Binary Colloidal Alloy Test-3 and 4: Critical Point

NASA Technical Reports Server (NTRS)

Weitz, David A.; Lu, Peter J.

2007-01-01

Binary Colloidal Alloy Test - 3 and 4: Critical Point (BCAT-3-4-CP) will determine phase separation rates and add needed points to the phase diagram of a model critical fluid system. Crewmembers photograph samples of polymer and colloidal particles (tiny nanoscale spheres suspended in liquid) that model liquid/gas phase changes. Results will help scientists develop fundamental physics concepts previously cloaked by the effects of gravity.

Self-assembly of metal nanostructures on binary alloy surfaces

PubMed Central

Duguet, T.; Han, Yong; Yuen, Chad; Jing, Dapeng; Ünal, Barış; Evans, J. W.; Thiel, P. A.

2011-01-01

Deposition of metals on binary alloy surfaces offers new possibilities for guiding the formation of functional metal nanostructures. This idea is explored with scanning tunneling microscopy studies and atomistic-level analysis and modeling of nonequilibrium island formation. For Au/NiAl(110), complex monolayer structures are found and compared with the simple fcc(110) bilayer structure recently observed for Ag/NiAl(110). We also consider a more complex codeposition system, (Ni + Al)/NiAl(110), which offers the opportunity for fundamental studies of self-growth of alloys including deviations for equilibrium ordering. A general multisite lattice-gas model framework enables analysis of structure selection and morphological evolution in these systems. PMID:21097706

Surface Segregation in Multicomponent Systems: Modeling of Surface Alloys and Alloy Surfaces

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John; Noebe, Ronald D.; Good, Brian; Honecy, Frank S.; Abel, Phillip

1999-01-01

The study of surface segregation, although of great technological importance, has been largely restricted to experimental work due to limitations associated with theoretical methods. However, recent improvements in both first-particle and semi-empirical methods are opening, the doors to an array of new possibilities for surface scientists. We apply one of these techniques, the Bozzolo, Ferrante and Smith (BFS) method for alloys, which is particularly suitable for complex systems, to several aspects of the computational modeling of surfaces and segregation, including alloy surface segregation, structure and composition of alloy surfaces, and the formation of surface alloys. We conclude with the study of complex NiAl-based binary, ternary and quaternary thin films (with Ti, Cr and Cu additions to NiAl). Differences and similarities between bulk and surface compositions are discussed, illustrated by the results of Monte Carlo simulations. For some binary and ternary cases, the theoretical predictions are compared to experimental results, highlighting the accuracy and value of this developing theoretical tool.

Development of binary and ternary titanium alloys for dental implants.

PubMed

Cordeiro, Jairo M; Beline, Thamara; Ribeiro, Ana Lúcia R; Rangel, Elidiane C; da Cruz, Nilson C; Landers, Richard; Faverani, Leonardo P; Vaz, Luís Geraldo; Fais, Laiza M G; Vicente, Fabio B; Grandini, Carlos R; Mathew, Mathew T; Sukotjo, Cortino; Barão, Valentim A R

2017-11-01

The aim of this study was to develop binary and ternary titanium (Ti) alloys containing zirconium (Zr) and niobium (Nb) and to characterize them in terms of microstructural, mechanical, chemical, electrochemical, and biological properties. The experimental alloys - (in wt%) Ti-5Zr, Ti-10Zr, Ti-35Nb-5Zr, and Ti-35Nb-10Zr - were fabricated from pure metals. Commercially pure titanium (cpTi) and Ti-6Al-4V were used as controls. Microstructural analysis was performed by means of X-ray diffraction and scanning electron microscopy. Vickers microhardness, elastic modulus, dispersive energy spectroscopy, X-ray excited photoelectron spectroscopy, atomic force microscopy, surface roughness, and surface free energy were evaluated. The electrochemical behavior analysis was conducted in a body fluid solution (pH 7.4). The albumin adsorption was measured by the bicinchoninic acid method. Data were evaluated through one-way ANOVA and the Tukey test (α=0.05). The alloying elements proved to modify the alloy microstructure and to enhance the mechanical properties, improving the hardness and decreasing the elastic modulus of the binary and ternary alloys, respectively. Ti-Zr alloys displayed greater electrochemical stability relative to that of controls, presenting higher polarization resistance and lower capacitance. The experimental alloys were not detrimental to albumin adsorption. The experimental alloys are suitable options for dental implant manufacturing, particularly the binary system, which showed a better combination of mechanical and electrochemical properties without the presence of toxic elements. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

First-principles study of intermetallic phase stability in the ternary Ti-Al-Nb alloy system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asta, M.; Ormeci, A.; Wills, J.M.

The stability of bcc-based phases in the Ti-Al-Nb alloy system has been studied from first-principles using a combination of ab-initio total energy and cluster variation method (CVM) calculations. Total energies have been computed for 18 binary and ternary bcc superstructures in order to determine low temperature ordering tendencies. From the results of these calculations a set of effective cluster interaction parameters have been derived. These interaction parameters are required input for CVM computations of alloy thermodynamic properties. The CVM has been used to study the effect of composition on finite-temperature ordering tendencies and site preferences for bcc-based phases. Strong orderingmore » tendencies are observed for binary Nb-Al and Ti-Al bcc phases as well as for ternary alloys with compositions near Ti{sub 2}AlNb. For selected superstructures we have also analyzed structural stabilities with respect to tetragonal distortions which transform the bcc into an fcc lattice. Instabilities with respect to such distortions are found to exist for binary but not ternary bcc compounds.« less

Fine structure of Fe-Co-Ga and Fe-Cr-Ga alloys with low Ga content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleinerman, Nadezhda M., E-mail: kleinerman@imp.uran.ru; Serikov, Vadim V., E-mail: kleinerman@imp.uran.ru; Vershinin, Aleksandr V., E-mail: kleinerman@imp.uran.ru

2014-10-27

Investigation of Ga influence on the structure of Fe-Cr and Fe-Co alloys was performed with the use of {sup 57}Fe Mössbauer spectroscopy and X-ray diffraction methods. In the alloys of the Fe-Cr system, doping with Ga handicaps the decomposition of solid solutions, observed in the binary alloys, and increases its stability. In the alloys with Co, Ga also favors the uniformity of solid solutions. The analysis of Mössbauer experiments gives some grounds to conclude that if, owing to liquation, clusterization, or initial stages of phase separation, there exist regions enriched in iron, some amount of Ga atoms prefer to entermore » the nearest surroundings of iron atoms, thus forming binary Fe-Ga regions (or phases)« less

Casting Characteristics of High Cerium Content Aluminum Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weiss, D; Rios, O R; Sims, Z C

This paper compares the castability of the near eutectic aluminum-cerium alloy system to the aluminum-silicon and aluminum-copper systems. The alloys are compared based on die filling capability, feeding characteristics and tendency to hot tear in both sand cast and permanent mold applications. The castability ranking of the binary Al–Ce systems is as good as the aluminum-silicon system with some deterioration as additional alloying elements are added. In alloy systems that use cerium in combination with common aluminum alloying elements such as silicon, magnesium and/or copper, the casting characteristics are generally better than the aluminum-copper system. In general, production systems formore » melting, de-gassing and other processing of aluminum-silicon or aluminum-copper alloys can be used without modification for conventional casting of aluminum-cerium alloys.« less

Hardness behavior of binary and ternary niobium alloys at 77 and 300 K

NASA Technical Reports Server (NTRS)

Stephens, J. R.; Witzke, W. R.

1974-01-01

The effects of alloy additions of zirconium, hafnium, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, and iridium on the hardness of niobium was determined. Both binary and ternary alloys were investigated by means of hardness tests at 77 K and 300 K. Results showed that atomic size misfit plays a dominant role in controlling hardness of binary niobium alloys. Alloy softening, which occurred at dilute solute additions, is most likely due to an extrinsic mechanism involving interaction between solute elements and interstitial impurities.

Multinary alloy electrodes for solid state batteries I. A phase diagram approach for the selection and storage properties determination of candidate electrode materials

NASA Astrophysics Data System (ADS)

Anani, A.; Huggins, R. A.

The desire to produce high specific energy rechargeable batteries has led to the investigation of ternary alloy systems for use as negative electrode components in lithium-based cells. The addition of a third component to a binary alloy electrode could result in a significant change in the thermodynamic and/or kinetic behavior of the electrode material, depending on the relevant phase diagram and the crystal structures of the phases present. The influence of ternary phase diagram characteristics upon the thermodynamic properties and specific energies of multi-component electrodes is discussed with lithiumsilicon-based systems as an illustration. It is shown that the electrode potentials (and thus specific energies of the ensuing cell) as well as the theoretical lithium capacities of electrodes based on these ternary alloy modifications can be significantly increased with respect to their present day binary counterpart.

First-principles study on the thermal expansion of Ni-X binary alloys based on the quasi-harmonic Debye model

NASA Astrophysics Data System (ADS)

Shin, Yongjin; Jung, Woo-Sang; Lee, Young-Su

2016-11-01

In this study, we use the quasi-harmonic Debye model to predict the coefficient of thermal expansion of Ni- X binary alloys. The method bridges between the macroscopic elastic behavior and thermodynamic properties of materials without an expensive calculation of the volume dependence of the phonon density of states. Furthermore, the Grüneisen parameter is derived from the volume dependence of the Debye temperature, which is calculated from the first-principles elastic stiffness constants. The experimental coefficient of thermal expansion (CTE) of pure nickel is well reproduced, especially in the low temperature region. Among the few alloying elements tested, Al is predicted to slightly decrease the CTE whereas Mo and W are more effective in reducing the CTE. For the cases of Ni-X binary alloy systems, where the variation in the CTE is relatively small, the method used here appears to perform better than certain other formulations that rely entirely on the energy vs. volume relationship.

Phase-field crystal modeling of compositional domain formation in ultrathin films.

PubMed

Muralidharan, Srevatsan; Haataja, Mikko

2010-09-17

Bulk-immiscible binary systems often form stress-induced miscible alloy phases when deposited on a substrate. Both alloying and surface dislocation formation lead to the decrease of the elastic strain energy, and the competition between these two strain-relaxation mechanisms gives rise to the emergence of pseudomorphic compositional nanoscale domains, often coexisting with a partially coherent single phase. In this work, we develop a phase-field crystal model for compositional patterning in monolayer aggregates of binary metallic systems. We first demonstrate that the model naturally incorporates the competition between alloying and misfit dislocations, and quantify the effects of misfit and line tension on equilibrium domain size. Then, we quantitatively relate the parameters of the phase-field crystal model to a specific system, CoAg/Ru(0001), and demonstrate that the simulations capture experimentally observed morphologies.

Numerical model for dendritic solidification of binary alloys

NASA Technical Reports Server (NTRS)

Felicelli, S. D.; Heinrich, J. C.; Poirier, D. R.

1993-01-01

A finite element model capable of simulating solidification of binary alloys and the formation of freckles is presented. It uses a single system of equations to deal with the all-liquid region, the dendritic region, and the all-solid region. The dendritic region is treated as an anisotropic porous medium. The algorithm uses the bilinear isoparametric element, with a penalty function approximation and a Petrov-Galerkin formulation. Numerical simulations are shown in which an NH4Cl-H2O mixture and a Pb-Sn alloy melt are cooled. The solidification process is followed in time. Instabilities in the process can be clearly observed and the final compositions obtained.

Effects of chemical alternation on damage accumulation in concentrated solid-solution alloys

DOE PAGES

Ullah, Mohammad W.; Xue, Haizhou; Velisa, Gihan; ...

2017-06-23

Single-phase concentrated solid-solution alloys (SP-CSAs) have recently gained unprecedented attention due to their promising properties. To understand effects of alloying elements on irradiation-induced defect production, recombination and evolution, an integrated study of ion irradiation, ion beam analysis and atomistic simulations are carried out on a unique set of model crystals with increasing chemical complexity, from pure Ni to Ni 80Fe 20, Ni 50Fe 50, and Ni 80Cr 20 binaries, and to a more complex Ni 40Fe 40Cr 20 alloy. Both experimental and simulation results suggest that the binary and ternary alloys exhibit higher radiation resistance than elemental Ni. The modelingmore » work predicts that Ni 40Fe 40Cr 20 has the best radiation tolerance, with the number of surviving Frenkel pairs being factors of 2.0 and 1.4 lower than pure Ni and the 80:20 binary alloys, respectively. While the reduced defect mobility in SP-CSAs is identified as a general mechanism leading to slower growth of large defect clusters, the effect of specific alloying elements on suppression of damage accumulation is clearly demonstrated. This work suggests that concentrated solid-solution provides an effective way to enhance radiation tolerance by creating elemental alternation at the atomic level. The demonstrated chemical effects on defect dynamics may inspire new design principles of radiation-tolerant structural alloys for advanced energy systems.« less

Binary titanium alloys as dental implant materials-a review.

PubMed

Liu, Xiaotian; Chen, Shuyang; Tsoi, James K H; Matinlinna, Jukka Pekka

2017-10-01

Titanium (Ti) has been used for long in dentistry and medicine for implant purpose. During the years, not only the commercially pure Ti but also some alloys such as binary and tertiary Ti alloys were used. The aim of this review is to describe and compare the current literature on binary Ti alloys, including Ti-Zr, Ti-In, Ti-Ag, Ti-Cu, Ti-Au, Ti-Pd, Ti-Nb, Ti-Mn, Ti-Mo, Ti-Cr, Ti-Co, Ti-Sn, Ti-Ge and Ti-Ga, in particular to mechanical, chemical and biological parameters related to implant application. Literature was searched using the PubMed and Web of Science databases, as well as google without limiting the year, but with principle key terms such as ' Ti alloy', 'binary Ti ', 'Ti-X' (with X is the alloy element), 'dental implant' and 'medical implant'. Only laboratory studies that intentionally for implant or biomedical applications were included. According to available literatures, we might conclude that most of the binary Ti alloys with alloying <20% elements of Zr, In, Ag, Cu, Au, Pd, Nb, Mn, Cr, Mo, Sn and Co have high potential as implant materials, due to good mechanical performance without compromising the biocompatibility and biological behaviour compare to cp-Ti.

Effect of Ag Addition on the Electrochemical Performance of Cu10Al in Artificial Saliva

PubMed Central

Salgado-Salgado, R. J.; Sotelo-Mazon, O.; Rodriguez-Diaz, R. A.; Salinas-Solano, G.

2016-01-01

In this work we proposed to evaluate the corrosion resistance of four different alloys by electrochemical techniques, a binary alloy Cu10Al, and three ternary alloys Cu10Al-xAg (x = 5, 10, and 15 wt.%) to be used like biomaterials in dental application. Biomaterials proposed were tested in artificial saliva at 37°C for 48 h. In addition, pure metals Cu, Al, Ag, and Ti as reference materials were evaluated. In general the short time tests indicated that the Ag addition increases the corrosion resistance and reduces the extent of localized attack of the binary alloy. Moreover, tests for 48 hours showed that the Ag addition increases the stability of the passive layer, thereby reducing the corrosion rate of the binary alloy. SEM analysis showed that Cu10Al alloy was preferably corroded by grain boundaries, and the Ag addition modified the form of attack of the binary alloy. Cu-rich phases reacted with SCN− anions forming a film of CuSCN, and the Ag-rich phase is prone to react with SCN− anions forming AgSCN. Thus, binary and ternary alloys are susceptible to tarnish in the presence of thiocyanate ions. PMID:27660601

Friction and wear of iron-base binary alloys in sliding contact with silicon carbide in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Multipass sliding friction experiments were conducted with various iron base binary alloys in contact with a single crystal silicon carbide surface in vacuum. Results indicate that the atomic size and concentration of alloy elements play important roles in controlling the transfer and friction properties of iron base binary alloys. Alloys having high solute concentration produce more transfer than do alloys having low solute concentration. The coefficient of friction during multipass sliding generally increases with an increase in the concentration of alloying element. The change of friction with succeeding passes after the initial pass also increases as the solute to iron, atomic radius ratio increases or decreases from unity.

Nonergodicity in binary alloys

NASA Astrophysics Data System (ADS)

Son, Leonid; Sidorov, Valery; Popel, Pjotr; Shulgin, Dmitry

2015-09-01

For binary liquids with limited miscibility of the components, we provide the corrections to the equation of state which arise from the nonergogic diffusivity. It is shown that these corrections result in lowering of critical miscibility point. In some cases, it may result in a bifurcation of miscibility curve: the mixtures near 50% concentration which are homogeneous at the microscopic level, occur to be too stable to provide a quasi - eutectic triple point. These features provide a new look on the phase diagrams of some binary systems. In present work, we discuss Ga-Pb, Fe-Cu, and Cu-Zr alloys. Our investigation corresponds their complex behavior in liquid state to the shapes of their phase diagrams.

Concentration dependence of electrical resistivity of binary liquid alloy HgZn: Ab-initio study

NASA Astrophysics Data System (ADS)

Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

2013-06-01

The electrical resistivity of HgZn liquid alloy has been made calculated using Troullier and Martins ab-initio pseudopotential as a function of concentration. Hard sphere diameters of Hg and Zn are obtained through the inter-ionic pair potential have been used to calculate partial structure factors. Considering the liquid alloy to be a ternary mixture Ziman's formula for calculating the resistivity of binary liquid alloys, modified for complex formation, has been used. These results suggest that ab-initio approach for calculating electrical resistivity is quite successful in explaining the electronic transport properties of binary Liquid alloys.

[Study on high temperature oxidation of Ni-Cr ceramic alloys. Effects of Cr and Mo].

PubMed

Mizutani, M

1990-03-01

The effects of Cr and Mo addition to Ni-Cr alloys on high temperature oxidation were investigated. The alloys were prepared with the composition of Cr ranging from 5 to 40 wt%. Also 2, 4 and 9 wt% of Mo was added to both Ni-5% Cr and Ni-20% Cr binary alloys. The alloys were heated at 800 degrees C, 900 degrees C and 1000 degrees C for 15 minutes in air, and the weight change after heat treatment was measured by electric automatic balance. The weight change during heating was measured by thermogravimetric measurement (TG). The products after heat treatment were characterized by X-ray diffraction and scanning electron microscopy (SEM). The results are summarized as follows: The Ni-Cr binary alloys were classified into three types of Cr ranging from 5 to 20 wt%, Cr 25% and Cr from 30 wt% to 40 wt% according to the weight gains with oxidation. In the case of the more than 25 wt% Cr content of the Ni-Cr binary alloys, the weight gain was extremely low and the heating temperature effects on the weight change were also small. X-ray diffraction study showed that NiO, NiCr2O4 and Cr2O3 formed on the surface of the Ni-Cr binary alloys whose composition of Cr ranged from 5 to 25 wt%, whereas NiO and NiCr2O4 rarely formed on the Ni-Cr binary alloys whose composition of Cr ranged from 30 to 40 wt%. This suggests that the formation of Cr2O3 prevents the formation of NiO on the alloy with a high Cr content. The weight gain of the Ni-Cr-Mo ternary alloys was smaller than that of the Ni-Cr binary alloys without Mo, and the temperature effects on the weight gain of the Ni-Cr-Mo ternary alloys were different for each Cr content. However, the effect of the amounts of Mo was small. NiO, NiCr2O4, Cr2O3 and MoO2 were identified by X-ray diffraction on the surface of the Ni-Cr-Mo ternary alloys. According to the SEM observation, it seems that NiO was formed at the outermost layer, both NiCr2O4 and Cr2O3 at the inside layer, and MoO2 at the innermost layer. The formation of both NiO and Cr2O3 on the Ni-Cr-Mo ternary alloys was restrained compared with that of the Ni-Cr binary alloys. However, the adhesion of oxides to the Ni-Cr-Mo ternary alloys was lower than that of the Ni-Cr binary alloys.

Formation of an amorphous phase and its crystallization in the immiscible Nb-Zr system by mechanical alloying

NASA Astrophysics Data System (ADS)

Al-Aqeeli, N.; Suryanarayana, C.; Hussein, M. A.

2013-10-01

Mechanical alloying of binary Nb-Zr powder mixtures was carried out to evaluate the formation of metastable phases in this immiscible system. The milled powders were characterized for their constitution and structure by X-ray diffraction and transmission electron microscopy methods. It was shown that an amorphous phase had formed on milling the binary powder mixture for about 10 h and that it had crystallized on subsequent milling up to 50-70 h, referred to as mechanical crystallization. Thermodynamic and structural arguments have been presented to explain the formation of the amorphous phase and its subsequent crystallization.

Ab initio atomistic thermodynamics study on the oxidation mechanism of binary and ternary alloy surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Shi-Yu, E-mail: buaasyliu@gmail.com; Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong; Liu, Shiyang

Utilizing a combination of ab initio density-functional theory and thermodynamics formalism, we have established the microscopic mechanisms for oxidation of the binary and ternary alloy surfaces and provided a clear explanation for the experimental results of the oxidation. We construct three-dimensional surface phase diagrams (SPDs) for oxygen adsorption on three different Nb-X(110) (X = Ti, Al or Si) binary alloy surfaces. On the basis of the obtained SPDs, we conclude a general microscopic mechanism for the thermodynamic oxidation, that is, under O-rich conditions, a uniform single-phase SPD (type I) and a nonuniform double-phase SPD (type II) correspond to the sustainedmore » complete selective oxidation and the non-sustained partial selective oxidation by adding the X element, respectively. Furthermore, by revealing the framework of thermodynamics for the oxidation mechanism of ternary alloys through the comparison of the surface energies of two separated binary alloys, we provide an understanding for the selective oxidation behavior of the Nb ternary alloy surfaces. Using these general microscopic mechanisms, one could predict the oxidation behavior of any binary and multi-component alloy surfaces based on thermodynamics considerations.« less

Short-Range-Order for fcc-based Binary Alloys Revisited from Microscopic Geometry

NASA Astrophysics Data System (ADS)

Yuge, Koretaka

2018-04-01

Short-range order (SRO) in disordered alloys is typically interpreted as competition between chemical effect of negative (or positive) energy gain by mixing constituent elements and geometric effects comes from difference in effective atomic radius. Although we have a number of theoretical approaches to quantitatively estimate SRO at given temperatures, it is still unclear to systematically understand trends in SRO for binary alloys in terms of geometric character, e.g., effective atomic radius for constituents. Since chemical effect plays significant role on SRO, it has been believed that purely geometric character cannot capture the SRO trends. Despite these considerations, based on the density functional theory (DFT) calculations on fcc-based 28 equiatomic binary alloys, we find that while conventional Goldschmidt or DFT-based atomic radius for constituents have no significant correlation with SRO, atomic radius for specially selected structure, constructed purely from information about underlying lattice, can successfully capture the magnitude of SRO. These facts strongly indicate that purely geometric information of the system plays central role to determine characteristic disordered structure.

Correction factors for on-line microprobe analysis of multielement alloy systems

NASA Technical Reports Server (NTRS)

Unnam, J.; Tenney, D. R.; Brewer, W. D.

1977-01-01

An on-line correction technique was developed for the conversion of electron probe X-ray intensities into concentrations of emitting elements. This technique consisted of off-line calculation and representation of binary interaction data which were read into an on-line minicomputer to calculate variable correction coefficients. These coefficients were used to correct the X-ray data without significantly increasing computer core requirements. The binary interaction data were obtained by running Colby's MAGIC 4 program in the reverse mode. The data for each binary interaction were represented by polynomial coefficients obtained by least-squares fitting a third-order polynomial. Polynomial coefficients were generated for most of the common binary interactions at different accelerating potentials and are included. Results are presented for the analyses of several alloy standards to demonstrate the applicability of this correction procedure.

First-principles prediction of stabilities and instabilities of compounds and alloys in the ternary B-As-P system

NASA Astrophysics Data System (ADS)

Ektarawong, A.; Simak, S. I.; Alling, B.

2017-07-01

We examine the thermodynamic stability of compounds and alloys in the ternary B-As-P system theoretically using first-principles calculations. We demonstrate that the icosahedral B12As2 is the only stable compound in the binary B-As system, while the zinc-blende BAs is thermodynamically unstable with respect to B12As2 and the pure arsenic phase at 0 K, and increasingly so at higher temperature, suggesting that BAs may merely exist as a metastable phase. On the contrary, in the binary B-P system, both zinc-blende BP and icosahedral B12P2 are predicted to be stable. As for the binary As-P system, As1 -xPx disordered alloys are predicted at elevated temperature—for example, a disordered solid solution of up to ˜75 at.% As in black phosphorus as well as a small solubility of ˜1 at.% P in gray arsenic at T =750 K, together with the presence of miscibility gaps. The calculated large solubility of As in black phosphorus explains the experimental syntheses of black-phosphorus-type As1 -xPx alloys with tunable compositions, recently reported in the literature. We investigate the phase stabilities in the ternary B-As-P system and demonstrate a high tendency for a formation of alloys in the icosahedral B12(As1 -xPx )2 structure by intermixing of As and P atoms at the diatomic chain sites. The phase diagram displays noticeable mutual solubility of the icosahedral subpnictides in each other even at room temperature as well as a closure of a pseudobinary miscibility gap around 900 K. As for pseudobinary BAs1 -xPx alloys, only a tiny amount of BAs is predicted to be able to dissolve in BP to form the BAs1 -xPx disordered alloys at elevated temperature. For example, less than 5% of BAs can dissolve in BP at T =1000 K. The small solubility limit of BAs in BP is attributed to the thermodynamic instability of BAs with respect to B12As2 and As.

How can we make stable linear monoatomic chains? Gold-cesium binary subnanowires as an example of a charge-transfer-driven approach to alloying.

