.

  16. Crystal plasticity aspects of a lamellar intermetallic microstructure

    SciTech Connect

    Schloegl, S.M.; Fischer, F.D.; Minchev, O.I.; Rammerstorfer, F.G.

    1995-12-31

    Two-phase TiAl intermetallics consisting of {gamma} (TiAl) and {alpha}{sub 2} (Ti{sub 3}Al) lamellae possess mechanical properties which significantly differ from that of single-phase alloys. There are many experimental results of polysynthetically twinned (PST) TiAl crystals, which contain only a single set of lamellae with a specific orientation. Their yield stress at room temperature depends strongly on the angle {theta} between the orientation of the lamellae and the load axis. Furthermore, when compression loads are applied in the direction of the lamellae some sort of {open_quote}microbuckling{close_quote} could be observed, especially at high temperature during the primary forming process. In the paper this nonlinear anisotropic behavior is simulated by micromechanical computational methods with regard to finding a constitutive law for a polycrystal with lamellar grains. The modeling is based on the unit-cell techniques using the finite element method. Because of the orientation relationship of (111){sub {gamma}} {parallel} (0001){sub {alpha}2} and {l_angle}1{rvec 1}0{r_angle}{sub {gamma}} {parallel} {l_angle}11{rvec 2}0{r_angle}{sub {alpha}2}, is necessary to use crystal plasticity. The major deformation modes of the -Y phase at room temperature are ordinary slip along (110) and deformation twinning, i.e., true twinning of the (111){l_angle}11{rvec 2} type. These two modes are simulated in the unit-cell analyses. Using the micromechanical models, stress-strain curves are calculated for orientation angles {theta} varying in the range of 0{degrees} {le} {theta} {le} 90{degrees}, and the computed yield stresses are compared with experimental results. The {open_quote}microbuckling{close_quote} of the lamellae under compression loading is studied as well.

  17. An MHD heat source based on intermetallic reactions

    SciTech Connect

    Sadjian, H.; Zavitsanos, P. ); Marston, C.H. )

    1991-05-06

    The main objective of this program was the development of an MHD heat source of potential use in Space - Based Multi Megawatt, MHD Power Systems. The approach is based on extension of high temperature chemical/ion release technology developed by the General Sciences, Incorporated (GSI) team and successfully applied in other Space Applications. Solid state reactions have been identified which can deliver energy densities and electrons in excess of those from high energy explosives as well as other conventional fuels. The use of intermetallic reactions can be used to generate hot hydrogen plasma from the reaction, to create a high level of seedant ionization, can be packaged as a cartridge type fuels for discrete pulses. The estimated weight for energizing a (100 MW - 1000 sec) Pulsed MHD Power System can range from 12 to 25 {times} 10{sup 3} kg depending on reaction system and strength of the magnetic field. The program consisted of two major tasks with eight subtasks designed to systematically evaluate these concepts in order to reduce fuel weight requirements. Laboratory measurements on energy release, reaction product identification and levels of ionization were conducted in the first task to screen candidate fuels. The second task addressed the development of a reaction chamber in which conductivity, temperature and pressure were measured. Instrumentation was developed to measure these parameters under high temperature pulsed conditions in addition to computer programs to reduce the raw data. Measurements were conducted at GSI laboratories for fuel weights of up to 120 grams and at the Franklin Research Center* for fuel weights up to 1 kilogram. The results indicate that fuel weight can be scaled using modular packaging. Estimates are presented for fuel weight requirements. 15 refs.

  18. Coatings Guide

    EPA Science Inventory

    The Coatings Guide is a free online information resource that focuses on alternative, low-emission coatings for metal, plastic, and architectural substrates. Developed cooperatively by the U.S. EPA's Office of Research and Development and Research Triangle Institute (RTI) Interna...

  19. The preparation of the Ti-Al alloys based on intermetallic phases

    NASA Astrophysics Data System (ADS)

    Kosova, N.; Sachkov, V.; Kurzina, I.; Pichugina, A.; Vladimirov, A.; Kazantseva, L.; Sachkova, A.

    2016-01-01

    This article deals with a method of obtaining materials in the Ti-Al system. Research was carried out in accordance with the phase diagram of the system state. It was established, that both single-phase and multiphase systems, containing finely dispersed intermetallic compositions of phases Ti3Al, TiAl and TiAl3, are formed. Additionally, it was found that the pure finely dispersed (coherent-scattering region (CSR) up to 100 nm) intermetallic compound TiAl3 is formed at molar ratio of Ti:Al = 1:3. Experimentally proved the possibility of produce the complex composition of alloys and intermetallic compounds and products based on them.

  20. Intermetallic negative electrodes for non-aqueous lithium cells and batteries

    DOEpatents

    Thackeray, Michael M.; Vaughey, John T.; Johnson, Christopher S.; Fransson, Linda M.; Edstrom, Ester Kristina; Henriksen, Gary

    2004-05-04

    A method of operating an electrochemical cell is disclosed. The cell has an intermetallic negative electrode of Cu.sub.6-x M.sub.x Sn.sub.5, wherein x is .ltoreq.3 and M is one or more metals including Si and a positive electrode containing Li in which Li is shuttled between the positive electrode and the negative electrode during charge and discharge to form a lithiated intermetallic negative electrode during charge. The voltage of the electrochemical cell is controlled during the charge portion of the charge-discharge cycles so that the potential of the lithiated intermetallic negative electrode in the fully charged electrochemical cell is less than 0.2 V but greater than 0 V versus metallic lithium.

  1. Effect of intermetallic phases on the anodic oxidation and corrosion of 5A06 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Li, Song-mei; Li, Ying-dong; Zhang, You; Liu, Jian-hua; Yu, Mei

    2015-02-01

    Intermetallic phases were found to influence the anodic oxidation and corrosion behavior of 5A06 aluminum alloy. Scattered intermetallic particles were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) after pretreatment. The anodic film was investigated by transmission electron microscopy (TEM), and its corrosion resistance was analyzed by electrochemical impedance spectroscopy (EIS) and Tafel polarization in NaCl solution. The results show that the size of Al-Fe-Mg-Mn particles gradually decreases with the iron content. During anodizing, these intermetallic particles are gradually dissolved, leading to the complex porosity in the anodic film beneath the particles. After anodizing, the residual particles are mainly silicon-containing phases, which are embedded in the anodic film. Electrochemical measurements indicate that the porous anodic film layer is easily penetrated, and the barrier plays a dominant role in the overall protection. Meanwhile, self-healing behavior is observed during the long immersion time.

  2. On the micromechanics of low temperature strength and toughness of intermetallic/metallic microlaminate composites

    SciTech Connect

    Heathcote, J.; Odette, G.R.; Lucas, G.E.; Rowe, R.G.; Skelly, D.W.

    1996-11-01

    Tensile strength and fracture resistance curves were measured for different combination of brittle intermetallic/ductile metallic microlaminates. Metal layer bridging, characterized by the closure stress ({sigma})-crack opening (u) displacement function, produced toughening by factors of 2--5. The key composite property, {sigma}(u), was evaluated by fitting resistance curves using a large scale bridging code coupled with independent estimates of the maximum stress and ligament height. These functions were used in a bridging-crack stability analysis of tensile strength controlled by pre-existing processing defects. Assuming similar flaws, the composites are roughly 4--6 times stronger than the intermetallic, with predicted strengths in agreement with experiment within a standard deviation of 45 MPa. Composite strength is primarily sensitive to the intermetallic toughness and the constrained strength of the metal layer. Greater strength can also be achieved by better control of the growth defects.

  3. Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

    DOEpatents

    Wright, Randy B.

    1992-01-01

    Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation).

  4. Regulatory Aspects of Coatings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter gives a history of the development and uses of edible coating regulations, detailed chapters on coating caracteristics, determination of coating properties, methods for making coatings, and discription of coating film formers (polysaccharieds, lipids, resins, proteins). The chapter also...

  5. Massive spalling of intermetallic compounds in solder-substrate reactions due to limited supply of the active element

    SciTech Connect

    Yang, S. C.; Ho, C. E.; Chang, C. W.; Kao, C. R.

    2007-04-15

    Massive spalling of intermetallic compounds has been reported in the literature for several solder/substrate systems, including SnAgCu soldered on Ni substrate, SnZn on Cu, high-Pb PbSn on Cu, and high-Pb PbSn on Ni. In this work, a unified thermodynamic argument is proposed to explain this rather unusual phenomenon. According to this argument, two necessary conditions must be met. The number one condition is that at least one of the reactive constituents of the solder must be present in a limited amount, and the second condition is that the soldering reaction has to be very sensitive to its concentration. With the growth of intermetallic, more and more atoms of this constituent are extracted out of the solder and incorporated into the intermetallic. As the concentration of this constituent decreases, the original intermetallic at the interface becomes a nonequilibrium phase, and the spalling of the original intermetallic occurs.

  6. Intermetallic NaAu2 as a heterogeneous catalyst for low-temperature CO oxidation.

    PubMed

    Xiao, Chaoxian; Wang, Lin-Lin; Maligal-Ganesh, Raghu V; Smetana, Volodymyr; Walen, Holly; Thiel, Patricia A; Miller, Gordon J; Johnson, Duane D; Huang, Wenyu

    2013-07-01

    The enhanced stability and modified electronic structure of intermetallic compounds provide discovery of superior catalysts for chemical conversions with high activity, selectivity, and stability. We find that the intermetallic NaAu2 is an active catalyst for CO oxidation at low temperatures. From density functional theory calculations, a reaction mechanism is suggested to explain the observed low reaction barrier of CO oxidation by NaAu2, in which a CO molecule reacts directly with an adsorbed O2 to form an OOCO* intermediate. The presence of surface Na increases the binding energy of O2 and decreases the energy barrier of the transition states. PMID:23758405

  7. Microstructure and Mechanical Properties of the Ti-45Al-5Fe Intermetallic Alloy

    NASA Astrophysics Data System (ADS)

    Nazarova, T. I.; Imayev, V. M.; Imayev, R. M.

    2015-10-01

    Microstructure including changes in the phase composition and mechanical compression properties of the Ti-45Al-5Fe (at.%) intermetallic alloy manufactured by casting and subjected to homogenization annealing are investigated as functions of the temperature. The initial alloy has a homogeneous predominantly lamellar structure with relatively small size of colonies of three intermetallic phases: γ(TiAl), τ2(Al2FeTi), and α2(Ti3Al) in the approximate volume ratio 75:20:5. Compression tests have revealed the enhanced strength at room temperature and the improved hot workability at 800°C compared to those of TNM alloys of last generation.

  8. Protective Coatings

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Ameron International Protective Coatings Group developed a special coating for NASA that would withstand the high temperatures generated by the Space Shuttle rocket engines. The coating remains intact for at least 10 minutes, and insulates the launch pad so that it does not exceed 150 degrees and buckle. The NASA formulation was from Ameron's Engineered Siloxane (PSX) chemistry, which employs an inorganic silicon-oxygen structure which the company states is stronger and more reliable than organic polymers. Some of Ameron's PSX product line is based on the NASA technology, used for everything from industrial equipment to bridges.

  9. Sprayed coatings

    NASA Astrophysics Data System (ADS)

    Steffens, H. D.

    1980-03-01

    Thermal spraying is shown to be an efficient means for the protection of surface areas against elevated temperature, wear, corrosion, hot gas corrosion, and erosion in structural aircraft components. Particularly in jet engines, numerous parts are coated by flame, detonation, or plasma spraying techniques. The applied methods of flame, detonation, and plasma spraying are explained, as well as electric arc spraying. Possibilities for spray coatings which meet aircraft service requirements are discussed, as well as methods for quality control, especially nondestructive test methods. In particular, coating characteristics and properties obtained by different spray methods are described, and special attention is paid to low pressure plasma spraying.

  10. Quaternary borocarbides: Relatively high Tc intermetallic superconductors and magnetic superconductors

    NASA Astrophysics Data System (ADS)

    Mazumdar, Chandan; Nagarajan, R.

    2015-07-01

    Discovery of superconductivity in Y-Ni-B-C (Tc ∼ 13 K) gave rise to the class of quaternary rare earth transition metal borocarbide superconductors. Before the discovery of Fe-based arsenide superconductors, this was the only class of materials containing a magnetic element, viz., Ni, yet exhibiting Tcs > 5 K. Many members of this class have high Tc (>10 K). Tc of ∼23 K in Y-Pd-B-C system equaled the record Tc known then, for intermetallics. Another feature that sets this class apart, is the occurrence of the exotic phenomenon of coexistence of superconductivity and magnetism at temperatures >5 K. Availability of large and electronically 'clean' single crystals and large Ginzburg-Landau (G-L) parameter, κ, have enabled detailed investigation of nonlocal effects of superconductivity. Intermediate value of upper critical field Hc2, has enabled detailed investigation of superconductivity in this class, over the complete H-T plane. This has revealed details of anisotropy of superconductivity (e.g., a fourfold symmetry in the square a-b plane is found) and raised questions on the symmetry of order parameter. After a brief outline of the discovery, this article gives a summary of the materials and highlights of superconducting properties of this class of materials. Interesting results from studies, using various techniques, on YNi2B2C (Tc ∼ 15 K) and LuNi2B2C (Tc ∼ 16 K) are presented, including observation of unusual square vortex lattice and its structural transformation with H and T. With conduction electrons involved in the magnetic order of this class of superconductors, the interplay of superconductivity and magnetism is intimate in these magnetic superconductors. With Tc (∼11 K) > TN (∼6 K) in ErNi2B2C, Tc (∼8 K) = TN (∼8 K) in HoNi2B2C and Tc (∼6 K) < TN (∼11 K) in DyNi2B2C, and with other parameters being favorable as mentioned earlier, this class of magnetic superconductors have become ideal materials to investigate the coexistence

  11. Surface integrity on grinding of gamma titanium aluminide intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Murtagian, Gregorio Roberto

    Gamma-TiAl is an ordered intermetallic compound characterized by high strength to density ratio, good oxidation resistance, and good creep properties at elevated temperatures. However, it is intrinsically brittle at room temperature. This thesis investigates the potential for the use of grinding to process TiAl into useful shapes. Grinding is far from completely understood, and many aspects of the individual mechanical interactions of the abrasive grit with the material and their effect on surface integrity are unknown. The development of new synthetic diamond superabrasives in which shape and size can be controlled raises the question of the influence of those variables on the surface integrity. The goal of this work is to better understand the fundamentals of the abrasive grit/material interaction in grinding operations. Experimental, analytical, and numerical work was done to characterize and predict the resultant deformation and surface integrity on ground lamellar gamma-TiAl. Grinding tests were carried out, by analyzing the effects of grit size and shape, workpiece speed, wheel depth of cut, and wear on the subsurface plastic deformation depth (PDD). A practical method to assess the PDD is introduced based on the measurement of the lateral material flow by 3D non-contact surface profilometry. This method combines the quantitative capabilities of the microhardness measurement with the sensitivity of Nomarski microscopy. The scope and limitations of this technique are analyzed. Mechanical properties were obtained by quasi-static and split Hopkinson bar compression tests. Residual stress plots were obtained by x-ray, and surface roughness and cracking were evaluated. The abrasive grit/material interaction was accounted by modeling the force per abrasive grit for different grinding conditions, and studying its correlation to the PDD. Numerical models of this interaction were used to analyze boundary conditions, and abrasive size effects on the PDD. An explicit 2D

  12. Versatile Coating

    NASA Technical Reports Server (NTRS)

    1990-01-01

    A radome at Logan Airport and a large parabolic antenna at the Wang Building in Massachusetts are protected from weather, corrosion and ultraviolet radiation by a coating, specially designed for antennas and radomes, known as CRC Weathertite 6000. The CRC 6000 line that emerged from Boyd Coatings Research Co., Inc. is a solid dispersion of fluorocarbon polymer and polyurethane that yields a tough, durable film with superior ultraviolet resistance and the ability to repel water and ice over a long term. Additionally, it provides resistance to corrosion, abrasion, chemical attacks and impacts. Material can be used on a variety of substrates, such as fiberglass, wood, plastic and concrete in addition to steel and aluminum. In addition Boyd Coatings sees CRC 6000 applicability as an anti-icing system coated on the leading edge of aircraft wings.

  13. Protective Coating

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Inorganic Coatings, Inc.'s K-Zinc 531 protective coating is water-based non-toxic, non-flammable and has no organic emissions. High ratio silicate formula bonds to steel, and in 30 minutes, creates a very hard ceramic finish with superior adhesion and abrasion resistance. Improved technology allows application over a minimal commercial sandblast, fast drying in high humidity conditions and compatibility with both solvent and water-based topcoats. Coating is easy to apply and provides long term protection with a single application. Zinc rich coating with water-based potassium silicate binder offers cost advantages in materials, labor hours per application, and fewer applications over a given time span.

  14. Summary of work on coatings and claddings for fossil energy applications

    SciTech Connect

    Swindeman, R.W.

    1993-05-01

    A summary of efforts to examine coatings and cladding materials for high-strength austenitic steels is provided. Chromized coatings on 17--14CuMo stainless steel and a modified type 316 (HT-UPS) stainless steel were investigated. Claddings included alloy 671, 690, and an iron-aluminide intermetallic alloy. Structural alloys that were clad included type 304 stainless steel, modified type 316 stainless steel, and modified alloy 800H. The capability of producing co-extruded tubing of the experimental alloys was demonstrated.

  15. Degradation of Si-Al aluminide coating after service of turbine blades made of ZhS6K superalloy

    NASA Astrophysics Data System (ADS)

    Chmiela, B.; Kianicová, M.; Sozańska, M.; Swadźba, L.

    2012-05-01

    Aero engine turbine blades made of nickel-based superalloys are characterized by very good mechanical properties, but their hot corrosion resistance is insufficient. Therefore, various protective coatings must be applied. These coatings are typically made of diffusive aluminide coatings based on the β-NiAl intermetallic phase. Although the oxidation resistance and hot corrosion resistance of these coatings are very good, their thermal resistance is relatively poor. As a result, turbine blades with aluminide coatings are prone to degradation in case of overheating. In this paper we study the degradation of the Si-Al aluminide coating on turbine blades made of ZhS6K superalloy during overheating in the DV2 jet engine.

  16. Investigations of intermetallic alloy hydriding mechanisms. Annual progress report, May 1 1979-April 30, 1980

    SciTech Connect

    Livesay, B.R.; Larsen, J.W.

    1980-05-01

    Investigations are being conducted on mechanisms involved with the hydrogen-metal interactions which control the absorption and desorption processes in intermetallic compounds. The status of the following investigations is reported: modeling of hydride formation; microbalance investigations; microstructure investigations; flexure experiments; resistivity experiments; and nuclear backscattering measurements. These investigations concern fundamental hydrogen interaction mechanisms involved in storage alloys.

  17. Epitaxial growth of intermetallic MnPt films on oxides and large exchange bias

    DOE PAGESBeta

    Liu, Zhiqi; Biegalski, Michael D.; Hsu, Shang-Lin; Shang, Shunli; Marker, Cassie; Liu, Jian; Li, Li; Fan, Lisha S.; Meyer, Tricia L.; Wong, Anthony T.; et al

    2015-11-05

    High-quality epitaxial growth of intermetallic MnPt films on oxides is achieved, with potential for multiferroic heterostructure applications. Antisite-stabilized spin-flipping induces ferromagnetism in MnPt films, although it is robustly antiferromagnetic in bulk. Thus, highly ordered antiferromagnetic MnPt films exhibit superiorly large exchange coupling with a ferromagnetic layer.

  18. Correlation between valence electronic structure and magnetic properties in RCo5 (R = rare earth) intermetallic compound

    NASA Astrophysics Data System (ADS)

    Zhi-Qin, Xue; Yong-Quan, Guo

    2016-06-01

    The magnetisms of RCo5 (R = rare earth) intermetallics are systematically studied with the empirical electron theory of solids and molecules (EET). The theoretical moments and Curie temperatures agree well with experimental ones. The calculated results show strong correlations between the valence electronic structure and the magnetic properties in RCo5 intermetallic compounds. The moments of RCo5 intermetallics originate mainly from the 3d electrons of Co atoms and 4f electrons of rare earth, and the s electrons also affect the magnetic moments by the hybridization of d and s electrons. It is found that moment of Co atom at 2c site is higher than that at 3g site due to the fact that the bonding effect between R and Co is associated with an electron transformation from 3d electrons into covalence electrons. In the heavy rare-earth-based RCo5 intermetallics, the contribution to magnetic moment originates from the 3d and 4f electrons. The covalence electrons and lattice electrons also affect the Curie temperature, which is proportional to the average moment along the various bonds. Project supported by the National Natural Science Foundation of China (Grant No. 11274110).

  19. Investigation of Laser Generation and Detection of Ultrasound in Ceramic Matrix Composites and Intermetallics

    NASA Technical Reports Server (NTRS)

    Ehrlich, Michael J.

    1998-01-01

    The goal of this program is to assess the feasibility of using laser based ultrasonic techniques for inspecting and characterizing materials of interest to NASA, specifically those used in propulsion and turbomachinery applications, such as ceramic composites, metal matrix composites, and intermetallics.

  20. First-principle studies of Ca-X (X=Si,Ge,Sn,Pb) intermetallic compounds

    SciTech Connect

    Yang Zhiwen; Shi Dongmin; Wen Bin; Melnik, Roderick; Yao Shan; Li Tingju

    2010-01-15

    The structural properties, elastic properties, heats of formation, electronic structures, and densities of states of 20 intermetallic compounds in the Ca-X (X=Si, Ge, Sn, Pb) systems have been systematically investigated by using first-principle calculations. Our computational results indicated that with increasing atomic weight of X, the bulk modulus of Ca-X intermetallic compounds decreases gradually. It was also found that Ca{sub 36}Sn{sub 23} and CaPb are mechanically unstable phases. Results on the electronic energy band and densities of states also indicated that Ca{sub 3}Si{sub 4} is an indirect band gap semiconductor with a band gap of 0.598 eV, and Ca{sub 2}Si, Ca{sub 2}Ge, Ca{sub 2}Sn, and Ca{sub 2}Pb are direct band gap semiconductors with band gaps of 0.324, 0.265, 0.06, and 0.07 eV, respectively. In addition, it is found that the absolute values of heats of formation for all Ca-X intermetallics are larger than 30 kJ/mol atom. - Graphical abstract: Calculated (a) bulk moduli and (b) shear moduli of Ca-X system intermetallic compounds.

  1. Exploratory Synthesis: The Fascinating and Diverse Chemistry of Polar Intermetallic Phases

    SciTech Connect

    Corbett, John D.

    2009-12-07

    Exploratory synthetic adventures regarding the inorganic chemistry of polar intermetallic phases have proven to be especially productive of novel compositions, new and unprecedented structures, and unusual bonding regimes. Reactions of diverse elements with widely different electronegativities allow the definition of two opposed classes of products: polycationic or polyanionic clusters or networks of metals paired with the corresponding monatomic anions or cations. These can be usefully viewed as intermetallic 'salts', redox products of simpler neutral intermetallic systems but with widely different factors governing their stabilities. Thus, combinations of rare-earth metals alone or with late transition metals form a novel variety of polymetal network structures with relatively isolated telluride (or halide) spacer anions. Similarly, extensions of traditional Zintl phases of the alkali or alkaline-earth metals from the later p elements to the earlier triels, Ga-Tl especially, yield many new and elegant polyanionic structures. The substitution or addition of still earlier p or late d metal components produces still electron-poorer and more condensed polar intermetallic phases with increasingly delocalized bonding, higher coordination numbers, and more unusual structures and bonding. These discoveries have also led to new approaches: electronic tuning via band calculations to generate new families of quasicrystals and their crystalline approximants with their characteristic structural regimes and regularities. Gold as a substituent generates particularly novel bonding in arrays of mixed metals or polygold anionic networks.

  2. Dissolution of iron intermetallics in Al-Si alloys through nonequilibrium heat treatment

    SciTech Connect

    Anantha Narayanan, L. |; Samuel, F.H.; Gruzleski, J.E.

    1995-08-01

    Conventional heat treatment techniques in Al-Si alloys to achieve optimum mechanical properties are limited to precipitation strengthening processes due to the presence of second-phase particles and spheroidization of silicon particles. The iron intermetallic compounds present in the microstructure of these alloys are reported to be stable, and they do not dissolve during conventional (equilibrium) heat treatments. The dissolution behavior of iron intermetallics on nonequilibrium heat treatment has been investigated by means of microstructure and mechanical property studies. The dissolution of iron intermetallics improves with increasing solution temperature. The addition of manganese to the alloy hinders the dissolution of iron intermetallics. Nonequilibrium heat treatment increases the strength properties of high iron alloys until a critical solution temperature is exceeded. Above this temperature, a large amount of liquid phase is formed as a result of interdendritic and grain boundary melting. The optimum solution treatment temperature for Al-6Si-3.5Cu-0.3Mg-1Fe alloys is found to be between 515 C and 520 C.

  3. X-Ray Diffraction of Intermetallic Compounds: A Physical Chemistry Laboratory Experiment

    ERIC Educational Resources Information Center

    Varberg, Thomas D.; Skakuj, Kacper

    2015-01-01

    Here we describe an experiment for the undergraduate physical chemistry laboratory in which students synthesize the intermetallic compounds AlNi and AlNi3 and study them by X-ray diffractometry. The compounds are synthesized in a simple one-step reaction occurring in the solid state. Powder X-ray diffractograms are recorded for the two compounds…

  4. Ni.sub.3 Al-based intermetallic alloys having improved strength above 850.degree. C.

    DOEpatents

    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.

  5. Advances in nanoscale alloys and intermetallics: low temperature solution chemistry synthesis and application in catalysis.

    PubMed

    Jana, Subhra

    2015-11-21

    Based on the bottom-up chemistry techniques, the size, shape, and composition controlled synthesis of nanoparticles can now be achieved uniformly, which is of great importance to the nanoscience community as well as in modern catalysis research. The low-temperature solution-phase synthesis approach represents one of the most attractive strategies and has been utilized to synthesize nanoscale metals, alloys and intermetallics, including a number of new metastable phases. This perspective will highlight the solution-based nanoparticle synthesis techniques, a low-temperature platform, for the synthesis of size and shape-tunable nanoscale transition metals, alloys, and intermetallics from the literature, keeping a focus on the utility of these nanomaterials in understanding the catalysis. For each solution-based nanoparticle synthesis technique, a comprehensive overview has been given for the reported nanoscale metals, alloys, and intermetallics, followed by critical comments. Finally, their enhanced catalytic activity and durability as novel catalysts have been discussed towards several hydrogenation/dehydrogenation reactions and also for different inorganic to organic reactions. Hence, the captivating advantages of this controllable low-temperature solution chemistry approach have several important implications and together with them this approach provides a promising route to the development of next-generation nanostructured metals, alloys, and intermetallics since they possess fascinating properties as well as outstanding catalytic activity. PMID:26477400

  6. Epitaxial Growth of Intermetallic MnPt Films on Oxides and Large Exchange Bias.

    PubMed

    Liu, Zhiqi; Biegalski, Michael D; Hsu, Shang-Lin; Shang, Shunli; Marker, Cassie; Liu, Jian; Li, Li; Fan, Lisha; Meyer, Tricia L; Wong, Anthony T; Nichols, John A; Chen, Deyang; You, Long; Chen, Zuhuang; Wang, Kai; Wang, Kevin; Ward, Thomas Z; Gai, Zheng; Lee, Ho Nyung; Sefat, Athena S; Lauter, Valeria; Liu, Zi-Kui; Christen, Hans M

    2016-01-01

    High-quality epitaxial growth of inter-metallic MnPt films on oxides is achieved, with potential for multiferroic heterostructure applications. Antisite-stabilized spin-flipping induces ferromagnetism in MnPt films, although it is robustly antiferromagnetic in bulk. Moreover, highly ordered antiferromagnetic MnPt films exhibit superiorly large exchange coupling with a ferromagnetic layer. PMID:26539758

  7. Bergman Clusters, Multiple Bonds, and Defect Planes: Synthetic Outcomes of Chemical Frustration in Ternary Intermetallic Systems

    NASA Astrophysics Data System (ADS)

    Hadler, Amelia Beth

    Intermetallics crystallize in a variety of complex structures, many of which show unusual bonding or intriguing properties. Understanding what factors drive this structural chemistry would be a valuable step towards designing new intermetallics with specific structures or properties. One pathway towards understanding and predicting the structures of complex intermetallics is chemical frustration, a design tool which harnesses competition between incompatible bonding or packing modes to induce complexity in ternary intermetallic systems. The research outlined in this thesis focuses on developing chemical frustration through exploratory synthesis in ternary systems designed to induce frustration between the tetrahedral close packing of many intermetallics and the simple cubic packing seen for ionic salts or elemental metals. Syntheses in three systems yielded six new ternary intermetallics, four of which crystallize in novel structure types. Three were discovered in the Ca-Cu-Cd system: Ca5Cu2Cd and Ca2Cu 2Cd9, which adopt ternary variants of binary structures, and Ca10Cu2Cd27, which crystallizes in a new structure built from Bergman clusters. All three structures can be traced to electronic packing frustration induced by the similar electronegativities but different metallic radii of Cu and Cd. The Gd-Fe-C system yielded the new carbometalate Gd13Fe 10C13 and an oxycarbide derivative. These phases crystallize in structures built from Gd tricapped trigonal prisms interpenetrated by an Fe-C network. Theoretical analyses reveal that Fe-Fe and Fe-C multiple bonding is found throughout this network. A theoretical investigation of similar carbides uncovers additional metal-metal, metal-carbon, and carbon-carbon multiple bonding. This unusual bonding stabilizes the carbides by satisfying preferred electron counts for their transition metal sites. One new phase, Mg4.5Pd5Ge1.5, was found in the Mg-Pd-Ge system. Its structure is closely related to the CsCl-type structure of

  8. The μ3 model of acids and bases: extending the Lewis theory to intermetallics.

    PubMed

    Stacey, Timothy E; Fredrickson, Daniel C

    2012-04-01

    A central challenge in the design of new metallic materials is the elucidation of the chemical factors underlying the structures of intermetallic compounds. Analogies to molecular bonding phenomena, such as the Zintl concept, have proven very productive in approaching this goal. In this Article, we extend a foundational concept of molecular chemistry to intermetallics: the Lewis theory of acids and bases. The connection is developed through the method of moments, as applied to DFT-calibrated Hückel calculations. We begin by illustrating that the third and fourth moments (μ(3) and μ(4)) of the electronic density of states (DOS) distribution tune the properties of a pseudogap. μ(3) controls the balance of states above and below the DOS minimum, with μ(4) then determining the minimum's depth. In this way, μ(3) predicts an ideal occupancy for the DOS distribution. The μ(3)-ideal electron count is used to forge a link between the reactivity of transition metals toward intermetallic phase formation, and that of Lewis acids and bases toward adduct formation. This is accomplished through a moments-based definition of acidity which classifies systems that are electron-poor relative to the μ(3)-ideal as μ(3)-acidic, and those that are electron-rich as μ(3)-basic. The reaction of μ(3) acids and bases, whether in the formation of a Lewis acid/base adduct or an intermetallic phase, tends to neutralize the μ(3) acidity or basicity of the reactants. This μ(3)-neutralization is traced to the influence of electronegativity differences at heteroatomic contacts on the projected DOS curves of the atoms involved. The role of μ(3)-acid/base interactions in intermetallic phases is demonstrated through the examination of 23 binary phases forming between 3d metals, the stability range of the CsCl type, and structural trends within the Ti-Ni system. PMID:22420716

  9. Development of intermetallic-hardened abrasion-resistant weld hardfacing alloys

    SciTech Connect

    School, M.R.

    1986-01-01

    Chromium and cobalt are strategic materials in the US and both are major constituents in many weld hardfacing alloys. Substitution for these materials or alternatives to their use was a primary direction of this investigation which was conducted in conjunction with the US Bureau of Mines. Minimization of the use of strategic materials was the criteria guiding the development of intermetallic-hardened abrasion resistant weld hardfacing materials. Other criteria were that the new alloy contain a hard intermetallic compound in an FCC matrix, and that these intermetallic compounds be stable at room temperature. A survey of ternary systems was made and the Fe-Mo-Ni system was selected to provide a basis for alloy development. Fe-Mo-Ni alloys synthesized by arc-melting and similar alloys made by welding possessed similar microstructures, a (Fe, Ni){sub 7}Mo{sub 6} intermetallic plus austenite eutectic in an austenitic matrix. These materials exhibited poor abrasive resistance. Silicon additions to the alloy promoted formation of a Laves phase FeMoSi intermetallic which helped increase the abrasive wear resistance. Through a series of alloy chemistry iterations a final composition of Fe-20Mo-15Ni-5Si was selected. Heat treatment of this alloy at 550 to 650 C caused second phase precipitation in the matrix and raised the hardness about 14 points HRC to 50 HRC. The alloy's wear rate, measured with the pin-on-drum abrasive wear test, was 6.3 to 6.5 mg/m. However this was twice the wear rate observed in commercial high-carbon high-chromium alloys. Based on examination of the alloy microstructures, their chemistry, and an analysis of the Fe-Mo-Si phase system; directions for further research are to increase the molybdenum and silicon content to produce a Fe-20Mo-10Ni-15Si composition.