PubMed

Choi, Young Cheol; Lee, Han Myoung; Kim, Woo Youn; Kwon, S K; Nautiyal, Tashi; Cheng, Da-Yong; Vishwanathan, K; Kim, Kwang S

2007-02-16

On the basis of first-principles calculations of clusters and one dimensional infinitely long subnanowires of the binary systems, we find that alkali-noble metal alloy wires show better linearity and stability than either pure alkali metal or noble metal wires. The enhanced alternating charge buildup on atoms by charge transfer helps the atoms line up straight. The cesium doped gold wires showing significant charge transfer from cesium to gold can be stabilized as linear or circular monoatomic chains.

Structural difference rule for amorphous alloy formation by ion mixing

NASA Technical Reports Server (NTRS)

Liu, B.-X.; Johnson, W. L.; Nicolet, M.A.; Lau, S. S.

1983-01-01

A rule is formulated which establishes a sufficient condition that an amorphous binary alloy will be formed by ion mixing of multilayered samples when the two constituent metals are of different crystalline structure, regardless of their atomic sizes and electronegativities. The rule is supported by the experimental results obtained on six selected binary metal systems, as well as by the previous data reported in the literature. The amorphization mechanism is discussed in terms of the competition between two different structures resulting in frustration of the crystallization process.

Atomistic modeling of grain boundary behavior under shear conditions in magnesium and magnesium-based binary alloys

NASA Astrophysics Data System (ADS)

Nahhas, M. K.; Groh, S.

2018-02-01

In this study, the structure, the energetic, and the strength of a { 10 1 bar 1 } < 11 2 bar 0 > symmetric tilt grain boundary in magnesium and magnesium binary alloys were analyzed in the framework of (semi-)empirical potentials. Following a systematic investigation of the transferability and accuracy of the interatomic potentials, atomistic calculations of the grain boundary energy, the grain boundary sliding energy, and the grain boundary strength were performed in pure magnesium and in binary MgX alloys (X = Al, Ca, Gd, Li, Sn, Y, Ag, Nd, and Pb). The data gained in this study were analyzed to identify the most critical material parameters controlling the strength of the grain boundary, and their consequence on atomic shuffling motions occurring at the grain boundary. From the methodology perspective, the role of in-plane and out-of plane relaxation on the grain boundary sliding energy curves was investigated. In pure magnesium, the results showed that in-plane relaxation is critical in activating b2{ 10 1 bar 1 } twinning dislocation resulting in grain boundary migration. In the alloy systems, however, grain boundary migration was disabled as a consequence of the pinning of the grain boundary by segregated elements. Finally, while the grain boundary energy, the shape of the grain boundary sliding energy curves, and the grain boundary sliding energy are critical parameters controlling the grain boundary strength in pure magnesium, only the grain boundary energy and the segregation energy of the alloying elements at the grain boundary were identified as critical material parameters in the alloys system.

Effects of alloying elements (Mn, Co, Al, W, Sn, B, C and S) on biodegradability and in vitro biocompatibility of pure iron.

PubMed

Liu, B; Zheng, Y F

2011-03-01

Pure iron was determined to be a valid candidate material for biodegradable metallic stents in recent animal tests; however, a much faster degradation rate in physiological environments was desired. C, Mn, Si, P, S, B, Cr, Ni, Pb, Mo, Al, Ti, Cu, Co, V and W are common alloying elements in industrial steels, with Cr, Ni, Mo, Cu, Ti, V and Si being acknowledged as beneficial in enhancing the corrosion resistance of iron. The purpose of the present work (using Fe-X binary alloy models) is to explore the effect of the remaining alloying elements (Mn, Co, Al, W, B, C and S) and one detrimental impurity element Sn on the biodegradability and biocompatibility of pure iron by scanning electron microscopy, X-ray diffraction, metallographic observation, tensile testing, microhardness testing, electrochemical testing, static (for 6 months) and dynamic (for 1 month with various dissolved oxygen concentrations) immersion testing, cytotoxicity testing, hemolysis and platelet adhesion testing. The results showed that the addition of all alloying elements except for Sn improved the mechanical properties of iron after rolling. Localized corrosion of Fe-X binary alloys was observed in both static and dynamic immersion tests. Except for the Fe-Mn alloy, which showed a significant decrease in corrosion rate, the other Fe-X binary alloy corrosion rates were close to that of pure iron. It was found that compared with pure iron all Fe-X binary alloys decreased the viability of the L929 cell line, none of experimental alloying elements significantly reduced the viability of vascular smooth muscle cells and all the elements except for Mn increased the viability of the ECV304 cell line. The hemolysis percentage of all Fe-X binary alloy models were less than 5%, and no sign of thrombogenicity was observed. In vitro corrosion and the biological behavior of these Fe-X binary alloys are discussed and a corresponding mechanism of corrosion of Fe-X binary alloys in Hank's solution proposed. As a concluding remark, Co, W, C and S are recommended as alloying elements for biodegradable iron-based biomaterials. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Adhesion and friction of iron-base binary alloys in contact with silicon carbide in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Single pass sliding friction experiments were conducted with various iron base binary alloys (alloying elements were Ti, Cr, Mn, Ni, Rh, and W) in contact with a single crystal silicon carbide /0001/ surface in vacuum. Results indicate that atomic size and concentration of alloying elements play an important role in controlling adhesion and friction properties of iron base binary alloys. The coefficient of friction generally increases with an increase in solute concentration. The coefficient of friction increases linearly as the solute to iron atomic radius ratio increases or decreases from unity. The chemical activity of the alloying elements was also an important parameter in controlling adhesion and friction of alloys, as these latter properties are highly dependent upon the d bond character of the elements.

Alloy hardening and softening in binary molybdenum alloys as related to electron concentration

NASA Technical Reports Server (NTRS)

Stephens, J. R.; Witzke, W. R.

1972-01-01

An investigation was conducted to determine the effects of alloy additions of hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum on hardness of molybdenum. Special emphasis was placed on alloy softening in these binary molybdenum alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to molybdenum, while those elements having an equal number or fewer s+d electrons that molybdenum failed to produce alloy softening. Alloy softening and alloy hardening can be correlated with the difference in number of s+d electrons of the solute element and molybdenum.

Binary titanium alloys as dental implant materials—a review

PubMed Central

Liu, Xiaotian; Chen, Shuyang; Matinlinna, Jukka Pekka

2017-01-01

Abstract Titanium (Ti) has been used for long in dentistry and medicine for implant purpose. During the years, not only the commercially pure Ti but also some alloys such as binary and tertiary Ti alloys were used. The aim of this review is to describe and compare the current literature on binary Ti alloys, including Ti–Zr, Ti–In, Ti–Ag, Ti–Cu, Ti–Au, Ti–Pd, Ti–Nb, Ti–Mn, Ti–Mo, Ti–Cr, Ti–Co, Ti–Sn, Ti–Ge and Ti–Ga, in particular to mechanical, chemical and biological parameters related to implant application. Literature was searched using the PubMed and Web of Science databases, as well as google without limiting the year, but with principle key terms such as ‘ Ti alloy’, ‘binary Ti ’, ‘Ti-X’ (with X is the alloy element), ‘dental implant’ and ‘medical implant’. Only laboratory studies that intentionally for implant or biomedical applications were included. According to available literatures, we might conclude that most of the binary Ti alloys with alloying <20% elements of Zr, In, Ag, Cu, Au, Pd, Nb, Mn, Cr, Mo, Sn and Co have high potential as implant materials, due to good mechanical performance without compromising the biocompatibility and biological behaviour compare to cp-Ti. PMID:29026646

Effect of deformation twin on toughness in magnesium binary alloys

NASA Astrophysics Data System (ADS)

Somekawa, Hidetoshi; Inoue, Tadanobu; Tsuzaki, Kaneaki

2015-08-01

The impact of alloying elements on toughness was investigated using eight kinds of Mg-0.3 at.% X (X = Al, Ag, Ca, Gd, Mn, Pb, Y and Zn) binary alloys with meso-grained structures. These binary alloys had an average grain size of approximately 20 μm. The fracture toughness and crack propagation behaviour were influenced by the alloying elements; the Mg-Ag and Mg-Pb alloys had the highest and the lowest toughness amongst the alloys, respectively, irrespective of presence in their ? type deformation twins. The twin boundaries affected the crack propagation behaviour in most of the alloys; in contrast, not only was the fracture related to the twin boundaries, but also the intergranular fracture occurred in the alloys that included rare earth elements. The influential factor for toughness in the meso- and the coarse-grained magnesium alloys, which readily formed deformation twins during plastic deformation, was not the change in lattice parameter with chemical composition, but the twin boundary segregation energy.

Temperature dependent structural and dynamical properties of liquid Cu80Si20 binary alloy

NASA Astrophysics Data System (ADS)

Suthar, P. H.; Shah, A. K.; Gajjar, P. N.

2018-05-01

Ashcroft and Langreth binary structure factor have been used to study for pair correlation function and the study of dynamical variable: velocity auto correlation functions, power spectrum and mean square displacement calculated based on the static harmonic well approximation in liquid Cu80Si20 binary alloy at wide temperature range (1140K, 1175K, 1210K, 1250K, 1373K, 1473K.). The effective interaction for the binary alloy is computed by our well established local pseudopotential along with the exchange and correction functions Sarkar et al(S). The negative dip in velocity auto correlation decreases as the various temperature is increases. For power spectrum as temperature increases, the peak of power spectrum shifts toward lower ω. Good agreement with the experiment is observed for the pair correlation functions. Velocity auto correlation showing the transferability of the local pseudopotential used for metallic liquid environment in the case of copper based binary alloys.

Ternary phase equilibria in transition metal-boron-carbon-silicon systems. Part I. Related binary systems, Volume III. Systems Mo-B and W-B. Technical documentary report, 1 November 1964-1 June 1965

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rudy, E.; Windisch.

1965-07-01

On the basis of X-ray, melting point, metallographic, and differential thermoanalytical studies on molybdenum-boron and tungsten-boron alloys, constitution diagrams for both binary systems are presented. In the high temperature regions, the newly established phase diagrams differ significantly from previously reported systems. The results are discussed and compared with available literature data.

Phase Segregation Behavior of Two-Dimensional Transition Metal Dichalcogenide Binary Alloys Induced by Dissimilar Substitution

DOE PAGES

Susarla, Sandhya; Kochat, Vidya; Kutana, Alex; ...

2017-08-15

Transition metal dichalcogenide (TMD) alloys form a broad class of two-dimensional (2D) layered materials with tunable bandgaps leading to interesting optoelectronic applications. In the bottom-up approach of building these atomically thin materials, atomic doping plays a crucial role. Here we demonstrate a single step CVD (chemical vapor deposition) growth procedure for obtaining binary alloys and heterostructures by tuning atomic composition. We show that a minute doping of tin during the growth phase of the Mo 1–xW xS 2 alloy system leads to formation of lateral and vertical heterostructure growth. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) imagingmore » and density functional theory (DFT) calculations also support the modified stacking and growth mechanism due to the nonisomorphous Sn substitution. Our experiments demonstrate the possibility of growing heterostructures of TMD alloys whose spectral responses can be desirably tuned for various optoelectronic applications.« less

Equivalent crystal theory of alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John

1991-01-01

Equivalent Crystal Theory (ECT) is a new, semi-empirical approach to calculating the energetics of a solid with defects. The theory has successfully reproduced surface energies in metals and semiconductors. The theory of binary alloys to date, both with first-principles and semi-empirical models, has not been very successful in predicting the energetics of alloys. This procedure is used to predict the heats of formation, cohesive energy, and lattice parameter of binary alloys of Cu, Ni, Al, Ag, Au, Pd, and Pt as functions of composition. The procedure accurately reproduces the heats of formation versus composition curves for a variety of binary alloys. The results are then compared with other approaches such as the embedded atom and lattice parameters of alloys from pure metal properties more accurately than Vegard's law is presented.

Alloy softening in binary molybdenum alloys

NASA Technical Reports Server (NTRS)

Stephens, J. R.; Witzke, W. R.

1972-01-01

An investigation was conducted to determine the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to Mo, while those elements having an equal number or fewer s+d electrons than Mo failed to produce alloy softening. Alloy softening and hardening can be correlated with the difference in number of s+d electrons of the solute element and Mo.

Effect of Cu content on wear resistance and mechanical behavior of Ti-Cu binary alloys

NASA Astrophysics Data System (ADS)

Yu, Feifei; Wang, Hefeng; Yuan, Guozheng; Shu, Xuefeng

2017-04-01

Arc melting with nonconsumable tungsten electrode and water-cooled copper crucible was used to fabricate Ti-Cu binary alloys with different Cu contents in an argon atmosphere. The compositions and phase structures of the fabricated alloys were investigated by glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). Nanoindentation tests through continuous stiffness measurement were then performed at room temperature to analyze the mechanical behaviors of the alloys. Results indicated that the composition of each Ti-Cu binary alloy was Ti(100- x) Cu x ( x = 43, 60, 69, and 74 at.%). The XRD analysis results showed that the alloys were composed of different phases, indicating that different Cu contents led to the variations in alloy hardness. The wear tests results revealed that elemental Cu positively affects the wear resistance properties of the Ti-Cu alloys. Nanoindentation testing results showed that the moduli of the Ti-Cu alloys were minimally changed at increasing Cu content, whereas their hardness evidently increased according to the wear test results.

[delta] precipitation in an Al-Li-Cu-Mg-Zr alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prasad, K.S.; Mukhopadhyay, A.K.; Gokhale, A.A.

1994-05-15

AlLi based [delta] phase has an NaTl structure (i.e., a diamond cubic) with a = 0.637nm and is an equilibrium phase in the binary Al-Li system. In heat treated binary Al-Li alloys of appropriate compositions, [delta] phase can format grain boundaries as well as within the grains. In commercially heat treated Al-Li-Cu alloys of 2090 specification, the grain boundary precipitate [delta] of the binary Al-Li system is replaced by a combination of T[sub 2](Al[sub 6]CuLi[sub 3]), R(Al[sub 5]CuLi[sub 3]) and T[sub 1](Al[sub 2]CuLi) phases. In similarly treated Al-Li-Cu-Mg alloys of 8090 specification, the copper rich T[sub 2] phase, present inmore » the form of Al[sub 6]CuLi[sub 3[minus]x]Mg[sub x], is known to be the major coarse g.b. precipitate. The presence of an Al-Li-Cu-Mg based C phase at the grain boundaries of the commercially heat treated 8090 alloys has also been documented. No detailed study has yet been carried out to verify whether the [delta] phase can be present at the grain boundaries of the commercially heat treated 8090 alloys. Given the correlations between the g.b. phase morphology, g.b. phase chemistry, and the stress corrosion cracking resistance of these alloys, it is important that the g.b. precipitates be examined and identified. In this paper results using TEM are presented to show that the [delta] phase can be present in varying amounts at the grain boundaries in an 8090 alloy when heat treated in the temperature range of 170--350 C. An examination is also made of the [delta] precipitation within the grain to establish that the T[sub 2]/[alpha]-Al interface is the dominant nucleation site for the noncoherent [delta] phase.« less

Prediction of A2 to B2 Phase Transition in the High Entropy Alloy Mo-Nb-Ta-W

NASA Astrophysics Data System (ADS)

Huhn, William; Widom, Michael

2014-03-01

In this talk we show that an effective Hamiltonian fit with first principles calculations predicts an order/disorder transition occurs in the high entropy alloy Mo-Nb-Ta-W. Using the Alloy Theoretic Automated Toolset, we find T=0K enthalpies of formation for all binaries containing Mo, Nb, Ta, and W, and in particular we find the stable structures for binaries at equiatomic concentrations are close in energy to the associated B2 structure, suggesting that at intermediate temperatures a B2 phase is stabilized in Mo-Nb-Ta-W. Our ``hybrid Monte Carlo/molecular dynamics'' results for the Mo-Nb-Ta-W system are analyzed to identify certain preferred chemical bonding types. A mean field free energy model incorporating nearest neighbor bonds will be presented, allowing us to predict the mechanism of the order/disorder transition. We find the temperature evolution of the system is driven by strong Mo-Ta bonding. Comparison of the free energy model and our MC/MD results suggest the existence of additional low-temperature phase transitions in the system likely ending with phase segregation into binary phases. We would like to thank DOD-DTRA for funding this research under contract number DTRA-11-1-0064.

Advanced hydrogen electrode for hydrogen-bromide battery

NASA Technical Reports Server (NTRS)

Kosek, Jack A.; Laconti, Anthony B.

1987-01-01

Binary platinum alloys are being developed as hydrogen electrocatalysts for use in a hydrogen bromide battery system. These alloys were varied in terms of alloy component mole ratio and heat treatment temperature. Electrocatalyst evaluation, performed in the absence and presence of bromide ion, includes floating half cell polarization studies, electrochemical surface area measurements, X ray diffraction analysis, scanning electron microscopy analysis and corrosion measurements. Results obtained to date indicate a platinum rich alloy has the best tolerance to bromide ion poisoning.

Thermal Conductivity of Ten Selected Binary Alloy Systems.

DTIC Science & Technology

1975-05-01

of Commercial Metals and Alloys. IL Aluminmnns," J. Appt. Pys., .1(3), 496-503, 1960. 58. Mikryukov , V . E . and Karagpyan, A. 0., "Thermal and...74, 1900. 136. Mikryukov , V . E ., "Thermal and Electrical Properties of Copper Alloys," Moscow Univ. Vest. Ser. Mat. Mekh. Astron. Fiz. Khim., 12(2... Mikryukov , V . E ., "Thermal and Electrical Properties of Copper Alloys, "Moscow Univ. Vest. Ser. Mat. Mekh. Astron. Fis. Ehim., 12(3), 57-64, 195?. 145

Nanophase diagram of binary eutectic Au-Ge nanoalloys for vapor-liquid-solid semiconductor nanowires growth

NASA Astrophysics Data System (ADS)

Lu, Haiming; Meng, Xiangkang

2015-06-01

Although the vapor-liquid-solid growth of semiconductor nanowire is a non-equilibrium process, the equilibrium phase diagram of binary alloy provides important guidance on the growth conditions, such as the temperature and the equilibrium composition of the alloy. Given the small dimensions of the alloy seeds and the nanowires, the known phase diagram of bulk binary alloy cannot be expected to accurately predict the behavior of the nanowire growth. Here, we developed a unified model to describe the size- and dimensionality-dependent equilibrium phase diagram of Au-Ge binary eutectic nanoalloys based on the size-dependent cohesive energy model. It is found that the liquidus curves reduce and shift leftward with decreasing size and dimensionality. Moreover, the effects of size and dimensionality on the eutectic composition are small and negligible when both components in binary eutectic alloys have the same dimensionality. However, when two components have different dimensionality (e.g. Au nanoparticle-Ge nanowire usually used in the semiconductor nanowires growth), the eutectic composition reduces with decreasing size.

Stochastic simulation of nucleation in binary alloys

NASA Astrophysics Data System (ADS)

L’vov, P. E.; Svetukhin, V. V.

2018-06-01

In this study, we simulate nucleation in binary alloys with respect to thermal fluctuations of the alloy composition. The simulation is based on the Cahn–Hilliard–Cook equation. We have considered the influence of some fluctuation parameters (wave vector cutoff and noise amplitude) on the kinetics of nucleation and growth of minority phase precipitates. The obtained results are validated by the example of iron–chromium alloys.

Electrical and Magnetic Properties of Binary Amorphous Transition Metal Alloys.

NASA Astrophysics Data System (ADS)

Liou, Sy-Hwang

The electrical, superconductive and magnetic properties of several binary transition metal amorphous and metastable crystalline alloys, Fe(,x)Ti(,100-x) (30 (LESSTHEQ) x (LESSTHEQ) 100), Fe(,x)Zr(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 93), Fe(,x)Hf(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 100), Fe(,x)Nb(,100 -x) (22 (LESSTHEQ) x (LESSTHEQ) 85), Ni(,x)Nb(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 80), Cu(,x)Nb(,100-x) (10 (LESSTHEQ) x (LESSTHEQ) 90) were studied over a wide composition range. Films were made using a magnetron sputtering system, and the structure of the films was investigated by energy dispersive x-ray diffraction. The composition region of each amorphous alloys system was determined and found in good agreement with a model proposed by Egami and Waseda. The magnetic properties and hyperfine interactions in the films were investigated using a conventional Mossbauer spectrometer and a ('57)Co in Rh matrix source. In all Fe-early transition metal binary alloys systems, Fe does not retain its moment in the low iron concentration region and the result is that the critical concentration for magnetic order (x(,c)) is much larger than anticipated from percolation considerations. A direct comparison between crystalline alloys and their amorphous counterparts of the same composition illustrate no clear correlation between crystalline and amorphous states. Pronounced discontinuities in the magnetic properties with variation in Fe content of all Fe-early transition metal alloys at phase boundaries separating amorphous and crystalline states have been observed. This is caused by the differences in the atomic arrangement and the electronic structure between crystalline and amorphous solids. The temperature dependence of resistivity, (rho)(T), of several binary amorphous alloys of Fe-TM (where TM = Ti, Zr, Hf, Nb etc.) has been studied from 2K to 300K. The Fe-poor (x < x(,c)) samples and the Fe-rich (x > x(,c)) samples have distinctive differences in (rho)(T) at low temperature (below 30K). All the magnetic samples show a logarithmic dependence at low temperature that can be described by Kondo scattering. In addition, there is a change in slope of (rho)(T) at a temperature close to the magnetic ordering temperature, indicating a contribution attributed to magnetic ordering. Several Nb-based amorphous alloys (Fe-Nb, Ni-Nb, Cu-Nb) have also been systematically studied. The effect of the magnetic species on superconductivity is investigated. The value of superconducting transition temperature (T(,s)) increases linearly with increasing Nb concentration. (Abstract shortened with permission of author.).

A new approximate sum rule for bulk alloy properties

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John

1991-01-01

A new, approximate sum rule is introduced for determining bulk properties of multicomponent systems, in terms of the pure components properties. This expression is applied for the study of lattice parameters, cohesive energies, and bulk moduli of binary alloys. The correct experimental trends (i.e., departure from average values) are predicted in all cases.

An approximate formula for recalescence in binary eutectic alloys

NASA Technical Reports Server (NTRS)

Ohsaka, K.; Trinh, E. H.

1993-01-01

In alloys, solidification takes place along various paths which may be ascertained via phase diagrams; while there would be no single formula applicable to all alloys, an approximate formula for a specific solidification path would be useful in estimating the fraction of the solid formed during recalescence. A formulation is here presented of recalescence in binary eutectic alloys. This formula is applied to Ag-Cu alloys which are of interest in containerless solidification, due to their formation of supersaturated solutions.

Influence of the alloying effect on nickel K-shell fluorescence yield in Ni Si alloys

NASA Astrophysics Data System (ADS)

Kalayci, Y.; Agus, Y.; Ozgur, S.; Efe, N.; Zararsiz, A.; Arikan, P.; Mutlu, R. H.

2005-02-01

Alloying effects on the K-shell fluorescence yield ωK of nickel in Ni-Si binary alloy system have been studied by energy dispersive X-ray fluorescence. It is found that ωK increases from pure Ni to Ni 2Si and then decreases from Ni 2Si to NiSi. These results are discussed in terms of d-occupation number on the Ni site and it is concluded that electronic configuration as a result of p-d hybridization explain qualitatively the observed variation of ωK in Ni-Si alloys.

First-principles interatomic potentials for transition-metal aluminides. III. Extension to ternary phase diagrams

NASA Astrophysics Data System (ADS)

Widom, Mike; Al-Lehyani, Ibrahim; Moriarty, John A.

2000-08-01

Modeling structural and mechanical properties of intermetallic compounds and alloys requires detailed knowledge of their interatomic interactions. The first two papers of this series [Phys. Rev. B 56, 7905 (1997); 58, 8967 (1998)] derived first-principles interatomic potentials for transition-metal (TM) aluminides using generalized pseudopotential theory (GPT). Those papers focused on binary alloys of aluminum with first-row transition metals and assessed the ability of GPT potentials to reproduce and elucidate the alloy phase diagrams of Al-Co and Al-Ni. This paper addresses the phase diagrams of the binary alloy Al-Cu and the ternary systems Al-Co-Cu and Al-Co-Ni, using GPT pair potentials calculated in the limit of vanishing transition-metal concentration. Despite this highly simplifying approximation, we find rough agreement with the known low-temperature phase diagrams, up to 50% total TM concentration provided the Co fraction is below 25%. Full composition-dependent potentials and many-body interactions would be required to correct deficiencies at higher Co concentration. Outside this troublesome region, the experimentally determined stable and metastable phases all lie on or near the convex hull of a scatter plot of energy versus composition. We verify, qualitatively, reported solubility ranges extending binary alloys into the ternary diagram in both Al-Co-Cu and Al-Co-Ni. Finally, we reproduce previously conjectured transition-metal positions in the decagonal quasicrystal phase.

Modeling the elastic energy of alloys: Potential pitfalls of continuum treatments.

PubMed

Baskaran, Arvind; Ratsch, Christian; Smereka, Peter

2015-12-01

Some issues that arise when modeling elastic energy for binary alloys are discussed within the context of a Keating model and density-functional calculations. The Keating model is a simplified atomistic formulation based on modeling elastic interactions of a binary alloy with harmonic springs whose equilibrium length is species dependent. It is demonstrated that the continuum limit for the strain field are the usual equations of linear elasticity for alloys and that they correctly capture the coarse-grained behavior of the displacement field. In addition, it is established that Euler-Lagrange equation of the continuum limit of the elastic energy will yield the same strain field equation. This is the same energy functional that is often used to model elastic effects in binary alloys. However, a direct calculation of the elastic energy atomistic model reveals that the continuum expression for the elastic energy is both qualitatively and quantitatively incorrect. This is because it does not take atomistic scale compositional nonuniformity into account. Importantly, this result also shows that finely mixed alloys tend to have more elastic energy than segregated systems, which is the exact opposite of predictions made by some continuum theories. It is also shown that for strained thin films the traditionally used effective misfit for alloys systematically underestimate the strain energy. In some models, this drawback is handled by including an elastic contribution to the enthalpy of mixing, which is characterized in terms of the continuum concentration. The direct calculation of the atomistic model reveals that this approach suffers serious difficulties. It is demonstrated that elastic contribution to the enthalpy of mixing is nonisotropic and scale dependent. It is also shown that such effects are present in density-functional theory calculations for the Si-Ge system. This work demonstrates that it is critical to include the microscopic arrangements in any elastic model to achieve even qualitatively correct behavior.

An Introduction to the BFS Method and Its Use to Model Binary NiAl Alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Noebe, Ronald D.; Ferrante, J.; Amador, C.

1998-01-01

We introduce the Bozzolo-Ferrante-Smith (BFS) method for alloys as a computationally efficient tool for aiding in the process of alloy design. An intuitive description of the BFS method is provided, followed by a formal discussion of its implementation. The method is applied to the study of the defect structure of NiAl binary alloys. The groundwork is laid for a detailed progression to higher order NiAl-based alloys linking theoretical calculations and computer simulations based on the BFS method and experimental work validating each step of the alloy design process.

Friction and wear with a single-crystal abrasive grit of silicon carbide in contact with iron base binary alloys in oil: Effects of alloying element and its content

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1979-01-01

Sliding friction experiments were conducted with various iron-base binary alloys (alloying elements were Ti, Cr, Mn, Ni, Rh, and W) in contact with a rider of 0.025-millimeter-radius, single-crystal silicon carbide in mineral oil. Results indicate that atomic size and content of alloying element play a dominant role in controlling the abrasive-wear and -friction properties of iron-base binary alloys. The coefficient of friction and groove height (wear volume) general alloy decrease, and the contact pressure increases in solute content. There appears to be very good correlation of the solute to iron atomic radius ratio with the decreasing rate of coefficient of friction, the decreasing rate of groove height (wear volume), and the increasing rate of contact pressure with increasing solute content C. Those rates increase as the solute to iron atomic radius ratio increases from unity.

Monte Carlo simulation of magnetic properties of mixed spin (3/2, 1) ferromagnetic and ferrimagnetic disordered binary alloys with amorphous structure

NASA Astrophysics Data System (ADS)

Motlagh, H. Nakhaei; Rezaei, G.

2018-01-01

Monte Carlo simulation is used to study the magnetic properties of mixed spin (3/2, 1) disordered binary alloys on simple cubic, hexagonal and amorphous magnetic ultra-thin films with 18 × 18 × 2 atoms. To this end, at the first approximation, the exchange coupling interaction between the spins is considered as a constant value and at the second one, the Ruderman-Kittel-Kasuya-Yosida (RKKY) model is used. Effects of concentration, structure, exchange interaction, single ion-anisotropy and the film size on the magnetic properties of disordered ferromagnetic and ferrimagnetic binary alloys are investigated. Our results indicate that the spontaneous magnetization and critical temperatures of rare earth-3d transition binary alloys are affected by these parameters. It is also found that in the ferrimagnetic state, the compensation temperature (Tcom) and the magnetic rearrangement temperature (TR) appear for some concentrations.

Role of alloying elements in adhesive transfer and friction of copper-base alloys

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1978-01-01

Sliding friction experiments were conducted in a vacuum with binary-copper alloy riders sliding against a conventional bearing-steel surface with normal residual oxides present. The binary alloys contained 1 atomic percent of various alloying elements. Auger spectroscopy analysis was used to monitor the adhesive transfer of the copper alloys to the bearing-steel surface. A relation was found to exist between adhesive transfer and the reaction potential and free energy of formation of the alloying element in the copper. The more chemically active the element and the more stable its oxide, the greater was the adhesive transfer and wear of the copper alloy. Transfer occurred in all the alloys except copper-gold after relatively few (25) passes across the steel surface.

Numerical simulation of freckle formation in directional solidification of binary alloys

NASA Technical Reports Server (NTRS)

Felicelli, Sergio D.; Heinrich, Juan C.; Poirier, David R.

1992-01-01

A mathematical model of solidification is presented which simulates the formation of segregation models known as 'freckles' during directional solidification of binary alloys. The growth of the two-phase or dendritic zone is calculated by solving the coupled equations of momentum, energy, and solute transport, as well as maintaining the thermodynamic constraints dictated by the phase diagram of the alloy. Calculations for lead-tin alloys show that the thermosolutal convection in the dendritic zone during solidification can produce heavily localized inhomogeneities in the composition of the final alloy.

Thermophysical property of undercooled liquid binary alloy composed of metallic and semiconductor elements

NASA Astrophysics Data System (ADS)

Wang, H. P.; Wei, B.

2009-02-01

The thermophysical properties of the liquid Ni-Si binary alloy system were investigated by the molecular dynamics method. The properties investigated include density, excessive volume, enthalpy, mixing enthalpy and specific heat at both superheated and undercooled states. It is found that the density decreases with an increase in the Si content, and so do the temperature coefficients. If the Si content is smaller than 30%, the density changes linearly with the temperature. If it is larger than 30%, the density is a quadratic function of the temperature. The simulated enthalpies of different composition alloys increase linearly with a rise in temperature. This indicates that the specific heats of Ni-Si alloys change little with temperature. The specific heat versus composition first decreases to a minimum value at 50% Si, then experiences a rise to a maximum value at 90% Si and finally falls again. According to the excessive volume and mixing enthalpy, it can be deduced that the Ni-Si alloy system seriously deviates from the ideal solution. Moreover, a comparison was also performed between the present results and the approximated values by the Neumann-Kopp rule. It reveals that this work provides reasonable data in a broad temperature range, especially for the metastable undercooled liquid state.

Development of a HTSMA-Actuated Surge Control Rod for High-Temperature Turbomachinery Applications

NASA Technical Reports Server (NTRS)

Padula, Santo, II; Noebe, Ronald; Bigelow, Glen; Culley, Dennis; Stevens, Mark; Penney, Nicholas; Gaydosh, Darrell; Quackenbush, Todd; Carpenter, Bernie

2007-01-01

In recent years, a demand for compact, lightweight, solid-state actuation systems has emerged, driven in part by the needs of the aeronautics industry. However, most actuation systems used in turbomachinery require not only elevated temperature but high-force capability. As a result, shape memory alloy (SMA) based systems have worked their way to the forefront of a short list of viable options to meet such a technological challenge. Most of the effort centered on shape memory systems to date has involved binary NiTi alloys but the working temperatures required in many aeronautics applications dictate significantly higher transformation temperatures than the binary systems can provide. Hence, a high temperature shape memory alloy (HTSMA) based on NiTiPdPt, having a transformation temperature near 300 C, was developed. Various thermo-mechanical processing schemes were utilized to further improve the dimensional stability of the alloy and it was later extruded/drawn into wire form to be more compatible with envisioned applications. Mechanical testing on the finished wire form showed reasonable work output capability with excellent dimensional stability. Subsequently, the wire form of the alloy was incorporated into a benchtop system, which was shown to provide the necessary stroke requirements of approx.0.125 inches for the targeted surge-control application. Cycle times for the actuator were limited to 4 seconds due to control and cooling constraints but this cycle time was determined to be adequate for the surge control application targeted as the primary requirement was initial actuation of a surge control rod, which could be completed in approximately one second.

Free energy change of off-eutectic binary alloys on solidification

NASA Technical Reports Server (NTRS)

Ohsaka, K.; Trinh, E. H.; Lin, J.-C.; Perepezko, J. H.

1991-01-01

A formula for the free energy difference between the undercooled liquid phase and the stable solid phase is derived for off-eutectic binary alloys in which the equilibrium solid/liquid transition takes place over a certain temperature range. The free energy change is then evaluated numerically for a Bi-25 at. pct Cd alloy modeled as a sub-subregular solution.

Kinetic Monte Carlo Simulations of Rod Eutectics and the Surface Roughening Transition in Binary Alloys

NASA Technical Reports Server (NTRS)

Bentz, Daniel N.; Betush, William; Jackson, Kenneth A.

2003-01-01

In this paper we report on two related topics: Kinetic Monte Carlo simulations of the steady state growth of rod eutectics from the melt, and a study of the surface roughness of binary alloys. We have implemented a three dimensional kinetic Monte Carlo (kMC) simulation with diffusion by pair exchange only in the liquid phase. Entropies of fusion are first chosen to fit the surface roughness of the pure materials, and the bond energies are derived from the equilibrium phase diagram, by treating the solid and liquid as regular and ideal solutions respectively. A simple cubic lattice oriented in the {100} direction is used. Growth of the rods is initiated from columns of pure B material embedded in an A matrix, arranged in a close packed array with semi-periodic boundary conditions. The simulation cells typically have dimensions of 50 by 87 by 200 unit cells. Steady state growth is compliant with the Jackson-Hunt model. In the kMC simulations, using the spin-one Ising model, growth of each phase is faceted or nonfaceted phases depending on the entropy of fusion. There have been many studies of the surface roughening transition in single component systems, but none for binary alloy systems. The location of the surface roughening transition for the phases of a eutectic alloy determines whether the eutectic morphology will be regular or irregular. We have conducted a study of surface roughness on the spin-one Ising Model with diffusion using kMC. The surface roughness was found to scale with the melting temperature of the alloy as given by the liquidus line on the equilibrium phase diagram. The density of missing lateral bonds at the surface was used as a measure of surface roughness.

New Approaches to the Computer Simulation of Amorphous Alloys: A Review.

PubMed

Valladares, Ariel A; Díaz-Celaya, Juan A; Galván-Colín, Jonathan; Mejía-Mendoza, Luis M; Reyes-Retana, José A; Valladares, Renela M; Valladares, Alexander; Alvarez-Ramirez, Fernando; Qu, Dongdong; Shen, Jun

2011-04-13

In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe 2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus) temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total) are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties.

New Approaches to the Computer Simulation of Amorphous Alloys: A Review

PubMed Central

Valladares, Ariel A.; Díaz-Celaya, Juan A.; Galván-Colín, Jonathan; Mejía-Mendoza, Luis M.; Reyes-Retana, José A.; Valladares, Renela M.; Valladares, Alexander; Alvarez-Ramirez, Fernando; Qu, Dongdong; Shen, Jun

2011-01-01

In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus) temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total) are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties. PMID:28879948

Electrical Transport Properties of Liquid Sn-Sb Binary Alloys

NASA Astrophysics Data System (ADS)

Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Jani, A. R.

2010-06-01

The study of electrical transport properties viz. electrical resistivity, thermo electrical power and thermal conductivity of liquid Sn-Sb binary alloys have been made by our well recognized single parametric model potential. In the present work, screening functions due to Hartree, Taylor, Ichimaru et al.. Farid et al.. and Sarkar et al.. have been employed to incorporate the exchange and correlation effects. The liquid alloy is studied as a function of its composition at temperature 823 K according to the Faber-Ziman model. Further, thermoelectric power and thermal conductivity have been predicted. The values of electrical resistivity of binary alloys computed with Ichimaru et al. and Farid et al.. screening function are in good agreement with the experimental data.

Electrical resistivity of Al-Cu liquid binary alloy

NASA Astrophysics Data System (ADS)

Thakor, P. P.; Patel, J. J.; Sonvane, Y. A.; Jani, A. R.

2013-06-01

Present paper deals with the electrical resistivity (ρ) of liquid Al-Cu binary alloy. To describe electron-ion interaction we have used our parameter free model potential along with Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. To see the influence of exchange and correlation effect, Hartree, Taylor and Sarkar et al local field correlation functions are used. From present results, it is seen that good agreements between present results and experimental data have been achieved. Lastly we conclude that our model potential successfully produces the data of electrical resistivity (ρ) of liquid Al-Cu binary alloy.

Thermal Stability of Nanocrystalline Alloys by Solute Additions and A Thermodynamic Modeling

NASA Astrophysics Data System (ADS)

Saber, Mostafa

Nanocrystalline alloys show superior properties due to their exceptional microstructure. Thermal stability of these materials is a critical aspect. It is well known that grain boundaries in nanocrystalline microstructures cause a significant increase in the total free energy of the system. A driving force provided to reduce this excess free energy can cause grain growth. The presence of a solute addition within a nanocrystalline alloy can lead to the thermal stability. Kinetic and thermodynamic stabilization are the two basic mechanisms with which stability of a nanoscale grain size can be achieved at high temperatures. The basis of this thesis is to study the effect of solute addition on thermal stability of nanocrystalline alloys. The objective is to determine the effect of Zr addition on the thermal stability of mechanically alloyed nanocrysatillne Fe-Cr and Fe-Ni alloys. In Fe-Cr-Zr alloy system, nanoscale grain size stabilization was maintained up to 900 °C by adding 2 at% Zr. Kinetic pinning by intermetallic particles in the nanoscale range was identified as a primary mechanism of thermal stabilization. In addition to the grain size strengthening, intermetallic particles also contribute to strengthening mechanisms. The analysis of microhardness, XRD data, and measured grain sizes from TEM micrographs suggested that both thermodynamic and kinetic mechanisms are possible mechanisms. It was found that alpha → gamma phase transformation in Fe-Cr-Zr system does not influence the grain size stabilization. In the Fe-Ni-Zr alloy system, it was shown that the grain growth in Fe-8Ni-1Zr alloy is much less than that of pure Fe and Fe-8Ni alloy at elevated temperatures. The microstructure of the ternary Fe-8Ni-1Zr alloy remains in the nanoscale range up to 700 °C. Using an in-situ TEM study, it was determined that drastic grain growth occurs when the alpha → gamma phase transformation occurs. Accordingly, there can be a synergistic relationship between grain growth and alpha → gamma phase transformation in Fe-Ni-Zr alloys. In addition to the experimental study of thermal stabilization of nanocrystalline Fe-Cr-Zr or Fe-Ni-Zr alloys, the thesis presented here developed a new predictive model, applicable to strongly segregating solutes, for thermodynamic stabilization of binary alloys. This model can serve as a benchmark for selecting solute and evaluating the possible contribution of stabilization. Following a regular solution model, both the chemical and elastic strain energy contributions are combined to obtain the mixing enthalpy. The total Gibbs free energy of mixing is then minimized with respect to simultaneous variations in the grain boundary volume fraction and the solute concentration in the grain boundary and the grain interior. The Lagrange multiplier method was used to obtained numerical solutions. Application are given for the temperature dependence of the grain size and the grain boundary solute excess for selected binary system where experimental results imply that thermodynamic stabilization could be operative. This thesis also extends the binary model to a new model for thermodynamic stabilization of ternary nanocrystalline alloys. It is applicable to strongly segregating size-misfit solutes and uses input data available in the literature. In a same manner as the binary model, this model is based on a regular solution approach such that the chemical and elastic strain energy contributions are incorporated into the mixing enthalpy DeltaHmix, and the mixing entropy DeltaSmix is obtained using the ideal solution approximation. The Gibbs mixing free energy Delta Gmix is then minimized with respect to simultaneous variations in grain growth and solute segregation parameters. The Lagrange multiplier method is similarly used to obtain numerical solutions for the minimum Delta Gmix. The temperature dependence of the nanocrystalline grain size and interfacial solute excess can be obtained for selected ternary systems. As an example, model predictions are compared to experimental results for Fe-Cr-Zr and Fe-Ni-Zr alloy systems. Consistency between the experimental results and the present model predictions provide a more rigorous criterion for investigating thermal stabilization. However, other possible contributions for grain growth stabilization should still be considered.

Walker photographs BCAT-5 (Binary Colloidal Alloy Test-5) payload

NASA Image and Video Library

2010-10-19

ISS025-E-008239 (19 Oct. 2010) --- NASA astronaut Shannon Walker, Expedition 25 flight engineer, uses a digital still camera to photograph Binary Colloidal Alloy Test-5 (BCAT-5) experiment samples in the Kibo laboratory of the International Space Station.

Thermodynamics of Liquid Alkali Metals and Their Binary Alloys

NASA Astrophysics Data System (ADS)

Thakor, P. B.; Patel, Minal H.; Gajjar, P. N.; Jani, A. R.

2009-07-01

The theoretical investigation of thermodynamic properties like internal energy, entropy, Helmholtz free energy, heat of mixing (ΔE) and entropy of mixing (ΔS) of liquid alkali metals and their binary alloys are reported in the present paper. The effect of concentration on the thermodynamic properties of Ac1Bc2 alloy of the alkali-alkali elements is investigated and reported for the first time using our well established local pseudopotential. To investigate influence of exchange and correlation effects, we have used five different local field correction functions viz; Hartree(H), Taylor(T), Ichimaru and Utsumi(IU), Farid et al. (F) and Sarkar et al. (S). The increase of concentration C2, increases the internal energy and Helmholtz free energy of liquid alloy Ac1Bc2. The behavior of present computation is not showing any abnormality in the outcome and hence confirms the applicability of our model potential in explaining the thermodynamics of liquid binary alloys.

In-situ investigation of stress-induced martensitic transformation in Ti–Nb binary alloys with low Young's modulus [In-situ high-energy X-ray diffraction investigation on stress-induced martensitic transformation in Ti-Nb binary alloys

DOE PAGES

Chang, L. L.; Wang, Y. D.; Ren, Y.

2015-11-04

Microstructure evolution, mechanical behaviors of cold rolled Ti-Nb alloys with different Nb contents subjected to different heat treatments were investigated. Here, optical microstructure and phase compositions of Ti-Nb alloys were characterized using optical microscopy and X-ray diffractometre, while mechanical behaviors of Ti-Nb alloys were examined by using tension tests. Stress-induced martensitic transformation in a Ti-30. at%Nb binary alloy was in-situ explored by synchrotron-based high-energy X-ray diffraction (HE-XRD). The results obtained suggested that mechanical behavior of Ti-Nb alloys, especially Young's modulus was directly dependent on chemical compositions and heat treatment process. According to the results of HE-XRD, α"-V1 martensite generated priormore » to the formation of α"-V2 during loading and a partial reversible transformation from α"-V1 to β phase was detected while α"-V2 tranformed to β completely during unloading.« less

Adhesion, friction, and wear of binary alloys in contact with single-crystal silicon carbide

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Sliding friction experiments, conducted with various iron base alloys (alloying elements are Ti, Cr, Mn, Ni, Rh and W) in contact with a single crystal silicon carbide /0001/ surface in vacuum are discussed. Results indicate atomic size misfit and concentration of alloying elements play a dominant role in controlling adhesion, friction, and wear properties of iron-base binary alloys. The controlling mechanism of the alloy properties is as an intrinsic effect involving the resistance to shear fracture of cohesive bonding in the alloy. The coefficient of friction generally increases with an increase in solute concentration. The coefficient of friction increases as the solute-to-iron atomic radius ratio increases or decreases from unity. Alloys having higher solute concentration produce more transfer to silicon carbide than do alloys having low solute concentrations. The chemical activity of the alloying element is also an important parameter in controlling adhesion and friction of alloys.

Chemical interactions and thermodynamic studies in aluminum alloy/molten salt systems

NASA Astrophysics Data System (ADS)

Narayanan, Ramesh

The recycling of aluminum and aluminum alloys such as Used Beverage Container (UBC) is done under a cover of molten salt flux based on (NaCl-KCl+fluorides). The reactions of aluminum alloys with molten salt fluxes have been investigated. Thermodynamic calculations are performed in the alloy/salt flux systems which allow quantitative predictions of the equilibrium compositions. There is preferential reaction of Mg in Al-Mg alloy with molten salt fluxes, especially those containing fluorides like NaF. An exchange reaction between Al-Mg alloy and molten salt flux has been demonstrated. Mg from the Al-Mg alloy transfers into the salt flux while Na from the salt flux transfers into the metal. Thermodynamic calculations indicated that the amount of Na in metal increases as the Mg content in alloy and/or NaF content in the reacting flux increases. This is an important point because small amounts of Na have a detrimental effect on the mechanical properties of the Al-Mg alloy. The reactions of Al alloys with molten salt fluxes result in the formation of bluish purple colored "streamers". It was established that the streamer is liquid alkali metal (Na and K in the case of NaCl-KCl-NaF systems) dissipating into the melt. The melts in which such streamers were observed are identified. The metal losses occurring due to reactions have been quantified, both by thermodynamic calculations and experimentally. A computer program has been developed to calculate ternary phase diagrams in molten salt systems from the constituting binary phase diagrams, based on a regular solution model. The extent of deviation of the binary systems from regular solution has been quantified. The systems investigated in which good agreement was found between the calculated and experimental phase diagrams included NaF-KF-LiF, NaCl-NaF-NaI and KNOsb3-TINOsb3-LiNOsb3. Furthermore, an insight has been provided on the interrelationship between the regular solution parameters and the topology of the phase diagram. The isotherms are flat (i.e. no skewness) when the regular solution parameters are zero. When the regular solution parameters are non-zero, the isotherms are skewed. A regular solution model is not adequate to accurately model the molten salt systems used in recycling like NaCl-KCl-LiF and NaCl-KCl-NaF.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

DOE PAGES

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.; ...

2017-11-26

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300–360 °C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N 2 gas. Lastly, results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300–360 °C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N 2 gas. Lastly, results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300-360°C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N2 gas. Results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

The modelling of heat, mass and solute transport in solidification systems

NASA Technical Reports Server (NTRS)

Voller, V. R.; Brent, A. D.; Prakash, C.

1989-01-01

The aim of this paper is to explore the range of possible one-phase models of binary alloy solidification. Starting from a general two-phase description, based on the two-fluid model, three limiting cases are identified which result in one-phase models of binary systems. Each of these models can be readily implemented in standard single phase flow numerical codes. Differences between predictions from these models are examined. In particular, the effects of the models on the predicted macro-segregation patterns are evaluated.

Low Pt content direct methanol fuel cell anode catalyst: nanophase PtRuNiZr

NASA Technical Reports Server (NTRS)

Whitacre, Jay F. (Inventor); Narayanan, Sekharipuram R. (Inventor)

2010-01-01

A method for the preparation of a metallic material having catalytic activity that includes synthesizing a material composition comprising a metal content with a lower Pt content than a binary alloy containing Pt but that displays at least a comparable catalytic activity on a per mole Pt basis as the binary alloy containing Pt; and evaluating a representative sample of the material composition to ensure that the material composition displays a property of at least a comparable catalytic activity on a per mole Pt basis as a representative binary alloy containing Pt. Furthermore, metallic compositions are disclosed that possess substantial resistance to corrosive acids.

Primary arm spacing in chill block melt spun Ni-Mo alloys

NASA Technical Reports Server (NTRS)

Tewari, S. N.; Glasgow, T. K.

1986-01-01

Chill block melt spun ribbons of Ni-Mo binary alloys containing 8.0 to 41.8 wt % Mo have been prepared under carefully controlled processing conditions. The growth velocity has been determined as a function of distance from the quench surface from the observed ribbon thickness dependence on the melt puddle residence time. Primary arm spacings measured at the midribbon thickness locations show a dependence on growth velocity and alloy composition which is expected from dendritic growth models for binary alloys directionally solidified in a positive temperature gradient.

Primary arm spacing in chill block melt spun Ni-Mo alloys

NASA Technical Reports Server (NTRS)

Tewari, S. N.; Glasgow, T. K.

1987-01-01

Chill block melt spun ribbons of Ni-Mo binary alloys containing 8.0 to 41.8 wt pct Mo have been prepared under carefully controlled processing conditions. The growth velocity has been determined as a function of distance from the quench surface from the observed ribbon thickness dependence on the melt puddle residence time. Primary arm spacing measured at the midribbon thickness locations show a dependence on growth velocity and alloy composition which is expected from dendritic growth models for binary alloys directionally solidified in a positive temperature gradient.

Modeling of the Structure of Disordered Metallic Alloys and Its Transformation Under Thermal Forcing

NASA Astrophysics Data System (ADS)

Cress, Ryan Paul

The morphology of disordered binary metallic alloys is investigated. The structure of disordered binary metallic alloys is modeled as a randomly close packed (RCP) assembly of atoms. It was observed through a 2-D binary hard sphere experiment that RCP structure can be modeled as a mixture of nano-crystallites and glassy matter. We define the degree of crystallinity as the fraction of atoms contained in nano-crystallites in an RCP medium. Nano-crystallites by size in a crystallite size distribution were determined experimentally to define the morphology of the RCP medium. Both the degree of crystallinity and the crystallite size distribution have been found to be determined by the composition of a given binary mixture. A 2-D Monte Carlo simulation was developed in order to replicate the RCP structure observed in the experiment which is then extended to cases of arbitrary composition. Crystallites were assumed to be spherical with isotropic cross sections. The number of atoms in an individual crystallite in 2-D is simply transformed into the number of atoms in 3-D; we then obtain the crystallite size distribution in 3-D. This experiment accounts for the contribution from the repulsive core of the inter-atomic potential. The attractive part of the potential is recovered by constructing spherical nano-crystallites of a given radius from a crystalline specimen of each given alloy. A structural model of a disordered alloy is thus obtained. With the basic structure of the RCP medium defined, the response to heating would be in the form of changes to the crystallite size distribution. This was first investigated in a hard sphere mechanical oven experiment. The experimental setup consists of a 2-D cell which is driven by two independent stepper motors. The motors drive a binary RCP bed of spheres on a slightly tilted plane according to a chaotic algorithmm. The motors are driven at four different speed settings. The RCP medium was analyzed using a sequence of digital images taken of the beds. The bursts of images provide a Gaussian distribution of particle speeds in x and y directions thus giving rise to the notion of "temperature." This temperature scales with the motor speed settings. The measured average degree of crystallinity is found to decrease as the effective temperature was raised suggesting that nano-crystallites dissociate under thermal forcing. The evolution of a specimen's structure is calculated rigorously by means of the law of mass action formalism. A system of thermal dissociation reaction equations is written out for the set of nano-crystallites according to the 3-D crystallite size distribution. The equilibrium treatment is justified because the energy differences between metastable RCP structures fall within kT. Thermal dissociation of one surface atom at a time is assumed because the energy cost in dissociation of a surface atom on a nano-crystallite is significantly less than that of a multi atom cluster. The full set of reaction equations cover all possible dissociation steps, which may amount to several thousand for a disordered alloy specimen. The primary determining factor in each of these dissociation equations is the dissociation potential or the amount of attractive energy needed to remove a surface atom on a nano-crystallite of a given size. The attractive potential between atoms is calculated using a Lennard-Jones potential between a pair of atoms for which quantum chemistry calculations exist in the literature. All interactions impinged on the surface atom by all other atoms in a crystallite are summed. As the nano-crystallites dissociate due to heating, the structure of the alloy changes, and this leads to modifications of alloy's transport properties. The model is found to predict the melting temperature of various disordered binary alloys as well as refractory metals in good agreement with known data. The structure model for disordered binary alloys gives an excellent characterization of the alloy morphology. It therefore provides fruitful avenues for making predictions about how thermophysical properties of disordered binary alloys change as the alloy temperature is raised by heating.