  10. The relationship between ordered intermetallic nanoparticle synthesis and the bulk phase diagram

    NASA Astrophysics Data System (ADS)

    DeSario, Douglas York

    In this thesis, a surfactant-free synthesis of binary and ternary metal nanoparticles via co-reduction of metal chloride precursors is used to investigate the relationship between the bulk phase diagram and the formation of ordered intermetallic structures. The majority of the synthesized phases are binary materials of the formula Pt-M (M = Sn, Sb, In, Bi), because of their propensity to form single-phase regions with very narrow phase widths, known as "line phases". These line phases are thermodynamically stable according to the bulk phase diagram; however, the relationship between bulk stability and stability in the nanoparticle regime - and the implications for nanoparticle growth and ordering behavior - have not been fully explored. The 1:1 Pt-Sn phase (PtSn) forms ordered intermetallic nanoparticles with small domain sizes (4.3 nm) at room temperature, without any thermal annealing required. Pt3Sn similarly orders at low temperature (200 oC), in contrast to the three Pt-rich line phases, all of which require higher annealing temperatures to form the intermetallic phase. Other Pt-M phases show varying degrees of ordering, but none are observed to have the same low-temperature ordering as the Pt-rich Pt-Sn phases. This behavior is extremely rare, with only one other phase to our knowledge (Pt-Bi) forming the intermetallic without annealing, and only under specific conditions. It is possible to make qualitative statements concerning which phases should easily order and form phase-pure products; however, in order to more quantitatively predict these patterns, a multivariate analysis utilizing many physical properties (e.g., melting point, whether a phase melts congruently or incongruently, crystal structure, etc) was conducted. Using principal components analysis, partial least squares regression, and logistic regression techniques, a model was constructed to determine which properties would be most predictive of phases that were able to be synthesized as pure

  11. Diamond Coatings

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Advances in materials technology have demonstrated that it is possible to get the advantages of diamond in a number of applications without the cost penalty, by coating and chemically bonding an inexpensive substrate with a thin film of diamond-like carbon (DLC). Diamond films offer tremendous technical and economic potential in such advances as chemically inert protective coatings; machine tools and parts capable of resisting wear 10 times longer; ball bearings and metal cutting tools; a broad variety of optical instruments and systems; and consumer products. Among the American companies engaged in DLC commercialization is Diamonex, Inc., a diamond coating spinoff of Air Products and Chemicals, Inc. Along with its own proprietary technology for both polycrystalline diamond and DLC coatings, Diamonex is using, under an exclusive license, NASA technology for depositing DLC on a substrate. Diamonex is developing, and offering commercially, under the trade name Diamond Aegis, a line of polycrystalline diamond-coated products that can be custom tailored for optical, electronic and engineering applications. Diamonex's initial focus is on optical products and the first commercial product is expected in late 1990. Other target applications include electronic heat sink substrates, x-ray lithography masks, metal cutting tools and bearings.

  12. High-temperature ordered intermetallic alloys II; Proceedings of the Second Symposium, Boston, MA, Dec. 2-4, 1986

    NASA Technical Reports Server (NTRS)

    Stoloff, N. S. (Editor); Koch, C. C. (Editor); Liu, C. T. (Editor); Izumi, O. (Editor)

    1987-01-01

    The papers presented in this volume provide on overview of recent theoretical and experimental research in the field of high-temperature ordered intermetallic alloys. The papers are gouped under the following headings: ordering behavior and theory, microstructures, mechanical behavior, alloy design and microstructural control, and metallurgical properties. Specific topics discussed include antiphase domains, disordered films and the ductility of ordered alloys based on Ni3Al; kinetics and mechanics of formation of Al-Ni intermetallics; deformability improvements of L1(2)-type intermetallic compounds; B2 aluminides for high-temperature applications; and rapidly solidified binary TiAl alloys.

  13. Factors controlling the multi-functional corrosion properties of pulsed thermal sprayed Aluminum-Cobalt -Cerium coatings

    NASA Astrophysics Data System (ADS)

    Tailleart, Nicole R.

    High density, low porosity Al-Co-Ce metallic coatings have been successfully applied to precipitation age hardened aerospace structural alloy AA 2024-T351 substrates using a pulsed thermal spray (PTS) process. The three proposed modes of corrosion protection were brought about by the metallurgical and physical attributes of the coating. These include formation of a localized corrosion barrier, a sacrificial anode to enable cathodic protection of any exposed AA 2024-T351, and a source of an active inhibitor. The inhibitor (e.g., cerium and cobalt cations) can be released by various chemical triggers, such as chloride and pH. These functions were verified for the first time in this study on Al-Co-Ce PTS coated substrates and were found to function simultaneously in dilute chloride solutions. However, the localized corrosion properties of the PTS applied coating samples were not equal to fully amorphous, melt spun ribbon variants of the same alloy composition when ribbons were produced from feedstock powders. The goal of this research was to elucidate the critical attributes that govern the ability of the Al-Co-Ce coatings to perform each of these three functions. A structure-property paradigm describing relationships between composition, structure, as well as physical attributes and resulting coating corrosion properties, was explored. The effects of various metallurgical, physical, and geometric characteristics of the coating, such as structure, composition, morphology, porosity, and thickness were investigated. The main emphasis was placed on the localized corrosion barrier properties. The inferior behavior of the PTS coatings was traced to various microstructural and physical defects (i.e., chiefly the formation of intermetallic particles as well as crystalline, a non-amorphous structures with chemical non-uniformities). However, this inferior behavior cannot be attributed to feedstock powder composition since melt spun ribbons were successfully made from

  14. Protective Coatings

    NASA Technical Reports Server (NTRS)

    1980-01-01

    General Magnaplate Corporation's pharmaceutical machine is used in the industry for high speed pressing of pills and capsules. Machine is automatic system for molding glycerine suppositories. These machines are typical of many types of drug production and packaging equipment whose metal parts are treated with space spinoff coatings that promote general machine efficiency and contribute to compliance with stringent federal sanitation codes for pharmaceutical manufacture. Collectively known as "synergistic" coatings, these dry lubricants are bonded to a variety of metals to form an extremely hard slippery surface with long lasting self lubrication. The coatings offer multiple advantages; they cannot chip, peel or be rubbed off. They protect machine parts from corrosion and wear longer, lowering maintenance cost and reduce undesired heat caused by power-robbing friction.

  15. Pack cementation Cr-Al coating of steels and Ge-doped silicide coating of Cr-Nb alloy

    SciTech Connect

    He, Y.R.; Zheng, M.H.; Rapp, R.A.

    1995-08-01

    Carbon steels or low-alloy steels used in utility boilers, heat exchangers, petrochemical plants and coal gasification systems are subjected to high temperature corrosion attack such as oxidation, sulfidation and hot corrosion. The pack cementation coating process has proven to be an economical and effective method to enhance the corrosion resistance by modifying the surface composition of steels. With the aid of a computer program, STEPSOL, pack cementation conditions to produce a ferrite Cr-Al diffusion coating on carbon-containing steels by using elemental Cr and Al powders have been calculated and experimentally verified. The cyclic oxidation kinetics for the Cr-Al coated steels are presented. Chromium silicide can maintain high oxidation resistance up to 1100{degrees}C by forming a SiO{sub 2} protective scale. Previous studies at Ohio State University have shown that the cyclic oxidation resistance of MOSi{sub 2} and TiSi{sub 2} can be further improved by Ge addition introduced during coating growth. The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating in a single processing step for the ORNL-developed Cr-Nb advanced intermetallic alloy. The oxidation behavior of the silicide-coated Cr-Nb alloy was excellent: weight gain of about 1 mg/cm{sup 2} upon oxidation at 1100{degrees}C in air for 100 hours.

  16. Gold Coating

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Epner Technology Inc. responded to a need from Goddard Space Flight Center for the ultimate in electroplated reflectivity needed for the Mars Global Surveyor Mars Orbiter Laser Altimeter (MOLA). Made of beryllium, the MOLA mirror was coated by Epner Technology Laser Gold process, specially improved for the project. Improved Laser Gold- coated reflectors have found use in an epitaxial reactor built for a large semiconductor manufacturer as well as the waveguide in Braun-Thermoscan tympanic thermometer and lasing cavities in various surgical instruments.

  17. Micro and nano-texturization of intermetallic oxide alloys by a single anodization step: preparation of artificial self-cleaning surfaces.

    PubMed

    Feil, Adriano F; Weibel, Daniel E; Corsetti, Rodrigo R; Pierozan, Matheus D; Michels, Alexandre F; Horowitz, Flavio; Amaral, Lívio; Teixeira, Sérgio R

    2011-10-01

    Micro- and nanostructures of Ti-γCu (γ = 0, 30, 50, 70, and 100 wt %) intermetallic alloys were produced through a single anodization step. It was found that the original alloy composition influences the final oxide morphology obtained after anodization which presented formation of a microstructure with nanotubes, nanoparticles or nanopillars on the surface. Pure Ti and Cu oxide metals and their alloys presented hydrophilic or superhydrophilic properties immediately after anodization. When the anodized pure metal and/or Ti-γCu surfaces were functionalized with trimethoxypropylsilane (TPMSi), by dipping and coating with a thin perfluorinated layer, the treated substrates became in all cases superhydrophobic (water contact angles in the range of 152-166°), showing excellent self-cleaning properties with hysteresis below 3°. These results can be explained by a combination of nanomicro morphologies with low surface energy compounds in the topmost monolayers. The decrease in hysteresis was associated with a higher M-OH bond concentration on the anodized surfaces, which allowed for more complete TMPSi coating coverage. This study also indicates that easy and effective fabrication of superhydrophobic surfaces in pure metals and alloys is possible without involving traditional multistep processes. PMID:21919435

  18. MCrAlY bond coat with enhanced Yttrium layer

    DOEpatents

    Jablonski, Paul D; Hawk, Jeffrey A

    2015-04-21

    One or more embodiments relates to an MCrAlY bond coat comprising an MCrAlY layer in contact with a Y--Al.sub.2O.sub.3 layer. The MCrAlY layer is comprised of a .gamma.-M solid solution, a .beta.-MAl intermetallic phase, and Y-type intermetallics. The Y--Al.sub.2O.sub.3 layer is comprised of Yttrium atoms coordinated with oxygen atoms comprising the Al.sub.2O.sub.3 lattice. Both the MCrAlY layer and the Y--Al.sub.2O.sub.3 layer have a substantial absence of Y--Al oxides, providing advantage in the maintainability of the Yttrium reservoir within the MCrAlY bulk. The MCrAlY bond coat may be fabricated through application of a Y.sub.2O.sub.3 paste to an MCrAlY material, followed by heating in a non-oxidizing environment.

  19. Method of producing an oxide dispersion strengthened coating and micro-channels

    SciTech Connect

    Kang, Bruce S; Chyu, Minking K; Alvin, Mary Anne; Gleeson, Brian M

    2013-12-17

    The disclosure provides a method for the production of composite particles utilizing a mechano chemical bonding process following by high energy ball milling on a powder mixture comprised of coating particles, first host particles, and second host particles. The composite particles formed have a grain size of less than one micron with grains generally characterized by a uniformly dispersed coating material and a mix of first material and second material intermetallics. The method disclosed is particularly useful for the fabrication of oxide dispersion strengthened coatings, for example using a powder mixture comprised of Y.sub.2O.sub.3, Cr, Ni, and Al. This particular powder mixture may be subjected to the MCB process for a period generally less than one hour following by high energy ball milling for a period as short as 2 hours. After application by cold spraying, the composite particles may be heat treated to generate an oxide-dispersion strengthened coating.

  20. Intermetallics Characterization of Lead-Free Solder Joints under Isothermal Aging

    NASA Astrophysics Data System (ADS)

    Choubey, Anupam; Yu, Hao; Osterman, Michael; Pecht, Michael; Yun, Fu; Yonghong, Li; Ming, Xu

    2008-08-01

    Solder interconnect reliability is influenced by environmentally imposed loads, solder material properties, and the intermetallics formed within the solder and the metal surfaces to which the solder is bonded. Several lead-free metallurgies are being used for component terminal plating, board pad plating, and solder materials. These metallurgies react together and form intermetallic compounds (IMCs) that affect the metallurgical bond strength and the reliability of solder joint connections. This study evaluates the composition and extent of intermetallic growth in solder joints of ball grid array components for several printed circuit board pad finishes and solder materials. Intermetallic growth during solid state aging at 100°C and 125°C up to 1000 h for two solder alloys, Sn-3.5Ag and Sn-3.0Ag-0.5Cu, was investigated. For Sn-3.5Ag solder, the electroless nickel immersion gold (ENIG) pad finish was found to result in the lowest IMC thickness compared to immersion tin (ImSn), immersion silver (ImAg), and organic solderability preservative (OSP). Due to the brittle nature of the IMC, a lower IMC thickness is generally preferred for optimal solder joint reliability. A lower IMC thickness may make ENIG a desirable finish for long-life applications. Activation energies of IMC growth in solid-state aging were found to be 0.54 ± 0.1 eV for ENIG, 0.91 ± 0.12 eV for ImSn, and 1.03 ± 0.1 eV for ImAg. Cu3Sn and Cu6Sn5 IMCs were found between the solder and the copper pad on boards with the ImSn and ImAg pad finishes. Ternary (Cu,Ni)6Sn5 intermetallics were found for the ENIG pad finish on the board side. On the component side, a ternary IMC layer composed of Ni-Cu-Sn was found. Along with intermetallics, microvoids were observed at the interface between the copper pad and solder, which presents some concern if devices are subject to shock and vibration loading.

  1. Optical properties of Group X-XII intermetallic compounds studied by HR-EELS.

    PubMed

    Sato, Yohei; Terauchi, Masami; Kameoka, Satoshi; Tsai, An-Pang

    2014-11-01

    Electronic structure of d orbital states in transition metals is a key factor for their physical properties and chemical functions. Copper and intermetallic compound PdZn have good catalysis function for the methanol steam reforming reaction. Tsai et al. showed that from results of XPS measurements the d electronic structure of PdZn was similar with that of copper, and the catalysis function should be related to the d electron states [1]. This similarity of d electronic states leads to another view point of the mechanism for coloring the intermetallic compounds. It is well-known that the characteristic red color of copper is caused by interband transition from the d electrons. Therefore, PdZn and Group X-XII intermetallic compounds are expected to be colored and the optical properties should depend on the d electronic states. In this study, the relations between optical properties and d electron states of Group X-XII intermetallic compounds were investigated by using high energy-resolution electron energy-loss spectroscopy (HR-EELS) based on transmission electron microscopy (TEM). From the relation between optical properties and d electronic states, the mechanism of colored intermetallic compounds will be discussed.Figure shows the optical reflectivity of NiZn, PdZn and PtZn, which were derived from EELS spectra by Kramers-Kronig analysis. Intensity drops (arrows) of the reflectivity were observed in visible energy region. These are caused by the interband transitions from d electronic states. The energy positions of the reflectivity drops have tendency of shifting to higher energy side with increasing atomic number of Group X elements (Ni → Pd → Pt). This indicates that the transition energies of d electrons become larger with the atomic number of the elements. First principle calculations (WIEN2k) confirmed that the interband transitions of d electronic states were excitations from bonding d states to hybrid states of anti-bonding s, p, and d states of Group

  2. Lightweight Intermetallics with Laves Structures as Potential Hydrogen Storage Materials

    NASA Astrophysics Data System (ADS)

    Billet, Beau Austin

    Hydrogen storage was identified by the US Department of Energy as a "grand challenge" for the implementation of hydrogen-powered fuel cell vehicles for reduced CO2 emissions from transportation vehicles. None of the hydrogen storage options currently developed can satisfy the high gravimetric, volumetric and system design requirements. Intermetallic compounds with Laves structures in the formula of AB2 have long been known to store hydrogen in their interstitial sites to serve as reversible hydrogen storage materials (A and B are metallic elements). They have the potential to be hydrided to a maximum of ~ AB2H6 due to the impeding H-H interactions at neighboring interstitial sites. To achieve the highest weight percent of hydrogen storage in AB2H6, the lowest combined atomic weight of AB2 is required. The CaLi2 compound is the lightest known Laves phase, but it could not maintain its Laves structure when it was hydrided. Existing work of Akiba's group showed that a ternary Laves phase CaLi1.8Mg0.2 could be hydrided to form a hydrogenated Laves phase, but the absorbed hydrogen could not be released for reversible storage. Substitutions (Ca,X)Li1.8Mg0.2 are explored in the present study to see whether heavier elements [X = Sr, Ba and Ce] in small quantities can make the lightweight Laves compounds reversibly store hydrogen. Induction melting was successful in obtaining the desired Laves phases. The base system, CaLi1.8Mg0.2, formed a single phase, consistent with the literature result. Both Ca0.9Ba0.1Li 1.8Mg0.2 and Ca0.9Ce0.1Li1.8Mg 0.2 also formed a single-phase C14 Laves, whereas both Ca0.9Sr 0.1Li1.8Mg0.2 and Ca0.8Sr0.2Li 1.8Mg0.2 formed two seperature Laves phases with the same crystal structure, indicating a phase separation. The Ca0.8Ba 0.2Li1.8Mg0.2 composition completely lost the Laves-phase structure, forming CaLi2, CaMg2, BaLi 4 and Ca. All compounds tested at temperatures from 25 °C to 150 °C show the characteristic "plateau" behavior in the pressure

  3. Atomic interaction of the MEAM type for the study of intermetallics in the Al-U alloy

    NASA Astrophysics Data System (ADS)

    Pascuet, M. I.; Fernández, J. R.

    2015-12-01

    Interaction for both pure Al and Al-U alloys of the MEAM type are developed. The obtained Al interatomic potential assures its compatibility with the details of the framework presently adopted. The Al-U interaction fits various properties of the Al2U, Al3U and Al4U intermetallics. The potential verifies the stability of the intermetallic structures in a temperature range compatible with that observed in the phase diagram, and also takes into account the greater stability of these structures relative to others that are competitive in energy. The intermetallics are characterized by calculating elastic and thermal properties and point defect parameters. Molecular dynamics simulations show a growth of the Al3U intermetallic in the Al/U interface in agreement with experimental evidence.

  4. Chemical Frustration. A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases, Final Report

    SciTech Connect

    Fredrickson, Daniel C

    2015-06-23

    Final technical report for "Chemical Frustration: A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases" funded by the Office of Science through the Materials Chemistry Program of the Office of Basic Energy Sciences.

  5. Forming metal-intermetallic or metal-ceramic composites by self-propagating high-temperature reactions

    DOEpatents

    Rawers, James C.; Alman, David E.; Petty, Jr., Arthur V.

    1996-01-01

    Industrial applications of composites often require that the final product have a complex shape. In this invention intermetallic or ceramic phases are formed from sheets of unreacted elemental metals. The process described in this invention allows the final product shape be formed prior to the formation of the composite. This saves energy and allows formation of shaped articles of metal-intermetallic composites composed of brittle materials that cannot be deformed without breaking.

  6. Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

    DOEpatents

    Wright, R.B.

    1992-01-14

    Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation). 23 figs.

  7. Extreme Poisson's ratios and their electronic origin in B2 CsCl-type AB intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Wang, X. F.; Jones, Travis E.; Li, W.; Zhou, Y. C.

    2012-04-01

    Negative Poisson's ratios have been observed in a variety of metals and alloys. However, the electronic origin of this effect remains unclear, as is evident by our limited knowledge about intermetallics showing this behavior. In an effort to clarify the electronic origin of a negative Poisson's ratio, we have performed a systematic and comprehensive study of extreme (both positive and negative) Poisson's ratios behavior in the B2 CsCl-type AB intermetallic family (including 14 common intermetallics and 128 rare-earth-metal transition or main-group-metal intermetallics) by way of density functional theory calculations. We found a pronounced correlation between the extreme Poisson's ratios and the elastic anisotropy, with approximately 70% of the B2 intermetallics showing intrinsic auxetic behavior. We went on to examine the topology and geometry of the electron charge density and found that the extreme Poisson's ratios are attributable to the directionality of the bonds of the material. Auxetic materials were found to have nondirectional bonds, and nonauxetic compounds had directional bonds. Our findings provide an essential electronic perspective to forecast the auxetic behavior, and suggest a new application for intermetallic compounds.

  8. Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound

    NASA Astrophysics Data System (ADS)

    Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

    2016-08-01

    The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys.

  9. Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound

    PubMed Central

    Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

    2016-01-01

    The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys. PMID:27488621

  10. Effects of intermetallic particles on the SCC initiation of zirconium alloys

    NASA Astrophysics Data System (ADS)

    Kubo, T.; Wakashima, Y.; Imahashi, H.; Nagai, M.

    1985-06-01

    In order to investigate effects of intermetallic particles on SCC initiation of zirconium alloys, tensile tests were conducted in an iodine atmosphere using zirconium plates with different amounts of impurities, and Zircaloy-2 plates. SCC susceptibility of zirconium increased significantly with its iron content. Even small amounts of iron could form the intermetallic compound ZrFe 2 whose particle size and number increased with iron content. In the case of Zircaloy-2, two different types of ternary compounds were detected, namely Zr(CrFe) 2 and Zr 2(NiFe). Metallographic examinations showed that the particles located at grain boundaries were important sites of SCC initiation in zirconium alloys. The initiation probability increased significantly with the amount of the particles, which supported the strong correlation between SCC susceptibility of zirconium and its iron content.

  11. Phase stability of laves intermetallics in stainless steel-zirconium alloys.

    SciTech Connect

    Abraham, D. P.

    1999-04-08

    Phase transformations occurring in a stainless steel-15 wt% zirconium (SS-15Zr) alloy were studied by in situ neutron diffraction. Neutron diffraction patterns as a function of time were obtained on alloys that were held at various elevated temperatures (1084-1275 C). As-cast SS-15Zr alloys contain ferrite, austenite, ZrFe{sub 2}-type Laves polytypes C36 and C15, and small amounts of a Fe{sub 23}Zr{sub 6}-type intermetallic. Annealing at high temperatures resulted in an increase of the Fe{sub 23}Zr{sub 6}, intermetallic content. The C15 Laves polytype is the equilibrium phase for T {le} 1230 C; C36 is the stable polytype at higher temperatures ({approximately}1275 C). Phase changes were slow for temperatures <1100 C.These findings have important implications for use of the SS-15Zr alloy as a nuclear waste form.

  12. A reliability study on tin based lead free micro joint including intermetallic and void evolution

    NASA Astrophysics Data System (ADS)

    Feyissa, Frezer Assefa

    In microelectronics soldering to Cu pad lead to formation of two intermetallic structures in the solder -pad interface. The growth of these layers is accompanied by microscopic voids that usually cause reliability concern in the industry. Therefore it is important to understand factors that contribute for the growth of IMC using various combination of reflow time, Sn thickness and aging temperature. Systematic study was conducted on Cu-Sn system to investigate the formation and growth of intermetallic compound (IMC) as well as voiding evolution for different solder thicknesses. The growth of the Cu6Sn5 IMC layer was found to be increasing as the Sn thicknesses increase after reflow while the Cu3Sn layer were decreasing under same conditions. Also after reflow and aging more voiding were shown to occur in the thin solder than thicker one.

  13. High-Performance Pd3Pb Intermetallic Catalyst for Electrochemical Oxygen Reduction.

    PubMed

    Cui, Zhiming; Chen, Hao; Zhao, Mengtian; DiSalvo, Francis J

    2016-04-13

    Extensive efforts to develop highly active and strongly durable electrocatalyst for oxygen reduction are motivated by a need for metal-air batteries and fuel cells. Here, we report a very promising catalyst prototype of structurally ordered Pd-based alloys, Pd3Pb intermetallic compound. Such structurally ordered Pd3Pb/C exhibits a significant increase in mass activity. More importantly, compared to the conventional Pt/C catalysts, ordered Pd3Pb/C is highly durable and exhibits a much longer cycle life and higher cell efficiency in Zn-air batteries. Interestingly, ordered Pd3Pb/C possesses very high methanol tolerance during electrochemical oxygen reduction, which make it an excellent methanol-tolerant cathode catalyst for alkaline polymer electrolyte membrane fuel cells. This study provides a promising route to optimize the synthesis of ordered Pd-based intermetallic catalysts for fuel cells and metal-air batteries. PMID:26848634

  14. Na-Au intermetallic compounds formed under high pressure at room temperature

    NASA Astrophysics Data System (ADS)

    Takemura, K.; Fujihisa, H.

    2011-07-01

    High-pressure powder x-ray diffraction experiments have revealed that sodium and gold react at room temperature and form Na-Au intermetallic compounds under high pressure. We have identified four intermetallic phases up to 60 GPa. The first phase (phase I) is the known Na2Au with the tetragonal CuAl2-type structure. It changed to the second phase (phase II) at ˜0.8 GPa, which has the composition Na3Au with the trigonal Cu3As-type or hexagonal Cu3P-type structure. Phase II further transformed to phase III at 3.6 GPa. Phase III has the same composition, Na3Au, with the cubic BiF3-type structure. Finally, phase III changed to phase IV at ˜54 GPa. Phase IV gives broad diffraction peaks, indicating large structural disorder.

  15. Self-assembling of atomic vacancies at an oxide/intermetallic alloy interface.

    PubMed

    Maurice, Vincent; Despert, Guillaume; Zanna, Sandrine; Bacos, Marie-Pierre; Marcus, Philippe

    2004-10-01

    Oxide layers grown on the surface provide an effective way of protecting metallic materials against corrosion for sustainable use in a broad range of applications. However, the growth of cavities at the metal/oxide interface weakens the adherence of the protective layer and can promote its spallation under service conditions, as observed for alumina layers formed by selective oxidation of aluminide intermetallic alloys used in high-temperature applications. Here we show that direct atomic-scale observations of the interface between an ultrathin protective oxide layer (alumina) grown on an intermetallic titanium aluminide substrate (TiAl) can be performed with techniques sensitive to the topmost atomic layers at the surface. Nanocavities resulting from the self-assembling of atomic vacancies injected at the interface by the growth mechanism of the protective oxide are observed for the first time, bringing new insight into the understanding of the fate of injected cavities in oxidation processes. PMID:15378049

  16. Gold–promoted structurally ordered intermetallic palladium cobalt nanoparticles for the oxygen reduction reaction

    SciTech Connect

    Kuttiyiel, Kurian A.; Sasaki, Kotaro; Su, Dong; Wu, Lijun; Zhu, Yimei; Adzic, Radoslav R.

    2014-11-06

    Considerable efforts to make palladium and palladium alloys active catalysts and a possible replacement for platinum have had a marginal success. Here, we report on a structurally ordered Au₁₀Pd₄₀Co₅₀ catalyst that exhibits comparable activity to conventional platinum catalysts in both acid and alkaline media. Electron microscopic techniques demonstrate that via addition of gold atoms PdCo nanoparticles undergo at elevated temperatures an atomic structural transition from core-shell to a rare intermetallic ordered structure with twin boundaries forming stable {111}, {110} and {100} facets. The superior stability of this catalyst compared to platinum after 10,000 potential cycles in alkaline media is attributed to the atomic structural order of PdCo nanoparticles along with protective effect of clusters of gold atoms on the surface. This strategy of making ordered palladium intermetallic alloy nanoparticles can be used in diverse heterogeneous catalysis where particle size and structural stability matters.

  17. Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound.

    PubMed

    Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

    2016-01-01

    The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys. PMID:27488621

  18. Carbon-coated nanoparticle superlattices for energy applications

    NASA Astrophysics Data System (ADS)

    Li, Jun; Yiliguma, Affa; Wang, Yifei; Zheng, Gengfeng

    2016-07-01

    Nanoparticle (NP) superlattices represent a unique material architecture for energy conversion and storage. Recent reports on carbon-coated NP superlattices have shown exciting electrochemical properties attributed to their rationally designed compositions and structures, fast electron transport, short diffusion length, and abundant reactive sites via enhanced coupling between close-packed NPs, which are distinctive from their isolated or disordered NP or bulk counterparts. In this minireview, we summarize the recent developments of highly-ordered and interconnected carbon-coated NP superlattices featuring high surface area, tailorable and uniform doping, high conductivity, and structure stability. We then introduce the precisely-engineered NP superlattices by tuning/studying specific aspects, including intermetallic structures, long-range ordering control, and carbon coating methods. In addition, these carbon-coated NP superlattices exhibit promising characteristics in energy-oriented applications, in particular, in the fields of lithium-ion batteries, fuel cells, and electrocatalysis. Finally, the challenges and perspectives are discussed to further explore the carbon-coated NP superlattices for optimized electrochemical performances.

  19. Carbon-coated nanoparticle superlattices for energy applications.

    PubMed

    Li, Jun; Yiliguma; Wang, Yifei; Zheng, Gengfeng

    2016-08-14

    Nanoparticle (NP) superlattices represent a unique material architecture for energy conversion and storage. Recent reports on carbon-coated NP superlattices have shown exciting electrochemical properties attributed to their rationally designed compositions and structures, fast electron transport, short diffusion length, and abundant reactive sites via enhanced coupling between close-packed NPs, which are distinctive from their isolated or disordered NP or bulk counterparts. In this minireview, we summarize the recent developments of highly-ordered and interconnected carbon-coated NP superlattices featuring high surface area, tailorable and uniform doping, high conductivity, and structure stability. We then introduce the precisely-engineered NP superlattices by tuning/studying specific aspects, including intermetallic structures, long-range ordering control, and carbon coating methods. In addition, these carbon-coated NP superlattices exhibit promising characteristics in energy-oriented applications, in particular, in the fields of lithium-ion batteries, fuel cells, and electrocatalysis. Finally, the challenges and perspectives are discussed to further explore the carbon-coated NP superlattices for optimized electrochemical performances. PMID:27432112

  20. The role of zinc on the chemistry of complex intermetallic compounds

    SciTech Connect

    Xie, Weiwei

    2014-01-01

    Combining experiments and electronic structure theory provides the framework to design and discover new families of complex intermetallic phases and to understand factors that stabilize both new and known phases. Using solid state synthesis and multiple structural determinations, ferromagnetic β-Mn type Co8+xZn12–x was analyzed for their crystal and electronic structures.

  1. Kinetically Controlling Surface Structure to Construct Defect-Rich Intermetallic Nanocrystals: Effective and Stable Catalysts.

    PubMed

    Rong, Hongpan; Mao, Junjie; Xin, Pingyu; He, Dongsheng; Chen, Yuanjun; Wang, Dingsheng; Niu, Zhiqiang; Wu, Yuen; Li, Yadong

    2016-04-01

    Kinetic control of surface defects is achieved, and cubic, concave cubic, and defect-rich cubic intermetallic Pt3 Sn nanocrystals are prepared for the electro-oxidation of formic acid. The generality of this kinetic approach is demonstrated by the fabrication of Pt-Mn nanocrystals with different surface defects. The defect-rich nanocrystals exhibit high catalytic activity and stability concurrently, indicating their potential application in fuel cells. PMID:26836038

  2. Hydrogen cycling-induced phase segregation in AB{sub 5}-type intermetallics

    SciTech Connect

    Mordkovich, V.Z.

    1998-12-31

    A study of hydrogen cycling-induced phase segregation in AB{sub 5}-type intermetallics is presented. Influence of temperature for the alloy compositions YNi{sub 4}Al, LaNi{sub 5}, Ce{sub 0.5}La{sub 0.5}Ni{sub 5} and Ce{sub 0.7}La{sub 0.3}Ni{sub 5} is shown. Morphology of the nanostructured particles formed is studied and discussed.

  3. Quantitative HAADF-STEM tomography of unsupported intermetallic Ga-Pd catalysts

    NASA Astrophysics Data System (ADS)

    Leary, Rowan; Saghi, Zineb; Armbrüster, Marc; Schlögl, Robert; Meurig Thomas, John; Midgley, Paul

    2012-07-01

    HAADF-STEM tomography has been used for characterisation of novel unsupported intermetallic Ga-Pd catalysts, with accompanying analysis by HRTEM and EDXS. Image processing techniques applied to the tomogram have facilitated segmentation and the subsequent extraction of size and shape parameters. The fidelity of the analysis has been critically examined, enabling identification of reconstruction artefacts and thereby more reliable determination of catalytically relevant properties. Further steps towards robust and accurate metrology by electron tomography are discussed.