A phase field model for segregation and precipitation induced by irradiation in alloys

NASA Astrophysics Data System (ADS)

Badillo, A.; Bellon, P.; Averback, R. S.

2015-04-01

A phase field model is introduced to model the evolution of multicomponent alloys under irradiation, including radiation-induced segregation and precipitation. The thermodynamic and kinetic components of this model are derived using a mean-field model. The mobility coefficient and the contribution of chemical heterogeneity to free energy are rescaled by the cell size used in the phase field model, yielding microstructural evolutions that are independent of the cell size. A new treatment is proposed for point defect clusters, using a mixed discrete-continuous approach to capture the stochastic character of defect cluster production in displacement cascades, while retaining the efficient modeling of the fate of these clusters using diffusion equations. The model is tested on unary and binary alloy systems using two-dimensional simulations. In a unary system, the evolution of point defects under irradiation is studied in the presence of defect clusters, either pre-existing ones or those created by irradiation, and compared with rate theory calculations. Binary alloys with zero and positive heats of mixing are then studied to investigate the effect of point defect clustering on radiation-induced segregation and precipitation in undersaturated solid solutions. Lastly, irradiation conditions and alloy parameters leading to irradiation-induced homogeneous precipitation are investigated. The results are discussed in the context of experimental results reported for Ni-Si and Al-Zn undersaturated solid solutions subjected to irradiation.

The surface-induced spatial-temporal structures in confined binary alloys

NASA Astrophysics Data System (ADS)

Krasnyuk, Igor B.; Taranets, Roman M.; Chugunova, Marina

2014-12-01

This paper examines surface-induced ordering in confined binary alloys. The hyperbolic initial boundary value problem (IBVP) is used to describe a scenario of spatiotemporal ordering in a disordered phase for concentration of one component of binary alloy and order parameter with non-linear dynamic boundary conditions. This hyperbolic model consists of two coupled second order differential equations for order parameter and concentration. It also takes into account effects of the “memory” on the ordering of atoms and their densities in the alloy. The boundary conditions characterize surface velocities of order parameter and concentration changing which is due to surface (super)cooling on walls confining the binary alloy. It is shown that for large times there are three classes of dynamic non-linear boundary conditions which lead to three different types of attractor’s elements for the IBVP. Namely, the elements of attractor are the limit periodic simple shock waves with fronts of “discontinuities” Γ. If Γ is finite, then the attractor contains spatiotemporal functions of relaxation type. If Γ is infinite and countable then we observe the functions of pre-turbulent type. If Γ is infinite and uncountable then we obtain the functions of turbulent type.

Influence of silicon on friction and wear of iron-cobalt alloys

NASA Technical Reports Server (NTRS)

Buckley, D. H.; Brainard, W. A.

1972-01-01

Sliding friction and wear experiments were conducted with ternary ordered alloys of iron and cobalt containing various amounts of silicon to 5 weight percent. The friction and wear of these alloys were compared to those for binary iron-cobalt alloys in the ordered and disordered states and to those for the conventionally used bearing material, 440-C. Environments in which experiments were conducted included air, argon, and 0.25percent stearic acid in hexadecane. Results indicate that a ternary iron - cobalt - 5-percent-silicon alloy exhibits lower friction and wear than the simple binary iron-cobalt alloy. It exhibits lower wear than 440-C in all three environments. Friction was lower for the alloy in argon than in air. Auger analysis of the surface of the ternary alloy indicated segregation of silicon at the surface as a result of sliding.

Predicted trends of core-shell preferences for 132 late transition-metal binary-alloy nanoparticles.

PubMed

Wang, Lin-Lin; Johnson, Duane D

2009-10-07

Transition-metal alloyed nanoparticles with core-shell features (shell enrichment by one of the metals) are becoming ubiquitous, from (electro-)catalysis to biomedical applications, due to their size control, performance, biocompatibility, and cost. We investigate 132 binary-alloyed nanoparticle systems (groups 8 to 11 in the Periodic Table) using density functional theory (DFT) and systematically explore their segregation energies to determine core-shell preferences. We find that core-shell preferences are generally described by two independent factors: (1) cohesive energy (related to vapor pressure) and (2) atomic size (quantified by the Wigner-Seitz radius), and the interplay between them. These independent factors are shown to provide general trends for the surface segregation preference for atoms in nanoparticles, as well as semi-infinite surfaces, and give a simple correlation (a "design map") for the alloying and catalytic behavior. Finally, we provide a universal description of core-shell preference via tight-binding theory (band-energy differences) that (i) quantitatively reproduces the DFT segregation energies and (ii) confirms the electronic origins and correlations for core-shell behavior.

Influence of compositional complexity on interdiffusion in Ni-containing concentrated solid-solution alloys

DOE PAGES

Jin, Ke; Zhang, Chuan; Zhang, Fan; ...

2018-03-07

To investigate the compositional effects on thermal-diffusion kinetics in concentrated solid-solution alloys, interdiffusion in seven diffusion couples with alloys from binary to quinary is systematically studied. The alloys with higher compositional complexity exhibit in general lower diffusion coefficients against homologous temperature, however, an exception is found that diffusion in NiCoFeCrPd is faster than in NiCoFeCr and NiCoCr. While the derived diffusion parameters suggest that diffusion in medium and high entropy alloys is overall more retarded than in pure metals and binary alloys, they strongly depend on specific constituents. The comparative features are captured by computational thermodynamics approaches using a self-consistentmore » database.« less

Large-Grain Tin-Rich Perovskite Films for Efficient Solar Cells via Metal Alloying Technique.

PubMed

Tavakoli, Mohammad Mahdi; Zakeeruddin, Shaik Mohammed; Grätzel, Michael; Fan, Zhiyong

2018-03-01

Fast research progress on lead halide perovskite solar cells has been achieved in the past a few years. However, the presence of lead (Pb) in perovskite composition as a toxic element still remains a major issue for large-scale deployment. In this work, a novel and facile technique is presented to fabricate tin (Sn)-rich perovskite film using metal precursors and an alloying technique. Herein, the perovskite films are formed as a result of the reaction between Sn/Pb binary alloy metal precursors and methylammonium iodide (MAI) vapor in a chemical vapor deposition process carried out at 185 °C. It is found that in this approach the Pb/Sn precursors are first converted to (Pb/Sn)I 2 and further reaction with MAI vapor leads to the formation of perovskite films. By using Pb-Sn eutectic alloy, perovskite films with large grain sizes up to 5 µm can be grown directly from liquid phase metal. Consequently, using an alloying technique and this unique growth mechanism, a less-toxic and efficient perovskite solar cell with a power conversion efficiency (PCE) of 14.04% is demonstrated, while pure Sn and Pb perovskite solar cells prepared in this manner yield PCEs of 4.62% and 14.21%, respectively. It is found that this alloying technique can open up a new direction to further explore different alloy systems (binary or ternary alloys) with even lower melting point. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Screening on binary Ti alloy with excellent mechanical property and castability for dental prosthesis application

PubMed Central

Li, H. F.; Qiu, K. J.; Yuan, W.; Zhou, F. Y.; Wang, B. L.; Li, L.; Zheng, Y. F.; Liu, Y. H.

2016-01-01

In the present study, the microstructure, mechanical property, castability, corrosion behavior and in vitro cytocompatibility of binary Ti–2X alloys with various alloying elements, including Ag, Bi, Ga, Ge, Hf, In, Mo, Nb, Sn and Zr, were systematically investigated, in order to assess their potential applications in dental field. The experimental results showed that all binary Ti‒2X alloys consisted entirely α–Ti phase. The tensile strength and microhardness of Ti were improved by adding alloying elements. The castability of Ti was significantly improved by separately adding 2 wt.% Bi, Ga, Hf, Mo, Nb, Sn and Zr. The corrosion resistance of Ti in both normal artificial saliva solution (AS) and extreme artificial saliva solution (ASFL, AS with 0.2 wt.% NaF and 0.3 wt.% lactic acid) has been improved by separately adding alloying elements. In addition, the extracts of studied Ti‒2X alloys produced no significant deleterious effect to both fibroblasts L929 cells and osteoblast-like MG63 cells, indicating a good in vitro cytocompatibility, at the same level as pure Ti. The combination of enhanced mechanical properties, castability, corrosion behavior, and in vitro cytocompatibility make the developed Ti‒2X alloys have great potential for future stomatological applications. PMID:27874034

Electrochemical synthesis of mesoporous Pt-Au binary alloys with tunable compositions for enhancement of electrochemical performance.

PubMed

Yamauchi, Yusuke; Tonegawa, Akihisa; Komatsu, Masaki; Wang, Hongjing; Wang, Liang; Nemoto, Yoshihiro; Suzuki, Norihiro; Kuroda, Kazuyuki

2012-03-21

Mesoporous Pt-Au binary alloys were electrochemically synthesized from lyotropic liquid crystals (LLCs) containing corresponding metal species. Two-dimensional exagonally ordered LLC templates were prepared on conductive substrates from diluted surfactant solutions including water, a nonionic surfactant, ethanol, and metal species by drop-coating. Electrochemical synthesis using such LLC templates enabled the preparation of ordered mesoporous Pt-Au binary alloys without phase segregation. The framework composition in the mesoporous Pt-Au alloy was controlled simply by changing the compositional ratios in the precursor solution. Mesoporous Pt-Au alloys with low Au content exhibited well-ordered 2D hexagonal mesostructures, reflecting those of the original templates. With increasing Au content, however, the mesostructural order gradually decreased, thereby reducing the electrochemically active surface area. Wide-angle X-ray diffraction profiles, X-ray photoelectron spectra, and elemental mapping showed that both Pt and Au were atomically distributed in the frameworks. The electrochemical stability of mesoporous Pt-Au alloys toward methanol oxidation was highly improved relative to that of nonporous Pt and mesoporous Pt films, suggesting that mesoporous Pt-Au alloy films are potentially applicable as electrocatalysts for direct methanol fuel cells. Also, mesoporous Pt-Au alloy electrodes showed a highly sensitive amperometric response for glucose molecules, which will be useful in next-generation enzyme-free glucose sensors.

Retraction Note to: Ultra-High Strength and Ductile Lamellar-Structured Powder Metallurgy Binary Ti-Ta Alloys

NASA Astrophysics Data System (ADS)

Liu, Yong; Xu, Shenghang; Wang, Xin; Li, Kaiyang; Liu, Bin; Wu, Hong; Tang, Huiping

2018-05-01

The editors and authors have retracted the article, "Ultra-High Strength and Ductile Lamellar-Structured Powder Metallurgy Binary Ti-Ta Alloys" by Yong Liu, Shenghang Xu, Xin Wang, Kaiyang Li, Bin Liu, Hong Wu, and Huiping Tang (https://doi.org/10.1007/s11837-015-1801-1).

Interrogation of bimetallic particle oxidation in three dimensions at the nanoscale

PubMed Central

Han, Lili; Meng, Qingping; Wang, Deli; Zhu, Yimei; Wang, Jie; Du, Xiwen; Stach, Eric A.; Xin, Huolin L.

2016-01-01

An understanding of bimetallic alloy oxidation is key to the design of hollow-structured binary oxides and the optimization of their catalytic performance. However, one roadblock encountered in studying these binary oxide systems is the difficulty in describing the heterogeneities that occur in both structure and chemistry as a function of reaction coordinate. This is due to the complexity of the three-dimensional mosaic patterns that occur in these heterogeneous binary systems. By combining real-time imaging and chemical-sensitive electron tomography, we show that it is possible to characterize these systems with simultaneous nanoscale and chemical detail. We find that there is oxidation-induced chemical segregation occurring on both external and internal surfaces. Additionally, there is another layer of complexity that occurs during the oxidation, namely that the morphology of the initial oxide surface can change the oxidation modality. This work characterizes the pathways that can control the morphology in binary oxide materials. PMID:27928998

Study of thermodynamic properties of liquid binary alloys by a pseudopotential method

NASA Astrophysics Data System (ADS)

Vora, Aditya M.

2010-11-01

On the basis of the Percus-Yevick hard-sphere model as a reference system and the Gibbs-Bogoliubov inequality, a thermodynamic perturbation method is applied with the use of the well-known model potential. By applying a variational method, the hard-core diameters are found which correspond to a minimum free energy. With this procedure, the thermodynamic properties such as the internal energy, entropy, Helmholtz free energy, entropy of mixing, and heat of mixing are computed for liquid NaK binary systems. The influence of the local-field correction functions of Hartree, Taylor, Ichimaru-Utsumi, Farid-Heine-Engel-Robertson, and Sarkar-Sen-Haldar-Roy is also investigated. The computed excess entropy is in agreement with available experimental data in the case of liquid alloys, whereas the agreement for the heat of mixing is poor. This may be due to the sensitivity of the latter to the potential parameters and dielectric function.

Generation and performance of special quasirandom structures for studying the elastic properties of random alloys: Application to Al-Ti

NASA Astrophysics Data System (ADS)

von Pezold, Johann; Dick, Alexey; Friák, Martin; Neugebauer, Jörg

2010-03-01

The performance of special-quasirandom structures (SQSs) for the description of elastic properties of random alloys was evaluated. A set of system-independent 32-atom-fcc SQS spanning the entire concentration range was generated and used to determine C11 , C12 , and C44 of binary random substitutional AlTi alloys. The elastic properties of these alloys could be described using the set of SQS with an accuracy comparable to the accuracy achievable by statistical sampling of the configurational space of 3×3×3 (108 atom, C44 ) and 4×4×4 (256 atom, C11 and C12 ) fcc supercells, irrespective of the impurity concentration. The smaller system size makes the proposed SQS ideal candidates for the ab initio determination of the elastic constants of random substitutional alloys. The set of optimized SQS is provided.

Effects of gravity reduction on phase equilibria. Part 1: Unary and binary isostructural solids

NASA Technical Reports Server (NTRS)

Larson, D. J., Jr.

1975-01-01

Analysis of the Skylab II M553 Experiment samples resulted in the hypothesis that the reduced gravity environment was altering the melting and solidification reactions. A theoretical study was conducted to define the conditions under which such alteration of phase relations is feasible, determine whether it is restricted to space processing, and, if so, ascertain which alloy systems or phase reactions are most likely to demonstrate such effects. Phase equilibria of unary and binary systems with a single solid phase (unary and isomorphous) were considered.

Electrotransfer in Liquid Binary Aluminum Alloys

NASA Astrophysics Data System (ADS)

Tekuchev, V. V.; Kalinkin, D. P.; Ivanova, I. V.

2018-07-01

The mobility of ions in a liquid binary metal system based on aluminum is calculated for the first time in a wide range of concentrations, based on studies of its resistivity and self-diffusion coefficient. It is established that in an Al-Cu system, the ions of aluminum move to the anode, while Al-Mg, Al-Sn, and Al-Sb move to the cathode; i.e., there is inversion of the electrotransfer of aluminum ions. When the concentration of a component is reduced, the mobility of its ions is increased by the module.

Structure and Properties of Titanium Tantalum Alloys for Biocompatibility

NASA Astrophysics Data System (ADS)

Huber, Daniel E.

In this thesis, the phase stability and elastic modulus of Ti-Ta simple binary alloys as well as alloys with small additions of ternary elements have been studied. The binary alloy from a nominal 8 to 28 wt.% Ta was first explored using a combinatorial approach. This approach included Laser Engineered Net Shape (LENSTM) processing of materials and subsequent characterization by instrumented indentation and site specific Transmission Electron Microscopy (TEM). The composition range of 15 to 75 wt.% Ta was further explored by more traditional methods that included vacuum arc melting high purity elements, X-Ray Diffraction (XRD) and modulus measurements made by ultrasonic methods. Beyond the simple binary, alloys with low levels of ternary elements, oxygen, aluminum, zirconium and small additions of rare earth oxides were investigated. The crystal structure with space group Cmcm was chosen for it applicability with P63/mmc and Im-3¯m sub group / super group symmetry. This provides a consistent crystal structure framework for the purpose of studying the alpha to beta transformation pathway and associated alpha' and alpha'' martensitic phases. In this case, the pathway is defined by both the lattice parameters and the value of the parameter "y", where the parameter "y" describes the atomic positions of the [002]alpha plane. It was found that the lattice parameter changes in the Ti-Ta binary alloys are similar to structures reported for compositions in the Ti-Nb system of similar atomic percentages. Although samples produced by the LENSTM; process and characterized by instrumented indentation demonstrated the correct trends in modulus behavior, absolute agreement was not seen with modulus values published in literature. Alloys of the binary Ti-Ta system produced from high purity materials do indeed show close agreement with literature where there exist two minima of modulus near the compositions of Ti-28Ta wt.% and Ti-68Ta wt.%. These two minima occur at the discreet boundary between alpha' / alpha'' and alpha'' / beta respectively. The role of oxygen as an alloying addition was studied as it relates to the stability of alpha' and alpha'' martensite, here it was found that oxygen will stabilize alpha' yet cause an increase in the Young's modulus. Rare earth additions to getter interstitial oxygen in the high purity materials show no further reduction in modulus. Conversely, additions of another alpha stabilizer, Al, proved to lower the alpha' stability, with one composition exhibiting a modulus as low as 53 GPa. Zirconium being a neutral element regarding alpha and beta stability slightly changed the structure and lattice parameter, while making a little or no difference in the observed modulus. Observations by TEM of quenched specimens indicate the rise in modulus observed between the two minima is not caused the appearance of o. Rather weak o reflections were observed in Ti-65Ta wt.% in the as arc-melted condition and on annealing for 450°C for 24 hours. Precipitates of o were not clearly identified by dark-field TEM imaging. High Resolution Scanning Transmission Electron Microscopy (HRSTEM) of the aged specimen indicated that o might exist as 3-5nm particles.

Gravity-induced anomalies in interphase spacing reported for binary eutectics.

PubMed

Smith, Reginald W

2002-10-01

It has been reasoned that desirable microstructural refinement in binary eutectics could result from freezing in reduced-gravity. It is recognized that the interphase spacing in a binary eutectic is controlled by solute transport and that, on Earth, buoyancy-driven convection may enhance this. Hence, it has been presumed that the interphase spacing ought to decrease when a eutectic alloy is frozen under conditions of much-reduced gravity, where such buoyancy effects would be largely absent. The result of such speculation has been that many workers have frozen various eutectics under reduced gravity and have reported that, although some eutectics became finer, others showed no change, and some even became coarser. This reported varied behavior will be reviewed in the light of long term studies by the author at Queen's University, including recent microgravity studies in which samples of two eutectic alloy systems, MnBi-Bi and MnSb-Sb, were frozen under very stable conditions and showed no change in interphase spacing.

Enthalpies of mixing of liquid systems for lead free soldering: Co–Sb–Sn

PubMed Central

Elmahfoudi, A.; Sabbar, A.; Flandorfer, H.

2012-01-01

The partial and integral enthalpy of mixing of molten ternary Co–Sb–Sn alloys was determined performing high temperature drop calorimetry in a large compositional range at 1273 K. Measurements have been done along five sections, xSb/xSn ≈ 1:1, xSb/xSn ≈ 1:3, xSb/xSn ≈ 3:1, xCo/xSn ≈ 1:4, and xCo/xSb ≈ 1:5. Additionally, binary alloys of the constituent systems Co–Sb and Co–Sn were investigated at the same temperature. All the binary data were evaluated by means of a standard Redlich–Kister polynomial fit whereas ternary data were fitted on the basis of an extended Redlich–Kister–Muggianu model for substitutional solutions. An iso-enthalpy plot of the ternary system was constructed. In addition, the extrapolation Model of Toop was applied and compared to our data. PMID:27087752

Enthalpies of mixing of liquid systems for lead free soldering: Co-Sb-Sn.

PubMed

Elmahfoudi, A; Sabbar, A; Flandorfer, H

2012-04-01

The partial and integral enthalpy of mixing of molten ternary Co-Sb-Sn alloys was determined performing high temperature drop calorimetry in a large compositional range at 1273 K. Measurements have been done along five sections, x Sb / x Sn  ≈ 1:1, x Sb / x Sn  ≈ 1:3, x Sb / x Sn  ≈ 3:1, x Co / x Sn  ≈ 1:4, and x Co / x Sb  ≈ 1:5. Additionally, binary alloys of the constituent systems Co-Sb and Co-Sn were investigated at the same temperature. All the binary data were evaluated by means of a standard Redlich-Kister polynomial fit whereas ternary data were fitted on the basis of an extended Redlich-Kister-Muggianu model for substitutional solutions. An iso-enthalpy plot of the ternary system was constructed. In addition, the extrapolation Model of Toop was applied and compared to our data.

Embedded atom method potential for studying mechanical properties of binary Cu–Au alloys

NASA Astrophysics Data System (ADS)

Gola, Adrien; Pastewka, Lars

2018-07-01

We present an embedded atom method (EAM) potential for the binary Cu–Au system. The unary phases are described by two well-tested unary EAM potentials for Cu and Au. We fitted the interaction between Cu and Au to experimental properties of the binary intermetallic phases Cu3Au, CuAu and CuAu3. Particular attention has been paid to reproducing stacking fault energies in order to obtain a potential suitable for studying deformation in this binary system. The resulting energies, lattice constant, elastic properties and melting points are in good agreement with available experimental data. We use nested sampling to show that our potential reproduces the phase boundaries between intermetallic phases and the disordered face-centered cubic solid solution. We benchmark our potential against four popular Cu–Au EAM parameterizations and density-functional theory calculations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geng, J.; Nlebedim, I. C.; Besser, M. F.

A bulk combinatorial approach for synthesizing alloy libraries using laser engineered net shaping (LENS; i.e., 3D printing) was utilized to rapidly assess material systems for magnetic applications. The LENS system feeds powders in different ratios into a melt pool created by a laser to synthesize samples with bulk (millimeters) dimensions. By analyzing these libraries with autosampler differential scanning calorimeter/thermal gravimetric analysis and vibrating sample magnetometry, we are able to rapidly characterize the thermodynamic and magnetic properties of the libraries. Furthermore, the Fe-Co binary alloy was used as a model system and the results were compared with data in the literature.

Alloy Design Data Generated for B2-Ordered Compounds

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Bozzolo, Guillermo; Abel, Phillip B.

2003-01-01

Developing alloys based on ordered compounds is significantly more complicated than developing designs based on disordered materials. In ordered compounds, the major constituent elements reside on particular sublattices. Therefore, the addition of a ternary element to a binary-ordered compound is complicated by the manner in which the ternary addition is made (at the expense of which binary component). When ternary additions are substituted for the wrong constituent, the physical and mechanical properties usually degrade. In some cases the resulting degradation in properties can be quite severe. For example, adding alloying additions to NiAl in the wrong combination (i.e., alloying additions that prefer the Al sublattice but are added at the expense of Ni) will severely embrittle the alloy to the point that it can literally fall apart during processing on cooling from the molten state. Consequently, alloying additions that strongly prefer one sublattice over another should always be added at the expense of that component during alloy development. Elements that have a very weak preference for a sublattice can usually be safely added at the expense of either element and will accommodate any deviation from stoichiometry by filling in for the deficient component. Unfortunately, this type of information is not known beforehand for most ordered systems. Therefore, a computational survey study, using a recently developed quantum approximate method, was undertaken at the NASA Glenn Research Center to determine the preferred site occupancy of ternary alloying additions to 12 different B2-ordered compounds including NiAl, FeAl, CoAl, CoFe, CoHf, CoTi, FeTi, RuAl, RuSi, RuHf, RuTi, and RuZr. Some of these compounds are potential high temperature structural alloys; others are used in thin-film magnetic and other electronic applications. The results are summarized. The italicized elements represent the previous sum total alloying information known and verify the computational method used to establish the table. Details of the computational procedures used to determine the preferred site occupancy can be found in reference 2. As further substantiation of the validity of the technique, and its extension to even more complicated systems, it was applied to two simultaneous alloying additions in an ordered alloy.

Microstructural Characterization of Base Metal Alloys with Conductive Native Oxides for Electrical Contact Applications

NASA Astrophysics Data System (ADS)

Senturk, Bilge Seda

Metallic contacts are a ubiquitous method of connecting electrical and electronic components/systems. These contacts are usually fabricated from base metals because they are inexpensive, have high bulk electrical conductivities and exhibit excellent formability. Unfortunately, such base metals oxidize in air under ambient conditions, and the characteristics of the native oxide scales leads to contact resistances orders of magnitude higher than those for mating bare metal surface. This is a critical technological issue since the development of unacceptably high contact resistances over time is now by far the most common cause of failure in electrical/electronic devices and systems. To overcome these problems, several distinct approaches are developed for alloying base metals to promote the formation of self-healing inherently conductive native oxide scales. The objective of this dissertation study is to demonstrate the viability of these approaches through analyzing the data from Cu-9La (at%) and Fe-V binary alloy systems. The Cu-9 La alloy structure consists of eutectic colonies tens of microns in diameter wherein a rod-like Cu phase lies within a Cu6La matrix phase. The thin oxide scale formed on the Cu phase was found to be Cu2O as expected while the thicker oxide scale formed on the Cu6La phase was found to be a polycrystalline La-rich Cu2O. The enhanced electrical conductivity in the native oxide scale of the Cu-9La alloy arises from heavy n-type doping of the Cu2O lattice by La3+. The Fe-V alloy structures consist of a mixture of large elongated and equiaxed grains. A thin polycrystalline Fe3O4 oxide scale formed on all of the Fe-V alloys. The electrical conductivities of the oxide scales formed on the Fe-V alloys are higher than that formed on pure Fe. It is inferred that this enhanced conductivity arises from doping of the magnetite with V+4 which promotes electron-polaron hopping. Thus, it has been demonstrated that even in simple binary alloy systems one can obtain a dramatic reduction in the contact resistances of alloy oxidized surfaces as compared with those of the pure base metals.

Magnetic properties of doped Mn-Ga alloys made by mechanical milling and heat treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Daniel R.; National High Magnetic Field Laboratory, Tallahassee, FL 32310; Han, Ke

2016-05-15

Mn-Ga alloys have shown hard magnetic properties, even though these alloys contain no rare-earth metals. However, much work is needed before rare-earth magnets can be replaced. We have examined the magnetic properties of bulk alloys made with partial replacement of both the Mn and Ga elements in the Mn{sub 0.8}Ga{sub 0.2} system. Bulk samples of Mn-Ga-Bi, Mn-Ga-Al, Mn-Fe-Ga and Mn-(FeB)-Ga alloys were fabricated and studied using mechanically milling and heat treatments while altering the atomic percentage of the third element between 2.5 and 20 at%. The ternary alloy exhibits all hard magnetic properties at room temperature with large coercivity. Annealedmore » Mn-Ga-X bulk composites exhibit high coercivities up to 16.6 kOe and remanence up to 9.8 emu/g, that is increased by 115% over the binary system.« less

Development of a Novel, Bicombinatorial Approach to Alloy Development, and Application to Rapid Screening of Creep Resistant Titanium Alloys

NASA Astrophysics Data System (ADS)

Martin, Brian

Combinatorial approaches have proven useful for rapid alloy fabrication and optimization. A new method of producing controlled isothermal gradients using the Gleeble Thermomechanical simulator has been developed, and demonstrated on the metastable beta-Ti alloy beta-21S, achieving a thermal gradient of 525-700 °C. This thermal gradient method has subsequently been coupled with existing combinatorial methods of producing composition gradients using the LENS(TM) additive manufacturing system, through the use of elemental blended powders. This has been demonstrated with a binary Ti-(0-15) wt% Cr build, which has subsequently been characterized with optical and electron microscopy, with special attention to the precipitate of TiCr2 Laves phases. The TiCr2 phase has been explored for its high temperature mechanical properties in a new oxidation resistant beta-Ti alloy, which serves as a demonstration of the new bicombinatorial methods developed as applied to a multicomponent alloy system.

Surface tension modelling of liquid Cd-Sn-Zn alloys

NASA Astrophysics Data System (ADS)

Fima, Przemyslaw; Novakovic, Rada

2018-06-01

The thermodynamic model in conjunction with Butler equation and the geometric models were used for the surface tension calculation of Cd-Sn-Zn liquid alloys. Good agreement was found between the experimental data for limiting binaries and model calculations performed with Butler model. In the case of ternary alloys, the surface tension variation with Cd content is better reproduced in the case of alloys lying on vertical sections defined by high Sn to Zn molar fraction ratio. The calculated surface tension is in relatively good agreement with the available experimental data. In addition, the surface segregation of liquid ternary Cd-Sn-Zn and constituent binaries has also been calculated.

Durable pd-based alloy and hydrogen generation membrane thereof

DOEpatents

Benn, Raymond C.; Opalka, Susanne M.; Vanderspurt, Thomas Henry

2010-02-02

A durable Pd-based alloy is used for a H.sub.2-selective membrane in a hydrogen generator, as in the fuel processor of a fuel cell plant. The Pd-based alloy includes Cu as a binary element, and further includes "X", where "X" comprises at least one metal from group "M" that is BCC and acts to stabilize the .beta. BCC phase for stability during operating temperatures. The metal from group "M" is selected from the group consisting of Fe, Cr, Nb, Ta, V, Mo, and W, with Nb and Ta being most preferred. "X" may further comprise at least one metal from a group "N" that is non-BCC, preferably FCC, that enhances other properties of the membrane, such as ductility. The metal from group "N" is selected from the group consisting of Ag, Au, Re, Ru, Rh, Y, Ce, Ni, Ir, Pt, Co, La and In. The at. % of Pd in the binary Pd--Cu alloy ranges from about 35 at. % to about 55 at. %, and the at. % of "X" in the higher order alloy, based on said binary alloy, is in the range of about 1 at. % to about 15 at. %. The metals are selected according to a novel process.

Contribution to the aluminum-tin-zinc ternary system

NASA Astrophysics Data System (ADS)

Drápala, J.; Kostiuková, G.; Losertová, M.

2017-11-01

The Sn-Zn-Al alloys are one of significant candidates in the proposal of alternative lead-free solders for higher temperature soldering. This paper deals with the study of the aluminum-tin-zinc system. Twenty Sn-Zn-Al alloys together with six binary Sn-Zn alloys were prepared and studied experimentally. Alloys were prepared from pure Sn, Zn and Al (melting and cooling in a vacuum resistance furnace). The specimens were studied metallographically including the micro-hardness measurements, complete chemical analysis (ICP-AES, OES), X-ray micro-analysis of alloys by SEM and EDX in order to determine the composition and identification of individual phases. Significant temperatures and enthalpies of phase transformations were determined by DTA. After long-term annealing of selected alloys in vacuum followed by quenching the structural and chemical microanalyses of the present phases and their limit concentrations were carried out. The achieved results were compared with the thermodynamic modelling of the ternary Sn-Zn-Al system (computer programs THERMOCALC, MTDATA, PANDAT and databases CALPHAD, COST). Electrical resistivity, density, magnetic susceptibility and wettability of Sn-Zn-Al solders were measured as well.

Superconducting compounds and alloys research

NASA Technical Reports Server (NTRS)

Otto, G.

1975-01-01

Resistivity measurements as a function of temperature were performed on alloys of the binary material system In sub(1-x) Bi sub x for x varying between 0 and 1. It was found that for all single-phase alloys (the pure elements, alpha-In, and the three intermetallic compounds) at temperatures sufficiently above the Debye-temperature, the resistivity p can be expressed as p = a sub o T(n), where a sub o and n are composition-dependent constants. The same exponential relationship can also be applied for the sub-system In-In2Bi, when the two phases are in compositional equilibrium. Superconductivity measurements on single and two-phase alloys can be explained with respect to the phase diagram. There occur three superconducting phases (alpha-In, In2Bi, and In5Bi3) with different transition temperatures in the alloying system. The magnitude of the transition temperatures for the various intermetallic phases of In-Bi is such that the disappearance or occurrence of a phase in two component alloys can be demonstrated easily by means of superconductivity measurements.

Analysis and Thermodynamic Prediction of Hydrogen Solution in Solid and Liquid Multicomponent Aluminum Alloys

NASA Astrophysics Data System (ADS)

Anyalebechi, P. N.

Reported experimentally determined values of hydrogen solubility in liquid and solid Al-H and Al-H-X (where X = Cu, Si, Zn, Mg, Li, Fe or Ti) systems have been critically reviewed and analyzed in terms of Wagner's interaction parameter. An attempt has been made to use Wagner's interaction parameter and statistic linear regression models derived from reported hydrogen solubility limits for binary aluminum alloys to predict the hydrogen solubility limits in liquid and solid (commercial) multicomponent aluminum alloys. Reasons for the observed poor agreement between the predicted and experimentally determined hydrogen solubility limits are discussed.

Prediction of novel alloy phases of Al with Sc or Ta

PubMed Central

Bilić, Ante; Gale, Julian D.; Gibson, Mark A.; Wilson, Nick; McGregor, Kathie

2015-01-01

Using the evolutionary optimization algorithm, as implemented in the USPEX crystal predictor program, and first principles total energy calculations, the compositional phase diagrams for Al-Sc and Al-Ta alloy systems at zero temperature and pressure have been calculated. In addition to the known binary intermetallic phases, new potentially stable alloys, AlSc3 and AlTa7, have been identified in the Al-poor region of the phase diagram. The dynamic and thermal stability of their lattices has been confirmed from the calculated vibrational normal mode spectra in the harmonic approximation. PMID:25950915

Phase Composition and Hardening of Castable Al - Ca - Ni - Sc Alloys Containing 0.3% Sc

NASA Astrophysics Data System (ADS)

Belov, N. A.; Naumova, E. A.; Bazlova, T. A.; Doroshenko, V. V.

2017-05-01

The phase composition of aluminum alloys of the Al - Ca - Ni - Sc system containing 0.3 wt.% Sc is studied. It is shown that the aluminum solid solution may be in equilibrium not only with binary phases (Al4Ca, Al3Sc and Al3Ni) but also with a ternary Al9NiCa compound. The temperature of attainment of maximum hardening due to precipitation of nanoparticles of phase Al3Sc is determined for all the alloys studied. Principal possibility of creation of castable alloys based on an (Al) + Al4Ca + Al9NiCa eutectic, the hardening heat treatment of which does not require quenching, is substantiated.

Mashing up metals with carbothermal shock

NASA Astrophysics Data System (ADS)

Skrabalak, Sara E.

2018-03-01

Different materials and the capabilities they enabled have marked the ages of civilization. For example, the malleable copper alloys of the Bronze Age provided harder and more durable tools. Most exploration of new alloys has focused on random alloys, in which the alloying metal sites have no metal preference. In binary and ternary metal systems, dissimilar elements do not mix readily at high concentrations, which has limited alloying studies to intermetallics (ordered multimetallic phases) and random alloys, in which minor components are added to a principal element. In 2004, crystalline metal alloys consisting of five or more principal elements in equal or nearly equal amounts (1, 2) were reported that were stabilized by their high configurational entropy. Unlike most random alloys, the “high-entropy” alloys (3, 4) reside in the centers of their multidimensional phase diagrams (see the figure, right). On page 1489 of this issue, Yao et al. (5) present an innovative and general route to high-entropy alloys that can mix up to eight elements into single-phase, size-controlled nanoparticles (NPs).

Mechanical Characterisation and Biomechanical and Biological Behaviours of Ti-Zr Binary-Alloy Dental Implants

PubMed Central

Jiménez-Garrudo, Antonio; Gil-Mur, Francisco Javier; Manero, José María; Punset-Fuste, Miquel; Chávarri-Prado, David; Diéguez-Pereira, Markel; Monticelli, Francesca

2017-01-01

The objective of the study is to characterise the mechanical properties of Ti-15Zr binary alloy dental implants and to describe their biomechanical behaviour as well as their osseointegration capacity compared with the conventional Ti-6Al-4V (TAV) alloy implants. The mechanical properties of Ti-15Zr binary alloy were characterised using Roxolid© implants (Straumann, Basel, Switzerland) via ultrasound. Their biomechanical behaviour was described via finite element analysis. Their osseointegration capacity was compared via an in vivo study performed on 12 adult rabbits. Young's modulus of the Roxolid© implant was around 103 GPa, and the Poisson coefficient was around 0.33. There were no significant differences in terms of Von Mises stress values at the implant and bone level between both alloys. Regarding deformation, the highest value was observed for Ti-15Zr implant, and the lowest value was observed for the cortical bone surrounding TAV implant, with no deformation differences at the bone level between both alloys. Histological analysis of the implants inserted in rabbits demonstrated higher BIC percentage for Ti-15Zr implants at 3 and 6 weeks. Ti-15Zr alloy showed elastic properties and biomechanical behaviours similar to TAV alloy, although Ti-15Zr implant had a greater BIC percentage after 3 and 6 weeks of osseointegration. PMID:29318142

Method for preparing homogeneous single crystal ternary III-V alloys

DOEpatents

Ciszek, Theodore F.

1991-01-01

A method for producing homogeneous, single-crystal III-V ternary alloys of high crystal perfection using a floating crucible system in which the outer crucible holds a ternary alloy of the composition desired to be produced in the crystal and an inner floating crucible having a narrow, melt-passing channel in its bottom wall holds a small quantity of melt of a pseudo-binary liquidus composition that would freeze into the desired crystal composition. The alloy of the floating crucilbe is maintained at a predetermined lower temperature than the alloy of the outer crucible, and a single crystal of the desired homogeneous alloy is pulled out of the floating crucible melt, as melt from the outer crucible flows into a bottom channel of the floating crucible at a rate that corresponds to the rate of growth of the crystal.

Interpreting the Combustion Process for High-Performance ZrNiSn Thermoelectric Materials.

PubMed

Hu, Tiezheng; Yang, Dongwang; Su, Xianli; Yan, Yonggao; You, Yonghui; Liu, Wei; Uher, Ctirad; Tang, Xinfeng

2018-01-10

The ZrNiSn alloy, a member of the half-Heusler family of thermoelectric materials, shows great potential for mid-to-high-temperature power generation applications due to its excellent thermoelectric properties, robust mechanical properties, and good thermal stability. The existing synthesis processes of half-Heusler alloys are, however, rather time and energy intensive. In this study, single-phase ZrNiSn bulk materials were prepared by self-propagating high-temperature synthesis (SHS) combined with spark plasma sintering (SPS) for the first time. The analysis of thermodynamic and kinetic processes shows that the SHS reaction in the ternary ZrNiSn alloy is different from the more usual binary systems. It consists of a series of SHS reactions and mass transfers triggered by the SHS fusion of the binary Ni-Sn system that eventually culminates in the formation of single-phase ternary ZrNiSn in a very short time, which reduced the synthesis period from few days to less than an hour. Moreover, the nonequilibrium feature induces Ni interstitials in the structure, which simultaneously enhances the electrical conductivity and decreases the thermal conductivity, which is favorable for thermoelectric properties. The maximum thermoelectric figure of merit ZT of the SHS + SPS-processed ZrNiSn 1-x Sb x alloy reached 0.7 at 870 K. This study opens a new avenue for the fast and low-cost fabrication of half-Heusler thermoelectric materials.

Nanostructured Platinum Alloys for Use as Catalyst Materials

NASA Technical Reports Server (NTRS)

Narayan, Sri R. (Inventor); Hays, Charles C. (Inventor)

2015-01-01

A series of binary and ternary Pt-alloys, that promote the important reactions for catalysis at an alloy surface; oxygen reduction, hydrogen oxidation, and hydrogen and oxygen evolution. The first two of these reactions are essential when applying the alloy for use in a PEMFC.

Nanostructured Platinum Alloys for Use as Catalyst Materials

NASA Technical Reports Server (NTRS)

Hays, Charles C. (Inventor); Narayan, Sri R. (Inventor)

2013-01-01

A series of binary and ternary Pt-alloys, that promote the important reactions for catalysis at an alloy surface; oxygen reduction, hydrogen oxidation, and hydrogen and oxygen evolution. The first two of these reactions are essential when applying the alloy for use in a PEMFC.

Enthalpy of mixing of liquid systems for lead free soldering: Ni-Sb-Sn system.

PubMed

Elmahfoudi, A; Fürtauer, S; Sabbar, A; Flandorfer, H

2012-04-20

The partial and integral enthalpies of mixing of liquid ternary Ni-Sb-Sn alloys were determined along five sections x Sb / x Sn  = 3:1, x Sb / x Sn  = 1:1, x Sb / x Sn  = 1:3, x Ni / x Sn  = 1:4, and x Ni / x Sb  = 1:4 at 1000 °C in a large compositional range using drop calorimetry techniques. The mixing enthalpy of Ni-Sb alloys was determined at the same temperature and described by a Redlich-Kister polynomial. The other binary data were carefully evaluated from literature values. Our measured ternary data were fitted on the basis of an extended Redlich-Kister-Muggianu model for substitutional solutions. Additionally, a comparison of these results to the extrapolation model of Toop is given. The entire ternary system shows exothermic values of Δ mix H ranging from approx. -1300 J/mol, the minimum in the Sb-Sn binary system down to approx. -24,500 J/mol towards Ni-Sb. No significant ternary interaction could be deduced from our data.

ZIRCONIUM ALLOY

DOEpatents

Wilhelm, H.A.; Ames, D.P.

1959-02-01

A binary zirconiuin--antimony alloy is presented which is corrosion resistant and hard containing from 0.07% to 1.6% by weight of Sb. The alloys have good corrosion resistance and are useful in building equipment for the chemical industry.

NUMERICAL ANALYSES FOR TREATING DIFFUSION IN SINGLE-, TWO-, AND THREE-PHASE BINARY ALLOY SYSTEMS

NASA Technical Reports Server (NTRS)

Tenney, D. R.

1994-01-01

This package consists of a series of three computer programs for treating one-dimensional transient diffusion problems in single and multiple phase binary alloy systems. An accurate understanding of the diffusion process is important in the development and production of binary alloys. Previous solutions of the diffusion equations were highly restricted in their scope and application. The finite-difference solutions developed for this package are applicable for planar, cylindrical, and spherical geometries with any diffusion-zone size and any continuous variation of the diffusion coefficient with concentration. Special techniques were included to account for differences in modal volumes, initiation and growth of an intermediate phase, disappearance of a phase, and the presence of an initial composition profile in the specimen. In each analysis, an effort was made to achieve good accuracy while minimizing computation time. The solutions to the diffusion equations for single-, two-, and threephase binary alloy systems are numerically calculated by the three programs NAD1, NAD2, and NAD3. NAD1 treats the diffusion between pure metals which belong to a single-phase system. Diffusion in this system is described by a one-dimensional Fick's second law and will result in a continuous composition variation. For computational purposes, Fick's second law is expressed as an explicit second-order finite difference equation. Finite difference calculations are made by choosing the grid spacing small enough to give convergent solutions of acceptable accuracy. NAD2 treats diffusion between pure metals which form a two-phase system. Diffusion in the twophase system is described by two partial differential equations (a Fick's second law for each phase) and an interface-flux-balance equation which describes the location of the interface. Actual interface motion is obtained by a mass conservation procedure. To account for changes in the thicknesses of the two phases as diffusion progresses, a variable grid technique developed by Murray and Landis is employed. These equations are expressed in finite difference form and solved numerically. Program NAD3 treats diffusion between pure metals which form a two-phase system with an intermediate third phase. Diffusion in the three-phase system is described by three partial differential expressions of Fick's second law and two interface-flux-balance equations. As with the two-phase case, a variable grid finite difference is used to numerically solve the diffusion equations. Computation time is minimized without sacrificing solution accuracy by treating the three-phase problem as a two-phase problem when the thickness of the intermediate phase is less than a preset value. Comparisons between these programs and other solutions have shown excellent agreement. The programs are written in FORTRAN IV for batch execution on the CDC 6600 with a central memory requirement of approximately 51K (octal) 60 bit words.

The structural, electronic, magnetic and optical properties of the half-metallic binary alloys ZCl3 (Z=Be, Mg, Ca, Sr): A first-principles study

NASA Astrophysics Data System (ADS)

Song, Jun-Tao; Zhang, Jian-Min

2018-06-01

The investigations of the electronic and magnetic properties show the binary Heusler alloys ZCl3 (Z = Be, Mg, Ca, Sr) are half-metallic (HM) ferromagnets with an integer magnetic moment (Mt) of 1 μB /f.u.. The alloy BeCl3 is thermodynamic meta-stable, while other alloys are thermodynamic stable according to their cohesive energies and formation energies. Moreover, wide HM regions for alloys ZCl3 (Z = Be, Mg, Ca, Sr) show their HM characters are robust when the lattices are expanded or compressed under uniform and tetragonal strains. Finally, some optical properties are analyzed in detail, such as the dielectric function, the absorption coefficient, the refractive index and the extinction coefficient.

The friction and wear of metals and binary alloys in contact with an abrasive grit of single-crystal silicon carbide

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1979-01-01

Sliding friction experiments were conducted with various metals and iron-base binary alloys (alloying elements Ti, Cr, Mn, Ni, Rh and W) in contact with single crystal silicon carbide riders. Results indicate that the friction force in the plowing of metal and the groove height (corresponding to the wear volume of the groove) decrease linearly as the shear strength of the bulk metal increases. The coefficient of friction and groove height generally decrease, and the contact pressure increases with an increase in solute content of binary alloys. There appears to be very good correlation of the solute to iron atomic ratio with the decreasing rate of change of coefficient of friction, the decreasing rate of change of groove height and the increasing rate of change of contact pressure with increasing solute content. These rates of change increase as the solute to iron atomic radius ratio increases or decreases from unity.

Diffuse scattering measurements of static atomic displacements in crystalline binary solid solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ice, G.E.; Sparks, C.J.; Jiang, X.

1997-09-01

Diffuse x-ray scattering from crystalline solid solutions is sensitive to both local chemical order and local bond distances. In short-range ordered alloys, fluctuations of chemistry and bond distances break the long-range symmetry of the crystal within a local region and contribute to the total energy of the alloy. Recent use of tunable synchrotron radiation to change the x-ray scattering contrast between elements has greatly advanced the measurement of bond distances between the three kinds of atom pairs found in crystalline binary alloys. The estimated standard deviation on these recovered static displacements approaches {+-}0.001 {angstrom} (0.0001 nm) which is an ordermore » of magnitude more precise than obtained with EXAFS. In addition, both the radial and tangential displacements can be recovered to five near neighbors and beyond. These static displacement measurements provide new information which challenges the most advanced theoretical models of binary crystalline alloys. 29 refs., 8 figs., 2 tabs.« less

Nonergodicity of microfine binary systems

NASA Astrophysics Data System (ADS)

Son, L. D.; Sidorov, V. E.; Popel', P. S.; Shul'gin, D. B.

2016-02-01

The correction to the equation of state that is related to the nonergodicity of diffusion dynamics is discussed for a binary solid solution with a limited solubility. It is asserted that, apart from standard thermodynamic variables (temperature, volume, concentration), this correction should be taken into account in the form of the average local chemical potential fluctuations associated with microheterogeneity in order to plot a phase diagram. It is shown that a low value of this correction lowers the miscibility gap and that this gap splits when this correction increases. This situation is discussed for eutectic systems and Ga-Pb, Fe-Cu, and Cu-Zr alloys.

Normal evaporation of binary alloys

NASA Technical Reports Server (NTRS)

Li, C. H.

1972-01-01

In the study of normal evaporation, it is assumed that the evaporating alloy is homogeneous, that the vapor is instantly removed, and that the alloy follows Raoult's law. The differential equation of normal evaporation relating the evaporating time to the final solute concentration is given and solved for several important special cases. Uses of the derived equations are exemplified with a Ni-Al alloy and some binary iron alloys. The accuracy of the predicted results are checked by analyses of actual experimental data on Fe-Ni and Ni-Cr alloys evaporated at 1600 C, and also on the vacuum purification of beryllium. These analyses suggest that the normal evaporation equations presented here give satisfactory results that are accurate to within an order of magnitude of the correct values, even for some highly concentrated solutions. Limited diffusion and the resultant surface solute depletion or enrichment appear important in the extension of this normal evaporation approach.

Viscosity and diffusivity in melts: from unary to multicomponent systems

NASA Astrophysics Data System (ADS)

Chen, Weimin; Zhang, Lijun; Du, Yong; Huang, Baiyun

2014-05-01

Viscosity and diffusivity, two important transport coefficients, are systematically investigated from unary melt to binary to multicomponent melts in the present work. By coupling with Kaptay's viscosity equation of pure liquid metals and effective radii of diffusion species, the Sutherland equation is modified by taking the size effect into account, and further derived into an Arrhenius formula for the convenient usage. Its reliability for predicting self-diffusivity and impurity diffusivity in unary liquids is then validated by comparing the calculated self-diffusivities and impurity diffusivities in liquid Al- and Fe-based alloys with the experimental and the assessed data. Moreover, the Kozlov model was chosen among various viscosity models as the most reliable one to reproduce the experimental viscosities in binary and multicomponent melts. Based on the reliable viscosities calculated from the Kozlov model, the modified Sutherland equation is utilized to predict the tracer diffusivities in binary and multicomponent melts, and validated in Al-Cu, Al-Ni and Al-Ce-Ni melts. Comprehensive comparisons between the calculated results and the literature data indicate that the experimental tracer diffusivities and the theoretical ones can be well reproduced by the present calculations. In addition, the vacancy-wind factor in binary liquid Al-Ni alloys with the increasing temperature is also discussed. What's more, the calculated inter-diffusivities in liquid Al-Cu, Al-Ni and Al-Ag-Cu alloys are also in excellent agreement with the measured and theoretical data. Comparisons between the simulated concentration profiles and the measured ones in Al-Cu, Al-Ce-Ni and Al-Ag-Cu melts are further used to validate the present calculation method.

Interrogation of bimetallic particle oxidation in three dimensions at the nanoscale

DOE PAGES

Han, Lili; Meng, Qingping; Wang, Deli; ...