  4. In situ XPS study of methanol reforming on PdGa near-surface intermetallic phases

    PubMed Central

    Rameshan, Christoph; Stadlmayr, Werner; Penner, Simon; Lorenz, Harald; Mayr, Lukas; Hävecker, Michael; Blume, Raoul; Rocha, Tulio; Teschner, Detre; Knop-Gericke, Axel; Schlögl, Robert; Zemlyanov, Dmitry; Memmel, Norbert; Klötzer, Bernhard

    2012-01-01

    In situ X-ray photoelectron spectroscopy and low-energy ion scattering were used to study the preparation, (thermo)chemical and catalytic properties of 1:1 PdGa intermetallic near-surface phases. Deposition of several multilayers of Ga metal and subsequent annealing to 503–523 K led to the formation of a multi-layered 1:1 PdGa near-surface state without desorption of excess Ga to the gas phase. In general, the composition of the PdGa model system is much more variable than that of its PdZn counterpart, which results in gradual changes of the near-surface composition with increasing annealing or reaction temperature. In contrast to near-surface PdZn, in methanol steam reforming, no temperature region with pronounced CO2 selectivity was observed, which is due to the inability of purely intermetallic PdGa to efficiently activate water. This allows to pinpoint the water-activating role of the intermetallic/support interface and/or of the oxide support in the related supported PdxGa/Ga2O3 systems, which exhibit high CO2 selectivity in a broad temperature range. In contrast, corresponding experiments starting on the purely bimetallic model surface in oxidative methanol reforming yielded high CO2 selectivity already at low temperatures (∼460 K), which is due to efficient O2 activation on PdGa. In situ detected partial and reversible oxidative Ga segregation on intermetallic PdGa is associated with total oxidation of intermediate C1 oxygenates to CO2. PMID:22875996

  5. The electron structure and magnetic properties of TiCo intermetallic

    NASA Astrophysics Data System (ADS)

    Grechnev, G. E.; Svechkarev, I. V.

    1987-05-01

    The energy band structure and magnetic and some thermodynamic characteristics of TiCo are investigated theoretically in the low-temperature region. The nature of the stability of this intermetallic is determined. It is shown that TiCo is characterized by a strong exchange enhancement of spin susceptibility. The factors responsible for the strong paramagnetism and superconductivity of TiCo are identified; the parameters of electron-photon and electron-paramagnon interactions are determined.

  6. Cavitation Erosion in Hydraulic Turbine Components and Mitigation by Coatings: Current Status and Future Needs

    NASA Astrophysics Data System (ADS)

    Singh, Raghuvir; Tiwari, S. K.; Mishra, Suman K.

    2012-07-01

    Cavitation erosion is a frequently observed phenomenon in underwater engineering materials and is the primary reason for component failure. The damage due to cavitation erosion is not yet fully understood, as it is influenced by several parameters, such as hydrodynamics, component design, environment, and material chemistry. This article gives an overview of the current state of understanding of cavitation erosion of materials used in hydroturbines, coatings and coating methodologies for combating cavitation erosion, and methods to characterize cavitation erosion. No single material property fully characterizes the resistance to cavitation erosion. The combination of ultimate resilience, hardness, and toughness rather may be useful to estimate the cavitation erosion resistance of material. Improved hydrodynamic design and appropriate surface engineering practices reduce damage due to cavitation erosion. The coatings suggested for combating the cavitation erosion encompasses carbides (WC Cr2C3, Cr3C2, 20CrC-80WC), cermets of different compositions (e.g., 56W2C/Ni/Cr, 41WC/Ni/Cr/Co), intermetallic composites, intermetallic matrix composites with TiC reinforcement, composite nitrides such as TiAlN and elastomers. A few of them have also been used commercially. Thermal spraying, arc plasma spraying, and high velocity oxy-fuel (HVOF) processes have been used commercially to apply the coatings. Boronizing, laser surface hardening and cladding, chemical vapor deposition, physical vapor deposition, and plasma nitriding have been tried for surface treatments at laboratory levels and have shown promise to be used on actual components.

  7. Engine Coatings

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Increasing the operating temperature of turbine engines reduces fuel consumption and increases engine efficiency. However, engine components must be protected from excessive heat. Lewis Research Center has successfully developed thermal barrier coatings (TBCs), which are deposited on the components. They insulate, offer oxidation and corrosion resistance and increase adherence. Surface temperatures can be reduced by 200 degrees centigrade or more. G. E. Aircraft Engines, a Lewis contractor, now uses a TBC based on the one developed at Lewis, on production engines. The system, which consists of a bond and a top coat extends component life from 1.3 to 2 times. The company is also testing TBCs on components that operate at higher temperatures.

  8. COATING METHOD

    DOEpatents

    Townsend, R.G.

    1959-08-25

    A method is described for protectively coating beryllium metal by etching the metal in an acid bath, immersing the etched beryllium in a solution of sodium zincate for a brief period of time, immersing the beryllium in concentrated nitric acid, immersing the beryhlium in a second solution of sodium zincate, electroplating a thin layer of copper over the beryllium, and finally electroplating a layer of chromium over the copper layer.

  9. Cerium-based, intermetallic-strengthened aluminum casting alloy: High-volume co-product development

    DOE PAGESBeta

    Sims, Zachary C.; Weiss, D.; McCall, S. K.; McGuire, M. A.; Ott, R. T.; Geer, Tom; Rios, Orlando; Turchi, P. A. E.

    2016-05-23

    Here, several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanicalmore » properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.« less

  10. Evolution, Interaction, and Intrinsic Properties of Dislocations in Intermetallics: Anisotropic 3D Dislocation Dynamics Approach

    SciTech Connect

    Qian Chen

    2008-08-18

    The generation, motion, and interaction of dislocations play key roles during the plastic deformation process of crystalline solids. 3D Dislocation Dynamics has been employed as a mesoscale simulation algorithm to investigate the collective and cooperative behavior of dislocations. Most current research on 3D Dislocation Dynamics is based on the solutions available in the framework of classical isotropic elasticity. However, due to some degree of elastic anisotropy in almost all crystalline solids, it is very necessary to extend 3D Dislocation Dynamics into anisotropic elasticity. In this study, first, the details of efficient and accurate incorporation of the fully anisotropic elasticity into 3D discrete Dislocation Dynamics by numerically evaluating the derivatives of Green's functions are described. Then the intrinsic properties of perfect dislocations, including their stability, their core properties and disassociation characteristics, in newly discovered rare earth-based intermetallics and in conventional intermetallics are investigated, within the framework of fully anisotropic elasticity supplemented with the atomistic information obtained from the ab initio calculations. Moreover, the evolution and interaction of dislocations in these intermetallics as well as the role of solute segregation are presented by utilizing fully anisotropic 3D dislocation dynamics. The results from this work clearly indicate the role and the importance of elastic anisotropy on the evolution of dislocation microstructures, the overall ductility and the hardening behavior in these systems.

  11. Preparation of nanocrystalline metal oxides and intermetallic phases by controlled thermolysis of organometallic coordination polymers

    NASA Astrophysics Data System (ADS)

    Rehbein, Marcus; Epple, Matthias; Fischer, R. Dieter

    2000-06-01

    Organometallic coordination polymers of the super-Prussian blue type [(Me 3Sn) nM(CN) 6] (Me=CH 3; n=3, 4; M=Fe, Co, Ru) were subjected to thermolysis in different atmospheres (air, argon, hydrogen/nitrogen). In air, oxides were found: Fe 2O 3/SnO 2 (crystalline and nanocrystalline), Co 2SnO 4 and RuO 2. In argon and in hydrogen, the intermetallic phases FeSn 2, CoSn 2, Ru 3Sn 7 and Fe 3SnC were obtained. A detailed mechanistic study was carried out using thermogravimetry (TG), X-ray diffraction (XRD), X-ray absorption spectroscopy (EXAFS) at Fe, Co, Ru and Sn K-edges, infrared spectroscopy (IR) and elemental analysis. Below 250°C, Me 3SnCN and (CN) 2 are released, whereas above 250°C oxidation or pyrolysis leads to the corresponding oxides or intermetallic phases. Polymeric cyanides containing at least two metals have turned out to be suitable precursors to prepare well-defined oxides and intermetallic phases at comparatively low temperature.

  12. Evolution of Intermetallic Phases in Soldering of the Die Casting of Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Song, Jie; Wang, Xiaoming; DenOuden, Tony; Han, Qingyou

    2016-06-01

    Most die failures are resulted from chemical reactions of dies and molten aluminum in the die casting of aluminum. The formation of intermetallic phases between a steel die and molten aluminum is investigated by stationary immersion tests and compared to a real die casting process. Three intermetallic phases are identified in the stationary immersion tests: a composite layer and two compact layers. The composite layer is a mixture of α bcc, Al, and Si phases. The α bcc phase changes in morphology from rod-like to spherical shape, while the growth rate of the layer changes from parabolic to linear pattern with immersion time. The first compact layer forms rapidly after immersion and maintains a relatively constant thickness. The second compact layer forms after 4 hours of immersion and exhibits parabolic growth with immersion time. In comparison, only a composite layer and the first compact layer are observed in a real die casting process. The fresh molten aluminum of high growth rate washes away the second intermetallic layer easily.

  13. Synthesis and densification of Ni{sub 3}(Si, Ti) intermetallics by hot isostatic pressing

    SciTech Connect

    Van Dyck, S.; Delaey, L.; Froyen, L.; Buekenhout, L.

    1996-12-31

    The production of complex parts from Ni{sub 3}(Si, Ti) intermetallic materials by reactive powder metallurgy offers significant advantages over more conventional processing techniques. The main problem associated with reactive powder metallurgy is controlling the exothermic reaction accompanying the synthesis of the intermetallic compound. The uncontrolled release of heat during the conversion of the reactants into nickel silicide leads to unacceptable deformation and melting of the part. The thermal evolution of a part during reactive synthesis of the intermetallic phase is described based on kinetic and heat transfer equations, giving the temperature and phase change as a function of the applied temperature cycle and the mass and size of the part under consideration. From this model, methods for controlling the exothermic reaction during synthesis are derived. When preparing nickel silicides by reactive powder metallurgy, the application of external pressure is required to eliminate porosity and to obtain good mechanical properties. The properties of materials produced by hot isostatic pressing, with different methods of reaction control, are compared to materials prepared from prealloyed powders. It is shown that by reactive HIP, materials can be obtained with a fracture strength exceeding 2,000 MPa.

  14. Prediction of Host-Guest Na-Fe Intermetallics at High Pressures.

    PubMed

    Zhou, Yuanyuan; Wang, Hui; Zhu, Chunye; Liu, Hanyu; Tse, John S; Ma, Yanming

    2016-07-18

    High pressure can fundamentally alter the electronic structure of elemental metals, leading to the unexpected formation of intermetallics with unusual structural features. In the present study, the phase stabilities and structural changes of Na-Fe intermetallics under pressure were studied using unbiased structure searching methods, combined with density functional theory calculations. Two intermetallics with stoichiometries Na3Fe and Na4Fe are found to be thermodynamically stable at pressures above 120 and 155 GPa, respectively. An interesting structural feature is that both have form a host-guest-like structure with Na sublattices constructed from small and large polygons similar to the host framework of the self-hosting incommensurate phases observed in Group I and II elements. Apart from the one-dimensional (1D) Fe chains running through the large channels, more interestingly, electrides are found to localize in the small channels between the layers. Electron topological analysis shows secondary bonding interactions between the Fe atoms and the interstitial electrides help to stabilize these structures. PMID:27341197

  15. Cerium-Based, Intermetallic-Strengthened Aluminum Casting Alloy: High-Volume Co-product Development

    NASA Astrophysics Data System (ADS)

    Sims, Zachary C.; Weiss, D.; McCall, S. K.; McGuire, M. A.; Ott, R. T.; Geer, Tom; Rios, Orlando; Turchi, P. A. E.

    2016-07-01

    Several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanical properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.

  16. Cerium-Based, Intermetallic-Strengthened Aluminum Casting Alloy: High-Volume Co-product Development

    NASA Astrophysics Data System (ADS)

    Sims, Zachary C.; Weiss, D.; McCall, S. K.; McGuire, M. A.; Ott, R. T.; Geer, Tom; Rios, Orlando; Turchi, P. A. E.

    2016-05-01

    Several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanical properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.

  17. Effects of Ti, Zr, and Hf on the Phase Stability of Mo-Mo3Si+Mo5SiB2 Alloys at 1600 C

    SciTech Connect

    Yang, Ying; Bei, Hongbin; Chen, Shuanglin; George, Easo P; Tiley, Jaimie; Chang, Y. Austin

    2010-01-01

    Understanding the stability of the three-phase Mo{_}+Mo{sub 3}Si+Mo{sub 5}SiB{sub 2} region is important for alloy design of Mo-Si-B-based refractory metal intermetallic composites. In this work, thermodynamic modeling is coupled with guided experiments to study phase stability in this three-phase region of the Mo-Si-B-X (X = Ti, Zr, Hf) system. Both the calculated and experimental results show that additions of Zr and Hf limit significantly the stability of the three-phase region because of the formation of the ternary phases MoSiZr and MoSiHf, while Ti addition leads to a much larger region of stability for the three-phase equilibrium.

  18. Ab Initio Calculated Thermodynamic Properties of Mo5SiB2 Phase and Nb5SiB2 Phase

    NASA Astrophysics Data System (ADS)

    Kim, Sungtae; Park, J. S.

    2013-11-01

    Due to their attractive high-temperature properties, multiphase Mo-Si-B alloys in the Mo-rich Mo-Si-B ternary system have been identified for high-temperature applications. The ternary intermetallic T2 (Mo5SiB2) phase is a central feature of the phase equilibria within this ternary system. Experimental stability analyses of the T2 phase shows its broad homogeneous composition ranges that can yield a constitutional defect structure such as vacancies for Mo-rich compositions and antisite defects for Mo-lean compositions. Previous thermodynamic model did not conform to the defect structures as reported in experiments, and thus subsequently a new sublattice thermodynamic model for the T2 phase is initiated in this study. To support the new sublattice thermodynamic model, ab initio calculations were implemented to compute formation energy data. The calculated formation energy data explain a source for broad compositional homogeneity range of T2 structure.

  19. Thermal radiative properties: Coatings.

    NASA Technical Reports Server (NTRS)

    Touloukian, Y. S.; Dewitt, D. P.; Hernicz, R. S.

    1972-01-01

    This volume consists, for the most part, of a presentation of numerical data compiled over the years in a most comprehensive manner on coatings for all applications, in particular, thermal control. After a moderately detailed discussion of the theoretical nature of the thermal radiative properties of coatings, together with an overview of predictive procedures and recognized experimental techniques, extensive numerical data on the thermal radiative properties of pigmented, contact, and conversion coatings are presented. These data cover metallic and nonmetallic pigmented coatings, enamels, metallic and nonmetallic contact coatings, antireflection coatings, resin coatings, metallic black coatings, and anodized and oxidized conversion coatings.

  20. NICKEL COATED URANIUM ARTICLE

    DOEpatents

    Gray, A.G.

    1958-10-01

    Nickel coatings on uranium and various methods of obtaining such coatings are described. Specifically disclosed are such nickel or nickel alloy layers as barriers between uranium and aluminum- silicon, chromium, or copper coatings.

  1. A Study on the Formation of Intermetallics During the Heat Treatment of Explosively Welded Al-Ti Multilayers

    NASA Astrophysics Data System (ADS)

    Foadian, Farzad; Soltanieh, Mansour; Adeli, Mandana; Etminanbakhsh, Majid

    2014-04-01

    Metallic-intermetallic laminate composites are promising materials for many applications, namely, in the aerospace industry. Ti/TiAl3 laminates are one of the interesting laminate composites, which are mostly used in aerospace applications. In this work, commercially pure aluminum and titanium sheets were explosively joined. The multilayer samples were annealed between 1 and 260 hours at 903 K (630 °C) in ambient atmosphere, and the formation and growth of the intermetallic compound at the Ti/Al interface were monitored. Microstructural investigations were carried out using optical and scanning electron microscopes equipped with energy-dispersive spectroscopy and the X-ray diffraction technique. The microhardness profile of the layers was also determined. The thickness and type of Al-Ti intermetallics were determined. It was found that the only intermetallic phase observed in the interfaces was TiAl3. It was also shown that two mechanisms for TiAl3 growth exist: reaction and diffusion controlled. The growth exponent was equal to 0.94 for the reaction-controlled mechanism (first step) and 0.31 for the diffusion-controlled mechanism (second step). These values were in good agreement with theoretical values (1 and 0.5 for the first and second steps, respectively). Based on the results of this research, a kinetic model for the formation and growth of TiAl3 intermetallic phase was proposed.

  2. Effect of Specific Energy Input on Microstructure and Mechanical Properties of Nickel-Base Intermetallic Alloy Deposited by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Awasthi, Reena; Kumar, Santosh; Chandra, Kamlesh; Vishwanadh, B.; Kishore, R.; Viswanadham, C. S.; Srivastava, D.; Dey, G. K.

    2012-12-01

    This article describes the microstructural features and mechanical properties of nickel-base intermetallic alloy laser-clad layers on stainless steel-316 L substrate, with specific attention on the effect of laser-specific energy input (defined as the energy required per unit of the clad mass, kJ/g) on the microstructure and properties of the clad layer, keeping the other laser-cladding parameters same. Defect-free clad layers were observed, in which various solidified zones could be distinguished: planar crystallization near the substrate/clad interface, followed by cellular and dendritic morphology towards the surface of the clad layer. The clad layers were characterized by the presence of a hard molybdenum-rich hexagonal close-packed (hcp) intermetallic Laves phase dispersed in a relatively softer face-centered cubic (fcc) gamma solid solution or a fine lamellar eutectic phase mixture of an intermetallic Laves phase and gamma solid solution. The microstructure and properties of the clad layers showed a strong correlation with the laser-specific energy input. As the specific energy input increased, the dilution of the clad layer increased and the microstructure changed from a hypereutectic structure (with a compact dispersion of characteristic primary hard intermetallic Laves phase in eutectic phase mixture) to near eutectic or hypoeutectic structure (with reduced fraction of primary hard intermetallic Laves phase) with a corresponding decrease in the clad layer hardness.

  3. Corrosion resistant coating

    DOEpatents

    Wrobleski, Debra A.; Benicewicz, Brian C.; Thompson, Karen G.; Bryan, Coleman J.

    1997-01-01

    A method of protecting a metal substrate from corrosion including coating a metal substrate of, e.g., steel, iron or aluminum, with a conductive polymer layer of, e.g., polyaniline, coating upon said metal substrate, and coating the conductive polymer-coated metal substrate with a layer of a topcoat upon the conductive polymer coating layer, is provided, together with the resultant coated article from said method.

  4. Corrosion resistant coating

    DOEpatents

    Wrobleski, D.A.; Benicewicz, B.C.; Thompson, K.G.; Bryan, C.J.

    1997-08-19

    A method of protecting a metal substrate from corrosion including coating a metal substrate of, e.g., steel, iron or aluminum, with a conductive polymer layer of, e.g., polyaniline, coating upon said metal substrate, and coating the conductive polymer-coated metal substrate with a layer of a topcoat upon the conductive polymer coating layer, is provided, together with the resultant coated article from said method.

  5. FIB and TEM observations of defects in hot-dip zinc coatings.

    PubMed

    Hong, Moon-Hi; Saka, Hiroyasu

    2004-01-01

    The characteristic ability of FIB (focused ion beam) fabrication to remove materials from a very small and/or precisely located slab using an accelerated Ga ion beam were employed to prepare cross-sectional thin films of zinc-coated steel sheets composed of Fe-Zn intermetallic compounds. A few defects observed frequently on the galvannealed (GA) coating surface were analyzed. Streaky marks indicated the rich concentration of oxides at the interface between the galvannealed coating and the steel substrate. The annealing experiment indicated the existence of Mn and Si oxides on the steel substrate. The grain size of ferrite in the extreme surface of the substrate was smaller as compared with conventional IF (Interstitial Free) steels. Furthermore, some superlattice spots were observed at the fine ferrite grain. Defects that are termed 'wavy pattern' and 'dross' were also analyzed by the combination of the FIB and TEM (Transmission Electron Microscope) techniques. PMID:15582963

  6. Laser Overlap Welding of Zinc-coated Steel on Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Kashani, Hamed Tasalloti; Kah, Paul; Martikainen, Jukka

    Local reinforcement of aluminum with laser welded patches of zinc-coated steel can effectively contribute to crashworthiness, durability and weight reduction of car body. However, the weld between Zn-coated steel and aluminum is commonly susceptible to defects such as spatter, cavity and crack. The vaporization of Zn is commonly known as the main source of instability in the weld pool and cavity formation, especially in a lap joint configuration. Cracks are mainly due to the brittle intermetallic compounds growing at the weld interface of aluminum and steel. This study provides a review on the main metallurgical and mechanical concerns regarding laser overlap welding of Zn-coated steel on Al-alloy and the methods used by researchers to avoid the weld defects related to the vaporization of Zn and the poor metallurgical compatibility between steel and aluminum.

  7. The Chemistry of Coatings.

    ERIC Educational Resources Information Center

    Griffith, James R.

    1981-01-01

    The properties of natural and synthetic polymeric "coatings" are reviewed, including examples and uses of such coatings as cellulose nitrate lacquers (for automobile paints), polyethylene, and others. (JN)

  8. Pulse electrodeposition of adherent nickel coatings onto anodized aluminium surfaces

    NASA Astrophysics Data System (ADS)

    Frantz, Cédric; Vichery, Charlotte; Zechner, Johannes; Frey, Damian; Bürki, Gerhard; Cebeci, Halil; Michler, Johann; Philippe, Laetitia

    2015-03-01

    Aluminium is one of the mostly used elements in the industry because of its abundance and low weight. However, the deposition of a metallic coating requires performing the so-called zincate pre-treatment in order to allow the formation of inter-metallic bonds and thereby achieving sufficient adherence. In this work, porous anodic aluminium oxide (AAO) is used as an anchoring intermediate layer for nickel coatings. AAO is grown anodically in sulfuric acid and nickel coatings are deposited by potentiostatic reverse pulse electrodeposition onto as-anodized aluminium surfaces. The electrodeposition of nickel is initiated onto the electrochemically thinned barrier layer of AAO and pursued until the complete covering of the oxide. The electrochemical behavior of Watts and sulfamate baths is investigated by cyclic voltammetry for different barrier layer thickness, allowing to validate the thinning conditions and to determine the appropriate deposition potential of nickel. GD-OES measurements show that low duty cycles are necessary to achieve high filling ratio of the AAO. SEM micrographs show that a smooth uniform coating is obtained when nickel is deposited in presence of additives.

  9. CaO insulator and Be intermetallic coatings on V-base alloys for liquid-lithium fusion blanket applications

    SciTech Connect

    Park, J.H.; Kassner, T.F.

    1995-08-01

    In the period of April 1, 1995 to June 30, 1995, a computational model for simulating particle motions turbulent flow condition is developed. The model was applied to the analysis of particle transport and deposition processes in a circular duct and in a plane recirculating region. The mean gas velocity and turbulence intensity fields were first estimated using the available experimental data, as well as those obtained from an earlier developed CFD code. A model for evaluating particle deposition rate in the presence of gravitational and electrical forces in turbulent flows was also formulated. Results concerning the deposition velocity of particles under various conditions were obtained. It was shown that the model predictions are in good agreement with the available experimental and digital simulation data. Experimental study of glass fiber transport and deposition rate is also initiated.

  10. Brittle intermetallic compound makes ultrastrong low-density steel with large ductility.

    PubMed

    Kim, Sang-Heon; Kim, Hansoo; Kim, Nack J

    2015-02-01

    Although steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 (refs 1, 2). This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others. PMID:25652998

  11. Determining factor of median diameter in intermetallic compound nanoparticles prepared by pulsed wire discharge

    NASA Astrophysics Data System (ADS)

    Nagasawa, Shinobu; Koishi, Tetsuya; Tokoi, Yoshinori; Suzuki, Tsuneo; Nakayama, Tadachika; Suematsu, Hisayuki; Niihara, Koichi

    2014-02-01

    The preparation of NiAl intermetallic compound nanoparticles was carried out by pulsed wire discharge (PWD) using twisted pure Ni and Al wires in N2 ambient gas with varying number of turns of the wire (Nt), energy ratio (K), and ambient gas pressure (P). From the voltage and current waveforms during the wire heating, the energy deposition ratio up to the voltage peak (Kp) was calculated. It increased with an increase in Nt to 0.4 turns/mm and with increases in K and P. Under all the conditions, with an increase in Kp, the Ni composition ratio of the prepared particles (CNi) became closer to that of the wire (= 51.2 mol %). Furthermore, the collection rate (Rc) increased and the median particle diameter (d50) decreased. In particular, the change in d50 due to the change in Nt was not predicted by the relationship of d50 and Dth in our previous report. Single-phase NiAl intermetallic compound nanoparticles were successfully prepared under the condition in which Nt is 0.4 turns/mm, K is 3.4, and P is 100 kPa, where relatively high value of Kp was obtained. From these results, Kp was determined to be an important factor that determines the composition, collection rate, and median diameter of intermetallic compound nanoparticles synthesized by PWD using different kinds of twisted wires under various experimental conditions. This may be because of the selective wire heating in high-resistance parts that are associated with the introduction of lattice defects and/or necks by overwinding.

  12. Dissolution of Cu/Mg Bearing Intermetallics in Al-Si Foundry Alloys

    NASA Astrophysics Data System (ADS)

    Javidani, Mousa; Larouche, Daniel; Grant Chen, X.

    2016-08-01

    Evolutions of the Cu/Mg bearing intermetallics were thoroughly investigated in four Al-Si hypoeutectic alloys containing various Cu (1 and 1.6 wt pct) and Mg (0.4 and 0.8 wt pct) contents. The area fractions of Cu/Mg bearing phases before and after solution heat treatment (SHT) were quantified to evaluate the solubility/stability of the phases. Two Mg-bearing intermetallics (Q-Al5Cu2Mg8Si6, π-Al8FeMg3Si6) which appear as gray color under optical microscope were discriminated by the developed etchant. Moreover, the concentrations of the elements (Cu, Mg, and Si) in α-Al were analyzed. The results illustrated that in the alloys containing ~0.4 pct Mg, Q-Al5Cu2Mg8Si6 phase was dissolved after 6 hours of SHT at 778 K (505 °C); but containing in the alloys ~0.8 pct Mg, it was insoluble/ partially soluble. Furthermore, after SHT at 778 K (505 °C), Mg2Si was partially substituted by Q-phase. Applying a two-step SHT [6 hours@778 K (505 °C) + 8 hours@798 K (525 °C)] in the alloys containing ~0.4 pct Mg helped to further dissolve the remaining Mg bearing intermetallics and further modified the microstructure, but in the alloys containing ~0.8 pct Mg, it caused partial melting of Q-phase. Thermodynamic calculations were carried out to assess the phase formation in equilibrium and in non-equilibrium conditions. There was an excellent agreement between the experimental results and the predicted results.

  13. Brittle intermetallic compound makes ultrastrong low-density steel with large ductility

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Heon; Kim, Hansoo; Kim, Nack J.

    2015-02-01

    Although steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 (refs 1, 2). This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others.

  14. Development and application of a dry ultramicrotomy technique for the preparation of galvanneal sheet coatings.

    PubMed

    Barreto, M P; Veillette, R; L'Espérance, G

    1995-07-01

    The formability of galvanneal steel sheets used in the automotive industry is influenced by the presence and distribution of brittle and difficult to distinguish Zn-Fe intermetallics in the coating. Characterization of these intermetallics requires a high spatial resolution technique such as analytical transmission electron microscopy (ATEM). Sample preparation by ion milling is impossible due to iron redeposition, and traditional ultramicrotomy using water affects the coating chemistry. A technique based on dry ultramicrotomy has therefore been developed. To optimize the technique, different parameters (knife angle, cutting medium, thickness setting on the ultramicrotome, cutting speed) have been investigated for the preparation of galvanneal coatings and pure A1 sections. Results show that dry cutting does not affect the coating chemistry but shortens the life of the knife. Knife quality (cleanliness, sharpness and absence of defects) is a major factor to obtain good dry sections. The best results for the more ductile pure A1 are obtained with a 35 degrees knife whilst for the harder galvanneal coating it is recommended to use a 55 degrees knife. These results suggest that the sectioning mechanism for the harder material involves more a cleavage-fracture mechanism whilst a greater amount of shear is involved when sectioning relatively ductile A1. The optimum parameters for sectioning galvanneal coatings are established and results obtained by parallel electron energy loss spectrum imaging and energy dispersive X-ray spectrometry in the TEM are given. This study shows that with a good control of all the sectioning parameters it is possible to obtain good sections repeatedly and rapidly. PMID:7549002

  15. Development of Thermal Spraying and Coating Techniques by Using Thixotropic Slurries Including Metals and Ceramics Particles

    NASA Astrophysics Data System (ADS)

    Kirihara, S.; Itakura, Y.; Tasaki, S.

    2013-03-01

    Thermal nanoparticles coating and microlines patterning were newly developed as novel technologies to fabricate fine ceramics layers and geometrical intermetallics patterns for mechanical properties modulations of practical alloys substrates. Nanometer sized alumina particles were dispersed into acrylic liquid resins, and the obtained slurries were sputtered by using compressed air jet. The slurry mists could blow into the arc plasma with argon gas spraying. On stainless steels substrates, the fine surface layers with high wear resistance were formed. In cross sectional microstructures of the coated layers, micromater sized cracks or pores were not observed. Subsequently, pure aluminum particles were dispersed into photo solidified acrylic resins, and the slurry was spread on the stainless steel substrates by using a mechanical knife blade. On the substrates, microline patterns with self similar fractal structures were drawn and fixed by using scanning of an ultra violet laser beam. The patterned pure metal particles were heated by the argon arc plasma spray assisting, and the intermetallics or alloys phases with high hardness were created through reaction diffusions. Microstructures in the coated layers and the patterned lines were observed by using a scanning electron microscopy.

  16. Mechanisms of Soldering Formation on Coated Core Pins

    NASA Astrophysics Data System (ADS)

    Song, Jie; Denouden, Tony; Han, Qingyou

    2012-02-01

    Die soldering is one of the major casting defects during the high-pressure die casting (HPDC) process, causing dimensional inaccuracy of the castings and increased downtimes of the HPDC machine. In this study, we analyzed actually failed core pins to determine the mechanism of soldering and its procedures. The results show that the soldering process starts from a local coating failure, involves a series of intermetallic phase formation from reactions between molten aluminum alloys and the H13 steel pin, and accelerates when an aluminum-rich, face-centered cubic (fcc) phase is formed between the intermetallic phases. It is the formation of the aluminum-rich fcc phase in the reaction region that joins the core pin with the casting, resulting in the sticking of the casting to the core pin. When undercuts are formed on the core pin, the ejection of castings from the die will lead to either a core pin failure or damages to the casting being ejected.

  17. MCrAlY bond coat with enhanced yttrium

    DOEpatents

    Jablonski, Paul D.; Hawk, Jeffrey A.

    2016-08-30

    One or more embodiments relates to a method of producing an MCrAlY bond coat comprising an MCrAlY layer in contact with a Y--Al.sub.2O.sub.3 layer. The MCrAlY layer is comprised of a .gamma.-M solid solution, a .beta.-MAl intermetallic phase, and Y-type intermetallics. The Y--Al.sub.2O.sub.3 layer is comprised of Yttrium atoms coordinated with oxygen atoms comprising the Al.sub.2O.sub.3 lattice. The method comprises depositing an MCrAlY material on a substrate, applying an Y.sub.2O.sub.3 paste, and heating the substrate in a non-oxidizing atmosphere at a temperature between 400-1300.degree. C. for a time sufficient to generate the Y--Al.sub.2O.sub.3 layer. Both the MCrAlY layer and the Y--Al.sub.2O.sub.3 layer have a substantial absence of Y.sub.2O.sub.3, YAG, and YAP phases.