2016-12-08

An understanding of bimetallic alloy oxidation is key to the design of hollow-structured binary oxides and the optimization of their catalytic performance. However, one roadblock encountered in studying these binary oxide systems is the difficulty in describing the heterogeneities that occur in both structure and chemistry as a function of reaction coordinate. This is due to the complexity of the three-dimensional mosaic patterns that occur in these heterogeneous binary systems. By combining real-time imaging and chemical-sensitive electron tomography, we show that it is possible to characterize these systems with simultaneous nanoscale and chemical detail. We find that there is oxidation-inducedmore » chemical segregation occurring on both external and internal surfaces. Additionally, there is another layer of complexity that occurs during the oxidation, namely that the morphology of the initial oxide surface can change the oxidation modality. As a result, this work characterizes the pathways that can control the morphology in binary oxide materials.« less

Plasma Processing Systems for the Manufacture of Refractory Metals and their Alloys for Military Needs

DTIC Science & Technology

1978-10-09

melting point is around 4000*K. An exceedingly interesting feature of these solidification composites is the formation of fibrous MC type carbide ...the matrix could be refractory metal binary alloys with copper or uranium and the eutectic phase could be carbide of tungsten, * molybdenum, tantalum or...42 Accs -n or - *DTTI Tf Avn ! -7ll ’ i CrDi t , l’’*i,;. LIST OF FIGURES FIG. 1 Flow Diagram of Cemented Carbide Manufacture

Effect of solution treatment on the microstructure, tensile properties, and corrosion behavior of the Mg-5Sn-2Zn-0.1Mn alloy

NASA Astrophysics Data System (ADS)

El Mahallawy, N.; Hammouda, R.; Shoeib, M.; Diaa, Alia A.

2018-01-01

Working on magnesium alloys containing relatively inexpensive alloying elements such as tin, zinc, and manganese have been a target for many studies. The binary Mg-Sn and Mg-Zn systems have a wide range of solid solubility which make them heat-treatable alloys. In the present study, the microstructure, tensile properties, and corrosion behavior of the Mg-5Sn-2Zn-0.1Mn alloy was studied in the as cast state and after heat treatment at a temperature reaching 450 °C for about 24 h. It was found that a noticeable enhancement in strength and corrosion resistance was achieved through heat treatment. The strength of the as cast alloy increased from 76.24 ± 6.21 MPa to 187.33 ± 10.3 MPa, while the corrosion rate decreased from 1.129 to 0.399 mm y-1.

Precipitation-Strengthened, High-Temperature, High-Force Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Draper, Susan L.; Nathal, Michael V.; Crombie, Edwin A.

2008-01-01

Shape memory alloys (SMAs) are an enabling component in the development of compact, lightweight, durable, high-force actuation systems particularly for use where hydraulics or electrical motors are not practical. However, commercial shape memory alloys based on NiTi are only suitable for applications near room temperature, due to their relatively low transformation temperatures, while many potential applications require higher temperature capability. Consequently, a family of (Ni,Pt)(sub 1-x)Ti(sub x) shape memory alloys with Ti concentrations ranging from about 15 to 25 at.% have been developed for applications in which there are requirements for SMA actuators to exert high forces at operating temperatures higher than those of conventional binary NiTi SMAs. These alloys can be heat treated in the range of 500 C to produce a series of fine precipitate phases that increase the strength of alloy while maintaining a high transformation temperature, even in Ti-lean compositions.

Magnetic response of a disordered binary ferromagnetic alloy to an oscillating magnetic field

NASA Astrophysics Data System (ADS)

Vatansever, Erol; Polat, Hamza

2015-08-01

By means of Monte Carlo simulation with local spin update Metropolis algorithm, we have elucidated non-equilibrium phase transition properties and stationary-state treatment of a disordered binary ferromagnetic alloy of the type ApB1-p on a square lattice. After a detailed analysis, we have found that the system shows many interesting and unusual thermal and magnetic behaviors, for instance, the locations of dynamic phase transition points change significantly depending upon amplitude and period of the external magnetic field as well as upon the active concentration of A-type components. Much effort has also been dedicated to clarify the hysteresis tools, such as coercivity, dynamic loop area as well as dynamic correlations between time dependent magnetizations and external time dependent applied field as a functions of period and amplitude of field as well as active concentration of A-type components, and outstanding physical findings have been reported in order to better understand the dynamic process underlying present system.

PLUTONIUM METALLIC FUELS FOR FAST REACTORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

STAN, MARIUS; HECKER, SIEGFRIED S.

2007-02-07

Early interest in metallic plutonium fuels for fast reactors led to much research on plutonium alloy systems including binary solid solutions with the addition of aluminum, gallium, or zirconium and low-melting eutectic alloys with iron and nickel or cobalt. There was also interest in ternaries of these elements with plutonium and cerium. The solid solution and eutectic alloys have most unusual properties, including negative thermal expansion in some solid-solution alloys and the highest viscosity known for liquid metals in the Pu-Fe system. Although metallic fuels have many potential advantages over ceramic fuels, the early attempts were unsuccessful because these fuelsmore » suffered from high swelling rates during burn up and high smearing densities. The liquid metal fuels experienced excessive corrosion. Subsequent work on higher-melting U-PuZr metallic fuels was much more promising. In light of the recent rebirth of interest in fast reactors, we review some of the key properties of the early fuels and discuss the challenges presented by the ternary alloys.« less

Directional solidification of a planar interface in the presence of a time-dependent electric current

NASA Technical Reports Server (NTRS)

Brush, L. N.; Coriell, S. R.; Mcfadden, G. B.

1990-01-01

Directional solidification of pure materials and binary alloys with a planar crystal-metal interface in the presence of a time-dependent electric current is considered. For a variety of time-dependent currents, the temperature fields and the interface velocity as functions of time are presented for indium antimonide and bismuth and for the binary alloys germanium-gallium and tin-bismuth. For the alloys, the solid composition is calculated as a function of position. Quantitative predictions are made of the effect of an electrical pulse on the solute distribution in the solidified material.

Quantitative evaluation of thermodynamic parameters of Li-Sn alloys related to their use in fusion reactor

NASA Astrophysics Data System (ADS)

Krasin, V. P.; Soyustova, S. I.

2018-07-01

Along with other liquid metals liquid lithium-tin alloys can be considered as an alternative to the use of solid plasma facing components of a future fusion reactor. Therefore, parameters characterizing both the ability to retain hydrogen isotopes and those that determine the extraction of tritium from a liquid metal can be of particular importance. Theoretical correlations based on the coordination cluster model have been used to obtain Sieverts' constants for solutions of hydrogen in liquid Li-Sn alloys. The results of theoretical computations are compared with the previously published experimental values for two alloys of the Li-Sn system. The Butler equation in combination with the equations describing the thermodynamic potentials of a binary solution is used to calculate the surface composition and surface tension of liquid Li-Sn alloys.

On the role of structure-dynamic relationship in determining the excess entropy of mixing and chemical ordering in binary square-well liquid alloys

NASA Astrophysics Data System (ADS)

Lalneihpuii, R.; Shrivastava, Ruchi; Mishra, Raj Kumar

2018-05-01

Using statistical mechanical model with square-well (SW) interatomic potential within the frame work of mean spherical approximation, we determine the composition dependent microscopic correlation functions, interdiffusion coefficients, surface tension and chemical ordering in Ag-Cu melts. Further Dzugutov universal scaling law of normalized diffusion is verified with SW potential in binary mixtures. We find that the excess entropy scaling law is valid for SW binary melts. The partial and total structure factors in the attractive and repulsive regions of the interacting potential are evaluated and then Fourier transformed to get partial and total radial distribution functions. A good agreement between theoretical and experimental values for total structure factor and the reduced radial distribution function are observed, which consolidates our model calculations. The well-known Bhatia-Thornton correlation functions are also computed for Ag-Cu melts. The concentration-concentration correlations in the long wavelength limit in liquid Ag-Cu alloys have been analytically derived through the long wavelength limit of partial correlation functions and apply it to demonstrate the chemical ordering and interdiffusion coefficients in binary liquid alloys. We also investigate the concentration dependent viscosity coefficients and surface tension using the computed diffusion data in these alloys. Our computed results for structure, transport and surface properties of liquid Ag-Cu alloys obtained with square-well interatomic interaction are fully consistent with their corresponding experimental values.

PLUTONIUM-THORIUM ALLOYS

DOEpatents

Schonfeld, F.W.

1959-09-15

New plutonium-base binary alloys useful as liquid reactor fuel are described. The alloys consist of 50 to 98 at.% thorium with the remainder plutonium. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are easy fabrication, phase stability, and the accompanying advantuge of providing a means for converting Th/sup 232/ into U/sup 233/.

Additive Manufacturing of Metastable Beta Titanium Alloys

NASA Astrophysics Data System (ADS)

Yannetta, Christopher J.

Additive manufacturing processes of many alloys are known to develop texture during the deposition process due to the rapid reheating and the directionality of the dissipation of heat. Titanium alloys and with respect to this study beta titanium alloys are especially susceptible to these effects. This work examines Ti-20wt%V and Ti-12wt%Mo deposited under normal additive manufacturing process parameters to examine the texture of these beta-stabilized alloys. Both microstructures contained columnar prior beta grains 1-2 mm in length beginning at the substrate with no visible equiaxed grains. This microstructure remained constant in the vanadium system throughout the build. The microstructure of the alloy containing molybdenum changed from a columnar to an equiaxed structure as the build height increased. Eighteen additional samples of the Ti-Mo system were created under different processing parameters to identify what role laser power and travel speed have on the microstructure. There appears to be a correlation in alpha lath size and power density. The two binary alloys were again deposited under the same conditions with the addition of 0.5wt% boron to investigate the effects an insoluble interstitial alloying element would have on the microstructure. The size of the prior beta grains in these two alloys were reduced with the addition of boron by approximately 50 (V) and 100 (Mo) times.

Au-Ge MEAM potential fitted to the binary phase diagram

NASA Astrophysics Data System (ADS)

Wang, Yanming; Santana, Adriano; Cai, Wei

2017-02-01

We have developed a modified embedded atom method potential for the gold-germanium (Au-Ge) binary system that is fitted to the experimental binary phase diagram. The phase diagram is obtained from the common tangent construction of the free energy curves calculated by the adiabatic switching method. While maintaining the accuracy of the melting points of pure Au and Ge, this potential reproduces the eutectic temperature, eutectic composition and the solubility of Ge in solid Au, all in good agreement with the experimental values. To demonstrate the self-consistency of the potential, we performed benchmark molecular dynamics simulations of Ge crystal growth and etching in contact with a Au-Ge liquid alloy.

Formation process of micro arc oxidation coatings obtained in a sodium phytate containing solution with and without CaCO3 on binary Mg-1.0Ca alloy

NASA Astrophysics Data System (ADS)

Zhang, R. F.; Zhang, Y. Q.; Zhang, S. F.; B. Qu; Guo, S. B.; Xiang, J. H.

2015-01-01

Micro arc oxidation (MAO) is an effective method to improve the corrosion resistance of magnesium alloys. In order to reveal the influence of alloying element Ca and CaCO3 electrolyte on the formation process and chemical compositions of MAO coatings on binary Mg-1.0Ca alloy, anodic coatings after different anodizing times were prepared on binary Mg-1.0Ca alloy in a base solution containing 3 g/L sodium hydroxide and 15 g/L sodium phytate with and without addition of CaCO3. The coating formation was studied by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results show that Mg-1.0Ca alloy is composed of two phases, the Mg phase and Mg2Ca phase. After treating for 5 s, the coating began to develop and was preferentially formed on the area nearby Mg2Ca phase, which may be resulted from the intrinsic electronegative potential of the Mg phase than that of Mg2Ca phase. Anodic coatings unevenly covered the total surface after 20 s. After 80 s, the coatings were uniformly developed on Mg-1.0Ca alloy with micro pores. During MAO process, some sodium phytate molecules are hydrolyzed into inorganic phosphate. CaCO3 has minor influence on the calcium content of the obtained MAO coatings.

Highly dispersed Pt-Ni nanoparticles on nitrogen-doped carbon nanotubes for application in direct methanol fuel cells.

PubMed

Jiang, Shujuan; Ma, Yanwen; Tao, Haisheng; Jian, Guoqiang; Wang, Xizhang; Fan, Yining; Zhu, Jianmin; Hu, Zheng

2010-06-01

Binary Pt-Ni alloyed nanoparticles supported on nitrogen-doped carbon nanotubes (NCNTs) have been facilely constructed without pre-modification by making use of the active sites in NCNTs due to the N-participation. So-obtained binary Pt-Ni alloyed nanoparticles have been highly dispersed on the outer surface of the support with the size of about 3-4 nm. The electrochemical properties of the catalysts for methanol oxidation have been systematically evaluated. Binary Pt-Ni alloyed composites with molar ratio (Pt:Ni) of 3:2 and 3:1 present enhanced electrocatalytic activities and improved tolerance to CO poisoning as well as the similar stability, in comparison with the commercial Pt/C catalyst and the monometallic Pt/NCNTs catalysts. These results imply that so-constructed nanocomposite catalysts have the potential for applications in direct methanol fuel cells.

Linear Stability of Binary Alloy Solidification for Unsteady Growth Rates

NASA Technical Reports Server (NTRS)

Mazuruk, K.; Volz, M. P.

2010-01-01

An extension of the Mullins and Sekerka (MS) linear stability analysis to the unsteady growth rate case is considered for dilute binary alloys. In particular, the stability of the planar interface during the initial solidification transient is studied in detail numerically. The rapid solidification case, when the system is traversing through the unstable region defined by the MS criterion, has also been treated. It has been observed that the onset of instability is quite accurately defined by the "quasi-stationary MS criterion", when the growth rate and other process parameters are taken as constants at a particular time of the growth process. A singular behavior of the governing equations for the perturbed quantities at the constitutional supercooling demarcation line has been observed. However, when the solidification process, during its transient, crosses this demarcation line, a planar interface is stable according to the linear analysis performed.

Unraveling Recrystallization Mechanisms Governing Texture Development from Rare Earth Element Additions to Magnesium

NASA Astrophysics Data System (ADS)

Imandoust, Aidin

The origin of texture components associated with rare-earth (RE) element additions in wrought magnesium (Mg) alloys is a long-standing problem in magnesium technology. The objective of this research is to identify the mechanisms accountable for rare-earth texture during dynamic recrystallization (DRX). Towards this end, we designed binary Mg-Cerium and Mg-Gadolinium alloys along with complex alloy compositions containing zinc, yttrium and Mischmetal. Binary alloys along with pure Mg were designed to individually investigate their effects on texture evolutions, while complex compositions are designed to develop randomized texture, and be used in automotive and aerospace applications. We selected indirect extrusion to thermo-mechanically process our materials. Different extrusion ratios and speeds were designed to produce partially and fully recrystallized microstructures, allowing us to analyze DRX from its early stages to completion. X-ray diffraction, electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) were used to conduct microstructure and texture analyses. Our analyses revealed that rare-earth elements in zinc-containing magnesium alloys promote discontinuous dynamic recrystallization at the grain boundaries. During nucleation, the effect of rare earth elements on orientation selection was explained by the concomitant actions of multiple Taylor axes in the same grain. Isotropic grain growth was observed due to rare earth elements segregating to grain boundaries, which lead to texture randomization. The nucleation in binary Mg-RE alloys took place by continuous formation of necklace structures. Stochastic relaxation of basal and non-basal dislocations into low-angle grain boundaries produced chains of embryos with nearly random orientations. Schmid factor analysis showed a lower net activation of dislocations in RE textured grains compared to ones on the other side of the stereographic triangle. Lower dislocation densities within RE grains favored their growth by setting the boundary migration direction toward grains with higher dislocation density, thereby decreasing the system energy. We investigated the influence of RE elements on extension twinning induced hardening. RE addition enhanced tensile twinning induced hardening significantly. EBSD analysis illustrated that tensile twins cross low angle grain boundaries in Mg-RE alloys, which produced large twins and facilitated transmutation of basal to prismatic dislocations. Higher activity of pyramidal II dislocations in Mg-RE alloys resulted in higher twinning induced hardening.

Ab initio simulations of molten Ni alloys

NASA Astrophysics Data System (ADS)

Woodward, Christopher; Asta, Mark; Trinkle, Dallas R.; Lill, James; Angioletti-Uberti, Stefano

2010-06-01

Convective instabilities responsible for misoriented grains in directionally solidified turbine airfoils are produced by variations in liquid-metal density with composition and temperature across the solidification zone. Here, fundamental properties of molten Ni-based alloys, required for modeling these instabilities, are calculated using ab initio molecular dynamics simulations. Equations of state are derived from constant number-volume-temperature ensembles at 1830 and 1750 K for elemental, binary (Ni-X, X=Al, W, Re, and Ta) and ternary (Ni-Al-X, X=W, Re, and Ta) Ni alloys. Calculated molar volumes agree to within 0.6%-1.8% of available measurements. Predictions are used to investigate the range of accuracy of a parameterization of molar volumes with composition and temperature based on measurements of binary alloys. Structural analysis reveals a pronounced tendency for icosahedral short-range order for Ni-W and Ni-Re alloys and the calculations provide estimates of diffusion rates and their dependence on compositions and temperature.

Bulk combinatorial synthesis and high throughput characterization for rapid assessment of magnetic materials: Application of laser engineered net shaping (LENS)

DOE PAGES

Geng, J.; Nlebedim, I. C.; Besser, M. F.; ...

2016-04-15

A bulk combinatorial approach for synthesizing alloy libraries using laser engineered net shaping (LENS; i.e., 3D printing) was utilized to rapidly assess material systems for magnetic applications. The LENS system feeds powders in different ratios into a melt pool created by a laser to synthesize samples with bulk (millimeters) dimensions. By analyzing these libraries with autosampler differential scanning calorimeter/thermal gravimetric analysis and vibrating sample magnetometry, we are able to rapidly characterize the thermodynamic and magnetic properties of the libraries. Furthermore, the Fe-Co binary alloy was used as a model system and the results were compared with data in the literature.

Calculation of Gallium-metal-Arsenic phase diagrams

NASA Technical Reports Server (NTRS)

Scofield, J. D.; Davison, J. E.; Ray, A. E.; Smith, S. R.

1991-01-01

Electrical contacts and metallization to GaAs solar cells must survive at high temperatures for several minutes under specific mission scenarios. The determination of which metallizations or alloy systems that are able to withstand extreme thermal excursions with minimum degradation to solar cell performance can be predicted by properly calculated temperature constitution phase diagrams. A method for calculating a ternary diagram and its three constituent binary phase diagrams is briefly outlined and ternary phase diagrams for three Ga-As-X alloy systems are presented. Free energy functions of the liquid and solid phase are approximated by the regular solution theory. Phase diagrams calculated using this method are presented for the Ga-As-Ge and Ga-As-Ag systems.

Study on the Mg-Li-Zn ternary alloy system with improved mechanical properties, good degradation performance and different responses to cells.

PubMed

Liu, Yang; Wu, Yuanhao; Bian, Dong; Gao, Shuang; Leeflang, Sander; Guo, Hui; Zheng, Yufeng; Zhou, Jie

2017-10-15

Novel Mg-(3.5, 6.5wt%)Li-(0.5, 2, 4wt%)Zn ternary alloys were developed as new kinds of biodegradable metallic materials with potential for stent application. Their mechanical properties, degradation behavior, cytocompatibility and hemocompatibility were studied. These potential biomaterials showed higher ultimate tensile strength than previously reported binary Mg-Li alloys and ternary Mg-Li-X (X=Al, Y, Ce, Sc, Mn and Ag) alloys. Among the alloys studied, the Mg-3.5Li-2Zn and Mg-6.5Li-2Zn alloys exhibited comparable corrosion resistance in Hank's solution to pure magnesium and better corrosion resistance in a cell culture medium than pure magnesium. Corrosion products observed on the corroded surface were composed of Mg(OH) 2 , MgCO 3 and Ca-free Mg/P inorganics and Ca/P inorganics. In vitro cytotoxicity assay revealed different behaviors of Human Umbilical Vein Endothelial Cells (HUVECs) and Human Aorta Vascular Smooth Muscle Cells (VSMCs) to material extracts. HUVECs showed increasing nitric oxide (NO) release and tolerable toxicity, whereas VSMCs exhibited limited decreasing viability with time. Platelet adhesion, hemolysis and coagulation tests of these Mg-Li-Zn alloys showed different degrees of activation behavior, in which the hemolysis of the Mg-3.5Li-2Zn alloy was lower than 5%. These results indicated the potential of the Mg-Li-Zn alloys as good candidate materials for cardiovascular stent applications. Mg-Li alloys are promising as absorbable metallic biomaterials, which however have not received significant attention since the low strength, controversial corrosion performance and the doubts in Li toxicity. The Mg-Li-Zn alloy in the present study revealed much improved mechanical properties higher than most reported binary Mg-Li and ternary Mg-Li-X alloys, with superior corrosion resistance in cell culture media. Surprisingly, the addition of Li and Zn showed increased nitric oxide release. The present study indicates good potential of Mg-Li-Zn alloy as absorbable cardiovascular stent material. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Determination of parameters of a new method for predicting alloy properties

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John

1992-01-01

Recently, a semiempirical method for alloys based on equivalent crystal theory was introduced. The method successfully predicts the concentration dependence of the heat of formation and lattice parameter of binary alloys. A study of the parameters of the method is presented, along with new results for (gamma)Fe-Pd and (gamma)Fe-Ni alloys.

Experimental Determination of Impurity and Interdiffusion Coefficients in Seven Ti and Zr Binary Systems Using Diffusion Multiples

NASA Astrophysics Data System (ADS)

Chen, Zhangqi; Liu, Zi-Kui; Zhao, Ji-Cheng

2018-05-01

Diffusion coefficients of seven binary systems (Ti-Mo, Ti-Nb, Ti-Ta, Ti-Zr, Zr-Mo, Zr-Nb, and Zr-Ta) at 1200 °C, 1000 °C, and 800 °C were experimentally determined using three Ti-Mo-Nb-Ta-Zr diffusion multiples. Electron probe microanalysis (EPMA) was performed to collect concentration profiles at the binary diffusion regions. Forward simulation analysis (FSA) was then applied to extract both impurity and interdiffusion coefficients in Ti-rich and Zr-rich part of the bcc phase. Excellent agreements between our results and most of the literature data validate the high-throughput approach combining FSA with diffusion multiples to obtain a large amount of systematic diffusion data, which will help establish the diffusion (mobility) databases for the design and development of biomedical and structural Ti alloys.

Experimental Determination of Impurity and Interdiffusion Coefficients in Seven Ti and Zr Binary Systems Using Diffusion Multiples

NASA Astrophysics Data System (ADS)

Chen, Zhangqi; Liu, Zi-Kui; Zhao, Ji-Cheng

2018-07-01

Diffusion coefficients of seven binary systems (Ti-Mo, Ti-Nb, Ti-Ta, Ti-Zr, Zr-Mo, Zr-Nb, and Zr-Ta) at 1200 °C, 1000 °C, and 800 °C were experimentally determined using three Ti-Mo-Nb-Ta-Zr diffusion multiples. Electron probe microanalysis (EPMA) was performed to collect concentration profiles at the binary diffusion regions. Forward simulation analysis (FSA) was then applied to extract both impurity and interdiffusion coefficients in Ti-rich and Zr-rich part of the bcc phase. Excellent agreements between our results and most of the literature data validate the high-throughput approach combining FSA with diffusion multiples to obtain a large amount of systematic diffusion data, which will help establish the diffusion (mobility) databases for the design and development of biomedical and structural Ti alloys.

Heat storage in alloy transformations

NASA Technical Reports Server (NTRS)

Birchenall, C. E.

1980-01-01

Heats of transformation of eutectic alloys were measured for many binary and ternary systems by differential scanning calorimetry and thermal analysis. Only the relatively cheap and plentiful elements Mg, Al, Si, P, Ca, Cu, Zn were considered. A method for measuring volume change during transformation was developed using x-ray absorption in a confined sample. Thermal expansion coefficients of both solid and liquid states of aluminum and of its eutectics with copper and with silicon also were determined. Preliminary evaluation of containment materials lead to the selection of silicon carbide as the initial material for study. Possible applications of alloy PCMs for heat storage in conventional and solar central power stations, small solar receivers and industrial furnace operations are under consideration.

Thermal stability comparison of nanocrystalline Fe-based binary alloy pairs

DOE PAGES

Clark, Blythe G.; Hattar, Khalid Mikhiel; Marshall, Michael Thomas; ...

2016-03-24

Here, the widely recognized property improvements of nanocrystalline (NC) materials have generated significant interest, yet have been difficult to realize in engineering applications due to the propensity for grain growth in these interface-dense systems. While traditional pathways to thermal stabilization can slow the mobility of grain boundaries, recent theories suggest that solute segregation in NC alloy can reduce the grain boundary energy such that thermodynamic stabilization is achieved. Following the predictions of Murdock et al., here we compare for the first time the thermal stability of a predicted NC stable alloy (Fe-10at.% Mg) with a predicted non-NC stable alloy (Fe-10at.%more » Cu) using the same processing and characterization methodologies. Results indicate improved thermal stability of the Fe-Mg alloy in comparison to the Fe-Cu, and observed microstructures are consistent with those predicted by Monte Carlo simulations.« less

Application of Molecular Interaction Volume Model for Phase Equilibrium of Sn-Based Binary System in Vacuum Distillation

NASA Astrophysics Data System (ADS)

Kong, Lingxin; Yang, Bin; Xu, Baoqiang; Li, Yifu

2014-09-01

Based on the molecular interaction volume model (MIVM), the activities of components of Sn-Sb, Sb-Bi, Sn-Zn, Sn-Cu, and Sn-Ag alloys were predicted. The predicted values are in good agreement with the experimental data, which indicate that the MIVM is of better stability and reliability due to its good physical basis. A significant advantage of the MIVM lies in its ability to predict the thermodynamic properties of liquid alloys using only two parameters. The phase equilibria of Sn-Sb and Sn-Bi alloys were calculated based on the properties of pure components and the activity coefficients, which indicates that Sn-Sb and Sn-Bi alloys can be separated thoroughly by vacuum distillation. This study extends previous investigations and provides an effective and convenient model on which to base refining simulations for Sn-based alloys.

From chemistry to mechanics: bulk modulus evolution of Li-Si and Li-Sn alloys via the metallic electronegativity scale.

PubMed

Li, Keyan; Xie, Hui; Liu, Jun; Ma, Zengsheng; Zhou, Yichun; Xue, Dongfeng

2013-10-28

Toward engineering high performance anode alloys for Li-ion batteries, we proposed a useful method to quantitatively estimate the bulk modulus of binary alloys in terms of metallic electronegativity (EN), alloy composition and formula volume. On the basis of our proposed potential viewpoint, EN as a fundamental chemistry concept can be extended to be an important physical parameter to characterize the mechanical performance of Li-Si and Li-Sn alloys as anode materials for Li-ion batteries. The bulk modulus of binary alloys is linearly proportional to the combination of average metallic EN and atomic density of alloys. We calculated the bulk moduli of Li-Si and Li-Sn alloys with different Li concentrations, which can agree well with the reported data. The bulk modulus of Li-Si and Li-Sn alloys decreases with increasing Li concentration, leading to the elastic softening of the alloys, which is essentially caused by the decreased strength of constituent chemical bonds in alloys from the viewpoint of EN. This work provides a deep understanding of mechanical failure of Si and Sn anodes for Li-ion batteries, and permits the prediction of the composition dependent bulk modulus of various lithiated alloys on the basis of chemical formula, metallic EN and cell volume (or alloy density), with no structural details required.

Phase equilibrium modeling for high temperature metallization on GaAs solar cells

NASA Technical Reports Server (NTRS)

Chung, M. A.; Davison, J. E.; Smith, S. R.

1991-01-01

Recent trends in performance specifications and functional requirements have brought about the need for high temperature metallization technology to be developed for survivable DOD space systems and to enhance solar cell reliability. The temperature constitution phase diagrams of selected binary and ternary systems were reviewed to determine the temperature and type of phase transformation present in the alloy systems. Of paramount interest are the liquid-solid and solid-solid transformations. Data are being utilized to aid in the selection of electrical contact materials to gallium arsenide solar cells. Published data on the phase diagrams for binary systems is readily available. However, information for ternary systems is limited. A computer model is being developed which will enable the phase equilibrium predictions for ternary systems where experimental data is lacking.

Fundamental Understanding of the Intrinsic Ductility in Nickel-Base L12 Type Alloys.

DTIC Science & Technology

1987-05-12

COSATI CO0ES I L SUBJE CT TIE RMS (Conue an eo e eee it necessary and identify by blb .un bPe) . ". Eo GROUP SUB. G. Nickel Aluminide , Single...Ni3Al alloys, three series of alloys were formulated and produced as singl’e--crtals. The alloying additions selected include tantalum, tin and titanium ...been completed-for a tantalum and a titanium -containing alloy. Relative .. to the binary alloy, the alloying additions were found to significantly

Auger electron spectroscopy study of surface segregation in the binary alloys copper-1 atomic percent indium, copper-2 atomic percent tin, and iron-6.55 atomic percent silicon

NASA Technical Reports Server (NTRS)

Ferrante, J.

1973-01-01

Auger electron spectroscopy was used to examine surface segregation in the binary alloys copper-1 at. % indium, copper-2 at. % tin and iron-6.55 at. % silicon. The copper-tin and copper-indium alloys were single crystals oriented with the /111/ direction normal to the surface. An iron-6.5 at. % silicon alloy was studied (a single crystal oriented in the /100/ direction for study of a (100) surface). It was found that surface segregation occurred following sputtering in all cases. Only the iron-silicon single crystal alloy exhibited equilibrium segregation (i.e., reversibility of surface concentration with temperature) for which at present we have no explanation. McLean's analysis for equilibrium segregation at grain boundaries did not apply to the present results, despite the successful application to dilute copper-aluminum alloys. The relation of solute atomic size and solubility to surface segregation is discussed. Estimates of the depth of segregation in the copper-tin alloy indicate that it is of the order of a monolayer surface film.

Rate dependent strengths of some solder joints

NASA Astrophysics Data System (ADS)

Williamson, D. M.; Field, J. E.; Palmer, S. J. P.; Siviour, C. R.

2007-08-01

The shear strengths of three lead-free solder joints have been measured over the range of loading rates 10-3 to ~105 mm min-1. Binary (SnAg), ternary (SnAgCu) and quaternary (Castin: SnAgCuSb) alloys have been compared to a conventional binary SnPb solder alloy. Results show that at loading rates from 10-3 to 102 mm min-1, all four materials exhibit a linear relationship between the shear strength and the loading rate when the data are plotted on a log-log plot. At the highest loading rate of 105 mm min-1, the strengths of the binary alloys were in agreement with extrapolations made from the lower loading rate data. In contrast, the strengths of the higher order alloys were found to be significantly lower than those predicted by extrapolation. This is explained by a change in failure mechanism on the part of the higher order alloys. Similar behaviour was found in measurements of the tensile strengths of solder joints using a novel high-rate loading tensile test. Optical and electron microscopy were used to examine the microstructures of interest in conjunction with energy dispersive x-ray analysis for elemental identification. The effect of artificial aging and reflow of the solder joints is also reported.

Strengthening by Substitutional Solutes and the Temperature Dependence of the Flow Stress in Ni3Al

DTIC Science & Technology

1989-05-26

stoichiometric composition in polycrystalline Ni3AI and Ni3Ga. 29 Fig. 3.1 The Ni-Al binary-alloy phase diagram in vacinity of Ni3A1 phase, as verified in...I <I- iai / I I- I I I I000 - - II 21 25 29 33 37 ATOMIC % Al Fig. 3.1 The Ni-Al binary-alloy phase diagram in vacinity of Ni3Al phase, as verified

Thermodynamic investigation of the effect of alkali metal impuries on the processing of aluminum and magnesium alloys

NASA Astrophysics Data System (ADS)

Zhang, Shengjun

2006-12-01

Aluminum and magnesium alloys are widely used in the automobile and aerospace industries as structural materials due to their light weight, high specific strength and good formability. However, they suffer from the poor hot rolling characteristics due to undesired impurities like calcium, potassium, lithium and sodium. They increase the hydrogen solubility in the melt and promote the formation of porosity in aluminum castings. During fabrication of aluminum alloys, they cause the hot-shortness and embrittlement due to cracking. They also led to "blue haze" corrosion which promotes the discoloration of aluminum under humid condition. The removal of these elements increases overall melt loss of aluminum alloys when aluminum products are remelted and recast. Na is one of the common impurities in the Al and Mg alloys. In industry, primary Al is produced by the Hall-Heroult process, through the electrolysis of the mixture of molten alumina and cryolite (Al2O3+Na 3AlF6), the latter being added to lower the melting point. Therefore, Al inevitably contains some Na (>0.002%) without further treatment. The Na content in Al is influenced by the thermodynamics and kinetics of the electrolysis. Similarly, in the electrolytic production and subsequent processing of Mg, Mg is commonly in contact with molten salt mixtures of NaCl and MgCl 2. Consequently, 2--20 wt. ppm Na is often found in Mg alloys. Besides originating from the industrial production process, Na can be introduced in laboratory experiments from alumina crucibles by the reaction between the molten Al-Mg alloys and the Na2O impurity in the alumina crucible. The trace element K plays a similar role in Al alloys although it is seldom discussed. No systematic theoretic research has been carried out to investigate the behavior of these impurities during the processing of aluminum alloys. The thermodynamic description of the Al-Ca-K-Li-Mg-Na system is needed to understand the effects of Ca, K, Li and Na on phase stability of aluminum and magnesium alloys. As the first step of the thermodynamic description of the high-order system, the constitutive-binary systems were modeled in the present work using the CALPHAD technique combined with first-principles calculations. Then, ternaries and higher order systems can be modeled. For ternary systems without experimental data, the thermodynamic description is extrapolated by combining three constitutive-binary systems. Alkali-metal induced high temperature embrittlement (HTE) and loss of ductility were investigated in Al-Li, Al-Mg and Mg-Li alloys. It was discovered that the alkali-metal-rich liquid-2 phase is the cause of HTE and the loss of ductility is proportional to the mole fraction of the liquid phase and the grain size. The calculated results are consistent with experimental observations in the literature and were used to determine HTE safe and sensitive zones, maximum and critical hot-rolling temperatures and the maximum allowable Na content in alloys, which can be used to industrial processing of Al and Mg alloys. The degree of HTE is proportional to the mole fraction of the liquid-2 phase and the grain size.

Electronic structure of alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehrenreich, H.; Schwartz, L.M.

1976-01-01

The description of electronic properties of binary substitutional alloys within the single particle approximation is reviewed. Emphasis is placed on a didactic exposition of the equilibrium properties of the transport and magnetic properties of such alloys. Topics covered include: multiple scattering theory; the single band alloy; formal extensions of the theory; the alloy potential; realistic model state densities; the s-d model; and the muffin tin model. 43 figures, 3 tables, 151 references. (GHT)

Application of computational thermodynamics in the study of magnsium alloys and bulk metallic glasses

NASA Astrophysics Data System (ADS)

Cao, Hongbo

In this thesis, the application of the computational thermodynamics has been explored on two subjects, the study of magnesium alloys (Chapter 1-5) and bulk metallic glasses (BMGs) (Chapter 6-9). For the former case, a strategy of experiments coupled with the CALPHAD approach was employed to establish a thermodynamic description of the quaternary system Mg-Al-Ca-Sr focusing on the Mg-rich phase equilibria. Multicomponent Mg-rich alloys based on the MgAl-Ca-Sr system are one of the most promising candidates for the high temperature applications in the transportation industry. The Mg-Al-Ca-Sr quaternary consists of four ternaries and six binaries. Thermodynamic descriptions of all constituent binaries are available in the literature. Thermodynamic descriptions of the two key ternaries, Mg-Al-Sr and Mg-Al-Ca, were obtained by an efficient and reliable methodology, combining computational thermodynamics with key experiments. The obtained thermodynamic descriptions were validated by performing extensive comparisons between the calculations and experimental information. Thermodynamic descriptions of the other two ternaries, MgCa-Sr and Al-Ca-Sr, were obtained by extrapolation. For the later case, a computational thermodynamic strategy was formulated to obtain a minor but optimum amount of additional element into a base alloy to improve its glass forming ability (GFA). This was done through thermodynamically calculating the maximum liquidus depressions caused by various alloying addition (or replacement) schemes. The success of this approach has been examined in two multicomponent systems, Zr-based Zr-Cu-Ni-Al-Ti and Cu-rich Cu-Zr-Ti-Y. For both cases, experimental results showed conclusively that the GFA increases more than 100% from the base alloy to the one with minor but optimal elemental addition. Furthermore, a thermodynamic computational approach was employed to identify the compositions of Zr-Ti-Ni-Cu-Al alloys exhibiting low-lying liquidus surfaces, which tend to favor the BMG formation. Guided by these calculations, several series of new Zr-based alloys with excellent GFA were synthesized. The approach using the thermodynamically calculated liquidus temperatures was proved to be robust in locating BMGs and can be considered as a universal method to predict novel BMGs not only of scientific interest but also potential technological applications.

Research and Development on Titanium Alloys

DTIC Science & Technology

1949-10-31

EVALUATION OF EPERIMENTAL TITANIUM-BASE ALLOYS• 65 Binary Alloys of Titanium . . . . .. 65 Titanium-Silver Alloys. . . . . ..... ... 68 Mechanical Properties...using a technique in melting designed to give more uniform distribution of the alloying additions. NMATTWLL MOMORIAL INSTITUTE 4...tc Dr. Derge for analysis. BATTELLE MEMORIAL INSTITUTE -107- 2TABLE 28. OXYGEN STANDARDS FOR ANALYSIS Wt fSapl Pein Cen Designation Sample lielting, 1

Tunable synthesis and acetylation of dendrimer-entrapped or dendrimer-stabilized gold-silver alloy nanoparticles.

PubMed

Liu, Hui; Shen, Mingwu; Zhao, Jinglong; Guo, Rui; Cao, Xueyan; Zhang, Guixiang; Shi, Xiangyang

2012-06-01

In this study, amine-terminated generation 5 poly(amidoamine) dendrimers were used as templates or stabilizers to synthesize dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy nanoparticles (NPs) with different gold atom/silver atom/dendrimer molar ratios with the assistance of sodium borohydride reduction chemistry. Following a one-step acetylation reaction to transform the dendrimer terminal amines to acetyl groups, a series of dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs with terminal acetyl groups were formed. The formed Au-Ag alloy NPs before and after acetylation reaction were characterized using different techniques. We showed that the optical property and the size of the bimetallic NPs were greatly affected by the metal composition. At the constant total metal atom/dendrimer molar ratio, the size of the alloy NPs decreased with the gold content. The formed Au-Ag alloy NPs were stable at different pH (pH 5-8) and temperature (4-50°C) conditions. X-ray absorption coefficient measurements showed that the attenuation of the binary NPs was dependent on both the gold content and the surface modification. With the increase of gold content in the binary NPs, their X-ray attenuation intensity was significantly enhanced. At a given metal composition, the X-ray attenuation intensity of the binary NPs was enhanced after acetylation. Cytotoxicity assays showed that after acetylation, the cytocompatibility of Au-Ag alloy NPs was significantly improved. With the controllable particle size and optical property, metal composition-dependent X-ray attenuation characteristics, and improved cytocompatibility after acetylation, these dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs should have a promising potential for CT imaging and other biomedical applications. Copyright © 2012 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plotkowski, A.; Rios, O.; Sridharan, N.

Our present research in metal additive manufacturing (AM) focuses on designing processing parameters around existing alloys designed for traditional manufacturing. However, to maximize the benefits of AM, alloys should be designed to specifically take advantage of the unique thermal conditions of these processes. Furthermore, our study focuses on the development of a design methodology for alloys in AM, using a newly developed Al-Ce alloy as an initial case study. To evaluate the candidacy of this system for fusion based additive manufacturing, single-line laser melts were made on cast Al-12Ce plates using three different beam velocities (100, 200, and 300 mm/min).more » The microstructure was evaluated in the as-melted and heat treated conditions (24 hrs at 300°C). An extremely fine microstructure was observed within the weld pools, evolving from eutectic at the outer solid-liquid boundaries to a primary Al FCC dendritic/cellular structure nearer the melt-pool centerline. We rationalized the observed microstructures through the construction of a microstructure selection map for the Al-Ce binary system, which will be used to enable future alloy design. Interestingly, the heat treated samples exhibited no microstructural coarsening.« less

Investigating the Electron-Phonon Coupling of Molecular Beam Epitaxy-Grown Hg1-x Cd x Se Semiconductor Alloys

NASA Astrophysics Data System (ADS)

Peiris, F. C.; Lewis, M. V.; Brill, G.; Doyle, Kevin; Myers, T. H.

2018-03-01

Using spectroscopic ellipsometry, the temperature-dependence of the dielectric functions of a series of Hg1-x Cd x Se thin films deposited on both ZnTe/Si(112) and GaSb(112) substrates were investigated. Initially, for each sample, room-temperature ellipsometric spectra were obtained from 35 meV to 6 eV using two different ellipsometers. Subsequently, ellipsometry spectra were obtained from 10 K to 300 K by incorporating a cryostat to the ellipsometer. Using a standard inversion technique, the spectroscopic ellipsometric data were modeled in order to obtain the temperature-dependent dielectric functions of each of the Hg1-x Cd x Se thin films. The results indicate that the E 1 critical point blue-shifts as a function of Cd-alloy concentration. The temperature-dependence of E 1 was fitted to a Bose-Einstein occupation distribution function, which consequently allowed us to determine the electron-phonon coupling of Hg1-x Cd x Se alloys. From the fitting results, we obtain a value of 17 ± 2 meV for the strength of the electron-phonon coupling for Hg1-x Cd x Se alloy system, which compares nominally with the binary systems, such as CdSe and CdTe, which have values around 38 meV and 16 meV, respectively. This implies that the addition of Hg into the CdSe binary system does not significantly alter its electron-phonon coupling strength. Raman spectroscopy measurements performed on all the samples show the HgSe-like transverse optic (TO) and longitudinal optic (LO) phonons (˜ 130 cm-1 and ˜ 160 cm-1, respectively) for all the samples. While there is a slight red-shift of the HgSe-like TO peak as a function of the Cd-concentration, HgSe-like LO peak does not significantly change with the alloy concentration.

Estimation of the Viscosities of Liquid Sn-Based Binary Lead-Free Solder Alloys

NASA Astrophysics Data System (ADS)

Wu, Min; Li, Jinquan

2018-01-01

The viscosity of a binary Sn-based lead-free solder alloy was calculated by combining the predicted model with the Miedema model. The viscosity factor was proposed and the relationship between the viscosity and surface tension was analyzed as well. The investigation result shows that the viscosity of Sn-based lead-free solders predicted from the predicted model shows excellent agreement with the reported values. The viscosity factor is determined by three physical parameters: atomic volume, electronic density, and electro-negativity. In addition, the apparent correlation between the surface tension and viscosity of the binary Sn-based Pb-free solder was obtained based on the predicted model.

Evaluation of an Al-Ce alloy for laser additive manufacturing

DOE PAGES

Plotkowski, A.; Rios, O.; Sridharan, N.; ...

2016-12-27

Our present research in metal additive manufacturing (AM) focuses on designing processing parameters around existing alloys designed for traditional manufacturing. However, to maximize the benefits of AM, alloys should be designed to specifically take advantage of the unique thermal conditions of these processes. Furthermore, our study focuses on the development of a design methodology for alloys in AM, using a newly developed Al-Ce alloy as an initial case study. To evaluate the candidacy of this system for fusion based additive manufacturing, single-line laser melts were made on cast Al-12Ce plates using three different beam velocities (100, 200, and 300 mm/min).more » The microstructure was evaluated in the as-melted and heat treated conditions (24 hrs at 300°C). An extremely fine microstructure was observed within the weld pools, evolving from eutectic at the outer solid-liquid boundaries to a primary Al FCC dendritic/cellular structure nearer the melt-pool centerline. We rationalized the observed microstructures through the construction of a microstructure selection map for the Al-Ce binary system, which will be used to enable future alloy design. Interestingly, the heat treated samples exhibited no microstructural coarsening.« less

Binary Colloidal Alloy Test-5: Three-Dimensional Melt

NASA Technical Reports Server (NTRS)

Yodh, Arjun G.

2008-01-01

Binary Colloidal Alloy Test - 5: Three-Dimensional Melt (BCAT-5-3DMelt) photographs initially randomized colloidal samples in microgravity to determine their resulting structure over time. BCAT-5-3D-Melt will allow the scientists to capture the kinetics (evolution) of their samples, as well as the final equilibrium state of each sample. BCAT-5-3D-Melt will look at the mechanisms of melting using three-dimensional temperature sensitive colloidal crystals. Results will help scientists develop fundamental physics concepts previously shadowed by the effects of gravity.

The surface alloying effect of silicon in a binary NiTi-base alloy on the corrosion resistance and biocompatibility of the material

NASA Astrophysics Data System (ADS)

Psakhie, S. G.; Lotkov, A. I.; Meisner, L. L.; Meisner, S. N.; Matveeva, V. A.

2013-02-01

The corrosion resistance behavior and cytotoxicity of binary NiTi-base alloy specimens subjected to surface modification by silicon ion beams and the proliferative ability of mesenchymal stem cells of rat marrow on an ion-implanted surface of the alloy have been studied. The silicon ion beam processing of specimen surfaces is shown to bring about a nearly two-fold improvement in the corrosion resistance of the material to attack by aqueous solutions of NaCl (artificial body fluid) and human plasma and a drastic decrease in the nickel concentration after immersion of the specimens into the solutions for ˜3400 and ˜6000 h, respectively (for the artificial plasma solution, a nearly 20-fold decrease in the Ni concentration is observed.)

Biomimetic superhydrophobic surface of high adhesion fabricated with micronano binary structure on aluminum alloy.

PubMed

Liu, Yan; Liu, Jindan; Li, Shuyi; Liu, Jiaan; Han, Zhiwu; Ren, Luquan

2013-09-25

Triggered by the microstructure characteristics of the surfaces of typical plant leaves such as the petals of red roses, a biomimetic superhydrophobic surface with high adhesion is successfully fabricated on aluminum alloy. The essential procedure is that samples were processed by a laser, then immersed and etched in nitric acid and copper nitrate, and finally modified by DTS (CH3(CH2)11Si(OCH3)3). The obtained surfaces exhibit a binary structure consisting of microscale crater-like pits and nanoscale reticula. The superhydrophobicity can be simultaneously affected by the micronano binary structure and chemical composition of the surface. The contact angle of the superhydrophobic surface reaches up to 158.8 ± 2°. Especially, the surface with micronano binary structure is revealed to be an excellent adhesive property with petal-effect. Moreover, the superhydrophobic surfaces show excellent stability in aqueous solution with a large pH range and after being exposed long-term in air. In this way, the multifunctional biomimetic structural surface of the aluminum alloy is fabricated. Furthermore, the preparation technology in this article provides a new route for other metal materials.

Influence of heat treatment and oxygen doping on the mechanical properties and biocompatibility of titanium-niobium binary alloys.

PubMed

da Silva, Luciano Monteiro; Claro, Ana Paula Rosifini Alves; Donato, Tatiani Ayako Goto; Arana-Chavez, Victor E; Moraes, João Carlos Silos; Buzalaf, Marília Afonso Rabelo; Grandini, Carlos Roberto

2011-05-01

The most commonly used titanium (Ti)-based alloy for biological applications is Ti-6Al-4V, but some studies associate the vanadium (V) with the cytotoxic effects and adverse reactions in tissues, while aluminum (Al) has been associated with neurological disorders. Ti-Nb alloys belong to a new class of Ti-based alloys with no presence of Al and V and with elasticity modulus values that are very attractive for use as a biomaterial. It is well known that the presence of interstitial elements (such as oxygen, for example) changes the mechanical properties of alloys significantly, particularly the elastic properties, the same way that heat treatments can change the microstructure of these alloys. This article presents the effect of heat treatment and oxygen doping in some mechanical properties and the biocompatibility of three alloys of the Ti-Nb system, characterized by density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, in vitro cytotoxicity, and mechanical spectroscopy. © 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Liquid-liquid phase separation and core-shell structure of ternary Al-In-Sn immiscible alloys

NASA Astrophysics Data System (ADS)

Zhao, Degang; Bo, Lin; Wang, Lin; Li, Shanshan

2018-04-01

In this study, the liquid-liquid phase separation of four kinds of ternary immiscible Al-In-Sn melts was investigated with resistivity and thermodynamics method. The nonlinear changes in ρ-T and DSC curves of Al-In-Sn immiscible alloys above monotectic reaction temperature revealed the occurrence of liquid-liquid phase separation of Al-In-Sn melts. The monotectic temperature, liquid phase separation temperature and immiscible gap of ternary Al-In-Sn alloys were lower than those of binary Al-In alloy. With the Al content decreasing, the immiscible gap of Al-In-Sn alloy decreased. The composition of Al80In10Sn10, Al70In15Sn15, Al60In20Sn20 and Al50In25Sn25 was located in the immiscible zone of Al-In-Sn system. Due to the differences of Stokes effect, Marangoni convection and immiscible gap, the solidification morphology of four kinds of Al-In-Sn monotectic alloy was different. The core–shell structure of Al-In-Sn monotectic alloy can form within a certain range of composition.

Contributions of phase and structural transformations in multicomponent Al-Mg alloys to the linear and nonlinear mechanisms of anelasticity

NASA Astrophysics Data System (ADS)

Golovin, I. S.; Bychkov, A. S.; Mikhailovskaya, A. V.; Dobatkin, S. V.

2014-02-01

The effects of the processes of severe plastic deformation (SPD), recrystallization, and precipitation of the β phase in multicomponent alloys of the Al-5Mg-Mn-Cr and Al-(4-5%)Mg-Mn-Zn-Sc systems on the mechanisms of grain-boundary relaxation and dislocation-induced microplasticity have been studied in some detail. To stabilize the ultrafine-grained structure and prevent grain growth, dispersed Al-transition-metal particles, such as Al3Zr, Al6Mn, Al7Cr, Al6(Mn,Cr), Al18Cr2Mg3 have been used. We have special interest in alloys with additions of scandium, which forms compounds of the Al3Sc type and favors the precipitation of finer particles compared to the aluminides of other transition metals. After SPD, Al-(4-5%)Mg-Mn-Zr-Sc alloys exhibit an enhanced recrystallization temperature. The general features of the dislocation and grain-boundary anelasticity that have been established for the binary Al-Mg alloys are retained; i.e., (1) the decrease in the dislocation density in the process of recrystallization of cold-worked alloys leads to the formation of a pseudo-peak in the curves of the temperature dependences of internal friction (TDIF) and to a decrease in the critical amplitude of deformation corresponding to the onset of dislocation motion in a stress field; (2) the precipitation of the β phase suppresses the grain-boundary relaxation; (3) the dissolution of the β phase, the passage of the magnesium atoms into the solid solution, and the precipitation of the β' phase upon heating hinder the motion of dislocations; (4) the coarsening of the highly dispersed particles containing Zr and Sc increases the dislocation mobility. The grain-boundary relaxation and dislocation-impurity interaction and their temperature dependences, as well as processes of the additional alloying of the binary alloys by Mn, Cr, Zr, and Sc, have been estimated quantitatively.

Correlation between crystallographic anisotropy and dendritic orientation selection of binary magnesium alloys.