  18. Processing, properties, and ballistic performance of titanium-aluminum titanium metal-intermetallic laminate (MIL) composites

    NASA Astrophysics Data System (ADS)

    Harach, David John

    2000-10-01

    A systematic investigation into the processing of Ti-Al3Ti metal-intermetallic laminate (MIL) composites from elemental titanium and aluminum foils in open air by a novel one step technique, and subsequent characterization, physical, mechanical and ballistic testing was carried out. Al3Ti is the only intermetallic phase to form, and no oxides or other phases are formed. Composites with Ti volume fractions of ˜0, 14, 20, 35, and 57 percent can be processed consistently, with measured density agreeing well with calculated density. The intermetallic reaction occurs in two parts that are linear with respect to Al3Ti growth with time: oxide controlled diffusion of Al, and the order of magnitude faster chemical reaction that occurs after the oxide layer breaks down and transient liquid phases are formed. A reaction model based on the production of Al3Ti spheroids that are ejected from the Ti reaction surface has been developed, and is titled reactive foil sintering. Quasi-static and dynamic compression tests resulted in maximum yield stresses for the 20Ti composite, and end-confined quasi-static and dynamic compression tests, tension tests, and 3-point bend tests resulted in maximum yield stresses and bending loads for the 35Ti composite. Maximum yield stresses occurred in specimens tested with layers parallel to the load. Arrester orientation R-curve testing was completed for the 14Ti composite under large-scale bridging conditions, with initiation toughness values obtained for 20Ti and 35Ti which developed cracks in the intermetallic layer growing perpendicular to the load axis. Divider orientation R-curves were obtained, with the 20Ti and 35Ti curves closely approaching calculated steady-state toughness values. Ballistics testing of bonded Ti, bonded Ti-Al, 5Ti, 14Ti, 35Ti, 57Ti, and Al3Ti at projectile velocities of 500--700 m/s resulted in the 14Ti and 35Ti having the best ballistic performance based on mass efficiency. Ballistics testing of 14Ti, 20Ti, and 35Ti

  19. Method of fabricating a homogeneous wire of inter-metallic alloy

    DOEpatents

    Ohriner, Evan Keith; Blue, Craig Alan

    2001-01-01

    A method for fabricating a homogeneous wire of inter-metallic alloy comprising the steps of providing a base-metal wire bundle comprising a metal, an alloy or a combination thereof; working the wire bundle through at least one die to obtain a desired dimension and to form a precursor wire; and, controllably heating the precursor wire such that a portion of the wire will become liquid while simultaneously maintaining its desired shape, whereby substantial homogenization of the wire occurs in the liquid state and additional homogenization occurs in the solid state resulting in a homogenous alloy product.

  20. Hydrogen occupancy in the RNi{sub 4}Mg (R=Y, La, Ce, and Nd) intermetallic compounds and hydrides

    SciTech Connect

    Hahn-Herrera, Otto; Orgaz, Emilio; Aburto, Andrea

    2009-10-15

    We have investigated the effect of hydrogen on the electronic strtucture of the RNi{sub 4}Mg (R=Y, La, Ce, Pr, and Nd) intermetallics. By means of a two-step approach, the projected plane-wave and linearized plane-waves methods, we studied the hydrogen-insertion energetics on the intermetallic matrix and the H-vacancy formation in the hydride compound. We found that particular interstitial sites in the intermetallics are suitable to allocate hydrogen and form a solid solution. The effect of these interstitials on the electronic structure is discussed. In the other hand, the hydrogen-occupied sites in the hydride are found to be energetically equivalent.

  1. Mechanical behavior of molybdenum-modified Cr{sub 3}Si/Cr{sub 5}Si{sub 3} intermetallics

    SciTech Connect

    Nazmy, M.; Noseda, C.; Augustin, S.; Lipetzky, P.; Stoloff, N.S.

    1997-12-31

    Two molybdenum-modified chromium silicide base intermetallics have been prepared by powder metallurgy and investigated with respect to the hardness, flexural strength and fracture toughness at different temperatures. As toughening phase, tungsten, Pt-6%Rh and Saphikon fibers were tried to improve the toughness of these two intermetallics. The tungsten fibers generated microcracks in the base material due to the large mismatch in the coefficients of thermal expansion (CTE) between the fiber and the intermetallic. The Pt-6%Rh and Saphikon fibers did not exhibit such cracking. An improvement in the fracture toughness was observed especially at elevated temperatures. The Saphikon fibers did not show interfacial reaction. Some limited diffusion of silicon was detected in the Pt-6%Rh phase after 1,400 C treatment.

  2. Influence of the cooling method on the structure of 55AlZn coatings

    NASA Astrophysics Data System (ADS)

    Mendala, J.

    2011-05-01

    In metallization processes, metals or metal alloys are used which have a low melting point and good anticorrosion properties. Moreover, they must form durable intermetallic compounds with iron or its alloys. The most common hot-dip metallization technology involves galvanizing, however, molten multi-component metal alloys are used as well. An addition of aluminium to the zinc bath causes an increase in corrosion resistance of the obtained coatings. The article presents results of tests of obtaining coatings by the batch hot-dip method in an 55AlZn bath. Kinetics of the coating growth in the tested alloys were determined in the changeable conditions of bath temperature, dip time and type of cooling. The structure of coatings and their phase composition were revealed. As a result of the tests performed, it has been found that an increase in total thickness of the coatings as a function of the dipping time at a constant temperature is almost of a parabolic nature, whereas an increase in the transient layer is of a linear nature. The structure was identified by the XRD analysis and the morphology of the coatings was tested by means of SEM. It has been found that the cooling process with the use of higher rates of cooling causes a size reduction of the structure in the outer layer and a reduction of thickness of both the intermediate diffusion layer and the whole coating by ca. 25 %.

  3. Electrocurtain coating process for coating solar mirrors

    SciTech Connect

    Kabagambe, Benjamin; Boyd, Donald W.; Buchanan, Michael J.; Kelly, Patrick; Kutilek, Luke A.; McCamy, James W.; McPheron, Douglas A.; Orosz, Gary R.; Limbacher, Raymond D.

    2013-10-15

    An electrically conductive protective coating or film is provided over the surface of a reflective coating of a solar mirror by flowing or directing a cation containing liquid and an anion containing liquid onto the conductive surface. The cation and the anion containing liquids are spaced from, and preferably out of contact with one another on the surface of the reflective coating as an electric current is moved through the anion containing liquid, the conductive surface between the liquids and the cation containing liquid to coat the conductive surface with the electrically conductive coating.

  4. Multi-layer coatings

    DOEpatents

    Maghsoodi, Sina; Brophy, Brenor L.; Abrams, Ze'ev R.; Gonsalves, Peter R.

    2016-06-28

    Disclosed herein are coating materials and methods for applying a top-layer coating that is durable, abrasion resistant, highly transparent, hydrophobic, low-friction, moisture-sealing, anti-soiling, and self-cleaning to an existing conventional high temperature anti-reflective coating. The top coat imparts superior durability performance and new properties to the under-laying conventional high temperature anti-reflective coating without reducing the anti-reflectiveness of the coating. Methods and data for optimizing the relative thickness of the under-layer high temperature anti-reflective coating and the top-layer thickness for optimizing optical performance are also disclosed.

  5. Gold–promoted structurally ordered intermetallic palladium cobalt nanoparticles for the oxygen reduction reaction

    DOE PAGESBeta

    Kuttiyiel, Kurian A.; Sasaki, Kotaro; Su, Dong; Wu, Lijun; Zhu, Yimei; Adzic, Radoslav R.

    2014-11-06

    Considerable efforts to make palladium and palladium alloys active catalysts and a possible replacement for platinum have had a marginal success. Here, we report on a structurally ordered Au₁₀Pd₄₀Co₅₀ catalyst that exhibits comparable activity to conventional platinum catalysts in both acid and alkaline media. Electron microscopic techniques demonstrate that via addition of gold atoms PdCo nanoparticles undergo at elevated temperatures an atomic structural transition from core-shell to a rare intermetallic ordered structure with twin boundaries forming stable {111}, {110} and {100} facets. The superior stability of this catalyst compared to platinum after 10,000 potential cycles in alkaline media is attributedmore » to the atomic structural order of PdCo nanoparticles along with protective effect of clusters of gold atoms on the surface. This strategy of making ordered palladium intermetallic alloy nanoparticles can be used in diverse heterogeneous catalysis where particle size and structural stability matters.« less

  6. Ultrafast and Highly Reversible Sodium Storage in Zinc-Antimony Intermetallic Nanomaterials

    SciTech Connect

    Nie, Anmin; Gan, Li-yong; Cheng, Yingchun; Tao, Xinyong; Yuan, Yifei; Sharifi-Asl, Soroosh; He, Kun; Asayesh-Ardakani, Hasti; Vasiraju, Venkata; Lu, Jun; Mashayek, Farzad; Klie, Robert; Vaddiraju, Sreeram; Schwingenschlögl, Udo; Shahbazian-Yassar, Reza

    2015-12-17

    The progress on sodium-ion battery technology faces many grand challenges, one of which is the considerably lower rate of sodium insertion/deinsertion in electrode materials due to the larger size of sodium (Na) ions and complicated redox reactions compared to the lithium-ion systems. Here, it is demonstrated that sodium ions can be reversibly stored in Zn-Sb intermetallic nanowires at speeds that can exceed 295 nm s-1. Remarkably, these values are one to three orders of magnitude higher than the sodiation rate of other nanowires electrochemically tested with in situ transmission electron micro­scopy. It is found that the nanowires display about 161% volume expansion after the first sodiation and then cycle with an 83% reversible volume expansion. Despite their massive expansion, the nanowires can be cycled without any cracking or facture during the ultrafast sodiation/desodiation process. Additionally, most of the phases involved in the sodiation/desodiation process possess high electrical conductivity. More specifically, the NaZnSb exhibits a layered structure, which provides channels for fast Na+ diffusion. This observation indicates that Zn-Sb intermetallic nanomaterials offer great promise as high rate and good cycling stability anodic materials for the next generation of sodium-ion batteries.

  7. Electric field gradients at Ta in Zr and Hf inter-metallic compounds

    NASA Astrophysics Data System (ADS)

    Terrazos, L. A.; Petrilli, H. M.; Marszalek, M.; Saitovitch, H.; Silva, P. R. J.; Blaha, P.; Schwarz, K.

    2002-03-01

    Here we calculate the electric field gradient (EFG) at the nucleus of the substitutional Ta impurity site in Zr 2T and Hf 2T (T=Cu, Ag, Au, and Pd) C11 b inter-metallic compounds. We use the ab initio FP-LAPW method as embodied in the Wien97 code in a super-cell approach and include lattice relaxations around the impurity. Our results are compared with EFG values inferred from measurements of the quadrupole coupling constants at the 111Ta probe in these compounds performed with the time differential perturbed angular correlation (TDPAC) technique. We also performed EFG calculations for the pure inter-metallic compounds. Through the comparison of theoretical and experimental EFGs in these cases, we elucidate the role played by the Ta probe in the TDPAC measurements of Hf and Zr compounds. Our results show that, although the EFGs at the Hf site are very similar to the EFGs at the Ta impurity, there is no direct correlation between the Zr and Ta EFGs.

  8. First-principles study of the binary intermetallics in the Au-Rb system

    NASA Astrophysics Data System (ADS)

    Benmechri, Achraf; Djaballah, Yassine; Amer, Ahmed Said; Belgacem-Bouzida, Aissa; Bouderba, Hichem

    2014-06-01

    First-principles calculations within density functional theory (DFT) with the projector augmented wave (PAW) technique were used to investigate the stabilities of intermetallics in the Au-Rb system at 0 K. Four intermetallics: Au7Rb3, Au3Rb2, Au5Rb and AuRb were investigated in their observed experimental structures. The Au2Rb compound, reported in the Au-Rb phase diagrams without specifying explicitly its structure, was also investigated by inspecting several hypothetical structures. A suspect compound (AuRb2) was also investigated. Results show that: (i) The Au3Rb2 and Au7Rb3 compounds, which were never reported in any Au-Rb phase diagram, are stable at 0 K. (ii) The Au2Rb compound is not a ground state for all the tested structures. (iii) Stability of the Au5Rb and AuRb compounds was confirmed. (iv) The new compound AuRb2, not yet reported experimentally, is found mechanically stable at 0 K.

  9. Mining for elastic constants of intermetallics from the charge density landscape

    NASA Astrophysics Data System (ADS)

    Kong, Chang Sun; Broderick, Scott R.; Jones, Travis E.; Loyola, Claudia; Eberhart, Mark E.; Rajan, Krishna

    2015-02-01

    There is a significant challenge in designing new materials for targeted properties based on their electronic structure. While in principle this goal can be met using knowledge of the electron charge density, the relationships between the density and properties are largely unknown. To help overcome this problem we develop a quantitative structure-property relationship (QSPR) between the charge density and the elastic constants for B2 intermetallics. Using a combination of informatics techniques for screening all the potentially relevant charge density descriptors, we find that C11 and C44 are determined solely from the magnitude of the charge density at its critical points, while C12 is determined by the shape of the charge density at its critical points. From this reduced charge density selection space, we develop models for predicting the elastic constants of an expanded number of intermetallic systems, which we then use to predict the mechanical stability of new systems. Having reduced the descriptors necessary for modeling elastic constants, statistical learning approaches may then be used to predict the reduced knowledge-based required as a function of the constituent characteristics.

  10. Properties Evaluation and Studying Production Mechanism of Nanocrystalline NiAl Intermetallic Compound by Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Khajesarvi, Ali; Akbari, Golamhossein

    2016-04-01

    Ni50Al50 intermetallic compound was synthesized by mechanical alloying (MA) of elemental mixtures of Ni and Al powders in a planetary ball mill. After 16 hours of milling and obtaining crystallites with a critical size, the initial NiAl compound was formed along with the combustive reaction after opening the vial lid. In the time interval of 16 to 128 hours, the reaction from combustive state reached the explosive state. Finally, after 128 hours of milling, the initial powders were wholly transformed into NiAl before completion of the milling time. Structural changes of powder particles during MA were studied by X-ray diffractometry and scanning electron microscopy. The crystallite size measurements revealed that the grain size of the NiAl phase decreased from 155 to 26 nm with increasing MA time from 8 to 128 hours. Microhardness for nanocrystalline Ni50Al50 intermetallic compound produced after 128 hours of milling was measured as about 350 Hv.

  11. Numerical Investigation of the Ballistic Performance of Metal-Intermetallic Laminate Composites

    NASA Astrophysics Data System (ADS)

    Cao, Yang; Zhu, Shifan; Guo, Chunhuan; Vecchio, Kenneth S.; Jiang, Fengchun

    2015-08-01

    Metal-intermetallic laminate composites (MIL) based on the Ti-aluminide system are a new class of lightweight structural materials that can be used as either appliqué or structural armor. The explicit 2D finite element code LS-DYNA was employed to investigate the ballistic performance and failure mechanism of MIL composite plate subjected to impact loading. For comparison's sake, the penetration simulation was also conducted for a monolithic intermetallic Al3Ti sample under the same conditions. Damage tolerant abilities of the two targets were evaluated based on the analysis of the projectile tail velocity, crack density and absorbed material energy. The simulation results indicated that when cracks initiated in the Al3Ti matrix propagated to the interface between the matrix and reinforcement, their directions changed due to the bridging effect of the reinforcement Ti, which enabled the MIL composite to consume more energy as a result of the increase of the crack path lengths created by the crack deflection and bifurcation. Additionally, some other energy-absorbing mechanisms, such as deflection of cracks, plastic deformation of the ductile Ti also play important roles in enhancing the energy-absorbing capacity of the MIL composites.

  12. Observations of a dynamical-to-kinematic diffraction transition in plastically deformed polycrystalline intermetallic YCu

    SciTech Connect

    Williams, Scott H.; Brown, Donald W.; Clausen, Bjorn; Russell, Alan; Gschneidner Jr., Karl A.

    2014-03-01

    Unlike most intermetallic compounds, polycrystalline YCu, a B2 (CsCl-type) intermetallic, is ductile at room temperature. The mechanisms for this behavior are not fully understood. In situ neutron diffraction was used to investigate whether a stress-induced phase transformation or twinning contribute to the ductility; however, neither mechanism was found to be active in YCu. Surprisingly, this study revealed that the intensities of the diffraction peaks increased after plastic deformation. It is thought that annealing the samples created nearly perfect crystallinity, and subsequent deformation reduced this high degree of lattice coherency, resulting in a modified mosaic structure that decreased or eliminated the extinction effect. Analysis of changes in diffraction peak intensity showed a region of primary plasticity that exhibits significant changes in diffraction behavior. Fully annealed samples initially contain diffracting volumes large enough to follow the dynamical theory of diffraction. When loaded beyond the yield point, dislocation motion disrupts the lattice perfection, and the diffracting volume is reduced to the point that diffraction follows the kinematic theory of diffraction. Since the sample preparation and deformation mechanisms present in this study are common in numerous material systems, this dynamical to kinematic diffraction transition should also be considered in other diffraction experiments. These measurements also suggest the possibility of a new method of investigating structural characteristics. (C) 2014 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.

  13. Strengthening by intermetallic nanoprecipitation in Fe–Cr–Al–Ti alloy

    DOE PAGESBeta

    Capdevila, C.; Aranda, M. M.; Rementeria, R.; Chao, J.; Urones-Garrote, E.; Aldazabal, J.; Miller, Michael K.

    2016-02-05

    In this paper, the strengthening mechanism observed during ageing at temperatures of 435 and 475 °C in the oxide dispersion strengthened (ODS) Fe–Cr–Al–Ti system has been investigated. Atom probe tomography (APT) and high-resolution transmission electron microscopy (HRTEM) analyses determined that the alloy undergoes simultaneous precipitation of Cr-rich (α' phase) and nanoscale precipitation of TiAl-rich intermetallic particles (β' phase). APT indicated that the composition of the intermetallic β' phase is Fe2AlTi0.6Cr0.4, and the evolving composition of α' phase with ageing time was also determined. The results obtained from HRTEM analyses allow us to confirm that the β' precipitates exhibit a cubicmore » structure and hence their crystallography is related to the Heusler-type Fe2AlTi (L21) structure. Finally, the strengthening could be explained on the basis of two hardening effects that occur simultaneously: the first is due to the α-α' phase separation through the modulus effect, and the second mechanism is due to the interaction of nanoscale β' particles with dislocations.« less

  14. Crystal structures of three intermetallic phases in the Mo-Pt-Si system

    SciTech Connect

    Joubert, J.-M.; Tokaychuk, Ya.; Cerny, R.

    2010-01-15

    The crystal structures of three ternary Mo-Pt-Si intermetallic compounds have been determined ab initio from powder X-ray diffraction data. All three structures are representative of new structure types. Both the X (MoPt{sub 2}Si{sub 3}, Pmc2{sub 1}, oP12, a=3.48438(6), b=9.1511(2), c=5.48253(8) A) and Y (MoPt{sub 3}Si{sub 4}, Pnma, oP32, a=5.51210(9), b=3.49474(7), c=24.3090(4) A) phases derive from PtSi (FeAs type) structure while the Z phase (ideal composition Mo{sub 32}Pt{sub 20}Si{sub 16}, refined composition Mo{sub 29.9(2)}Pt{sub 21.0(3)}Si{sub 17.1(1)}, Cc, mC68, a=13.8868(3), b=8.0769(2), c=9.6110(2) A, beta=100.898(1){sup o}) present similarities with the group of Frank-Kasper phases. - Graphical abstract: The crystal structures of three ternary Mo-Pt-Si intermetallic compounds have been determined ab initio from powder X-ray diffraction data. The three structures represent new structure types.

  15. Theoretical Prediction of Transition Metal Alloying Effects on the Lightweight TiAl Intermetallic

    NASA Astrophysics Data System (ADS)

    Liu, Shuai; Tang, Chenghuang; Zhan, Yongzhong

    2016-03-01

    The structural, mechanical properties and Debye temperature of doped intermetallic Ti7Al8X (X = Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W) have been investigated by employing the pseudo-potential plane-wave approach based on density functional theory, within the generalized gradient approximation (GGA) function. The calculated lattice constants of TiAl are found to be within 1 pct error, compared with the experimental values. The stability of calculated structures of Ti7Al8X at 0 GPa is measured by studying mechanical stability conditions and formation energy. All the single crystals are proved to be elastically anisotropic. The Young's modulus as a function of crystal orientations has been systematically investigated. Mechanical properties of polycrystals are computed from values of shear modulus ( G), bulk modulus ( B), Young's modulus ( E), Poisson's ratio ( υ), and microhardness parameter ( H) for Ti7Al8X. It is indicated that addition of alloying elements reduces the brittleness and microhardness of TiAl intermetallic. Debye temperature of TiAl calculated using elastic data of the present work is found to be influenced by the addition of alloying elements, which is further confirmed by the phonon dispersions of Ti8Al8, Ti7Al8Zr, and Ti7Al8Hf.

  16. Fabrication of NiAl intermetallic from dense elemental powder blends via solid state reactions

    SciTech Connect

    Farber, L.; Gotman, I.; Gutmanas, E.Y.

    1997-12-31

    Dense NiAl intermetallic was synthesized from very fine elemental powders via solid state reactions. Homogeneous blends of micron size Ni and Al powders were consolidated to full density and heat treated in a 425--800 C temperature range. During heat treatment, formation of various intermediate intermetallics phases: NiAl{sub 3}, Ni{sub 2}Al{sub 3}, Ni{sub 3}Al and NiAl was observed. The sequence and kinetics of these phase formations at different temperatures were studied employing X-ray diffraction analysis (XRD). A model for a description of synthesis reaction kinetics in Ni-Al blends was developed. Based on the obtained results, the synthesis of NiAl was performed in two stages: reactions in 425--550 C range with consumption of Al, followed by a reaction at up to 800 C. It allowed uncontrolled SHS (self propagating high temperature synthesis, resulting in the occurrence of liquid phases and in formation of reaction products in a very fast/explosive manner) to be avoided. The synthesis temperatures are considerably lower than those used currently in processing of NiAl.

  17. Surface structures of In-Pd intermetallic compounds. II. A theoretical study

    SciTech Connect

    Gaudry, É.; McGuirk, G. M.; Ledieu, J.; Fournée, V.

    2014-08-28

    The (110) surface of the InPd intermetallic compound and the In–Pd surface alloy properties are investigated in the framework of the density functional theory, within the projector augmented plane-wave method. Surface segregation is calculated to be energetically unfavorable at stoichiometric InPd(110) surfaces, while indium antisites are shown to segregate to the surface in off-stoichiometric InPd(110) systems. Concerning surface alloys obtained by burying In-doped Pd layers in Pd(111), we demonstrated that the most stable ones are those presenting atomic indium concentrations below 50 at. % (11 at. %, 25 at. %, 33 at. %). According to our calculations, the In-doped Pd layers with concentration above or equal to 50% lead to In-doped Pd multilayers, each presenting an atomic indium concentration below 50 at. %. Alloying and segregation effects in InPd intermetallic compound and In–Pd surface alloys clearly agree with the larger bonding strength of In–Pd (−0.44 eV) compared to In–In (−0.29 eV) and Pd–Pd (−0.31 eV)

  18. Effect of sample size on intermetallic Al2Cu microstructure and orientation evolution during directional solidification

    NASA Astrophysics Data System (ADS)

    Gao, Ka; Li, Shuangming; Xu, Lei; Fu, Hengzhi

    2014-05-01

    Al-40% Cu hypereutectic alloy samples were successfully directionally solidified at a growth rate of 10 μm/s in different sizes (4 mm, 1.8 mm, and 0.45 mm thickness in transverse section). Using the serial sectioning technique, the three-dimensional (3D) microstructures of the primary intermetallic Al2Cu phase of the alloy can be observed with various growth patterns, L-shape, E-shape, and regular rectangular shape with respect to growth orientations of the (110) and (310) plane. The L-shape and regular rectangular shape of Al2Cu phase are bounded by {110} facets. When the sample size was reduced from 4 mm to 0.45 mm, the solidified microstructures changed from multi-layer dendrites to single-layer dendrite along the growth direction, and then the orientation texture was at the plane (310). The growth mechanism for the regular faceted intermetallic Al2Cu at different sample sizes was interpreted by the oriented attachment mechanism (OA). The experimental results showed that the directionally solidified Al-40% Cu alloy sample in a much smaller size can achieve a well-aligned morphology with a specific growth texture.

  19. Development and commercialization status of Fe{sub 3}Al-based intermetallic alloys

    SciTech Connect

    Sikka, V.K.; Viswanathan, S.; McKamey, C.G.

    1993-06-01

    The Fe{sub 3}Al-based intermetallic alloys offer unique benefits of excellent oxidation and sulfidation resistance, limited by poor room-temperature (RT) ductility and low high-temperature strength. Recent understanding of environmental effects on RT ductility of these alloys has led to progress toward taking commercial advantage of Fe{sub 3}Al-based materials. Cause of low ductility appears to be related to hydrogen formed from reaction with moisture. The environmental effect has been reduced in these intermetallic alloys by two methods. The first deals with producing a more hydrogen-resistant microstructure through thermomechanical processing, and the second dealed with compositional modification. The alloys showing reduced environmental effect have been melted and processed by many different methods. Laboratory and commercial heats have been characterized. Tests have been conducted in both air and controlled environments to quantify environmental effects on these properties. These materials were also tested for aqueous corrosion and resistance to stress corrosion cracking. Oxidation and sulfidation data were generated and effects of minor alloying elements on were also investigated. Several applications have been identified for the newly developed iron aluminides. Commercialization status of these alloys is described.

  20. Femtosecond laser ablation and nanoparticle formation in intermetallic NiAl

    NASA Astrophysics Data System (ADS)

    Jorgensen, David J.; Titus, Michael S.; Pollock, Tresa M.

    2015-10-01

    The ablation behavior of a stoichiometric intermetallic compound β-NiAl subjected to femtosecond laser pulsing in air has been investigated. The single-pulse ablation threshold for NiAl was determined to be 83 ± 4 mJ/cm2 and the transition to the high-fluence ablation regime occurred at 2.8 ± 0.3 J/cm2. Two sizes of nanoparticles consisting of Al, NiAl, Ni3Al and NiO were formed and ejected from the target during high-fluence ablation. Chemical analysis revealed that smaller nanoparticles (1-30 nm) tended to be rich in Al while larger nanoparticles (>100 nm) were lean in Al. Ablation in the low-fluence regime maintained this trend. Redeposited material and nanoparticles remaining on the surface after a single 3.7 J/cm2 pulse, one hundred 1.7 J/cm2 pulses, or one thousand 250 mJ/cm2 pulses were enriched in Al relative to the bulk target composition. Further, the surface of the irradiated high-fluence region was depleted in Al indicating that the fs laser ablation removal rate of the intermetallic constituents in this regime does not scale with the individual pure element ablation thresholds.

  1. Ab Initio Studies of Shock-Induced Chemical Reactions of Inter-Metallics

    NASA Astrophysics Data System (ADS)

    Zaharieva, Roussislava; Hanagud, Sathya

    2009-06-01

    Shock-induced and shock assisted chemical reactions of intermetallic mixtures are studied by many researchers, using both experimental and theoretical techniques. The theoretical studies are primarily at continuum scales. The model frameworks include mixture theories and meso-scale models of grains of porous mixtures. The reaction models vary from equilibrium thermodynamic model to several non-equilibrium thermodynamic models. The shock-effects are primarily studied using appropriate conservation equations and numerical techniques to integrate the equations. All these models require material constants from experiments and estimates of transition states. Thus, the objective of this paper is to present studies based on ab initio techniques. The ab inito studies, to date, use ab inito molecular dynamics. This paper presents a study that uses shock pressures, and associated temperatures as starting variables. Then intermetallic mixtures are modeled as slabs. The required shock stresses are created by straining the lattice. Then, ab initio binding energy calculations are used to examine the stability of the reactions. Binding energies are obtained for different strain components super imposed on uniform compression and finite temperatures. Then, vibrational frequencies and nudge elastic band techniques are used to study reactivity and transition states. Examples include Ni and Al.

  2. Structure and plasticity in hot deformed FeAl intermetallic phase base alloy

    SciTech Connect

    Kuc, Dariusz; Niewielski, Grzegorz; Bednarczyk, Iwona

    2009-10-15

    This paper constitutes part of research conducted on the possibility of forming alloys based on intermetallic phases from the Fe-Al system via thermoplastic processing. Insufficient plasticity, which is an inhibitor of further development of these intermetallics as construction materials, makes the range of their applications limited. In the paper, an analysis is conducted of the influence of deformation parameters on the structure of an alloy of Fe-Al with the B2 type structure. Axi-symmetric compression tests were carried out at temperatures ranging from 600 deg. C to 1200 deg. C and at a deformation rate from 0.001 s{sup 1} to 10 s{sup -1}. Structural examination was carried out using light microscopy and transmission electron microscopy. A quantitative evaluation of the structure was made with the use of 'Met-Ilo'. The results obtained will be used for the development of mathematical models determining the influence of deformation parameters on the alloy structure.

  3. Self-irradiation damage to the local structure of plutonium and plutonium intermetallics

    SciTech Connect

    Booth, C. H.; Jiang Yu; Medling, S. A.; Wang, D. L.; Costello, A. L.; Schwartz, D. S.; Mitchell, J. N.; Tobash, P. H.; Bauer, E. D.; McCall, S. K.; Wall, M. A.; Allen, P. G.

    2013-03-07

    The effect of self-irradiation damage on the local structure of {delta}-Pu, PuAl{sub 2}, PuGa{sub 3}, and other Pu intermetallics has been determined for samples stored at room temperature using the extended x-ray absorption fine-structure (EXAFS) technique. These measurements indicate that the intermetallic samples damage at a similar rate as indicated in previous studies of PuCoGa{sub 5}. In contrast, {delta}-Pu data indicate a much slower damage accumulation rate. To explore the effect of storage temperature and possible room temperature annealing effects, we also collected EXAFS data on a {delta}-Pu sample that was held at less than 32 K for a two month period. This sample damaged much more quickly. In addition, the measurable damage was annealed out at above only 135 K. Data from samples of {delta}-Pu with different Ga concentrations and results on all samples collected from different absorption edges are also reported. These results are discussed in terms of the vibrational properties of the materials and the role of Ga in {delta}-Pu as a network former.

  4. Coating life prediction

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Gedwill, Michael A.

    1985-01-01

    The investigation combines both experimental studies and numerical modeling to predict coating life in an oxidizing environment. The experimental work provides both input to and verification of two numerical models. The coatings being examined are an aluminide coating on Udimet 700 (U-700), a low-pressure plasma spray (LPPS) Ni-18Co-17Cr-24Al-0.2Y overlay coating also on U- 700, and bulk deposits of the LPPS NiCoCrAlY coating.

  5. Flow coating apparatus and method of coating

    SciTech Connect

    Hanumanthu, Ramasubrahmaniam; Neyman, Patrick; MacDonald, Niles; Brophy, Brenor; Kopczynski, Kevin; Nair, Wood

    2014-03-11

    Disclosed is a flow coating apparatus, comprising a slot that can dispense a coating material in an approximately uniform manner along a distribution blade that increases uniformity by means of surface tension and transfers the uniform flow of coating material onto an inclined substrate such as for example glass, solar panels, windows or part of an electronic display. Also disclosed is a method of flow coating a substrate using the apparatus such that the substrate is positioned correctly relative to the distribution blade, a pre-wetting step is completed where both the blade and substrate are completed wetted with a pre-wet solution prior to dispensing of the coating material onto the distribution blade from the slot and hence onto the substrate. Thereafter the substrate is removed from the distribution blade and allowed to dry, thereby forming a coating.

  6. Results on powder injection molding of Ni{sub 3}Al and application to other intermetallic compositions

    SciTech Connect

    Cooper, R.M.

    1992-12-31

    Net forming processes are under development to allow affordable production of intermetallic components. Powder injection molding (PIM) mav be employed for the production of complex-shaped intermetallic geometries. Proper choice of powder parameters and processing conditions can lead to the formation of fullv dense structures through pressure-less sintering. In this study, Ni{sub 3}Al with 0.04 wt.-% boron has been successfully injection molded and sintered to full density. A yield strength of 340 MPa, ultimate tensile strength (UTS) of 591 MPa, and 8% elongation were attained for injection molded and sintered tensile bars. Powder characteristics and sintering behavior are given for the nickel aluminide employed in this study to highlight the powder attributes needed for injection molding. Molding parameters, debinding and sintering schedules, along, with mechanical properties are presented to indicate the viability of PIM for intermetallics. This approach based on the understanding of key powder characteristics and use of the reactive synthesis powder process mav be extended to the successful injection molding of other intermetallic systems.

  7. Results on powder injection molding of Ni[sub 3]Al and application to other intermetallic compositions

    SciTech Connect

    Cooper, R.M.

    1992-01-01

    Net forming processes are under development to allow affordable production of intermetallic components. Powder injection molding (PIM) mav be employed for the production of complex-shaped intermetallic geometries. Proper choice of powder parameters and processing conditions can lead to the formation of fullv dense structures through pressure-less sintering. In this study, Ni[sub 3]Al with 0.04 wt.-% boron has been successfully injection molded and sintered to full density. A yield strength of 340 MPa, ultimate tensile strength (UTS) of 591 MPa, and 8% elongation were attained for injection molded and sintered tensile bars. Powder characteristics and sintering behavior are given for the nickel aluminide employed in this study to highlight the powder attributes needed for injection molding. Molding parameters, debinding and sintering schedules, along, with mechanical properties are presented to indicate the viability of PIM for intermetallics. This approach based on the understanding of key powder characteristics and use of the reactive synthesis powder process mav be extended to the successful injection molding of other intermetallic systems.

  8. A ship-in-a-bottle strategy to synthesize encapsulated intermetallic nanoparticle catalysts: Exemplified for furfural hydrogenation

    DOE PAGESBeta

    Maligal-Ganesh, Raghu V.; Xiao, Chaoxian; Goh, Tian Wei; Wang, Lin -Lin; Gustafson, Jeffrey; Pei, Yuchen; Qi, Zhiyuan; Johnson, Duane D.; Zhang, Shiran; Tao, Franklin; et al

    2016-01-28

    In this paper, intermetallic compounds are garnering increasing attention as efficient catalysts for improved selectivity in chemical processes. Here, using a ship-in-a-bottle strategy, we synthesize single-phase platinum-based intermetallic nanoparticles (NPs) protected by a mesoporous silica (mSiO2) shell by heterogeneous reduction and nucleation of Sn, Pb, or Zn in mSiO2-encapsulated Pt NPs. For selective hydrogenation of furfural to furfuryl alcohol, a dramatic increase in activity and selectivity is observed when intermetallic NPs catalysts are used in comparison to Pt@mSiO2. Among the intermetallic NPs, PtSn@mSiO2 exhibits the best performance, requiring only one-tenth of the quantity of Pt used in Pt@mSiO2 for similarmore » activity and near 100% selectivity to furfuryl alcohol. A high-temperature oxidation–reduction treatment easily reverses any carbon deposition-induced catalyst deactivation. X-ray photoelectron spectroscopy shows the importance of surface composition to the activity, whereas density functional theory calculations reveal that the enhanced selectivity on PtSn compared to Pt is due to the different furfural adsorption configurations on the two surfaces.« less

  9. Enhanced cycling stability of hybrid Li-air batteries enabled by ordered Pd3Fe intermetallic electrocatalyst.

    PubMed

    Cui, Zhiming; Li, Longjun; Manthiram, Arumugam; Goodenough, John B

    2015-06-17

    We report an ordered Pd3Fe intermetallic catalyst that exhibits significantly enhanced activity and durability for the oxygen reduction reaction under alkaline conditions. Ordered Pd3Fe enables a hybrid Li-air battery to exhibit the best reported full-cell cycling performance (220 cycles, 880 h). PMID:26020366

  10. Growth of a Au-Ni-Sn intermetallic compound on the solder-substrate interface after aging

    SciTech Connect

    Minor, Andrew M.; Morris, J.W., Jr.

    1999-12-16

    Au/Ni metallization has become increasingly common in microelectronic packaging when Cu pads are joined with Pb-Sn solder. The outermost Au layer serves to protect the pad from corrosion and oxidation and the Ni layer provides a diffusion barrier to inhibit detrimental growth of Cu-Sn intermetallics. As a result of reflowing eutectic Pb-Sn on top of Au/Ni metallization, the as-solidified joints have AuSn{sub 4} precipitates distributed throughout the bulk of the solder joint, and Ni{sub 3}Sn{sub 4} intermetallics at the interface. Recent work has shown that the Au-Sn redeposits onto the interface during aging, compromising the strength of the joint. The present work shows that the redeposited intermetallic layer is a ternary compound with stoichiometry Au{sub 0.5}Ni{sub 0.5}Sn{sub 4}. The growth of this intermetallic layer was investigated, and results show that the ternary compound is observed to grow after as little as 3 hours at 150 C and after 3 weeks at 150 C has grown to a thickness of 10 {micro}m. Additionally, methods for inhibiting the growth of the ternary layer were investigated and it was determined that multiple reflows, both with and without additional aging can substantially limit the thickness of the ternary layer.

  11. Apparatus for coating powders

    DOEpatents

    Makowiecki, Daniel M.; Kerns, John A.; Alford, Craig S.; McKernan, Mark A.

    2000-01-01

    A process and apparatus for coating small particles and fibers. The process involves agitation by vibrating or tumbling the particles or fibers to promote coating uniformly, removing adsorbed gases and static charges from the particles or fibers by an initial plasma cleaning, and coating the particles or fibers with one or more coatings, a first coating being an adhesion coating, and with subsequent coatings being deposited in-situ to prevent contamination at layer interfaces. The first coating is of an adhesion forming element (i.e. W, Zr, Re, Cr, Ti) of a 100-10,000 .ANG. thickness and the second coating or final coating of a multiple (0.1-10 microns) being Cu or Ag, for example for brazing processes, or other desired materials that defines the new surface related properties of the particles. An essential feature of the coating process is the capability to deposit in-situ without interruption to prevent the formation of a contaminated interface that could adversely affect the coating adhesion. The process may include screening of the material to be coated and either continuous or intermittent vibration to prevent agglomeration of the material to be coated.

  12. Coated laser mirror and method of coating

    SciTech Connect

    Shuskus, A.J.; Cowher, M.E.

    1984-04-24

    A method of applying an intermediate bond coat on a laser mirror substrate is described comprising surface polishing the mirror substrate followed by depositing a layer of amorphous silicon, amorphous germanium, or mixtures thereof on the mirror surface, and polishing the thus coated mirror surface to a substantially void-free surface finish. Laser mirror substrates such as graphite fiber reinforced glass, molybdenum and silicon carbide coated by such process are also described.

  13. The mechanical reliability of alumina scales and coatings

    SciTech Connect

    Alexander, K.B.; Pruebner, K.; Tortorelli, P.F.

    1996-08-01

    The mechanical integrity of oxide scales ultimately determines their ability to protect materials from corrosion and other environmental effects arising from deleterious reactions with gases and condensable products. The microstructure and mechanical behavior of alumina products thermally grown or deposited on Fe-28 at.% Al intermetallic alloys are being characterized in order to develop the knowledge and means to control the mechanical reliability of alumina scales by microstructural manipulation through design and processing. Mechanical characterization involved gravimetric data from cyclic oxidation experiments, in-situ observation of oxidized specimens undergoing flexural loading in a scanning electron microscope, and measurements of hardness, elastic modulus and cracking resistance by nanoindentation. Values of cracking thresholds for Al{sub 2}O{sub 3} scales were consistent with other measurements for surface and bulk alumina. The oxidation behavior of Fe{sub 3}Al alloys coated with a thin (0.5 - 1 {mu}m) alumina film deposited by plasma synthesis has been studied. During exposure in the oxidizing environment, new oxide was formed between the coating and the substrate. The presence of the deposited amorphous oxide inhibited the subsequent thermal oxidation of the metal. Because the thermally grown alumina forms under the deposit, the adherence of the coating is controlled by the strength of the metal/oxide interface that develops during oxidation.

  14. Self Healing in Coatings at High Temperatures

    NASA Astrophysics Data System (ADS)

    Sloof, Wim G.

    Alloys for high temperature applications in an oxidizing environment depend on the formation of a protective and slow growing oxide scale. The composition of these alloys is such that a continuous layer of a thermodynamically stable oxide is formed through selective oxidation of one of the constituting elements. Then, the oxide layer forms a barrier between the environment and the underlying alloy. The alloys for high temperature applications can be divided into alumina (Al2O3), silica (SiO2), or chromia (Cr2O3) formers, such as stainless steels, superalloys (Reed 2006), and intermetallics (MX, where M is Ti, Fe, Co or Ni, and X denotes Al, Si, or Cr). These materials are successfully applied in for example gas turbine engines (aero, marine, and industrial), heating equipment and automotive converters etc. In this chapter, the focus will be on alumina forming alloys encountered as coating material for blades and vanes in gas turbine engines. However, the principles addressed also apply to the other mentioned classes of high temperature alloys.

  15. Ir-coated dispenser cathode for CRT

    NASA Astrophysics Data System (ADS)

    Kimura, Sakae; Yakabe, Toru; Matsumoto, Sadao; Miyazaki, Daisuke; Yoshii, Tsuyoshi

    1990-12-01

    A compact dispenser cathode has been developed for application to CRTs. A cathode emitter, comprising BaO, CaO, and Al2O3 in a molar ratio of 4:1:1, was impregnated into a porous tungsten pellet. An intermetallic compound of tungsten and iridium was formed on the cathode pellet. Heater ratings were 6.3 V x 0.2 A. Emission characteristics were measured by using color CRTs. As a result, a cathode peak loading of 15 A/sq cm was ensured in the space-charge region. Furthermore, life tests with a peak loading of 7.5 A/sq cm were conducted over 10,000 h. The decrease in emission current after 10 000 h was within only 10 percent of the initial value. Reliability of cathode performance was assured in terms of breakdown potential between the heater and the cathode, emission characteristics, life performance, grid emission, and the drift in cutoff potential. In addition, the effects of the coating thickness on the emission characteristics are discussed.

  16. Structure of nanocrystalline arc-PVD (Ti, Al)N coatings modified with nickel

    NASA Astrophysics Data System (ADS)

    Blinkov, I. V.; Belov, D. S.; Volkhonskii, A. O.; Blinkov, V. I.; Shatalov, R. L.

    2015-05-01

    The introduction of nickel into the composition of ion-plasma vacuum-arc (Ti, Al)N coatings refines nitride-phase crystallites from 100-120 to 15-18 nm when the nickel content is varied from zero to 12 at %. The size of nitride blocks is in agreement with that of ceramic-phase grains. Some (Ti, Al)N grains grow with the nickel content up to 30-35 nm. The structure changes from columnar to equiaxed during modifying the (Ti, Al)N coatings with nickel. Nickel in a coating is in an amorphous state (detected by X-ray diffraction) when its content is no more than 12-13 at %. A further increase in its content leads to the formation of the TiNi intermetallic compound, which results in structure porosity in the deposited coating. A transition zone forms at the boundary between a (Ti, Al)N-Ni coating and the VK6-alloy substrate, which is characterized by an element concentration gradient from the coating to the substrate and vice versa.

  17. Multiconfigurational nature of 5f orbitals in uranium and plutonium and their intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Booth, Corwin

    2013-03-01

    The structural, electronic, and magnetic properties of U and Pu elements and intermetallics remain poorly understood despite decades of effort, and currently represent an important scientific frontier toward understanding matter. The last decade has seen great progress both due to the discovery of superconductivity in PuCoGa5 and advances in theory that finally can explain fundamental ground state properties in elemental plutonium, such as the phonon dispersion curve, the non-magnetic ground state, and the volume difference between the α and δ phases. A new feature of the recent calculations is the presence not only of intermediate valence of the Pu 5f electrons, but of multiconfigurational ground states, where the different properties of the α and δ phases are primarily governed by the different relative weights of the 5f4, 5f5, and 5f6 electronic configurations. The usual method for measuring multiconfigurational states in the lanthanides is to measure the lanthanide LIII-edge x-ray absorption near-edge structure (XANES), a method that is severely limited for the actinides because the spectroscopic features are not well enough separated. Advances in resonant x-ray emission spectroscopy (RXES) have now allowed for spectra with sufficient resolution to resolve individual resonances associated with the various actinide valence states. Utilizing a new spectrometer at the Stanford Synchrotron Radiation Lightsource (SSRL), RXES data have been collected that show, for the first time, spectroscopic signatures of each of these configurations and their relative changes in various uranium and plutonium intermetallic compounds. In combination with conventional XANES spectra on related compounds, these data indicate such states may be ubiquitous in uranium and plutonium intermetallics, providing a new framework toward understanding properties ranging from heavy fermion behavior, superconductivity, and intermediate valence to mechanical and fundamental bonding behavior in

  18. Focused ion beam induced microstructural alterations: texture development, grain growth, and intermetallic formation.

    PubMed

    Michael, Joseph R

    2011-06-01

    Copper, gold, and tungsten thin films have been exposed to 30 kV Ga+ ion irradiation, and the resulting microstructural modifications are studied as a function of ion dose. The observed microstructural changes include texture development with respect to the easy channeling direction in the target, and in the case of Cu, an additional intermetallic phase is produced. Texture development in these target materials is a function of the starting materials grain size, and these changes are not observed in large grained materials. The accepted models of differential damage driven grain growth are not supported by the results of this study. The implications of this study to the use of focused ion beam tools for sample preparation are discussed. PMID:21466753

  19. Intermetallic formation and interdiffusion in diffusion couples made of uranium and single crystal iron

    NASA Astrophysics Data System (ADS)

    Chen, Tianyi; Smith, Travis A.; Gigax, Jonathan G.; Chen, Di; Balerio, Robert; Shao, Lin; Sencer, Bulent H.; Kennedy, J. Rory

    2015-12-01

    We studied the interfacial phase formation and diffusion kinetics in uranium-iron diffusion couples. A comparison was made between polycrystalline uranium (U) bonded with polycrystalline iron (FeP) and polycrystalline uranium bonded with single crystalline Fe (FeSC). After thermal annealing at 575 °C, 600 °C, 625 °C and 650 °C, respectively, diffusion and microstructures at the interface were characterized by scanning electron microscopy and transmission electron miscopy. The presence of grain boundaries in iron has a significant influence on interface reactions. In comparison with U-FeP system, interdiffusion coefficients of the U-FeSC system are significantly lower and were governed by much higher activation energies. Integrated interdiffusion coefficients and intrinsic diffusion coefficients were obtained. The intrinsic diffusion coefficients show faster diffusion of iron atoms in both U6Fe and UFe2 intermetallic phases than uranium.

  20. A novel process for breakdown forging of coarse-grain intermetallic alloys

    SciTech Connect

    Semiatin, S.L. . Materials Directorate); McQuay, P.A. . Asian Office of Aerospace R and D); Seetharaman, V. )

    1993-11-01

    The objective of the present work was to develop a novel hot forging process for breakdown of high-temperature intermetallic alloys which exhibit dynamic recrystallization during hot working. During typical forging processes in hydraulic processes, be they based on isothermal or conventional approaches, the ram speed (or sometimes the effective strain rate) is held constant during the forging stroke. In the method introduced here, the ram speed is increased substantially during the forging stroke as the material recrystallizes to a finer-grained structure and its hot workability increases. By this means, fracture is avoided, grain size is reduced, and processing time is decreased, thus improving material quality and reducing cost. The material used to develop and demonstrate the novel forging process was the single phase gamma titanium aluminide, Ti-51Al-2Mn.

  1. TDPAC Study of the Intermetallic Compound HfCo3B2

    NASA Astrophysics Data System (ADS)

    Yaar, I.; Halevy, I.; Salhov, S.; Caspi, E. N.; Dubman, M.; Kahane, S.; Berant, Z.

    2004-11-01

    The electronic properties of the intermetallic compound HfCo3B2 were investigated using combined TDPAC measurements and first principles LAPW calculations. The V zz value at the hafnium site is determined from dominant positive p p contribution, with less than 20%, negative s d and d d contributions. Based on the calculated density of state (DOS) at 0 K, a band contribution ( γ band) of 7.26 (mJ/mol/K2) to the value of the electronic specific heat coefficient ( γ) was obtained. This relatively low γ band value is attributed to the hybridization between hafnium d-states, boron 2 p-states and cobalt 3 d-states, formed at the energy interval below E Fermi. This hybridization, together with the dip in the DOS around E Fermi, implies a possible reduction of the low temperature magnetic moment in this compound.

  2. Comparison of the Thermal Expansion Behavior of Several Intermetallic Silicide Alloys Between 293 and 1523 K

    NASA Astrophysics Data System (ADS)

    Raj, S. V.

    2015-03-01

    Thermal expansion measurements were conducted on hot-pressed CrSi2, TiSi2, WSi2 and a two-phase Cr-Mo-Si intermetallic alloy between 303 and 1523 K during three heat-cool cycles. The corrected thermal expansion, (Δ L/ L 0)thermal, varied with the absolute temperature, T, as where, A, B, C, and D are regression constants. Excellent reproducibility was observed for most of the materials after the first heat-up cycle. In some cases, the data from first heat-up cycle deviated from those determined in the subsequent cycles. This deviation was attributed to the presence of residual stresses developed during processing, which are relieved after the first heat-up cycle.

  3. Distribution of intermetallic particles and its effects on SCC of Zirconium alloys

    NASA Astrophysics Data System (ADS)

    Kubo, T.; Wakashima, Y.; Imahashi, H.; Nagai, M.

    1986-04-01

    In order to investigate effects of the distribution of intermetallic particles on the SCC of zirconium alloys, SCC tests were carried out on non-irradiated Zircaloy-2 and zirconium which were heat-treated under various conditions. Relatively large particles were randomly dispersed in samples annealed at temperatures in the α-phase domain. Quenching from relatively low temperatures in the (α + β)-phase domain, such as 1148 K, produced the grain boundary segregation of very small particles. Widmanstätten structures were seldom formed by the quenching. The frequency of transgranular cracks increased with the volume fraction of the particles on grain boundaries, while that of intergranular cracks increased with the averaged spacing of grain boundary particles. Not intergranular cracks, but transgranular cracks propagated rapidly enough to cause short time brittle fracture, and SCC susceptibility increased with the volume fraction of grain boundary particles.

  4. Slow plastic strain rate compressive flow in binary CoAl intermetallics

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1985-01-01

    Constant-velocity elevated temperature compression tests have been conducted on a series of binary CoAl intermetallics produced by hot extrusion of blended prealloyed powders. The as-extruded materials were polycrystalline, and they retained their nominal 10-micron grain size after being tested between 1100 and 1400 K at strain rates ranging from 2 x 10 to the -4th to 2 x 10 to the -7th per sec. Significant plastic flow was obtained in all cases; while cracking was observed, much of this could be due to failure at matrix-oxide interfaces along extrusion stringers rather than to solely intergranular fracture. A maximum in flow strength occurs at an aluminum-to-cobalt ratio of 0.975, and the stress exponent appears to be constant for aluminum-to-cobalt ratios of 0.85 or more. It is likely that very aluminum-deficient materials deform by a different mechanism than do other compositions.

  5. Comparison of the Thermal Expansion Behavior of Several Intermetallic Silicide Alloys Between 293 and 1523 K

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2014-01-01

    Thermal expansion measurements were conducted on hot-pressed CrSi(sub 2), TiSi(sub 2), W Si(sub 2) and a two-phase Cr-Mo-Si intermetallic alloy between 293 and 1523 K during three heat-cool cycles. The corrected thermal expansion, (L/L(sub 0)(sub thermal), varied with the absolute temperature, T, as (deltaL/L(sub 0)(sub thermal) = A(T-293)(sup 3) + B(T-293)(sup 2) + C(T-293) + D, where A, B, C and D are regression constants. Excellent reproducibility was observed for most of the materials after the first heat-up cycle. In some cases, the data from the first heatup cycle deviated from those determined in the subsequent cycles. This deviation was attributed to the presence of residual stresses developed during processing, which are relieved after the first heat-up cycle.

  6. Layered antiferromagnetism with high Neel temperature in the intermetallic compound Mn2Au

    NASA Astrophysics Data System (ADS)

    Khmelevskyi, Sergii; Mohn, Peter

    2008-10-01

    On the basis of earlier experimental studies the intermetallic compound Mn2Au has been characterized as a nonmagnetically ordered material. Here we report the results of first-principles calculations based on local spin-density approximation that describes Mn2Au to have a narrow band ground state with rigid local moments on the Mn sites. Calculations of the interatomic exchange constants based on the magnetic force theorem and a Monte Carlo modeling of the resulting Heisenberg-like Hamiltonian predict a high Neel temperature of ˜1600 K. This temperature is considerably higher than for the other known high-temperature antiferromagnetic L10-type Mn based binary alloys used in magnetic storage applications.

  7. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    DOEpatents

    Anderson, I.E.; Lograsso, B.K.; Ellis, T.W.

    1994-11-29

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material. 9 figures.

  8. Influence of magnetic fluctuations in the magnetocaloric effect on rare-earth intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Álvarez, P.; Gorria, P.; Blanco, J. A.

    2011-07-01

    A theoretical model including both crystal-field and exchange interactions that considers the effect of magnetic fluctuations is developed to evaluate the temperature dependence of the isothermal magnetic entropy changes in ferromagnetic rare-earth-based intermetallic compounds. The Green’s functions are derived from their equation of motion. The magnetic moment correlation functions are determined beyond the random phase approximation by incorporating a measure of magnetic spontaneous fluctuations in a way that ensures self-consistency with regard to the fluctuation-dissipation theorem. In particular, the exact magnitude of the entropy change without magnetic moment fluctuations depends on the ratio of both the crystal-field first- and the crystal-field third-order magnetic susceptibilities at the Curie temperature, TC. These theoretical predictions are compared with experimental data on cubic RM2 (R=rareearth and M=Al and Ni) compounds, where the principal crystal-field and exchange parameters are well known.

  9. First principles calculations of the optical and plasmonic response of Au alloys and intermetallic compounds.

    PubMed

    Keast, V J; Barnett, R L; Cortie, M B

    2014-07-30

    Pure Au is widely used in plasmonic applications even though its use is compromised by significant losses due to damping. There are some elements that are less lossy than Au (e.g. Ag or Al) but they will normally oxidize or corrode under ambient conditions. Here we examine whether alloying Au with a second element would be beneficial for plasmonic applications. In order to evaluate potential alternatives to pure Au, the density of states (DOS), dielectric function and plasmon quality factor have been calculated for alloys and compounds of Au with Al, Cd, Mg, Pd, Pt, Sn, Ti, Zn and Zr. Substitutional alloying of Au with Al, Cd, Mg and Zn was found to slightly improve the plasmonic response. Of the large number of intermetallic compounds studied, only AuAl2, Au3Cd, AuMg, AuCd and AuZn were found to be suitable for plasmonic applications. PMID:25001413

  10. Technetium Incorporation into C14 and C15 Laves Intermetallic Phases

    SciTech Connect

    Buck, Edgar C.; Schemer-Kohrn, Alan L.; Wierschke, Jonathan B.

    2013-01-23

    Laves-type intermetallics have been observed to be the dominant phases in a series of alloy compositions being designed for the immobilization technetium in a metallic waste form. The dominant metals in the alloy compositions were Fe-Mo and Fe-Mo-Zr. Alloy composition, Fe-Mo-Zr, also contained Pd, Zr, Cr, and Ni. Both non-radioactive rhenium-containing and radioactive technetium-bearing alloy compositions were investigated. In the Fe-Mo series, phases were observed Fe2Mo (C14 Laves phase) and ferrite in agreement with predictions. Both Tc and Re resided predominantly in the Laves phase. In the Fe-Mo-Zr system, the phases included hexagonal C14 with the composition (Fe,Cr)2Mo, cubic C15 phase with a (Fe,Ni)2Zr composition, and the hcp phase Pd2Zr.

  11. Electronic structure, elasticity, bonding features and mechanical behaviour of zinc intermetallics: A DFT study

    NASA Astrophysics Data System (ADS)

    Fatima, Bushra; Acharya, Nikita; Sanyal, Sankar P.

    2016-05-01

    The structural stability, electronic structure, elastic and mechanical properties of TiZn and ZrZn intermetallics have been studied using ab-initio full potential linearized augmented plane wave (FP-LAPW) method within generalized gradient approximation for exchange and correlation potentials. The various structural parameters, such as lattice constant (a0), bulk modulus (B), and its pressure derivative (B') are analysed and compared. The investigation of elastic constants affirm that both TiZn and ZrZn are elastically stable in CsCl (B2 phase) structure. The electronic structures have been analysed quantitatively from the band structure which reveals the metallic nature of these compounds. To better illustrate the nature of bonding and charge transfer, we have also studied the Fermi surfaces. The three well known criterion of ductility namely Pugh's rule, Cauchy's pressure and Frantsevich rule elucidate the ductile nature of these compounds.

  12. Fatigue life prediction of an intermetallic matrix composite at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Bartolotta, Paul A.

    1991-01-01

    A strain-based fatigue life prediction method is proposed for an intermetallic matrix composite (IMC) under tensile cyclic loadings at elevated temperatures. Styled after the Universal Slopes method, the model utilizes the composite's tensile properties to estimate fatigue life. Factors such as fiber volume ratio, number of plys and temperature dependence are implicitly incorporated into the model through these properties. The model constants are determined by using unidirectional fatigue data at temperatures of 425 and 815 C. Fatigue lives from two independent sources are used to verify the model at temperatures of 650 and 760 C. Cross-ply lives at 760 C are also predicted. It is demonstrated that the correlation between experimental and predicted lives is within a factor of two.

  13. Fatigue life prediction of an intermetallic matrix composite at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Bartolotta, P. A.

    1991-01-01

    A strain-based fatigue life prediction method is proposed for an intermetallic matrix composite (IMC) under tensile cyclic loadings at elevated temperatures. Styled after the 'Universal Slopes' method, the model utilizes the composite's tensile properties to estimate fatigue life. Factors such as fiber volume ratio (Vf), number of plys and temperature dependence are implicitly incorporated into the model through these properties. The model constants are determined by using unidirectional fatigue data at temperatures of 425 and 815 C. Fatigue lives from two independent sources are used to verify the model at temperatures of 650 and 760 C. Cross-ply lives at 760 C are also predicted. It is demonstrated that the correlation between experimental and predicted lives is within a factor of two.

  14. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    SciTech Connect

    Anderson, Iver E.; Lograsso, Barbara K.; Ellis, Timothy W.

    1994-01-01

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material.

  15. Towards the role of interfacial shear in shock-induced intermetallic reactions

    NASA Astrophysics Data System (ADS)

    Collinson, Mark; Chapman, David; Williamson, David; Burchell, Mark; Eakins, Daniel

    2011-06-01

    Shock-induced intermetallic reactions have previously been shown to occur on a nanosecond timescale, within the rise time of the applied shock wave. Work in this area to date has however concentrated on continuum scale measurements, raising questions as to the processes occurring at micro and meso scales. Mass transfer due to inter-facial shear at material interfaces has been suggested as a possible explanation. We will present initial work examining the role of friction on this mass mixing process across a binary interface. This work includes plate impact experiments on an inert stainless steel - aluminum friction pair, employing spatially resolved interferometry. Results from a series of metal ball-on-angled plate impact experiments at 1-2 km/s will also be presented, supported by high-speed imaging and target recovery.

  16. High-yield growth of carbon nanofilaments on nickel foam using nickel-tin intermetallic catalysts.

    PubMed

    Jeong, Namjo; Hwang, Kyo Sik; Yang, Seung Cheol

    2014-10-01

    The integration of nanomaterials into macroscopic structures is of importance to their practical use. We report the direct synthesis of carbon nanofilaments on Ni foam using Ni-Sn intermetallic nanoparticles. The use of SnO2 nanoparticles was highly effective for the high-yield growth of carbon nanofilaments without the occurrence of surface breakup, resulting from excessive carbon accumulation in the Ni foam. Carbon nanofilaments with a diameter of 50 nm were synthesized and contained Ni3Sn nanoparticles at the tip, indicating a tip-growth mechanism. Higher vacuum conditions led to the growth of highly crystalline carbon nanofilaments. The results obtained using different sources of hydrocarbon revealed that in contrast to C2H2, CH4 or C3H8 did not induce carbon nanofilament formation on Ni foam. PMID:25942857

  17. First principles calculations of the optical and plasmonic response of Au alloys and intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Keast, V. J.; Barnett, R. L.; Cortie, M. B.

    2014-07-01

    Pure Au is widely used in plasmonic applications even though its use is compromised by significant losses due to damping. There are some elements that are less lossy than Au (e.g. Ag or Al) but they will normally oxidize or corrode under ambient conditions. Here we examine whether alloying Au with a second element would be beneficial for plasmonic applications. In order to evaluate potential alternatives to pure Au, the density of states (DOS), dielectric function and plasmon quality factor have been calculated for alloys and compounds of Au with Al, Cd, Mg, Pd, Pt, Sn, Ti, Zn and Zr. Substitutional alloying of Au with Al, Cd, Mg and Zn was found to slightly improve the plasmonic response. Of the large number of intermetallic compounds studied, only AuAl2, Au3Cd, AuMg, AuCd and AuZn were found to be suitable for plasmonic applications.

  18. Nonisothermal kinetics study of phase evolution of Zn-Fe intermetallics

    SciTech Connect

    Uwakweh, O.N.C.; Liu, Z.T.; Boisson, M.

    1996-12-31

    Through mechanical alloying of pure elemental powders of Fe and Zn, true homogeneous alloys of {Gamma} (Fe{sub 3}Zn{sub 10}), {Gamma}{sub 1} (Fe{sub 5}Zn{sub 21}), {delta} (FeZn{sub 7}) and {zeta} (FeZn{sub 13}) intermetallic phases are formed. Based on nonisothermal kinetics analyses, the highest activation energies associated with the metastable to stable transformations of these phases are determined as follows: 170 {+-} 1 kJ/mol, 251 {+-} 2 kJ/mol, 176 {+-} 1 kJ/mol and 737 {+-} 4 kJ/mol for the {Gamma}, {Gamma}{sub 1}, {delta} and {zeta}-phases, respectively. These values reflect different diffusion/thermally induced processes associated with the transition of each of these phases.

  19. Pressure tuning of competing magnetic interactions in intermetallic CeFe2

    SciTech Connect

    Wang, Jiyang; Feng, Yejun; Jaramillo, R.; van Wezel, Jasper; Canfield, Paul C.; Rosenbaum, T.F.

    2012-07-20

    We use high-pressure magnetic x-ray diffraction and numerical simulation to determine the low-temperature magnetic phase diagram of stoichiometric CeFe2. Near 1.5 GPa we find a transition from ferromagnetism to antiferromagnetism, accompanied by a rhombohedral distortion of the cubic Laves crystal lattice. By comparing pressure and chemical substitution we find that the phase transition is controlled by a shift of magnetic frustration from the Ce-Ce to the Fe-Fe sublattice. Notably the dominant Ce-Fe magnetic interaction, which sets the temperature scale for the onset of long-range order, remains satisfied throughout the phase diagram but does not determine the magnetic ground state. Our results illustrate the complexity of a system with multiple competing magnetic energy scales and lead to a general model for magnetism in cubic Laves phase intermetallic compounds.

  20. Advances in processing of NiAl intermetallic alloys and composites for high temperature aerospace applications

    NASA Astrophysics Data System (ADS)

    Bochenek, Kamil; Basista, Michal

    2015-11-01

    Over the last few decades intermetallic compounds such as NiAl have been considered as potential high temperature structural materials for aerospace industry. A large number of investigations have been reported describing complex fabrication routes, introducing various reinforcing/alloying elements along with theoretical analyses. These research works were mainly focused on the overcoming of main disadvantage of nickel aluminides that still restricts their application range, i.e. brittleness at room temperature. In this paper we present an overview of research on NiAl processing and indicate methods that are promising in solving the low fracture toughness issue at room temperature. Other material properties relevant for high temperature applications are also addressed. The analysis is primarily done from the perspective of NiAl application in aero engines in temperature regimes from room up to the operating temperature (over 1150 °C) of turbine blades.

  1. Cutting tool performance characteristics in the machining of a nickel aluminide intermetallic compound

    SciTech Connect

    Chatterjee, S.; Srivatsan, T.S.; Giusti, P.

    1994-05-01

    Ductile nickel aluminide, Ni{sub 3}Al, containing traces of boron, is an intermetallic compound with high strength, making it a promising structural material for elevated, ambient and cryogenic temperature applications. In order to be able to use alloys, they must be capable of being fabricated by machining. The machinability of a cast nickel aluminide, Ni{sub 3}Al, alloy containing boron was studied by conventional machining using the lathe. Three different cutting tool inserts and two types of coolants, namely kerosene oil mist and soluble oil, were chosen. The machining performance of the cutting tool insert and the influence of coolant type were established through measurements of volume of material removed and tool wear. The tool wear analysis was made using microscopic examination of the cutting tool insert in order to elucidate information of the influence of machining parameters and choice of coolant on performance capability of the insert. The overall machinability performance of these materials is rationalized.

  2. Electrocatalytic oxidation of formic acid at an ordered intermetallic PtBi surface.

    PubMed

    Casado-Rivera, Emerilis; Gál, Zoltán; Angelo, A C D; Lind, Cora; DiSalvo, Francis J; Abruña, Héctor D

    2003-02-17

    The electrocatalytic oxidation of formic acid at a PtBi ordered intermetallic electrode surface has been investigated using cyclic voltammetry, rotating disk electrode (RDE) voltammetry and differential electrochemical mass spectrometry (DEMS). The results are compared to those at a polycrystalline platinum electrode surface. The PtBi electrode exhibits superior properties when compared to polycrystalline platinum in terms of oxidation onset potential, current density, and a much diminished poisoning effect by CO. Using the RDE technique, a value of 1.4 x 10(-4) cm s-1 was obtained for the heterogeneous charge transfer rate constant. The PtBi surface did not appear to be poisoned when exposed to a CO saturated solution for periods exceeding 0.5 h. The results for PtBi are discussed within the framework of the dual-path mechanism for the electrocatalytic oxidation of formic acid, which involves formation of a reactive intermediate and a poisoning pathway. PMID:12619419

  3. Multiconfigurational nature of 5f orbitals in uranium and plutonium intermetallics

    PubMed Central

    Booth, C.H.; Jiang, Yu; Wang, D.L.; Mitchell, J.N.; Tobash, P.H.; Bauer, E.D.; Wall, M.A.; Allen, P.G.; Sokaras, D.; Nordlund, D.; Weng, T.-C.; Torrez, M.A.; Sarrao, J.L.

    2012-01-01

    Uranium and plutonium’s 5f electrons are tenuously poised between strongly bonding with ligand spd-states and residing close to the nucleus. The unusual properties of these elements and their compounds (e.g., the six different allotropes of elemental plutonium) are widely believed to depend on the related attributes of f-orbital occupancy and delocalization for which a quantitative measure is lacking. By employing resonant X-ray emission spectroscopy (RXES) and X-ray absorption near-edge structure (XANES) spectroscopy and making comparisons to specific heat measurements, we demonstrate the presence of multiconfigurational f-orbital states in the actinide elements U and Pu and in a wide range of uranium and plutonium intermetallic compounds. These results provide a robust experimental basis for a new framework toward understanding the strongly-correlated behavior of actinide materials. PMID:22706643

  4. High hardness in the biocompatible intermetallic compound β-Ti3Au.

    PubMed

    Svanidze, Eteri; Besara, Tiglet; Ozaydin, M Fevsi; Tiwary, Chandra Sekhar; Wang, Jiakui K; Radhakrishnan, Sruthi; Mani, Sendurai; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Ajayan, Pulickel M; Morosan, E

    2016-07-01

    The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti-Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials. PMID:27453942

  5. Lattice dynamics of the mixed-conducting intermetallic compound,. beta. -LiAl

    SciTech Connect

    Brun, T.O.; Robinson, J.E.; Susman, S.; Mildner, D.F.R.; Dejus, R.; Skoeld K.

    1983-04-01

    The intermetallic compound, ..beta..-LiAl, that crystallizes in the uncommon Zintl structure is a mixed-conducting electrode and has many unusual properties pointing to the existence of unusual bonding in the semi-metallic compound. In order to elucidate the nature of the bonding in LiAl, we have studied the lattice dynamics of ..beta..-LiAl by inelastic neutron scattering. Results for the phonon dispersion curves have been obtained for the principal symmetry directions. A force constant fit to the results indicates that the Al-Al force constants are unusually large. Pair potentials were constructed by conventional pseudopotential calculations. The pair interactions favoring the Zintl structure were used to compute phonon dispersion curves. Good agreement between theory and experiment can be obtained for the acoustic branches.

  6. Role of defect coordination environment on point defects formation energies in Ni-Al intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Tennessen, Emrys; Rondinelli, James

    We present a relationship among the point defect formation energies and the bond strengths, lengths, and local coordination environment for Ni-Al intermetallic alloys based on density functional calculations, including Ni3Al, Ni5Al3, NiAl,Ni3Al4, Ni2Al3 and NiAl3. We find the energetic stability of vacancy and anti-site defects for the entire family can be attributed primarily to changes in interactions among first nearest neighbors, owing to spatially localized charge density reconstructions in the vicinity of the defect site. We also compare our interpretation of the local coordination environment with a DFT-based cluster expansion and discuss the performance of each approach in predicting defect stability in the Ni-Al system.

  7. Comparative NMR study of copper-based intermetallics with ZrCuSiAs-type structure

    NASA Astrophysics Data System (ADS)

    Lue, C. S.; ChangJen, W. J.; Su, T. H.

    2010-07-01

    The electronic characteristics of ZrCuGe2, ZrCuSi2, and HfCuSi2 are systematically investigated using C63u NMR spectroscopy. The quadrupole splittings, Knight shifts, and spin-lattice relaxation times on each individual compound have been identified. We found that the observed electric field gradient is consistent with the covalent bonding nature within the Cu atomic layers. The Knight shifts together with relaxation rates provide a measure of Cu d partial Fermi-level density of states, Nd(EF). Universally small Nd(EF) was found in all studied materials, suggests that the Cu d states are well below the Fermi energy and therefore the characteristic electronic structure near EF is primarily of sp type. We further pointed out that the low Nd(EF) value is an important factor for the lack of superconductivity in these Cu-based intermetallics within the ZrCuSiAs-type structure.

  8. Chemical route for formation of intermetallic Zn{sub 4}Sb{sub 3} phase

    SciTech Connect

    Denoix, A.; Solaiappan, A.; Ayral, R.M.; Rouessac, F.; Tedenac, J.C.

    2010-05-15

    Synthesis of intermetallic zinc antimonide phases via low temperature solution route was investigated. Trial experiments were carried out under inert atmosphere at 70 deg. C using metallic Zn, SbCl{sub 3} and NaBH{sub 4} as reactants and tetrahydrofuran (THF), dimethylsulfoxide (DMSO) as organic media. Powder X-ray analysis confirmed the nucleation and growth of ZnSb phases in presence of excess Zn. SEM analysis revealed the existence of core-shell structure comprising of Zn core and Sb shell. Such particles get transformed into Zn{sub 4}Sb{sub 3} crystalline phases upon thermal treatment at 300 deg. C/6 h in a silica tube closed under high secondary vacuum. - Graphical abstract: TEM observation of the Zn{sub 4}Sb{sub 3} powder synthesized by soft chemistry.

  9. Complex antiferromagnetic structure in the intermediate-valence intermetallic Ce2RuZn4

    NASA Astrophysics Data System (ADS)

    Hartwig, Steffen; Prokeš, Karel; Hansen, Thomas; Ritter, Clemens; Gerke, Birgit; Pöttgen, Rainer; Mydosh, J. A.; Förster, Tobias

    2015-07-01

    Neutron powder diffraction experiments were performed on the intermediate-valence Ce2RuZn4 intermetallic compound and combined with magnetic bulk measurements including high magnetic field experiments up to 58 T. Previous theoretical studies suggest that only one (here Ce1) out of two inequivalent Ce sites is magnetically active. Ce2RuZn4 orders antiferromagnetically at TN=2.3 K . The magnetic structure is characterized by an incommensurate propagation vector qm=(0.384 ,0.384 ,1/2 ). Assuming that the Ce2 site does not carry any substantial moment, Ce1 magnetic moments are confined to the (110)-type planes and transversely modulated with an amplitude of 1.77 (3 )μB.

  10. High hardness in the biocompatible intermetallic compound β-Ti3Au

    PubMed Central

    Svanidze, Eteri; Besara, Tiglet; Ozaydin, M. Fevsi; Tiwary, Chandra Sekhar; Wang, Jiakui K.; Radhakrishnan, Sruthi; Mani, Sendurai; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Ajayan, Pulickel M.; Morosan, E.

    2016-01-01

    The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti–Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials. PMID:27453942

  11. Intermetallic compounds, copper and palladium alloys in Au-Pd ore of the Skaergaard pluton, Greenland

    NASA Astrophysics Data System (ADS)

    Rudashevsky, N. S.; Rudashevsky, V. N.; Nielsen, T. F. D.

    2015-12-01

    Copper-palladium intermetallic compounds and alloys (2314 grains) from the Au-Pd ore of the Skaergaard layered gabbroic pluton have been studied. Skaergaardite PdCu, nielsenite PdCu3, (Cu,Pd)β, (Cu,Pd)α, (Pd,Cu,Au,Pt) alloys, and native palladium have been identified as a result of 1680 microprobe analyses. The average compositions and various chemical varieties of these minerals are characterized, as well as vertical and lateral zoning in distribution of noble metals. The primary Pd-Cu alloys were formed within a wide temperature interval broadly synchronously with cooling and crystallization of host gabbro and in close association with separation of Fe-Cu sulfide liquid. In the course of crystallization of residual gabbroic melt enriched in iron, noble and heavy metals and saturated with the supercritical aqueous fluid, PGE and Au are selectively concentrated in the Fe-Cu sulfide phase as Pd-Cu and Cu-Au alloys.

  12. Numerical simulations of interfacial debonding in ductile-phase reinforced intermetallic matrix composites

    SciTech Connect

    Henshall, G.A.; Zywicz, E.; Strum, M.J.

    1993-08-10

    The fracture toughness of brittle intermetallic compounds can be improved by ductile-phase reinforcements. Effectiveness of the ductile phase in bridging cracks, and therefore increasing, the composite toughness, is known qualitatively to depend upon the extent of debonding, between the two phases. Numerical crack-growth simulations are used here to provide semi-quantitative predictions of the influence of interfacial debonding on the macroscopic stress-displacement behavior and, hence, the fracture toughness of an idealized Pb/glass composite. The interfacial toughness required to cause debonding, characterized by a constant critical energy release rate, is varied parametrically. As expected, higher interfacial toughness results in less interphase debonding, higher composite strength, and greater ductile-phase constraint. Consequently, the increase in ductile-phase triaxiality can potentially accelerate internal void formation and growth or facilitate cleavage fracture, either of which would likely decrease the toughness of the composite.

  13. Intermetallic Compound Formation Mechanisms for Cu-Sn Solid-Liquid Interdiffusion Bonding

    NASA Astrophysics Data System (ADS)

    Liu, H.; Wang, K.; Aasmundtveit, K. E.; Hoivik, N.

    2012-09-01

    Cu-Sn solid-liquid interdiffusion (SLID) bonding is an evolving technique for wafer-level packaging which features robust, fine pitch and high temperature tolerance. The mechanisms of Cu-Sn SLID bonding for wafer-level bonding and three-dimensional (3-D) packaging applications have been studied by analyzing the microstructure evolution of Cu-Sn intermetallic compounds (IMCs) at elevated temperature up to 400°C. The bonding time required to achieve a single IMC phase (Cu3Sn) in the final interconnects was estimated according to the parabolic growth law with consideration of defect-induced deviation. The effect of predominantly Cu metal grain size on the Cu-Sn interdiffusion rate is discussed. The temperature versus time profile (ramp rate) is critical to control the morphology of scallops in the IMC. A low temperature ramp rate before reaching the bonding temperature is believed to be favorable in a SLID wafer-level bonding process.

  14. Corrosion inhibiting organic coatings

    SciTech Connect

    Sasson, E.

    1984-10-16

    A corrosion inhibiting coating comprises a mixture of waxes, petroleum jelly, a hardener and a solvent. In particular, a corrosion inhibiting coating comprises candelilla wax, carnauba wax, microcrystalline waxes, white petrolatum, an oleoresin, lanolin and a solvent.

  15. Thermal barrier coating system

    NASA Technical Reports Server (NTRS)

    Stecura, S. (Inventor)

    1984-01-01

    A high temperature oxidation resistant, thermal barrier coating system is disclosed for a nickel cobalt, or iron base alloy substrate. An inner metal bond coating contacts the substrate, and a thermal barrier coating covers the bond coating. NiCrAlR, FeCrAlR, and CoCrAlR alloys are satisfactory as bond coating compositions where R=Y or Yb. These alloys contain, by weight, 24.9-36.7% chromium, 5.4-18.5% aluminum, and 0.05 to 1.55% yttrium or 0.05 to 0.53% ytterbium. The coatings containing ytterbium are preferred over those containing yttrium. An outer thermal barrier coating of partial stabilized zirconium oxide (zirconia) which is between 6% and 8%, by weight, of yttrium oxide (yttria) covers the bond coating. Partial stabilization provides a material with superior durability. Partially stabilized zirconia consists of mixtures of cubic, tetragonal, and monoclinic phases.

  16. ORGANIC COATING REMOVAL

    EPA Science Inventory

    Cleaner coating removal technologies are developing rapidly to meet a variety of industrial needs to replace solvent strippers having toxic properties. his guide describes cleaner technologies that can be used to reduce waste in coating removal operations. nformation is presented...

  17. Heat Treatment of Thermal Spray Duplex Coating System of Aluminum-Nickel Chromium Alloy on Carbon Steel

    NASA Astrophysics Data System (ADS)

    Quoc Ly, Cuong; Thu Le, Quy; Van Nguyen, Tuan; Thi To Phung, Hang; The Ngo, Dien

    2013-12-01

    This paper presents our study on the influence of heat treatment at 550 °C on microstructure and microhardness of an Al-NiCr20 duplex coating prepared on low carbon steel CT38 by electric-arc thermal spray. The annealing duration was in a range of 2-8 h. It was found that after annealing, metallic grains inside the coatings became flatter and the coating's porosity decreased considerably. The phase analysis by SEM-EDS in combination with microstructural observation using an optical microscope showed a formation of two diffusion layers at the interfaces "NiCr20-Al" and "Al-steel" with very high microhardness > 900 HV. Based on chemical analysis by SEM-EDS, the chemical formulas of the formed intermetallic compounds are proposed.

  18. Fundamental study about CO2 laser welding of titanium aluminide intermetallic compound

    NASA Astrophysics Data System (ADS)

    Kuwahara, Gaku; Yamaguchi, Shigeru; Nanri, Kenzo; Ootani, Masanori; Tetsuka, Masato; Seto, Sachio; Arai, Mikiya; Fujioka, Tomoo

    2000-11-01

    Titanium aluminide intermetallic compound is attracting attentions as heat-resistant and high-specific strength material in the next generation, especially, it is promising material in the field of aerospace components. Conventional machining process including welding, however, can be hardly applied due to its very low ductility. The objective of this study, as a first stage, is to find out paying attention to crack and hardness the fundamental good conditions of the bead-on-plate welding of TiAl intermetallic compound using CO2 laser irradiation. In the experiment, we used the casting gamma titanium aluminide contained iron, vanadium and boron with a thickness of 2mm. We carried out bead-on-plate laser welding in the titanium aluminide material in inert gas environment filled with argon. We measured fused depth, Vickers hardness, transverse crack numbers and so on as major parameters of welding speed from 1000 to 4600 mm/min and initial temperature of specimen from R.T. to 873 K with a beam spot size of 0.5 mm and an output power of 1.5 kW. In addition, the specimens were analyzed by Electron Probe X-ray Micro Analyzer, Energy Dispersive X-ray Spectroscopy and X-ray Diffractometry. As a result of experiments, transverse crack-free welding was achieved, when initial temperature was at 873 K. In every condition, the value of Vickers hardness of fused zone increased compared with base. We think the reason of it is an increase of (alpha) 2(Ti3Al) phase, which is caused by rapid cooling, taking in Oxygen, fine structure and so on.

  19. Photoemission Study of the Rare Earth Intermetallic Compounds: RNi2Ge2 (R=Eu, Gd)

    SciTech Connect

    Jongik Park

    2004-12-19

    EuNi{sub 2}Ge{sub 2} and GdNi{sub 2}Ge{sub 2} are two members of the RT{sub 2}X{sub 2} (R = rare earth, T = transition metal and X = Si, Ge) family of intermetallic compounds, which has been studied since the early 1980s. These ternary rare-earth intermetallic compounds with the tetragonal ThCr{sub 2}Si{sub 2} structure are known for their wide variety of magnetic properties, Extensive studies of the RT{sub 2}X{sub 2} series can be found in Refs [ 1,2,3]. The magnetic properties of the rare-earth nickel germanides RNi{sub 2}Ge{sub 2} were recently studied in more detail [4]. The purpose of this dissertation is to investigate the electronic structure (both valence band and shallow core levels) of single crystals of EuNi{sub 2}Ge{sub 2} and GdNi{sub 2}Ge{sub 2} and to check the assumptions that the f electrons are non-interacting and, consequently, the rigid-band model for these crystals would work [11], using synchrotron radiation because, to the best of our knowledge, no photoemission measurements on those have been reported. Photoemission spectroscopy has been widely used to study the detailed electronic structure of metals and alloys, and especially angle-resolved photoemission spectroscopy (ARPES) has proven to be a powerful technique for investigating Fermi surfaces (FSs) of single-crystal compounds.

  20. Growth of new ternary intermetallic phases from Ca/Zn eutectic flux

    SciTech Connect

    Stojanovic, Milorad Latturner, Susan E.

    2007-03-15

    The eutectic 7.3:2.7 molar ratio mixture of calcium and zinc metal melts at 394 deg. C and was explored as a solvent for the growth of new intermetallic phases for potential use as hydrogen storage materials. The reaction of nickel in this molten mixture produces two new phases-the CaCu{sub 5}-related structure CaNi{sub 2}Zn{sub 3} (P6/mmm, a=8.9814(5) A, c=4.0665(5) A) and a new cubic structure Ca{sub 21}Ni{sub 2}Zn{sub 36} (Fd-3m, a=21.5051(4) A). Palladium-containing reactions produced CaPd{sub 0.85}Zn{sub 1.15} with the orthorhombic TiNiSi structure type (Pnma, a=7.1728(9) A, b=4.3949(5) A, c=7.7430(9) A). Reactions of platinum in the Ca/Zn mixture produce Ca{sub 6}Pt{sub 3}Zn{sub 5}, with an orthorhombic structure related to that of W{sub 3}CoB{sub 3} (Pmmn, a=13.7339(9) A, b=4.3907(3) A, c=10.7894(7) A). - Graphical abstract: The calcium/zinc eutectic is a useful synthesis medium for the growth of new intermetallic phases. Addition of group 10 transition metals to this flux produces ternary phases CaNi{sub 2}Zn{sub 3}, Ca{sub 21}Ni{sub 2}Zn{sub 36}, CaPd{sub 0.85}Zn{sub 1.15}, and Ca{sub 6}Pt{sub 3}Zn{sub 5}. The nickel-centered zinc icosahedron surrounded by a pentagonal dodecahedron of calcium atoms is found in Ca{sub 21}Ni{sub 2}Zn{sub 36}.

  1. METHOD FOR TESTING COATINGS

    DOEpatents

    Johns, I.B.; Newton, A.S.

    1958-09-01

    A method is described for detecting pin hole imperfections in coatings on uranium-metal objects. Such coated objects are contacted with a heated atmosphere of gaseous hydrogen and imperfections present in the coatings will allow the uranlum to react with the hydrogen to form uranium hydride. Since uranium hydride is less dense than uranium metal it will swell, causing enlargement of the coating defeot and rendering it visible.

  2. Plasma electrolytic oxidation coatings on γTiAl alloy for potential biomedical applications.

    PubMed

    Lara Rodriguez, L; Sundaram, P A; Rosim-Fachini, E; Padovani, A M; Diffoot-Carlo, N

    2014-07-01

    In an attempt to enhance the potential of gamma titanium aluminide intermetallic alloy as a biomaterial, its surface characteristics were successfully modified using a calcium and phosphorous rich electrolyte through the application of plasma electrolytic oxidation. Scanning electron microscopy and atomic force microscopy were used to characterize the morphology and topographical features of the resulting coating while X-ray diffraction and energy dispersive spectroscopy were used to determine the surface oxide composition. The mechanical properties of the surface coating were characterized by nanoindentation studies. The results observed show the formation of a submicron scale porous structure and a concomitant increase in the surface roughness. The surface oxide was composed of rutile and anatase phases. Composition gradients of Ca and P were also present which can possibly enhance the biomaterial application potential of this treated surface. Nanoindentation measurements indicate the formation of a fairly compact oxide during the process. PMID:24259371

  3. Ceramic with zircon coating

    NASA Technical Reports Server (NTRS)

    Wang, Hongyu (Inventor)

    2003-01-01

    An article comprises a silicon-containing substrate and a zircon coating. The article can comprise a silicon carbide/silicon (SiC/Si) substrate, a zircon (ZrSiO.sub.4) intermediate coating and an external environmental/thermal barrier coating.

  4. Spin coating of electrolytes

    DOEpatents

    Stetter, Joseph R.; Maclay, G. Jordan

    1989-01-01

    Methods for spin coating electrolytic materials onto substrates are disclosed. More particularly, methods for depositing solid coatings of ion-conducting material onto planar substrates and onto electrodes are disclosed. These spin coating methods are employed to fabricate electrochemical sensors for use in measuring, detecting and quantifying gases and liquids.

  5. PIT Coating Requirements Analysis

    SciTech Connect

    MINTEER, D.J.

    2000-10-20

    This study identifies the applicable requirements for procurement and installation of a coating intended for tank farm valve and pump pit interior surfaces. These requirements are intended to be incorporated into project specification documents and design media. This study also evaluates previously recommended coatings and identifies requirement-compliant coating products.

  6. X-ray Fluorescence Investigation of Ordered Intermetallic Phases as Electrocatalysts towards the Oxidation of Small Organic Molecules

    SciTech Connect

    Liu, Yi; Lowe, Michael A.; Finkelstein, Ken D.; Dale, Darren S.; DiSalvo, Francis J.; Abruña, Héctor D.

    2010-10-13

    The composition of ordered intermetallic nanoparticles (PtBi and PtPb) has been quantitatively studied by in situ X-ray fluorescence (XRF) during active electrochemical control in solutions of supporting electrolyte and small organic molecules (SOMs). Because the Pt Lβ1,2 lines and the Bi Lα1,2 lines are only separated by 200 eV, an energy-dispersive detector and a multiple-channel analyzer (MCA) were used to record the major fluorescent emission lines from these two elements. The molar ratios of platinum to the less-noble elements (Bi, Pb) in the nanoparticles dramatically changed as a function of the applied upper limit potentials (Eulp) in cyclic voltammetric (CV) characterization. Similar to previous investigations for bulk intermetallic surfaces, the less-noble elements leached out from the surfaces of the intermetallic nanoparticles. For PtBi nanoparticles, the ratios of fluorescence intensities of Pt/Bi in the samples were 0.42, 0.96, and 1.36 for Eulp=+0.40, +0.80, and 1.20 V, respectively, while cycling the potential from -0.20 V to the Eulp value for 10 cycles. The leaching-out process of the less-noble elements occurred at more negative Eulp values than expected. After cycling to relatively positive Eulp values, nonuniform PtM (M=Bi of Pb) nanoparticles formed with a Pt-rich shell and intermetallic PtM core. When the supporting solutions contained active fuel molecules in addition to the intermetallic nanoparticles (formic acid for PtBi, formic acid and methanol for PtPb), kinetic stabilization effects were observed for Eulp=+0.80 V, in a way similar to the response of the bulk materials. It was of great importance to quantitatively explore the change in composition and structure of the intermetallic nanoparticles under active electrochemical control. More importantly, this approach represents a simple, universal, and multifunctional method for the study of multi

  7. Microstructural evolution and intermetallic formation in Al-8wt% Si-0.8wt% Fe alloy due to grain refiner and modifier additions

    NASA Astrophysics Data System (ADS)

    Hassani, Amir; Ranjbar, Khalil; Sami, Sattar

    2012-08-01

    An alloy of Al-8wt% Si-0.8wt% Fe was cast in a metallic die, and its microstructural changes due to Ti-B refiner and Sr modifier additions were studied. Apart from usual refinement and modification of the microstructure, some mutual influences of the additives took place, and no mutual poisoning effects by these additives, in combined form, were observed. It was noticed that the dimensions of the iron-rich intermetallics were influenced by the additives causing them to become larger. The needle-shaped intermetallics that were obtained from refiner addition became thicker and longer when adding the modifier. It was also found that α-Al and eutectic silicon phases preferentially nucleate on different types of intermetallic compounds. The more iron content of the intermetallic compounds and the more changes in their dimensions occurred. Formation of the shrinkage porosities was also observed.

  8. Effect of ultrasonic melt treatment on the refinement of primary Al3Ti intermetallic in an Al-0.4Ti alloy

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Eskin, Dmitry; Connolley, Thomas; Mi, Jiawei

    2016-02-01

    High intensity ultrasonic melt treatment was applied to an Al-0.4 wt% Ti alloy over three selected temperature ranges: 810 to 770 °C (above liquidus), 770 to 730 °C (across liquidus), and 730 to 690 °C (below liquidus). The size and morphology of the primary Al3Ti intermetallic particles were studied by scanning electron microscopy. It was found that the primary Al3Ti intermetallics were refined as a result of ultrasonication over all three temperature ranges and their morphology changed from typical large dendritic plates to small compact tablets. Quenching experiments before and after the ultrasonication were also carried out to capture the high-temperature stage of intermetallic formation. Based on the size and morphology observations, the mechanisms for the refinement of primary Al3Ti intermetallics at different solidification stages are discussed.

  9. Thermal barrier coating system

    NASA Technical Reports Server (NTRS)

    Stecura, S.; Leibert, C. H. (Inventor)

    1977-01-01

    A coating system which contains a bond coating and a thermal barrier coating is applied to metal surfaces such as turbine blades and provides both low thermal conductivity and improved adherence when exposed to high temperature gases or liquids. The bond coating contains NiCrAlY and the thermal barrier coating contains a reflective oxide. The reflective oxides ZrO2-Y2O3 and ZrO2-MgO have demonstrated significant utility in high temperature turbine applications.

  10. Metallic coating of microspheres

    SciTech Connect

    Meyer, S.F.

    1980-08-15

    Extremely smooth, uniform metal coatings of micrometer thicknesses on microscopic glass spheres (microspheres) are often needed as targets for inertial confinement fusion (ICF) experiments. The first part of this paper reviews those methods used successfully to provide metal coated microspheres for ICF targets, including magnetron sputtering, electro- and electroless plating, and chemical vapor pyrolysis. The second part of this paper discusses some of the critical aspects of magnetron sputter coating of microspheres, including substrate requirements, the sticking of microspheres during coating (preventing a uniform coating), and the difficulties in growing the desired dense, smooth, uniform microstructure on continuously moving spherical substrates.

  11. Aircraft surface coatings

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Liquid, spray on elastomeric polyurethanes are selected and investigated as best candidates for aircraft external protective coatings. Flight tests are conducted to measure drag effects of these coatings compared to paints and a bare metal surface. The durability of two elastometric polyurethanes are assessed in airline flight service evaluations. Laboratory tests are performed to determine corrosion protection properties, compatibility with aircraft thermal anti-icing systems, the effect of coating thickness on erosion durability, and the erosion characteristics of composite leading edges-bare and coated. A cost and benefits assessment is made to determine the economic value of various coating configurations to the airlines.

  12. Antibacterial polymer coatings.

    SciTech Connect

    Wilson, Mollye C.; Allen, Ashley N.; Barnhart, Meghan; Tucker, Mark David; Hibbs, Michael R.

    2009-09-01

    A series of poly(sulfone)s with quaternary ammonium groups and another series with aldehyde groups are synthesized and tested for biocidal activity against vegetative bacteria and spores, respectively. The polymers are sprayed onto substrates as coatings which are then exposed to aqueous suspensions of organisms. The coatings are inherently biocidal and do not release any agents into the environment. The coatings adhere well to both glass and CARC-coated coupons and they exhibit significant biotoxicity. The most effective quaternary ammonium polymers kills 99.9% of both gram negative and gram positive bacteria and the best aldehyde coating kills 81% of the spores on its surface.

  13. Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    1993-01-01

    In order to reduce heat transfer between a hot gas heat source and a metallic engine component, a thermal insulating layer of material is placed between them. This thermal barrier coating is applied by plasma spray processing the thin films. The coating has been successfully employed in aerospace applications for many years. Lewis Research Center, a leader in the development engine components coating technology, has assisted Caterpillar, Inc. in applying ceramic thermal barrier coatings on engines. Because these large engines use heavy fuels containing vanadium, engine valve life is sharply decreased. The barrier coating controls temperatures, extends valve life and reduces operating cost. Additional applications are currently under development.

  14. Lubricant Coating Process

    NASA Technical Reports Server (NTRS)

    1989-01-01

    "Peen Plating," a NASA developed process for applying molybdenum disulfide, is the key element of Techniblast Co.'s SURFGUARD process for applying high strength solid lubricants. The process requires two machines -- one for cleaning and one for coating. The cleaning step allows the coating to be bonded directly to the substrate to provide a better "anchor." The coating machine applies a half a micron thick coating. Then, a blast gun, using various pressures to vary peening intensities for different applications, fires high velocity "media" -- peening hammers -- ranging from plastic pellets to steel shot. Techniblast was assisted by Rural Enterprises, Inc. Coating service can be performed at either Techniblast's or a customer's facility.

  15. Coating Life Prediction

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Gedwill, M. A.

    1984-01-01

    Hot-section gas-turbine components typically require some form of coating for oxidation and corrosion protection. Efficient use of coatings requires reliable and accurate predictions of the protective life of the coating. Currently engine inspections and component replacements are often made on a conservative basis. As a result, there is a constant need to improve and develop the life-prediction capability of metallic coatings for use in various service environments. The purpose of this present work is aimed at developing of an improved methodology for predicting metallic coating lives in an oxidizing environment and in a corrosive environment.

  16. Deposition Mechanisms and Oxidation Behaviors of Ti-Ni Coatings Deposited in Low-Temperature HVOF Spraying Process

    NASA Astrophysics Data System (ADS)

    Lin, Q. S.; Zhou, K. S.; Deng, C. M.; Liu, M.; Xu, L. P.; Deng, C. G.

    2014-08-01

    Three kinds of Ti-Ni powders were deposited on 316L stainless steel by low-temperature high-velocity oxygen fuel (LT-HVOF) spraying process, respectively. Deposition mechanisms and oxidation behaviors of the coatings were researched in this paper. The coating deposited from TiNi intermetallic powder had obvious laminar structure and the oxygen content was the highest among the three kinds of coatings. The oxygen content of the coating deposited from small-sized Ni-clad Ti powder was still high due to the melting of parts of particles. However, most of the coarse Ni-clad Ti powder was deposited in solid states without changes of chemical compositions and phase compositions. The oxygen content of the coating deposited from coarse Ni-clad Ti powder was the lowest among the three kinds of coatings. It indicated that the deposition behavior of the coating could effectively preserve the inner titanium from oxidation. The results of the present research demonstrated that it is entirely feasible to deposit active metal materials such as titanium and titanium alloy through the optimizing selection of powder in the LT-HVOF process.

  17. Polymer derived ceramic composites as environmental barrier coatings on steel

    NASA Astrophysics Data System (ADS)

    Torrey, Jessica D.

    Polymer derived ceramics have shown promise as a novel way to process low-dimensional ceramics such as fibers and coatings. They offer advantages over traditional ceramic processing routes including lower pyrolysis temperatures and the ability to employ polymeric processing techniques. The main drawback to preceramic polymers is that they undergo a shrinkage during pyrolysis that can be greater than 50-volume%. One way to overcome this shrinkage is to add filler particles, usually elemental or binary metals, which will expand upon reaction with the pyrolysis atmosphere, thereby compensating for the shrinkage of the polymer. The aim of this study is to develop a polymer derived ceramic composite coating on steel as a barrier to oxidation and carburization, while concurrently gaining insight as to the fundamental mechanisms for compositional and microstructural evolution within the system. A systematic approach to selecting the preceramic polymer and expansion agents was taken. Six commercially available poly(silsesquioxane) polymers and a polysiloxane were studied. Several metals and an intermetallic were considered as potential expansion agents. The most desirable polymer/expansion agent combination was achieved with poly(hydridomethylsiloxane) as the matrix and titanium disilicide as the filler. Processing parameters have been optimized and a relationship derived to predict final coating thickness based on slurry viscosity and dip coating withdrawal speed. Microstructural analysis reveals an amorphous composite coating of oxidized filler particles in a silica matrix. A diffusion layer is visible at the coating-steel interface, indicating good bonding. The optimized coatings are ˜18mum thick, have some residual porosity and a density of 2.57g/cm3. A systematic study of the phase transformations and microstructural changes in the coating and its components during pyrolysis in air is also presented. The system evolves from a polymer filled with a binary metal at

  18. Vacuum plasma spray coating

    NASA Technical Reports Server (NTRS)

    Holmes, Richard R.; Mckechnie, Timothy N.

    1989-01-01

    Currently, protective plasma spray coatings are applied to space shuttle main engine turbine blades of high-performance nickel alloys by an air plasma spray process. Originally, a ceramic coating of yttria-stabilized zirconia (ZrO2.12Y2O3) was applied for thermal protection, but was removed because of severe spalling. In vacuum plasma spray coating, plasma coatings of nickel-chromium-aluminum-yttrium (NiCrAlY) are applied in a reduced atmosphere of argon/helium. These enhanced coatings showed no spalling after 40 MSFC burner rig thermal shock cycles between 927 C (1700 F) and -253 C (-423 F), while current coatings spalled during 5 to 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2.8Y2O3 to the turbine blades of first-stage high-pressure fuel turbopumps utilizing the enhanced NiCrAlY bond-coating process. NiCrAlY bond coating is applied first, with ZrO2.8Y2O3 added sequentially in increasing amounts until a thermal barrier coating is obtained. The enchanced thermal barrier coating has successfully passed 40 burner rig thermal shock cycles.

  19. Coatings for directional eutectics

    NASA Technical Reports Server (NTRS)

    Rairden, J. R.; Jackson, M. R.

    1976-01-01

    Significant advances have been made in the development of an environmentally stable coating for a very high strength, directionally solidified eutectic alloy designated NiTaC-13. Three duplex (two-layer) coatings survived 3,000 hours on a cyclic oxidation test (1,100 C to 90 C). These coatings were fabricated by first depositing a layer of NiCrAl(Y) by vacuum evaporation from an electron beam heated source, followed by depositing an aluminizing overlayer. The alloy after exposure with these coatings was denuded of carbide fibers at the substrate/coating interface. It was demonstrated that TaC fiber denudation can be greatly retarded by applying a carbon-bearing coating. The coating was applied by thermal spraying followed by aluminization. Specimens coated with NiCrAlCY+Al survived over 2,000 hours in the cyclic oxidation test with essentially no TaC denudation. Coating ductility was studied for coated and heat-treated bars, and stress rupture life at 871 C and 1,100 C was determined for coated and cycled bars.

  20. Coated Aerogel Beads

    NASA Technical Reports Server (NTRS)

    Littman, Howard (Inventor); Plawsky, Joel L. (Inventor); Paccione, John D. (Inventor)

    2014-01-01

    Methods and apparatus for coating particulate material are provided. The apparatus includes a vessel having a top and a bottom, a vertically extending conduit having an inlet in the vessel and an outlet outside of the vessel, a first fluid inlet in the bottom of the vessel for introducing a transfer fluid, a second fluid inlet in the bottom of the vessel for introducing a coating fluid, and a fluid outlet from the vessel. The method includes steps of agitating a material, contacting the material with a coating material, and drying the coating material to produce a coated material. The invention may be adapted to coat aerogel beads, among other materials. A coated aerogel bead and an aerogel-based insulation material are also disclosed.

  1. Strain isolated ceramic coatings

    NASA Technical Reports Server (NTRS)

    Tolokan, R. P.; Brady, J. B.; Jarrabet, G. P.

    1985-01-01

    Plasma sprayed ceramic coatings are used in gas turbine engines to improve component temperature capability and cooling air efficiency. A compliant metal fiber strain isolator between a plasma sprayed ceramic coating and a metal substrate improves ceramic durability while allowing thicker coatings for better insulation. Development of strain isolated coatings has concentrated on design and fabrication of coatings and coating evaluation via thermal shock testing. In thermal shock testing, five types of failure are possible: buckling failure im compression on heat up, bimetal type failure, isothermal expansion mismatch failure, mudflat cracking during cool down, and long term fatigue. A primary failure mode for thermally cycled coatings is designated bimetal type failure. Bimetal failure is tensile failure in the ceramic near the ceramic-metal interface. One of the significant benefits of the strain isolator is an insulating layer protecting the metal substrate from heat deformation and thereby preventing bimetal type failure.

  2. Phase diagram of the Co-Al-W system. structure and phase transformations near the Co3(Al, W) intermetallic composition range

    NASA Astrophysics Data System (ADS)

    Kazantseva, N. V.; Demakov, S. L.; Yurovskikh, A. S.; Stepanova, N. N.; Vinogradova, N. I.; Davydov, D. I.; Lepikhin, S. V.

    2016-07-01

    Low-temperature portion of the polythermal section for the Co-Al-W system in the vicinity of the Co3(Al, W) intermetallic composition has been studied experimentally using electron microscopy and hightemperature X-ray diffraction analysis. Low-temperature structural phase transformations and temperature ranges of the existence of phases have been determined. The morphology of Co3(Al, W) intermetallic particles was studied as a function of the tungsten content in alloys.

  3. Combustion chemical vapor desposited coatings for thermal barrier coating systems

    SciTech Connect

    Hampikian, J.M.; Carter, W.B.

    1995-10-01

    The new deposition process, combustion chemical vapor deposition, shows a great deal of promise in the area of thermal barrier coating systems. This technique produces dense, adherent coatings, and does not require a reaction chamber. Coatings can therefore be applied in the open atmosphere. The process is potentially suitable for producing high quality CVD coatings for use as interlayers between the bond coat and thermal barrier coating, and/or as overlayers, on top of thermal barrier coatings.

  4. Structure of anodized Al-Zr sputter deposited coatings and effect on optical appearance

    NASA Astrophysics Data System (ADS)

    Gudla, Visweswara Chakravarthy; Canulescu, Stela; Shabadi, Rajashekhara; Rechendorff, Kristian; Dirscherl, Kai; Ambat, Rajan

    2014-10-01

    The mechanism of interaction of light with the microstructure of anodized layer giving specific optical appearance is investigated using Al-Zr sputter deposited coating as a model system on an AA6060 substrate. Differences in the oxidative nature of various microstructural components result in the evolution of typical features in the anodized layer, which are investigated as a function of microstructure and correlated with its optical appearance. The Zr concentration in the coating was varied from 6 wt.% to 23 wt.%. Heat treatment of the coated samples was carried out at 550 °C for 4 h in order to evolve Al-Zr based second phase precipitates in the microstructure. Anodizing was performed using 20 wt.% sulphuric acid at 18 °C with an intention to study the effect of anodizing on the Al-Zr based precipitates in the coating. Detailed microstructural characterization of the coating and anodized layer was carried out using high resolution scanning and transmission electron microscopy, grazing incidence X-ray diffraction analysis, glow discharge optical emission spectroscopy, and optical appearance using spectrophotometry. The evolution of microstructure in the anodized layer as a function of anodizing parameters and their influence on the interaction of light is investigated and the results in general are applicable to discolouration of anodized layer on recycled aluminium alloys due to intermetallics.

  5. A diffraction based study of the deformation mechanisms in anomalously ductile B2 intermetallics

    NASA Astrophysics Data System (ADS)

    Mulay, Rupalee Prashant

    For many decades, the brittle nature of most intermetallic compounds (e.g. NiAl) has been the limiting factor in their practical application. Many B2 (CsCl prototypical structure) intermetallics are known to exhibit slip on the <001>{110} slip mode, which provides only 3 independent slip systems and, hence, is unable to satisfy the von Mises (a.k.a. Taylor) criterion for polycrystalline ductility. As a result, inherent polycrystalline ductility is unexpected. Recent discovery of a number of ductile B2 intermetallics has raised questions about possible violation of the von Mises criterion by these alloys. These ductile intermetallic compounds are MR (metal (M) combined with a rare earth metal or group IV refractory metal (R)) alloys and are stoichiometric, ordered compounds. Single crystal slip trace analyses have only identified the presence of <100>{011} or <100>{010} slip systems. More than 100 other B2 MR compounds are known to exist and many of them have already been shown to be ductile (e.g., CuY, AgY, CuDy, CoZr, CoTi, etc.). Furthermore, these alloys exhibit a large Bauschinger effect. The present work uses several diffraction based techniques including electron back scattered diffraction (EBSD), X-ray diffraction (XRD) and in-situ neutron diffraction; in conjunction with scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical testing, and crystal plasticity modeling, to elucidate the reason for ductility in select B2 alloys, explore the spread of this ductility over the B2 family, and understand the Bauschinger effect in these alloys. Several possible explanations (e.g., slip of <111> dislocations, strong texture, phase transformations and twinning) for the anomalous ductility were explored. An X-ray diffraction based analysis ruled out texture, phase purity and departure from order as explanations for the anomalous ductility in MR alloys. In-situ neutron diffraction and post deformation SEM, EBSD, and TEM were unable to

  6. Deformation-induced dissolution of the intermetallics Ni3Ti and Ni3Al in austenitic steels at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Sagaradze, V. V.; Shabashov, V. A.; Kataeva, N. V.; Zavalishin, V. A.; Kozlov, K. A.; Kuznetsov, A. R.; Litvinov, A. V.; Pilyugin, V. P.

    2016-06-01

    An anomalous deformation-induced dissolution of the intermetallics Ni3Al and Ni3Ti in the matrix of austenitic Fe-Ni-Al(Ti) alloys has been revealed in experiment at cryogenic temperatures (down to 77 K) under rolling and high pressure torsion. The observed phenomenon is explained as the result of migration of deformation-stipulated interstitial atoms from a particle into the matrix in the stress field of moving dislocations. With increasing the temperature of deformation, the dissolution is replaced by the deformation-induced precipitation of the intermetallics, which is accelerated due to a sufficient amount of point defects in the matrix, gained as well in the course of deformation at lower temperatures.

  7. A review on the synthesis, crystal growth, structure and physical properties of rare earth based quaternary intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Mumbaraddi, Dundappa; Sarkar, Sumanta; Peter, Sebastian C.

    2016-04-01

    This review highlights the synthesis and crystal growth of quaternary intermetallic compounds based on rare earth metals. In the first part of this review, we highlight briefly about intermetallics and their versatile properties in comparison to the constituent elements. In the next part, we have discussed about various synthesis techniques with more focus on the metal flux technique towards the well shaped crystal growth of novel compounds. In the subsequent parts, several disordered quaternary compounds have been reviewed and then outlined most known ordered quaternary compounds with their complex structure. A special attention has been given to the ordered compounds with structural description and relation to the parent binary and ternary compounds. The importance of electronic and structural feature is highlighted as the key roles in designing these materials for emerging applications.

  8. Magnetic susceptibility and parameters of electronic structure of Al2REM (Gd, Dy, and Ho) intermetallic compounds at high temperatures

    NASA Astrophysics Data System (ADS)

    Uporova, N. S.; Uporov, S. A.; Sidorov, V. E.

    2011-08-01

    The magnetic susceptibility of Al2REM (REM = Gd, Dy, and Ho) intermetallic compounds is experimentally investigated by the Faraday method in a wide temperature interval (290-2000 K) in different magnetic fields (0.3-1.3 T). In the crystalline state, the temperature dependences of the susceptibility follow the generalized Curie-Weiss law. In the liquid phase, the magnetic susceptibility of these intermetallic compounds above the melting point increases for all examined samples. The parameters of the electronic structure of the compounds are calculated based on the experimental data. It is established that the effective magnetic moment per rareearth metal atom is smaller than that characteristic of the free REM+ ion.

  9. Preparation and characterization of Fe-Al intermetallic layer on the surface of T91 heat-resistant steel

    NASA Astrophysics Data System (ADS)

    Shi, Zimu; Cao, Jianbo; Han, Fusheng

    2014-04-01

    A Fe-Al intermetallic layer was formed on the surface of T91 heat-resistant steel by a molten aluminum hot-dipping and heat diffusion treatment. It is shown that the layer was composed of Al, FeAl3 and Fe2Al5 phases in the as-dipped state while only Fe3Al phase retained after the heat treatment. The intermetallic layer exhibited typical columnar grain structure after the heat treatment, and the thickness of aluminizing layer was increased from 55 μm at 760 °C to around 100 μm at 1050 °C heat treatment. Such a phase composition and grain morphology are favorable for the oxidation and corrosion resistance of T91 steel.

  10. Intermetallic and ceramic matrix composites for 815 to 1370 C (1500 to 2500F) gas turbine engine applications

    SciTech Connect

    Stephens, J.R.

    1989-01-01

    Light weight and potential high temperature capability of intermetallic compounds, such as the aluminides, and structural ceramics, such as the carbides and nitrides, make these materials attractive for gas turbine engine applications. In terms of specific fuel consumption and specific thrust, revolutionary improvements over current technology are being sought by realizing the potential of these materials through their use as matrices combined with high strength, high temperature fibers. The U.S. along with other countries throughout the world have major research and development programs underway to characterize these composites materials; improve their reliability; identify and develop new processing techniques, new matrix compositions, and new fiber compositions; and to predict their life and failure mechanisms under engine operating conditions. The status is summarized of NASA's Advanced High Temperature Engine Materials Technology Program (HITEMP) and the potential benefits are described to be gained in 21st century transport aircraft by utilizing intermetallic and ceramic matrix composite materials.

  11. Intermetallic and ceramic matrix composites for 815 to 1370 C (1500 to 2500 F) gas turbine engine applications

    NASA Technical Reports Server (NTRS)

    Stephens, Joseph R.

    1989-01-01

    Light weight and potential high temperature capability of intermetallic compounds, such as the aluminides, and structural ceramics, such as the carbides and nitrides, make these materials attractive for gas turbine engine applications. In terms of specific fuel consumption and specific thrust, revolutionary improvements over current technology are being sought by realizing the potential of these materials through their use as matrices combined with high strength, high temperature fibers. The U.S. along with other countries throughout the world have major research and development programs underway to characterize these composites materials; improve their reliability; identify and develop new processing techniques, new matrix compositions, and new fiber compositions; and to predict their life and failure mechanisms under engine operating conditions. The status is summarized of NASA's Advanced High Temperature Engine Materials Technology Program (HITEMP) and the potential benefits are described to be gained in 21st century transport aircraft by utilizing intermetallic and ceramic matrix composite materials.

  12. High-voltage electron microscope high-temperature in situ straining experiments to study dislocation dynamics in intermetallics and quasicrystals.

    PubMed

    Messerschmidt, U

    2001-07-01

    The dynamic behaviour of dislocations in several intermetallic alloys, studied by in situ straining experiments in a high-voltage electron microscope, is compared at room temperature and at high temperatures. In contrast to room temperature, the dislocations move viscously at high temperatures, which is explained by diffusion processes in the dislocation cores. In quasicrystals, the viscous dislocation motion can be interpreted by models on the cluster scale. PMID:11454156

  13. Intermetallic and ceramic matrix composites for 815 to 1370 C (1500 to 2500 F) gas turbine engine applications

    NASA Technical Reports Server (NTRS)

    Stephens, Joseph R.

    1990-01-01

    Revolutionary improvements in gas turbine engine specific fuel consumption and specific thrust are expected to be gained through incorporation of CMCs and of MMCs (whose intermetallic matrices are reinforced by highly refractory ceramic fibers). A status development evaluation is presented for NASA's Advanced High Temperature Engine Materials Technology Program, with a view to projections of early-21st century transport aircraft performance levels obtainable through the use of MMCs and CMCs in ultrahigh bypass turbofan engines.

  14. Fabrication and corrosion resistance of HVOF-sprayed Ni2Si intermetallic compound

    NASA Astrophysics Data System (ADS)

    Verdian, M. M.; Raeissi, K.; Salehi, M.

    2013-05-01

    In this study, Ni2Si powders were deposited onto 420 stainless steel substrate using high velocity oxy-fuel (HVOF) process. The coatings were characterized by X-ray diffractometery, optical and scanning electron microscopy and microhardness measurements. Tafel polarization tests and electrochemical impedance spectroscopy (EIS) measurements were employed to study corrosion performance of the coatings in 70% H2SO4 media at room temperature. Here, a dense sintered Ni2Si was used as reference material. The results showed the phase composition of HVOF coating is similar to that of feedstock powders. The corrosion rate of HVOF Ni2Si coatings was much lower than that of 420 stainless steel substrate but slightly higher than that of bulk Ni2Si. Further investigation showed that both thermally sprayed and sintered (reference) Ni2Si alloys exhibited similar anodic polarization behavior including a narrow active section followed by a wide passive region.

  15. Size-Dependent Disorder-Order Transformation in the Synthesis of Monodisperse Intermetallic PdCu Nanocatalysts.

    PubMed

    Wang, Chenyu; Chen, Dennis P; Sang, Xiahan; Unocic, Raymond R; Skrabalak, Sara E

    2016-06-28

    The high performance of Pd-based intermetallic nanocatalysts has the potential to replace Pt-containing catalysts for fuel-cell reactions. Conventionally, intermetallic particles are obtained through the annealing of nanoparticles of a random alloy distribution. However, this method inevitably leads to sintering of the nanoparticles and generates polydisperse samples. Here, monodisperse PdCu nanoparticles with the ordered B2 phase were synthesized by seed-mediated co-reduction using PdCu nanoparticle seeds with a random alloy distribution (A1 phase). A time-evolution study suggests that the particles must overcome a size-dependent activation barrier for the ordering process to occur. Characterization of the as-prepared PdCu B2 nanoparticles by electron microscopy techniques revealed surface segregation of Pd as a thin shell over the PdCu core. The ordered nanoparticles exhibit superior activity and durability for the oxygen reduction reaction in comparison with PdCu A1 nanoparticles. This seed-mediated co-reduction strategy produced monodisperse nanoparticles ideally suited for structure-activity studies. Moreover, the study of their growth mechanism provides insights into the size dependence of disorder-order transformations of bimetallic alloys at the nanoscale, which should enable the design of synthetic strategies toward other intermetallic systems. PMID:27214313

  16. Kinetics of accumulation of the intermetallic compound of nickel and cadmium during storage of charged cadmium electrodes in alkali

    SciTech Connect

    Reshetov, V.A.; Grachev, D.K.; Pen'kova, L.I.; L'vova, L.A.; Ryabskaya, I.A.; Logvinets, N.P.

    1983-05-20

    When charged cadmium electrodes containing nickelous hydroxide (NHO) are stored in alkali an intermetallic compound (IMC) of the composition Ni/sub 5/Cd/sub 21/ is formed. The appearance of a step corresponding to oxidation of the IMC at a potential more positive by 0.12-0.18 V than the potential of the principal discharge process leads to appreciable lowering of the electrode capacity after storage. A systematic study was carried out of the kinetics of accumulation of the IMC at various temperatures and with additions of various amounts of NHO in order to elucidate the mechanism of formation of the intermetallic compound and to examine the possibility of predicting the loss of capacity of cadmium electrodes during storage. A kinetic equation, which can be used for predicting capacity losses of charged cadmium electrodes because of formation of the intermetallic compound Ni/sub 5/Cd/sub 21/ in them during storage, is proposed. The two-step form of the kinetic curves indicates that the IMC can be formed in cadmium electrodes during storage by two parallel mechanisms, involving both Ni/sup 0/ and Ni/sup 2 +/.

  17. SDAS, Si and Cu Content, and the Size of Intermetallics in Al-Si-Cu-Mg-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Sivarupan, Tharmalingam; Taylor, John Andrew; Cáceres, Carlos Horacio

    2015-05-01

    Plates of Al-(a)Si-(b)Cu-Mg-(c)Fe alloys with varying content of (mass pct) Si ( a = 3, 4.5, 7.5, 9, 10, or 11), Cu ( b = 0, 1, or 4), and Fe ( c = 0.2, 0.5 or 0.8) were cast in sand molds with a heavy chill at one end to ensure quasi-directional solidification over a wide range of Secondary Dendrite Arm Spacing (SDAS). Statistical analysis on the size of the β-Al5FeSi, α-Al8Fe2Si, or Al2Cu intermetallics on Backscattered Electron images showed that a high Si content reduced the size of the β platelets in alloys with up to 0.5 Fe content regardless of the SDAS, whereas at small SDAS the refining effect extended up to 0.8 Fe, and involved α-phase intermetallics which replaced the beta platelets at those concentrations. At low Si contents, a high Cu level appeared to have similar refining effects as increased Si, through the formation of α-phase particles in the post-eutectic stage which agglomerated with the Al2Cu intermetallics. A high content of Si appears to make the overall refining process less critical in terms of SDAS/cooling rate.

  18. Rare-earth transition-metal intermetallics: Structure-bonding-property relationships

    SciTech Connect

    Han, M.K.

    2006-05-06

    The explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding property relationships. The work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe{sub 13-x}Si{sub x} system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn{sub 13}-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides Re{sub 2-x}Fe{sub 4}Si{sub 14-y} and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi{sub 2}: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb{sub 3}Zn{sub 3.6}Al{sub 7.4}: Partially ordered structure of Tb{sub 3}Zn{sub 3.6}Al{sub 7.4} compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn{sub 39}(Cr{sub x}Al{sub 1-x}){sub 81}: These layered structures are similar to icosahedral Mn-Al quasicrystalline

  19. Rare-Earth Transition-Metal Intermetallics: Structure-bonding-Property Relationships

    SciTech Connect

    Mi-Kyung Han

    2006-05-01

    Our explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding-property relationships. Our work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe{sub 13-x}Si{sub x} system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn{sub 13}-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides RE{sub 2-x}Fe{sub 4}Si{sub 14-y} and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi{sub 2}: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb{sub 3}Zn{sub 3.6}Al{sub 7.4}: Partially ordered structure of Tb{sub 3}Zn{sub 3.6}Al{sub 7.4} compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn{sub 39}(Cr{sub x}Al{sub 1-x}){sub 81}: These layered structures are similar to icosahedral Mn-Al quasicrystalline

  20. Kinetic Stabilization of Ordered Intermetallic Phases as Fuel Cell Anode Materials

    SciTech Connect

    Liu, Yi; Lowe, Michael A.; DiSalvo, Francis J.; Abruña, Héctor D.

    2010-08-16

    The influence of fuel molecules on the stability of the ordered intermetallic PtBi and PtPb phases has been extensively studied by synchrotron-based in situ X-ray grazing incidence diffraction under active electrochemical control. Cycling the potential to increasingly positive values resulted in little change to the surface composition and crystalline structure when specific fuel molecules (such as formic acid for PtBi and formic acid or methanol for PtPb) were oxidized at the intermetallic electrode surface. This was demonstrated by the absence of diffraction peaks due to Pt domains that would be generated by the leaching out of the less noble metal. This phenomenon has been rationalized as a competition process between the oxidation of fuel molecules at the electrode surface and corrosion and damage of the surface due to the electrochemical treatment. For example, PtBi electrodes, which exhibit excellent catalytic activity toward the oxidation of formic acid, could be kinetically stabilized to such a corrosion/degradation process in the presence of formic acid even at relatively positive potentials. An analogous effect was observed for PtPb in the presence of methanol as fuel. In the absence of fuel molecules (formic acid for PtBi and formic acid and/or methanol for PtPb), various surface layers were generated by different electrochemical pretreatments in the presence of only a supporting electrolyte. Crystalline oxidized bismuth species (such as Bi2O3) with an ~50 nm domain size were formed on the PtBi electrode surface by holding the potential at +1.00 V or beyond for at least 30 min. On the other hand, platinum nanopaticles with an ~5 nm crystalline domain size were formed when cycling the potential to higher values. In the case of PtPb, the only detected corrosion product was PbSO 4, whose diffraction peaks were utilized to qualitatively analyze the lead leaching-out and dissolution processes. No crystalline lead oxide species

  1. Coatings for graphite fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Graphite fibers released from composites during burning or an explosion caused shorting of electrical and electronic equipment. Silicon carbide, silica, silicon nitride and boron nitride were coated on graphite fibers to increase their electrical resistances. Resistances as high as three orders of magnitude higher than uncoated fiber were attained without any significant degradation of the substrate fiber. An organo-silicone approach to produce coated fibers with high electrical resistance was also used. Celion 6000 graphite fibers were coated with an organo-silicone compound, followed by hydrolysis and pyrolysis of the coating to a silica-like material. The shear and flexural strengths of composites made from high electrically resistant fibers were considerably lower than the shear and flexural strengths of composites made from the lower electrically resistant fibers. The lower shear strengths of the composites indicated that the coatings on these fibers were weaker than the coating on the fibers which were pyrolyzed at higher temperature.

  2. Beneficial Role of Copper in the Enhancement of Durability of Ordered Intermetallic PtFeCu Catalyst for Electrocatalytic Oxygen Reduction.

    PubMed

    Arumugam, Balamurugan; Tamaki, Takanori; Yamaguchi, Takeo

    2015-08-01

    Design of Pt alloy catalysts with enhanced activity and durability is a key challenge for polymer electrolyte membrane fuel cells. In the present work, we compare the durability of the ordered intermetallic face-centered tetragonal (fct) PtFeCu catalyst for the oxygen reduction reaction (ORR) relative to its counterpart bimetallic catalysts, i.e., the ordered intermetallic fct-PtFe catalyst and the commercial catalyst from Tanaka Kikinzoku Kogyo, TKK-PtC. Although both fct catalysts initially exhibited an ordered structure and mass activity approximately 2.5 times higher than that of TKK-Pt/C, the presence of Cu at the ordered intermetallic fct-PtFeCu catalyst led to a significant enhancement in durability compared to that of the ordered intermetallic fct-PtFe catalyst. The ordered intermetallic fct-PtFeCu catalyst retained more than 70% of its mass activity and electrochemically active surface area (ECSA) over 10 000 durability cycles carried out at 60 °C. In contrast, the ordered intermetallic fct-PtFe catalyst maintained only about 40% of its activity. The temperature of the durability experiment is also shown to be important: the catalyst was more severely degraded at 60 °C than at room temperature. To obtain insight into the observed enhancement in durability of fct-PtFeCu catalyst, a postmortem analysis of the ordered intermetallic fct-PtFeCu catalyst was carried out using scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX) line scan. The STEM-EDX line scans of the ordered intermetallic fct-PtFeCu catalyst over 10 000 durability cycles showed a smaller degree of Fe and Cu dissolution from the catalyst. Conversely, large dissolution of Fe was identified in the ordered intermetallic fct-PtFe catalyst, indicating a lesser retention of Fe that causes the destruction of ordered structure and gives rise to poor durability. The enhancement in the durability of the ordered intermetallic fct-PtFeCu catalyst is ascribed to

  3. Optical coating in space

    NASA Technical Reports Server (NTRS)

    Bunner, A. N.

    1983-01-01

    A technological appraisal of the steps required to approach the goal of in-situ optical coating, cleaning and re-coating the optical elements of a remote telescope in space is reported. Emphasis is placed on the high ultraviolet throughput that a telescope using bare aluminum mirrors would offer. A preliminary design is suggested for an Orbital Coating Laboratory to answer basic technical questions.

  4. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2004-08-31

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  5. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2003-10-14

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  6. Thermally sprayed coatings

    SciTech Connect

    Diaz, D.J.; Blann, G.A. )

    1991-05-01

    Standardization of specimen preparation for microstructural evaluation of thermally sprayed coatings is considered. Metallographic specimen preparation procedures including sectioning, encapsulation, planar grinding, and power lapping of thermally sprayed coatings are described. A Co-Ni-Cr-W coating on an AISI 410 stainless steel substrate is used as a control sample. Specimen-preparation techniques have been evaluated through scanning electron microscopy for determining the percentage of apparent porosity and energy dispersive spectroscopy for determining elemental composition.

  7. Amorphous alumina oxidation protective coatings for Zircaloy based on a compositional gradient layer system

    NASA Astrophysics Data System (ADS)

    Park, Sang Tae

    Waterside corrosion of the Zircaloy cladding encasing the uranium oxide pellets is one of the primary factors limiting high "burn up" of nuclear fuel in pressurized water reactors (PWRs). High "burn up" can significantly impact plant safety and economics. Amorphous aluminum oxide coatings with aluminum-based compositional gradient layers (CGLs) were fabricated to develop ceramic coating corrosion protection systems for Zircaloy. Aluminum films were deposited on Zircaloy substrates by electron-beam evaporation, and two-step heat treatments were performed at near the melting temperature of aluminum. Amorphous alumina coatings by rf magnetron sputtering were overcoated on the CGL structures. Morphological and compositional studies were completed using field emission scanning electron microscopy (FE SEM), energy dispersive x-ray analysis (EDX), and auger electron spectroscopy (AES). The AES depth profiles of the annealed coatings showed that gradient compositions of Al, Zr, and O were obtained. Glancing angle x-ray diffraction (GAXRD) analysis showed that a variety of intermetallic and oxide phases (such as Al3Zr, Al2Zr3, Al2O3, ZrO2 and Zr3O) were formed in the coatings during processing. The intermetallic layers improved the adhesion property of the alumina overcoating to Zircaloy substrate, and functioned as oxidation resistant layers. In spite of the successful construction of the compositional gradient layer system with a good adhesion and thermal stability, and the report about the stability of pure alumina and amorphous ceramics in hydrothermal conditions, the amorphous alumina coatings in our study were not stable under nuclear reactor conditions of subcritical water at 350°C and 20.1 MPa (3000 psi). We investigated the behavior of amorphous alumina thin films deposited on Zircaloy substrates in the near-supercritical water. When the coatings were exposed to the subcritical conditions, hydrothermally grown well-faceted crystallite formation was observed

  8. Zinc phosphate conversion coatings

    DOEpatents

    Sugama, T.

    1997-02-18

    Zinc phosphate conversion coatings for producing metals which exhibit enhanced corrosion prevention characteristics are prepared by the addition of a transition-metal-compound promoter comprising a manganese, iron, cobalt, nickel, or copper compound and an electrolyte such as polyacrylic acid, polymethacrylic acid, polyitaconic acid and poly-L-glutamic acid to a phosphating solution. These coatings are further improved by the incorporation of Fe ions. Thermal treatment of zinc phosphate coatings to generate {alpha}-phase anhydrous zinc phosphate improves the corrosion prevention qualities of the resulting coated metal. 33 figs.

  9. Zinc phosphate conversion coatings

    DOEpatents

    Sugama, Toshifumi

    1997-01-01

    Zinc phosphate conversion coatings for producing metals which exhibit enhanced corrosion prevention characteristics are prepared by the addition of a transition-metal-compound promoter comprising a manganese, iron, cobalt, nickel, or copper compound and an electrolyte such as polyacrylic acid, polymethacrylic acid, polyitaconic acid and poly-L-glutamic acid to a phosphating solution. These coatings are further improved by the incorporation of Fe ions. Thermal treatment of zinc phosphate coatings to generate .alpha.-phase anhydrous zinc phosphate improves the corrosion prevention qualities of the resulting coated metal.

  10. Aircraft surface coatings

    NASA Technical Reports Server (NTRS)

    1983-01-01

    A series of studies in which films and liquid spray-on materials were evaluated in the laboratory for transport aircraft external surface coatings are summarized. Elastomeric polyurethanes were found to best meet requirements. Two commercially available products, CAAPCO B-274 and Chemglaze M313, were subjected to further laboratory testing, airline service evaluations, and drag-measurement flight tests. It was found that these coatings were compatible with the severe operating environment of airlines and that coatings reduced airplane drag. An economic analysis indicated significant dollar benefits to airlines from application of the coatings.

  11. Oxide coating development

    SciTech Connect

    Stinton, D.P.

    1995-06-01

    Monolithic SiC heat exchangers and fiber-reinforced SiC-matrix composite heat exchangers and filters are susceptible to corrosion by alkali metals at elevated temperatures. Protective coatings are currently being developed to isolate the SiC materials from the corrodants. Unfortunately, these coatings typically crack and spall when applied to SiC substrates. The purpose of this task is to determine the feasibility of using a compliant material between the protective coating and the substrate. The low-modulus compliant layer could absorb stresses and eliminate cracking and spalling of the protective coatings.

  12. Coatings for Graphite Fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Several approaches for applying high resistance coatings continuously to graphite yarn were investigated. Two of the most promising approaches involved (1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber followed by oxidation, and (2) drawing the graphite yarn through an organo-silicone solution followed by heat treatments. In both methods, coated fibers were obtained which exhibited increased electrical resistances over untreated fibers and which were not degraded. This work was conducted in a previous program. In this program, the continuous CVD SiC coating process used on HTS fiber was extended to the coating of HMS, Celion 6000, Celion 12000 and T-300 graphite fiber. Electrical resistances three order of magnitude greater than the uncoated fiber were measured with no significant degradation of the fiber strength. Graphite fibers coated with CVD Si3N4 and BN had resistances greater than 10(exp 6) ohm/cm. Lower pyrolysis temperatures were used in preparing the silica-like coatings also resulting in resistances as high as three orders of magnitude higher than the uncoated fiber. The epoxy matrix composites prepared using these coated fibers had low shear strengths indicating that the coatings were weak.

  13. Characterization of ceramics and intermetallics fabricated by self-propagating high-temperature synthesis

    NASA Technical Reports Server (NTRS)

    Hurst, Janet B.

    1989-01-01

    Three efforts aimed at investigating the process of self-propagating high temperature synthesis (SHS) for the fabrication of structural ceramics and intermetallics are summarized. Of special interest was the influence of processing variables such as exothermic dopants, gravity, and green state morphology in materials produced by SHS. In the first effort directed toward the fabrication of SiC, exothermic dopants of yttrium and zirconium were added to SiO2 or SiO2 + NiO plus carbon powder mix and processed by SHS. This approach was unsuccessful since it did not produce the desired product of crystalline SiC. In the second effort, the influence of gravity was investigated by examining Ni-Al microstructures which were produced by SHS combustion waves traveling with and opposite the gravity direction. Although final composition and total porosities of the combusted Ni-Al compounds were found to be gravity independent, larger pores were created in those specimens which were combusted opposite to the gravity force direction. Finally, it was found that green microstructure has a significant effect on the appearance of the combusted piece. Severe pressing laminations were observed to arrest the combustion front for TiC samples.

  14. On the site preferences of ternary additions to triple defect B2 intermetallic compounds

    SciTech Connect

    Pike, L.M.; Chen, S.L.; Chang, Y.A.

    1995-12-31

    Knowledge of the site preference of ternary solute additions is essential to developing an understanding of how these solutes affect the properties of B2 intermetallic compounds. A quasichemical model will be presented which is able to predict the site preferences of dilute solute additions to triple defect B2 compounds. The only parameters required are enthalpies of formation at the stoichiometric composition. General equations are developed which can be used to determine site occupations and defect concentrations for dilute as well as non-dilute solute additions. These equations use atom pair bond enthalpies as the parameters. It is found that the site preferences of dilute additions are not always in agreement with predictions based on the solubility lobes in ternary Gibbs isotherms, Predictions for dilute additions to NiAl and FeAl are compared to experimental results found in the literature. Satisfactory correlation is found between the model and the experimental results. In addition, the predictions from the model on vacancy concentrations in Fe doped NiAl are compared to recent experimental results by the authors.

  15. Optimized Cu-Sn Wafer-Level Bonding Using Intermetallic Phase Characterization

    NASA Astrophysics Data System (ADS)

    Luu, Thi-Thuy; Duan, Ani; Aasmundtveit, Knut E.; Hoivik, Nils

    2013-12-01

    The objective of this study is to optimize the Cu/Sn solid-liquid interdiffusion process for wafer-level bonding applications. To optimize the temperature profile of the bonding process, the formation of intermetallic compounds (IMCs) which takes place during the bonding process needs to be well understood and characterized. In this study, a simulation model for the development of IMCs and the unreacted remaining Sn thickness as a function of the bonding temperature profile was developed. With this accurate simulation model, we are able to predict the parameters which are critical for bonding process optimization. The initial characterization focuses on a kinetics model of the Cu3Sn thickness growth and the amount of Sn thickness that reacts with Cu to form IMCs. As-plated Cu/Sn samples were annealed using different temperatures (150°C to 300°C) and durations (0 min to 320 min). The kinetics model is then extracted from the measured thickness of IMCs of the annealed samples.

  16. Investigation of Dissolution Behavior of Metallic Substrates and Intermetallic Compound in Molten Lead-free Solders

    NASA Astrophysics Data System (ADS)

    Yen, Yee-Wen; Chou, Weng-Ting; Tseng, Yu; Lee, Chiapyng; Hsu, Chun-Lei

    2008-01-01

    This study investigates the dissolution behavior of the metallic substrates Cu and Ag and the intermetallic compound (IMC)-Ag3Sn in molten Sn, Sn-3.0Ag-0.5Cu, Sn-58Bi and Sn-9Zn (in wt.%) at 300, 270 and 240°C. The dissolution rates of both Cu and Ag in molten solder follow the order Sn > Sn-3.0Ag-0.5Cu >Sn-58Bi > Sn-9Zn. Planar Cu3Sn and scalloped Cu6Sn5 phases in Cu/solders and the scalloped Ag3Sn phase in Ag/solders are observed at the metallic substrate/solder interface. The dissolution mechanism is controlled by grain boundary diffusion. The planar Cu5Zn8 layer formed in the Sn-9Zn/Cu systems. AgZn3, Ag5Zn8 and AgZn phases are found in the Sn-9Zn/Ag system and the dissolution mechanism is controlled by lattice diffusion. Massive Ag3Sn phases dissolved into the solders and formed during solidification processes in the Ag3Sn/Sn or Sn-3.0Ag-0.5Cu systems. AgZn3 and Ag5Zn8 phases are formed at the Sn-9Zn/Ag3Sn interface. Zn atoms diffuse through Ag-Zn IMCs to form (Ag, Zn)Sn4 and Sn-rich regions between Ag5Zn8 and Ag3Sn.

  17. Physical properties and electronic structure of La3Co and La3Ni intermetallic superconductors

    NASA Astrophysics Data System (ADS)

    Strychalska, J.; Roman, M.; Sobczak, Z.; Wiendlocha, B.; Winiarski, M. J.; Ronning, F.; Klimczuk, T.

    2016-09-01

    La3Co and La3Ni are reported superconductors with transition temperatures of 4.5 and 6 K, respectively. Here, we reinvestigate the physical properties of these two intermetallic compounds with magnetic susceptibility χ, specific heat Cp and electrical resistivity ρ measurements down to 1.9 K. Although bulk superconductivity is confirmed in La3Co, as observed previously, only a trace of it is found in La3Ni, indicating that the superconductivity in La3Ni originates from an impurity phase. Superconducting state parameters for La3Co, including lower and upper critical fields and the superconducting gap, are estimated. Results of the theoretical calculations of the electronic structure for both materials are also presented, and comparison of the Fermi level location in La3Co versus La3Ni explains its larger superconducting Tc. A major discrepancy between band structure calculations and the experimentally measured Sommerfeld coefficient is found. The measured electronic density of states is about 2.5 times larger than the theoretical value for La3Co. This effect cannot be explained by the electron-phonon interaction alone. Renormalization of γ, as well as an ∼T2 behavior of the resistivity, suggests the presence of spin fluctuations in both systems.

  18. Incorporation of Interfacial Intermetallic Morphology in Fracture Mechanism Map for Sn-Ag-Cu Solder Joints

    NASA Astrophysics Data System (ADS)

    Huang, Z.; Kumar, P.; Dutta, I.; Sidhu, R.; Renavikar, M.; Mahajan, R.

    2014-01-01

    A fracture mechanism map (FMM) is a powerful tool which correlates the fracture behavior of a material to its microstructural characteristics in an explicit and convenient way. In the FMM for solder joints, an effective thickness of the interfacial intermetallic compound (IMC) layer ( t eff) and the solder yield strength ( σ ys,eff) are used as abscissa and ordinate axes, respectively, as these two predominantly affect the fracture behavior of solder joints. Earlier, a definition of t eff, based on the uniform thickness of IMC ( t u) and the average height of the IMC scallops ( t s), was proposed and shown to aptly explain the fracture behavior of solder joints on Cu. This paper presents a more general definition of t eff that is more widely applicable to a range of metallizations, including Cu and electroless nickel immersion gold (ENIG). Using this new definition of t eff, mode I FMM for SAC387/Cu joints has been updated and its validity was confirmed. A preliminary FMM for SAC387/Cu joints with ENIG metallization is also presented.

  19. Discovery and characterization of magnetism in sigma-phase intermetallic Fe-Re compounds

    SciTech Connect

    Cieślak, J. Dubiel, S. M.; Tobola, J.; Reissner, M.

    2014-11-14

    Systematic experimental studies (vibrating sample magnetometry) supported by theoretical calculations (electronic structure by spin self-consistent Korringa-Kohn-Rostoker Green's function method) were performed on a series of intermetallic sigma-phase Fe{sub 100−x}Re{sub x} (x = 43–53) compounds. All investigated samples exhibit magnetism with an ordering temperature ranging between ∼65 K for x = 43 and ∼23 K for x = 53. The magnetism was revealed to be itinerant and identified as a spin-glass (SG) possibly having a re-entrant character. The SG was found to be heterogeneous, viz., two regimes could be distinguished as far as irreversibility in temperature dependence of magnetization is concerned: (1) of a weak irreversibility and (2) of a strong one. According to the theoretical calculations, the main contribution to the magnetism comes from Fe atoms occupying all five sub lattices, while Re atoms have rather small magnetic moments. However, the calculated average magnetic moments highly (ferromagnetic ordering model) or moderately (antiparallel ordering model) overestimate the experimental data.

  20. Shock response of Ni/Al reactive inter-metallic composites

    NASA Astrophysics Data System (ADS)

    Cherukara, Mathew; Germann, Timothy; Kober, Edward; Strachan, Alejandro

    2014-03-01

    Intermolecular reactive composites find diverse applications in defense, microelectronics and medicine, where strong, localized sources of heat are required. Motivated by experimental work which has shown that high-energy ball milling can significantly improve the reactivity as well as the ease of ignition of Ni/Al inter-metallic composites, we present large scale (~41 million atom) molecular dynamics simulations of shock-induced chemistry in porous, polycrystalline, lamellar Ni/Al nano-composites, which are designed to capture the microstructure that is obtained post milling. Shock propagation in these porous, lamellar materials is observed to be extremely diffuse, leading to substantial inhomogeneity in the local stress states of the material. We describe the importance of pores as sites of initiation, where local temperatures can rise to several thousands of degrees, and chemical mixing is accelerated by vortex formation and jetting in the pore. We also follow the evolution of the chemistry after the shock passage by allowing the sample to ``cook'' under the shock induced pressures and temperatures for up to 0.5 ns. Multiple ``tendril-like'' reaction fronts, born in the cauldron of the pores, propagate rapidly through the sample, consuming it within a nanosecond. US Defense Threat Reduction Agency, Contract No. HDTRA1-10-1-0119.

  1. Surface structure of the Ag-In-(rare earth) complex intermetallics

    NASA Astrophysics Data System (ADS)

    Hars, S. S.; Sharma, H. R.; Smerdon, J. A.; Yadav, T. P.; Al-Mahboob, A.; Ledieu, J.; Fournée, V.; Tamura, R.; McGrath, R.

    2016-05-01

    We present a study of the surface structure of the Ag-In-RE (RE: rare-earth elements Gd, Tb, and Yb) complex intermetallics using scanning tunneling microscopy and low-energy electron diffraction. The surface of the Ag-In-Yb approximant prepared by sputter-annealing methods under ultrahigh-vacuum conditions produces a flat (100) surface with no facets. However, the Ag-In-Gd and Ag-In-Tb 1/1 approximants, which have a surface miscut of about 12∘ relative to the (100) plane, develop surface facets along various crystallographic directions. The structure of each facet can be explained as a truncation of the rhombic triacontahedral clusters, i.e., the main building blocks of these systems. Despite their differences in atomic structure, symmetry, and density, the facets show common features. The facet planes are In rich. The analysis of the nearest-neighbor atom distances suggests that In atoms form bonds with the RE atoms, which we suggest is a key factor that stabilizes even low-density facet planes.

  2. Intermetallic Formation at Interface of Al/Cu Clad Fabricated by Hydrostatic Extrusion and Its Properties.

    PubMed

    Lee, Jongbeom; Jeong, Haguk

    2015-11-01

    Al/Cu clad composed of Al core and Cu sheath has been produced by hydrostatic extrusion at 523 K, at an extrusion rate of 27. The prepared specimen was post-annealed at temperatures of 673 K and 773 K for various time durations, and the effect of annealing conditions have been analyzed. The hardness at the interface between Al and Cu matrix of the Al/Cu bimetal clad increases because of annealing. Results indicate that the hardness is more sensitive to annealing temperature than the annealing time. Three kinds of intermetallic compounds (IMC), namely, CuAl, Cu3Al2, and CuAl2, are formed at the Al-Cu interface, upon annealing at 673 K. On the other hand, four kinds of IMCs, namely, Cu4Al3, CuAl, Cu3Al2, CuAl2, are formed at the annealing temperature of 773 K. The growth of each IMC follows the parabolic law as a function of annealing times at certain annealing temperature. The growth rate of each IMC is limited to its interdiffusion rate constant. The IMC Cu4Al3 appears upon annealing at 773 K, and not during annealing at 673 K, because of the higher value of activation energy associated with its formation, when compared to other IMCs. PMID:26726557

  3. Structural properties, phase stability, elastic properties and electronic structures of Cu-Ti intermetallics

    NASA Astrophysics Data System (ADS)

    Chen, Shuai; Duan, Yong-Hua; Huang, Bo; Hu, Wen-Cheng

    2015-11-01

    The structural properties, phase stabilities, anisotropic elastic properties and electronic structures of Cu-Ti intermetallics have been systematically investigated using first principles based on the density functional theory. The calculated equilibrium structural parameters agree well with available experimental data. The ground-state convex hull of formation enthalpies as a function of Cu content is slightly symmetrical at CuTi with a minimal formation enthalpy (-13.861 kJ/mol of atoms), which indicates that CuTi is the most stable phase. The mechanical properties, including elastic constants, polycrystalline moduli and anisotropic indexes, were evaluated. G/B is more pertinent to hardness than to the shear modulus G due to the high power indexes of 1.137 for G/B. The mechanical anisotropy was also characterized by describing the three-dimensional (3D) surface constructions. The order of elastic anisotropy is Cu4Ti3 > Cu3Ti2 > α-Cu4Ti > Cu2Ti > CuTi > β-Cu4Ti > CuTi2. Finally, the electronic structures were discussed and Cu2Ti is a semiconductor.

  4. Layered antiferromagnetism with high Neel temperature in the intermetallic compound Mn2Au

    NASA Astrophysics Data System (ADS)

    Khmelevskyi, Sergii; Mohn, Peter

    2009-03-01

    On the basis of earlier experimental studies the intermetallic compound Mn2Au has been characterized as a non-magnetically ordered material. Here we report the results of first-principles calculations based on Local Spin-Density Approximation which describe Mn2Au to have a narrow band antiferromagnetic ground state with rigid local moments on the Mn sites. Calculations of the inter-atomic exchange constants based on the magnetic force theorem and a Monte-Carlo modeling of the resulting Heisenberg-like Hamiltonian predict a very high Neel-temperature of ˜1580K. This temperature is considerably higher than for the other known high-temperature antiferromagnetic L10-type Mn based binary alloys, which are widely used in magnetic storage applications. The source of the difficulties in determining magnetic order from the earlier experiments is discussed. The observed meta-magnetic like behavior and a susceptibility anomaly at low temperatures are linked to the frustrated magnetism on Mn anti-site impurities. We believe that the high temperature antiferromagnetism of Mn2Au may have quite an impact in technology. In particular, it can be considered as a candidate for the application as a ``pinning'' layer in GMR devices.

  5. Crystallization behavior of iron-containing intermetallic compounds in 319 aluminum alloy

    SciTech Connect

    Narayanan, L.A.; Samuel, F.H. ); Gruzleski, J.E. . Dept. of Mining and Metallurgical Engineering)

    1994-08-01

    The crystallization behavior of iron-containing intermetallic compounds in industrial grade 319 aluminum alloy has been investigated by means of thermal analysis and metallography. In the absence of manganese, the iron compound crystallizes in the [beta] phase, at all cooling rates ranging from 0.1 C/s to 20 C/s under normal casting temperatures (750 C). However, when the melt is superheated to a high temperature (about 200 to 300 degrees above the liquidus temperature), the iron compound crystallizes in the [alpha] phase at high cooling rates. This is due to the fact that [gamma] alumina, which forms at low melt temperatures ([<=]750 C), acts as a nucleus for crystallization of [beta] phase. When the melt is superheated to high temperatures ([>=] 850 C), the [gamma] alumina transforms to [alpha] alumina. This is a poor nucleus for the [beta]-phase crystallization, and as a result, [alpha] phase forms. The importance of nucleation and growth undercooling for the crystallization of iron compounds is highlighted. In the presence of manganese, the iron compound crystallizes in [alpha] phase at low cooling rates and in both the [alpha] and [beta] phases at high cooling rates. This reverse crystallization behavior is explained in terms of phase diagram relationships.

  6. Oxidation behavior of plasma sintered beryllium-titanium intermetallic compounds as an advanced neutron multiplier

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Hwan; Nakamichi, Masaru

    2013-07-01

    Beryllium intermetallic compounds (beryllides) such as Be12Ti are very promising candidates for advanced neutron multiplier materials in a demonstration fusion power reactor (DEMO). However, beryllides are too brittle to be fabricated either into pebble-type or rod-type shapes via conventional methods (i.e. arc melting and hot isostatic pressing). We have proposed a plasma sintering technique as a new method for beryllide fabrication, and our studies on the properties of plasma sintered beryllides are ongoing. In the present work, the oxidation properties of plasma sintered beryllides were investigated at 1273 K for 24 h in a dry air atmosphere to evaluate the high temperature properties of this material. Thermal gravimetry measurements indicate that specimens with larger fractions of Be12Ti phase corresponding to samples that have been sintered for longer time periods, exhibit superior oxidation properties. Our evaluation of the oxidation behavior of each phase in our beryllide samples is as follows: Be12Ti and Be17Ti2 both have good oxidation resistance, owing to the formation of dense and protective scales, while the Be and Be2Ti phases are mainly responsible for thermal-gravimetry (TG) weight gains, which is indicative of severe oxidation. We attribute the degradation in oxidation resistance specifically to Be2Ti that transforms into TiO2, and also find this phase to be the cause of deterioration in the mechanical properties of samples, owing to cracks near Be2Ti phase conglomerates.

  7. Investigation of the Growth of Intermetallic Compounds Between Cu Pillars and Solder Caps

    NASA Astrophysics Data System (ADS)

    Lin, Jui-Ching; Qin, Yi; Woertink, Julia

    2014-11-01

    In flip chip applications, Cu pillars with solder caps are regarded as next-generation electronic interconnection technology, because of high input/output density. However, because of diffusion and reaction of Sn and Cu during the high-temperature reflow process, intermetallic compounds (IMC) are formed, and grow, at the interface between the cap and the pillar. Understanding the growth behavior of interfacial IMC is critical in the design of solder interconnections, because excessive growth of IMC can reduce the reliability of connections. In this study, the growth of IMC during thermal cycling, an accelerated method of testing the service environment of electronic devices, was studied by use of focused ion beam-scanning electron microscopy. Under alternating high and low-temperature extremes, growth of Cu6Sn5 ( η-phase) and Cu3Sn ( ɛ-phase) IMC was imaged and measured as a function of the number of cycles. The total IMC layer grew significantly thicker but became more uniform during thermal cycling. The Cu3Sn layer was initially thinner than the Cu6Sn5 layer but outgrew the Cu6Sn5 layer after 1000 cycles. It was found that, with limited Cu and Sn diffusion, consumption of Cu6Sn5 for growth of the Cu3Sn layer can result in a thinner Cu6Sn5 layer after thermal cycling.

  8. Intermetallic compound layer growth kinetics in non-lead bearing solders

    SciTech Connect

    Vianco, P.T.; Kilgo, A.C.; Grant, R.

    1995-04-01

    The introduction of alternative, non-lead bearing solders into electronic assemblies requires a thorough investigation of product manufacturability and reliability. Both of these attributes can be impacted by the excessive growth of intermetallic compound (IMC) layers at the solder/substrate interface. An extensive study has documented the stoichiometry and solid state growth kinetics of IMC layers formed between copper and the lead-free solders: 96.5Sn-3.5Ag (wt.%), 95Sn-5Sb, 100Sn, and 58Bi-42Sn. Aging temperatures were 70--205 C for the Sn-based solders and 55--120 C for the Bi-rich solder. Time periods were 1--400 days for all of the alloys. The Sn/Cu, Sn-Ag/Cu, and Sn-Sb/Cu IMC layers exhibited sub-layers of Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn; the latter composition was present only following prolonged aging times or higher temperatures. The total layer growth exhibited a time exponent of n = 0.5 at low temperatures and a value of n = 0.42 at higher temperatures in each of the solder/Cu systems. Similar growth kinetics were observed with the low temperature 58Bi-42Sn solder; however, a considerably more complex sub-layer structure was observed. The kinetic data will be discussed with respect to predicting IMC layer growth based upon solder composition.

  9. Heat and mass transfer in the sorption of hydrogen by intermetallic compounds

    SciTech Connect

    Svinarev, S.V.; Trushevskii, S.N.

    1984-06-01

    Intermetallic compounds (IMC), which reversibly absorb hydrogen, are currently the subject of many investigations re their possible use in hydrogen accumulators, thermal machines, thermal pumps and accumulators, sorptional compressors, etc. The dynamics of hydrogen sorption in IMC must be investigated for the analysis and design of such devices. Trends in such studies can be distinguished: the study of the true chemical kinetics of sorption; the investigation of the sorption dynamics in extended IMC layers of dimensions characteristic for practical applications. However, these do not give criteria by which the experimental conditions may be chosen, and often the conditions themselves are not completely described. In connection with this, calculations of the sorption process in which the heat liberation and filtration of hydrogen through the IMC layer are taken into account are of interest both for practical applications and for the elucidation of the conditions in which the process may be regarded as purely kinetic or controlled by the heat and mass transfer in the layer. The authors devote themselves to this aspect in this presentation.

  10. Launch Load Resistant Spacecraft Mechanism Bearings Made From NiTi Superelastic Intermetallic Materials

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Moore, Lewis E.

    2014-01-01

    Compared to conventional bearing materials (tool steel and ceramics), emerging Superelastic Intermetallic Materials (SIMs), such as 60NiTi, have significantly lower elastic modulus and enhanced strain capability. They are also immune to atmospheric corrosion (rusting). This offers the potential for increased resilience and superior ability to withstand static indentation load without damage. In this paper, the static load capacity of hardened 60NiTi 50mm bore ball-bearing races are measured to correlate existing flat-plate indentation load capacity data to an actual bearing geometry through the Hertz stress relations. The results confirmed the validity of using the Hertz stress relations to model 60NiTi contacts; 60NiTi exhibits a static stress capability (3.1GPa) between that of 440C (2.4GPa) and REX20 (3.8GPa) tool steel. When the reduced modulus and extended strain capability are taken into account, 60NiTi is shown to withstand higher loads than other bearing materials. To quantify this effect, a notional space mechanism, a 5kg mass reaction wheel, was modeled with respect to launch load capability when supported on 440C, 60NiTi and REX20 tool steel bearings. For this application, the use of REX20 bearings increased the static load capability of the mechanism by a factor of three while the use of 60NiTi bearings resulted in an order of magnitude improvement compared to the baseline 440C stainless steel bearings.

  11. Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis

    NASA Astrophysics Data System (ADS)

    Ohmi, Tatsuya; Mizuma, Kiminori; Matsuura, Kiyotaka; Iguchi, Manabu

    2008-02-01

    A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

  12. An intermetallic Au24Ag20 superatom nanocluster stabilized by labile ligands.

    PubMed

    Wang, Yu; Su, Haifeng; Xu, Chaofa; Li, Gang; Gell, Lars; Lin, Shuichao; Tang, Zichao; Häkkinen, Hannu; Zheng, Nanfeng

    2015-04-01

    An intermetallic nanocluster containing 44 metal atoms, Au24Ag20(2-SPy)4(PhC≡C)20Cl2, was successfully synthesized and structurally characterized by single-crystal analysis and density funtional theory computations. The 44 metal atoms in the cluster are arranged as a concentric three-shell Au12@Ag20@Au12 Keplerate structure having a high symmetry. For the first time, the co-presence of three different types of anionic ligands (i.e., phenylalkynyl, 2-pyridylthiolate, and chloride) was revealed on the surface of metal nanoclusters. Similar to thiolates, alkynyls bind linearly to surface Au atoms using their σ-bonds, leading to the formation of two types of surface staple units (PhC≡C-Au-L, L = PhC≡C(-) or 2-pyridylthiolate) on the cluster. The co-presence of three different surface ligands allows the site-specific surface and functional modification of the cluster. The lability of PhC≡C(-) ligands on the cluster was demonstrated, making it possible to keep the metal core intact while removing partial surface capping. Moreover, it was found that ligand exchange on the cluster occurs easily to offer various derivatives with the same metal core but different surface functionality and thus different solubility. PMID:25803406

  13. Synthesis, Structure and bonding Analysis of the Polar Intermetallic Phase Ca2Pt2Cd

    SciTech Connect

    Samal, Saroj L.; Corbett, John D.

    2012-08-14

    The polar intermetallic phase Ca2Pt2Cd was discovered during explorations of the Ca-Pt-Cd system. The compound was synthesized by high temperature reactions, and its structure refined by single-crystal X-ray diffraction as orthorhombic, Immm, a = 4.4514(5), b = 5.8415(6), c = 8.5976(9) Å, Z = 2. The structure formally contains infinite, planar networks of [Pt2Cd]4– along the ab plane, which can be described as tessellation of six and four-member rings of the anions, with cations stuffed between the anion layers. The infinite condensed platinum chains show a substantial long–short distortion of 0.52 Å, an appreciable difference between Ca2Pt2Cd (26 valence electrons) and the isotypic but regular Ca2Cu2Ga (29 VE). The relatively large cation proportion diminishes the usual dominance of polar (Pt–Cd) and 5d–5d (Pt–Pt) contributions to the total Hamilton populations.

  14. A new approach to study vacancy defects in high-temperature intermetallic compounds

    SciTech Connect

    Collins, G.S.; Sinha, P.

    1995-08-01

    Perturbed angular correlations of gamma rays (PAC) is being applied to study defects in ordered intermetallic alloys. Vacancies on both Pd and In sublattices in the B2 system PdIn were detected after quenching through quadrupole interactions induced at nearby {sup 111}In probe atoms. Fractions of probe atoms having each type of neighboring defect were observed to increase monotonically with quenching temperature over the range 825--1,500 K. For compositions close to 50.15 at.% Pd, nearly equal site fractions were observed for Pd and In vacancies, indicating that the Schottky vacancy-pair defect is the thermal defect at high temperature. The formation enthalpy of the Schottky defect was determined to be 1.3(2) eV through analysis of quenching data from in the range 825--1,200 K. Above 1200 K, however, the vacancy concentration was observed to saturate at a value of 1.4(2) atomic percent, perhaps due to breakdown of the law of mass action for high defect concentrations.

  15. Atomic disorder induced by mechanical milling in the intermetallic compound CoAl

    NASA Astrophysics Data System (ADS)

    Di, L. M.; Bakker, H.; de Boer, F. R.

    1992-10-01

    The stoichiometric intermetallic compound CoAl with the CsCl-structure was subjected to ball milling. Structural changes during ball milling were studied by measurements of the magnetization and the lattice parameter. The behaviour of Coal upon milling turns out to be quite similar to that of CoGa. The increase of the magnetization and the decrease of the lattice parameter with the milling time show that, similar to CoGa, triple-defect disorder is generated by ball milling. By comparing the measured magnetization to the magnetization of Co xAl 100- x compounds with excess Co, the concentration of defects is derived for milled samples. In order to interpret our results, the existing experimental data of lattice parameters, X-ray densities calculated from the lattice parameters and macroscopic densities for Co xAl 100- x compounds were analyzed according to Edelin's equations. The defect volumes for vacancies and anti-site atoms obtained by fitting these experimental data have reasonable values. By means of the defect concentrations obtained from our magnetization measurements and the defect volumes by fitting the experimental data, the change of the lattice parameter was calculated by means of Edelin's equation. The agreement between the calculated lattice parameter and the measured lattice parameter is quite satisfactory.

  16. Growth kinetics of Al–Fe intermetallic compounds during annealing treatment of friction stir lap welds

    SciTech Connect

    Movahedi, M.; Kokabi, A.H.; Seyed Reihani, S.M.; Najafi, H.; Farzadfar, S.A.; Cheng, W.J.; Wang, C.J.

    2014-04-01

    In this study, we explored the growth kinetics of the Al–Fe intermetallic (IM) layer at the joint interface of the St-12/Al-5083 friction stir lap welds during post-weld annealing treatment at 350, 400 and 450 °C for 30 to 180 min. Optical microscope (OM), field emission gun scanning electron microscope (FEG-SEM) and transmission electron microscope (TEM) were employed to investigate the structure of the weld zone. The thickness and composition of the IM layers were evaluated using image analysis system and electron back-scatter diffraction (EBSD), respectively. Moreover, kernel average misorientation (KAM) analysis was performed to evaluate the level of stored energy in the as-welded state. The results showed that the growth kinetics of the IM layer was not governed by a parabolic diffusion law. Presence of the IM compounds as well as high stored energy near the joint interface of the as-welded sample was recognized to be the origin of the observed deviation from the parabolic diffusion law. - Highlights: • This work provided a new insight into growth kinetics of Al–Fe IM thickness. • The growth kinetics of IM layer was not governed by a parabolic diffusion law. • IM near the joint interface was the origin of deviation from the parabolic law. • High stored energy at joint interface was origin of deviation from parabolic law.

  17. Disturbing the dimers: Electron and hole doping in the intermetallic insulator FeGa3

    NASA Astrophysics Data System (ADS)

    Botana, Antia S.; Quan, Yundi; Pickett, Warren E.

    2015-10-01

    Insulating FeGa3 poses peculiar puzzles beyond the occurrence of an electronic gap in an intermetallic compound. This Fe-based material has a very distinctive structural characteristic with the Fe atoms occurring in dimers. The insulating gap can be described comparably well in either the weakly correlated limit or the strongly correlated limit within density functional theory viewpoints, where the latter corresponds to singlet formation on the Fe2 dimers. Though most of the calculated occupied Wannier functions are an admixture of Fe 3 d and Ga 4 s or 4 p states, there is a single bonding-type Wannier function per spin centered on each Fe2 dimer. Density functional theory methods have been applied to follow the evolution of the magnetic properties and electronic spectrum with doping, where unusual behavior is observed experimentally. Both electron and hole doping are considered, by Ge and Zn on the Ga site, and by Co and Mn on the Fe site, the latter introducing direct disturbance of the Fe2 dimer. Results from weakly and strongly correlated pictures are compared. Regardless of the method, magnetism including itinerant phases appears readily with doping. The correlated picture suggests that in the low doping limit Mn (for Fe) produces an in-gap hole state, while Co (for Fe) introduces a localized electronic gap state.

  18. Theoretical and positron annihilation study of point defects in intermetallic compound Ni{sub 3}Al

    SciTech Connect

    Jian Sun; Dongliang Lin

    1994-01-01

    The equilibrium equation of point defects in Ll{sub 2} types of intermetallic compounds was established in a new simple method, which is independent of the chemical potentials. The formation energies of the relevant point defects in Ni{sub 3}Al were calculated by EAM potentials and statical relaxations. The concentration of point defects at 1,000 K as a function of bulk composition and the effect of temperature on them were studied for Ni{sub 3}Al alloy. The results show that the Al-antisites are the constitutional defects in hypostoichiometric Ni{sub 3}Al, and the Ni-antisite defects in hyperstoichiometric Ni{sub 3}Al. The two types of vacancies belong to thermal defects. The positron annihilation technique was also conducted to measure the concentration of vacancies in Ni{sub 3}Al alloys with and without boron. Although vacancies interact with the boron dopant, the changes of vacancy concentration Ni{sub 3}Al alloys can not be considered as the main reason in explaining the effect of stoichiometry on the segregation of boron. The effect of stoichiometry on diffusion in Ni{sub 3}Al alloys was discussed additionally.

  19. Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis

    SciTech Connect

    Ohmi, Tatsuya; Matsuura, Kiyotaka; Iguchi, Manabu; Mizuma, Kiminori

    2008-02-15

    A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

  20. In situ HVEM investigation of catastrophic swelling in uranium intermetallic fuels

    SciTech Connect

    Birtcher, R.C.; Allen, C.W.; Hofman, G.L.; Rehn, L.E.

    1988-02-01

    The swelling of intermetallic materials depends upon the crystalline or amorphous state of the material. When U/sub 3/Si is irradiated at temperatures above its amorphization limit, it remains crystalline and does not suffer extraordinary swelling. However, when it is irradiated at temperatures below its amorphization limit, body forces associated with the irradiation cause any internal free volume to suffer a rapid growth, and the material swells at an anomalously fast rate. As has been previously noted, fission-gas bubbles are not directly responsible for this swelling; however, once formed, the bubble volume, as any interior volume, may increase rapidly. An unusual and important result is that once U/sub 3/Si has been irradiated to a high fluence, (above 2 /times/ 10/sup 20/ Kr m/sup /minus/2/), the irradiation behavior appropriate for the initial irradiation temperature is locked in, at least temporarily, and that behavior persists even at irradiation temperatures that normally result in the opposite behavior. For example, after a 620/degree/K irradiation, the crystalline state is retained during subsequent irradiation at 420/degree/K to more than ten times the fluence required to amorphize unirradiated material at 420/degree/K. 19 refs., 3 figs.