PubMed

Du, Jinglian; Guo, Zhipeng; Zhang, Ang; Yang, Manhong; Li, Mei; Xiong, Shoumei

2017-10-19

Both synchrotron X-ray tomography and EBSD characterization revealed that the preferred growth directions of magnesium alloy dendrite change as the type and amount of solute elements. Such growth behavior was further investigated by evaluating the orientation-dependent surface energy and the subsequent crystallographic anisotropy via ab-initio calculations based on density functional theory and hcp lattice structure. It was found that for most binary magnesium alloys, the preferred growth direction of the α-Mg dendrite in the basal plane is always [Formula: see text], and independent on either the type or concentration of the additional elements. In non-basal planes, however, the preferred growth direction is highly dependent on the solute concentration. In particular, for Mg-Al alloys, this direction changes from [Formula: see text] to [Formula: see text] as the Al-concentration increased, and for Mg-Zn alloys, this direction changes from [Formula: see text] to [Formula: see text] or [Formula: see text] as the Zn-content varied. Our results provide a better understanding on the dendritic orientation selection and morphology transition of magnesium alloys at the atomic level.

On the transformation behaviour, mechanical properties and biocompatibility of two niti-based shape memory alloys: NiTi42 and NiTi42Cu7.

PubMed

Es-Souni, M; Es-Souni, M; Brandies, H F

2001-08-01

The transformation behaviour, mechanical properties and cytotoxicity of a binary NiTi42 and a ternary NiTi42Cu7 alloy have been investigated. The transformation temperatures were determined via differential scanning calorimetry, the mechanical properties have been investigated in 3-point bending tests in the temperature range between 6 and 60 degrees C. The cytotoxicity tests were performed on both alloys in cultured epithelial cells from human gingiva. The cytotoxicity investigations included both MTT tests and morphological observations. It is shown that although the ternary alloy is characterised by a narrower hysteresis and superior mechanical properties, including fatigue resistance, its cytotoxicity is higher than that of the binary alloy. This is thought to arise from the release of copper ions in the medium, which upon atomic absorption spectroscopy measurements amount to approximately 2.8 microg cm(-2) for an incubation period of 7 days.

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods.

PubMed

Chanbi, Daoud; Ogam, Erick; Amara, Sif Eddine; Fellah, Z E A

2018-05-07

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density.

Fabrication of cobalt-nickel binary nanowires in a highly ordered alumina template via AC electrodeposition

PubMed Central

2013-01-01

Cobalt-nickel (Co-Ni) binary alloy nanowires of different compositions were co-deposited in the nanopores of highly ordered anodic aluminum oxide (AAO) templates from a single sulfate bath using alternating current (AC) electrodeposition. AC electrodeposition was accomplished without modifying or removing the barrier layer. Field emission scanning electron microscope was used to study the morphology of templates and alloy nanowires. Energy-dispersive X-ray analysis confirmed the deposition of Co-Ni alloy nanowires in the AAO templates. Average diameter of the alloy nanowires was approximately 40 nm which is equal to the diameter of nanopore. X-ray diffraction analysis showed that the alloy nanowires consisted of both hexagonal close-packed and face-centered cubic phases. Magnetic measurements showed that the easy x-axis of magnetization is parallel to the nanowires with coercivity of approximately 706 Oe. AC electrodeposition is very simple, fast, and is useful for the homogenous deposition of various secondary nanostuctured materials into the nanopores of AAO. PMID:23941234

Fabrication of (Ba,K)Fe2As2 tapes by ex situ PIT process using Ag-Sn alloy single sheath

NASA Astrophysics Data System (ADS)

Togano, K.; Gao, Z.; Matsumoto, A.; Kikuchi, A.; Kumakura, H.

2017-01-01

Instead of ordinal pure Ag, Ag-based Sn binary alloys (up to 7.5 at%Sn) with higher mechanical strength are used for the sheath material of ex situ powder-in-tube (PIT)-processed (Ba,K)Fe2As2(Ba-122) tapes. We found that the use of the Ag-Sn alloy enhances the densification and texturing of the Ba-122 core, resulting in higher transport, J c. Moreover, the optimum heat treatment temperature for a high J c can be lowered by around 100 °C due to the higher packing density of the Ba-122 core prior to the final heat treatment. We also found that the smoothness of the interface between the sheath and Ba-122 core is significantly improved by using the Ag-Sn binary alloy sheaths. These results show that the Ag-Sn alloy is promising as a sheath material in PIT-processed Ba-122 superconducting wires.

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods

PubMed Central

Chanbi, Daoud; Amara, Sif Eddine; Fellah, Z. E. A.

2018-01-01

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density. PMID:29735946

Model many-body Stoner Hamiltonian for binary FeCr alloys

NASA Astrophysics Data System (ADS)

Nguyen-Manh, D.; Dudarev, S. L.

2009-09-01

We derive a model tight-binding many-body d -electron Stoner Hamiltonian for FeCr binary alloys and investigate the sensitivity of its mean-field solutions to the choice of hopping integrals and the Stoner exchange parameters. By applying the local charge-neutrality condition within a self-consistent treatment we show that the negative enthalpy-of-mixing anomaly characterizing the alloy in the low chromium concentration limit is due entirely to the presence of the on-site exchange Stoner terms and that the occurrence of this anomaly is not specifically related to the choice of hopping integrals describing conventional chemical bonding between atoms in the alloy. The Bain transformation pathway computed, using the proposed model Hamiltonian, for the Fe15Cr alloy configuration is in excellent agreement with ab initio total-energy calculations. Our investigation also shows how the parameters of a tight-binding many-body model Hamiltonian for a magnetic alloy can be derived from the comparison of its mean-field solutions with other, more accurate, mean-field approximations (e.g., density-functional calculations), hence stimulating the development of large-scale computational algorithms for modeling radiation damage effects in magnetic alloys and steels.

Roman bronze artefacts from Thamusida (Morocco): Chemical and phase analyses

NASA Astrophysics Data System (ADS)

Gliozzo, E.; Kockelmann, W.; Bartoli, L.; Tykot, R. H.

2011-02-01

Twenty-six objects (1st to the 3rd century AD) found at the archaeological site of Thamusida (Morocco), which is a military settlement between the 1st and the 3rd century AD, have been investigated by means of portable X-ray fluorescence and time of flight-neutron diffraction. The combination of element-sensitive X-ray fluorescence and structure-sensitive neutron diffraction yields, in a totally non-destructive way, the necessary information to discriminate the copper alloy from corrosion and alteration layers. Results allowed dividing the repertory into five groups: (a) unalloyed copper, (b) binary alloys made of Cu and Sn, frequently leaded; (c) unleaded binary alloys made of Cu and Zn; (d) ternary alloys made of Cu, Sn and Zn, both leaded and unleaded; (e) quaternary alloys made of Cu, Sn, Zn and As. The choice of alloy is heterogeneous, mainly depending on availability and costs of raw and/or scrap materials and on technological constraints. Interestingly, the reconstruction obtained for Thamusida could either anticipate the important change in the Roman use of copper alloys generally referred as 'zinc decline', or more likely, indicate that brass never conspicuously entered the local metal-working activities of this military site.

Determination of 200 °C Isothermal Section of Al-Ag-Ga Phase Diagram by Microanalysis, X-ray Diffraction, Hardness and Electrical Conductivity Measurements

NASA Astrophysics Data System (ADS)

Premović, Milena; Tomović, Milica; Minić, Duško; Manasijević, Dragan; Živković, Dragana; Ćosović, Vladan; Grković, Vladan; Đorđević, Aleksandar

2017-04-01

Ternary Al-Ag-Ga system at 200 °C was experimentally and thermodynamically assessed. Isothermal section was extrapolated using optimized thermodynamic parameters for constitutive binary systems. Microstructure and phase composition of the selected alloy samples were analyzed using light microscopy, scanning electron microscopy combined with energy-dispersive spectrometry and x-ray powder diffraction technique. The obtained experimental results were found to be in a close agreement with the predicted phase equilibria. Hardness and electrical conductivity of the alloy samples from four vertical sections Al-Ag80Ga20, Al-Ag60Ga40, Ag-Al80Ga20 and Ag-Al60Ga40 of the ternary Al-Ag-Ga system at 200 °C were experimentally determined using Brinell method and eddy current measurements. Additionally, hardness of the individual phases present in the microstructure of the studied alloy samples was determined using Vickers microhardness test. Based on experimentally obtained results, isolines of Brinell hardness and electrical conductivity were calculated for the alloys from isothermal section of the ternary Al-Ag-Ga system at 200 °C.

Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique

PubMed Central

Nigl, Thomas P.; Smith, Nathan D.; Lichtenstein, Timothy; Gesualdi, Jarrod; Kumar, Kuldeep; Kim, Hojong

2017-01-01

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline earth-liquid metal alloys as functions of both composition and temperature in order to acquire thermodynamic data. The cell consists of a chemically stable solid-state CaF2-AF2 electrolyte (where A is the alkaline-earth element such as Ca, Sr, or Ba), with binary A-B alloy (where B is the liquid metal such as Bi or Sb) working electrodes, and a pure A metal reference electrode. Emf data are collected over a temperature range of 723 K to 1,123 K in 25 K increments for multiple alloy compositions per experiment and the results are analyzed to yield activity values, phase transition temperatures, and partial molar entropies/enthalpies for each composition. PMID:29155770

First-principles-based kinetic Monte Carlo studies of diffusion of hydrogen in Ni–Al and Ni–Fe binary alloys

DOE PAGES

Tafen, De Nyago

2015-02-14

The diffusion of dilute hydrogen in fcc Ni–Al and Ni–Fe binary alloys was examined using kinetic Monte Carlo method with input kinetic parameters obtained from first-principles density functional theory. The simulation involves the implementation of computationally efficient energy barrier model that describes the configuration dependence of the hydrogen hopping. The predicted hydrogen diffusion coefficients in Ni and Ni 89.4Fe 10.6 are compared well with the available experimental data. In Ni–Al, the model predicts lower hydrogen diffusivity compared to that in Ni. Overall, diffusion prefactors and the effective activation energies of H in Ni–Fe and Ni–Al are concentration dependent of themore » alloying element. Furthermore, the changes in their values are the results of the short-range order (nearest-neighbor) effect on the interstitial diffusion of hydrogen in fcc Ni-based alloys.« less

Identification of the heat transfer coefficient in the two-dimensional model of binary alloy solidification

NASA Astrophysics Data System (ADS)

Hetmaniok, Edyta; Hristov, Jordan; Słota, Damian; Zielonka, Adam

2017-05-01

The paper presents the procedure for solving the inverse problem for the binary alloy solidification in a two-dimensional space. This is a continuation of some previous works of the authors investigating a similar problem but in the one-dimensional domain. Goal of the problem consists in identification of the heat transfer coefficient on boundary of the region and in reconstruction of the temperature distribution inside the considered region in case when the temperature measurements in selected points of the alloy are known. Mathematical model of the problem is based on the heat conduction equation with the substitute thermal capacity and with the liquidus and solidus temperatures varying in dependance on the concentration of the alloy component. For describing this concentration the Scheil model is used. Investigated procedure involves also the parallelized Ant Colony Optimization algorithm applied for minimizing a functional expressing the error of approximate solution.

An Undergraduate Experiment Using Differential Scanning Calorimetry: A Study of the Thermal Properties of a Binary Eutectic Alloy of Tin and Lead

ERIC Educational Resources Information Center

D'Amelia, Ronald P.; Clark, Daniel; Nirode, William

2012-01-01

An alloy is an intimate association of two or more metals, with or without a definite composition, which has metallic properties. Heterogeneous alloys, such as tin-lead (Sn/Pb) solders, consist of a mixture of crystalline phases with different compositions. A homogeneous alloy with a unique composition having the lowest possible melting point is…

Surface Segregation in Ternary Alloys

NASA Technical Reports Server (NTRS)

Good, Brian; Bozzolo, Guillermo H.; Abel, Phillip B.

2000-01-01

Surface segregation profiles of binary (Cu-Ni, Au-Ni, Cu-Au) and ternary (Cu-Au-Ni) alloys are determined via Monte Carlo-Metropolis computer simulations using the BFS method for alloys for the calculation of the energetics. The behavior of Cu or Au in Ni is contrasted with their behavior when both are present. The interaction between Cu and Au and its effect on the segregation profiles for Cu-Au-Ni alloys is discussed.

Thermoelastic martensitic transformations in ternary Ni50Mn50- z Ga z alloys

NASA Astrophysics Data System (ADS)

Belosludtseva, E. S.; Kuranova, N. N.; Marchenkova, E. B.; Popov, A. G.; Pushin, V. G.

2016-01-01

We have studied the effect of gallium alloying on the structure, phase composition, and physical properties of ternary alloys of the Ni50Mn50- z Ga z (0 ≤ z ≤ 25 at %) quasi-binary section in a broad temperature range. Dependences of the type of crystalline structure of the high-temperature austenite phase and martensite, as well as the critical temperatures of martensitic transformations on the alloy composition, are determined. A phase diagram of the structural and magnetic transformations is constructed. Concentration boundaries of the existence of tetragonal L10 (2 M) martensite and martensitic phases (10 M and 14 M) with complex multilayer crystalline lattices are found. It is established that the predominant martensite morphology is determined by the hierarchy of packets of thin coherent nano- and submicrocrystalline plates with habit planes close to {011} B2, pairwise twinned along one of 24 equivalent {011}<011> B2 twinning shear systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Susarla, Sandhya; Kochat, Vidya; Kutana, Alex

Transition metal dichalcogenide (TMD) alloys form a broad class of two-dimensional (2D) layered materials with tunable bandgaps leading to interesting optoelectronic applications. In the bottom-up approach of building these atomically thin materials, atomic doping plays a crucial role. Here we demonstrate a single step CVD (chemical vapor deposition) growth procedure for obtaining binary alloys and heterostructures by tuning atomic composition. We show that a minute doping of tin during the growth phase of the Mo 1–xW xS 2 alloy system leads to formation of lateral and vertical heterostructure growth. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) imagingmore » and density functional theory (DFT) calculations also support the modified stacking and growth mechanism due to the nonisomorphous Sn substitution. Our experiments demonstrate the possibility of growing heterostructures of TMD alloys whose spectral responses can be desirably tuned for various optoelectronic applications.« less

Containerless processing of Nb-Ge alloys in a long drop tube

NASA Technical Reports Server (NTRS)

Bayuzick, R. J.

1982-01-01

The thirty-two meter drop tube at the Marshall Space Flight Center was used to study the effect of zero gravity containerless processing on the structure and properties of materials. The concept involves the suppression of heterogeneous nucleation of solid in liquid and, therefore, solidification accompanied by large degrees of undercooling. Under these conditions metastable phases can be formed or, at the very least, unique nonequilibrium microstructures (containing equilibrium phases) with unique properties can be produced. The drop tube solidification was applied to niobium base alloys with emphasis on the Nb-Ge binary system in an effort to produce metastable phases with high superconducting transition temperatures in bulk specimens. In the past, only lower Ge alloys (Nb-13 a/o, Nb-18 a/o, and Nb-22 a/o) could be undercooled. Higher Ge alloys (e.g., Nb-25 a/o Ge and Nb-27 a/o Ge) can now be undercooled on a routine basis.

Phase-field model for isothermal phase transitions in binary alloys

NASA Technical Reports Server (NTRS)

Wheeler, A. A.; Boettinger, W. J.; Mcfadden, G. B.

1992-01-01

A new phase field model is described which models isothermal phase transitions between ideal binary alloy solution phases. Equations are developed for the temporal and spatial variation of the phase field, which describes the identity of the phase, and of the composition. An asymptotic analysis, as the gradient energy coefficient of the phase field becomes small, was conducted. From the analysis, it is shown that the model recovers classical sharp interface models of this situation when the interfacial layers are thin, and they show how to relate the parameters appearing in the phase field model to material and growth parameters in real systems. Further, three stages of temporal evolution are identified: the first corresponding to interfacial genesis which occurs very rapidly; the second to interfacial motion controlled by the local energy difference across the interface and diffusion; the last taking place on a long time scale in which curvature effects are important and which correspond to Ostwald ripening. The results of the numerical calculations are presented.

Directional Solidification of a Binary Alloy into a Cellular Convective Flow: Localized Morphologies

NASA Technical Reports Server (NTRS)

Chen, Y.- J.; Davis, S. H.

1999-01-01

A steady, two dimensional cellular convection modifies the morphological instability of a binary alloy that undergoes directional solidification. When the convection wavelength is far longer than that of the morphological cells, the behavior of the moving front is described by a slow, spatial-temporal dynamics obtained through a multiple-scale analysis. The resulting system has a "parametric-excitation" structure in space, with complex parameters characterizing the interactions between flow, solute diffusion, and rejection. The convection stabilizes two dimensional disturbances oriented with the flow, but destabilizes three dimensional disturbances in general. When the flow is weak, the morphological instability behaves incommensurably to the flow wavelength, but becomes quantized and forced to fit into the flow-box as the flow gets stronger. At large flow magnitudes the instability is localized, confined in narrow envelopes with cells traveling with the flow. In this case the solutions are discrete eigenstates in an unbounded space. Their stability boundary and asymptotics are obtained by the WKB analysis.

In vitro corrosion and biocompatibility of binary magnesium alloys.

PubMed

Gu, Xuenan; Zheng, Yufeng; Cheng, Yan; Zhong, Shengping; Xi, Tingfei

2009-02-01

As bioabsorbable materials, magnesium alloys are expected to be totally degraded in the body and their biocorrosion products not deleterious to the surrounding tissues. It's critical that the alloying elements are carefully selected in consideration of their cytotoxicity and hemocompatibility. In the present study, nine alloying elements Al, Ag, In, Mn, Si, Sn, Y, Zn and Zr were added into magnesium individually to fabricate binary Mg-1X (wt.%) alloys. Pure magnesium was used as control. Their mechanical properties, corrosion properties and in vitro biocompatibilities (cytotoxicity and hemocompatibility) were evaluated by SEM, XRD, tensile test, immersion test, electrochemical corrosion test, cell culture and platelet adhesion test. The results showed that the addition of alloying elements could influence the strength and corrosion resistance of Mg. The cytotoxicity tests indicated that Mg-1Al, Mg-1Sn and Mg-1Zn alloy extracts showed no significant reduced cell viability to fibroblasts (L-929 and NIH3T3) and osteoblasts (MC3T3-E1); Mg-1Al and Mg-1Zn alloy extracts indicated no negative effect on viabilities of blood vessel related cells, ECV304 and VSMC. It was found that hemolysis and the amount of adhered platelets decreased after alloying for all Mg-1X alloys as compared to the pure magnesium control. The relationship between the corrosion products and the in vitro biocompatibility had been discussed and the suitable alloying elements for the biomedical applications associated with bone and blood vessel had been proposed.

Compressive creep behavior of alloys based on B2 FeAl

NASA Technical Reports Server (NTRS)

Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.

1986-01-01

Alloys based on FeAl are attractive alternate materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.

Compressive creep behavior of alloys based on B2 FeAl

NASA Technical Reports Server (NTRS)

Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.

1987-01-01

Alloys based on FeAl are attractive alternative materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.

Observing Tin-Lead Alloys by Scanning Electron Microscopy: A Physical Chemistry Experiment Investigating Macro-Level Behaviors and Micro-Level Structures

ERIC Educational Resources Information Center

Wang, Yue; Xu, Xinhua; Wu, Meifen; Hu, Huikang; Wang, Xiaogang

2015-01-01

Scanning electron microscopy (SEM) was introduced into undergraduate physical chemistry laboratory curriculum to help students observe the phase composition and morphology characteristics of tin-lead alloys and thus further their understanding of binary alloy phase diagrams. The students were captivated by this visual analysis method, which…

Microstructural development from interdiffusion and reaction between Usbnd Mo and AA6061 alloys annealed at 600° and 550 °C

NASA Astrophysics Data System (ADS)

Perez, E.; Keiser, D. D.; Sohn, Y. H.

2016-08-01

The U.S. Material Management and Minimization Reactor Conversion Program is developing low enrichment fuel systems encased in Al-alloy for use in research and test reactors. Monolithic fuel plates have local regions where the Usbnd Mo fuel plate may come into contact with the Al-alloy 6061 (AA6061) cladding. This results in the development of interdiffusion zones with complex microstructures with multiple phases. In this study, the microstructural development of diffusion couples, Usbnd 7 wt%Mo, Usbnd 10 wt%Mo, and Usbnd 12 wt%Mo vs. AA6061, annealed at 600 °C for 24 h and at 550 °C for 1, 5, and 20 h, were analyzed by scanning electron microscopy with x-ray energy dispersive spectroscopy. The microstructural development and kinetics were compared to diffusion couples Usbnd Mo vs. high purity Al and binary Alsbnd Si alloys. The diffusion couples developed complex interaction regions where phase development was influenced by the alloying additions of the AA6061.

Binary Colloidal Alloy Test-5: Compete

NASA Technical Reports Server (NTRS)

Frisken, Barbara J.; Bailey, Arthur E.; Weitz, David A.

2008-01-01

The Binary Colloidal Alloy Test - 5: Compete (BCAT-5-Compete) investigation will photograph andomized colloidal samples onboard the International Space Station (ISS) to determine their resulting structure over time. The use of EarthKAM software and hardware will allow the scientists to capture the kinetics (evolution) of their samples, as well as the final equilibrium state of each sample. BCAT-5-Compete will utilize samples 6 - 8 in the BCAT-5 hardware to study the competition between phase separation and crystallization, which is important in the manufacture of plastics and other materials.

Binary Colloidal Alloy Test-5: Phase Separation

NASA Technical Reports Server (NTRS)

Lynch, Matthew; Weitz, David A.; Lu, Peter J.

2008-01-01

The Binary Colloidal Alloy Test - 5: Phase Separation (BCAT-5-PhaseSep) experiment will photograph initially randomized colloidal samples onboard the ISS to determine their resulting structure over time. This allows the scientists to capture the kinetics (evolution) of their samples, as well as the final equilibrium state of each sample. BCAT-5-PhaseSep studies collapse (phase separation rates that impact product shelf-life); in microgravity the physics of collapse is not masked by being reduced to a simple top and bottom phase as it is on Earth.

Cohesive Relations for Surface Atoms in the Iron-Technetium Binary System

DOE PAGES

Taylor, Christopher D.

2011-01-01

Iron-technetium alloys are of relevance to the development of waste forms for disposition of radioactive technetium-99 obtained from spent nuclear fuel. Corrosion of candidate waste forms is a function of the local cohesive energy () of surface atoms. A theoretical model for calculating is developed. Density functional theory was used to construct a modified embedded atom (MEAM) potential for iron-technetium. Materials properties determined for the iron-technetium system were in good agreement with the literature. To explore the relationship between local structure and corrosion, MEAM simulations were performed on representative iron-technetium alloys and intermetallics. Technetium-rich phases have lower , suggesting thatmore » these phases will be more noble than iron-rich ones. Quantitative estimates of based on numbers of nearest neighbors alone can lead to errors up to 0.5 eV. Consequently, atomistic corrosion simulations for alloy systems should utilize physics-based models that consider not only neighbor counts, but also local compositions and atomic arrangements.« less

High-Throughput Study of Diffusion and Phase Transformation Kinetics of Magnesium-Based Systems for Automotive Cast Magnesium Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Alan A; Zhao, Ji-Cheng; Riggi, Adrienne

The objective of the proposed study is to establish a scientific foundation on kinetic modeling of diffusion, phase precipitation, and casting/solidification, in order to accelerate the design and optimization of cast magnesium (Mg) alloys for weight reduction of U.S. automotive fleet. The team has performed the following tasks: 1) study diffusion kinetics of various Mg-containing binary systems using high-throughput diffusion multiples to establish reliable diffusivity and mobility databases for the Mg-aluminum (Al)-zinc (Zn)-tin (Sn)-calcium (Ca)-strontium (Sr)-manganese (Mn) systems; 2) study the precipitation kinetics (nucleation, growth and coarsening) using both innovative dual-anneal diffusion multiples and cast model alloys to provide largemore » amounts of kinetic data (including interfacial energy) and microstructure atlases to enable implementation of the Kampmann-Wagner numerical model to simulate phase transformation kinetics of non-spherical/non-cuboidal precipitates in Mg alloys; 3) implement a micromodel to take into account back diffusion in the solid phase in order to predict microstructure and microsegregation in multicomponent Mg alloys during dendritic solidification especially under high pressure die-casting (HPDC) conditions; and, 4) widely disseminate the data, knowledge and information using the Materials Genome Initiative infrastructure (http://www.mgidata.org) as well as publications and digital data sharing to enable researchers to identify new pathways/routes to better cast Mg alloys.« less

Engineered Zircaloy Cladding Modifications for Improved Accident Tolerance of LWR Nuclear Fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heuser, Brent; Stubbins, James; Kozlowski, Tomasz

The DOE NEUP sponsored IRP on accident tolerant fuel (ATF) entitled Engineered Zircaloy Cladding Modifications for Improved Accident Tolerance of LWR Nuclear Fuel involved three academic institutions, Idaho National Laboratory (INL), and ATI Materials (ATI). Detailed descriptions of the work at the University of Illinois (UIUC, prime), the University of Florida (UF), the University of Michigan (UMich), and INL are included in this document as separate sections. This summary provides a synopsis of the work performed across the IRP team. Two ATF solution pathways were initially proposed, coatings on monolithic Zr-based LWR cladding material and selfhealing modifications of Zr-based alloys.more » The coating pathway was extensively investigated, both experimentally and in computations. Experimental activities related to ATF coatings were centered at UIUC, UF, and UMich and involved coating development and testing, and ion irradiation. Neutronic and thermal hydraulic aspects of ATF coatings were the focus of computational work at UIUC and UMich, while materials science aspects were the focus of computational work at UF and INL. ATI provided monolithic Zircaloy 2 and 4 material and a binary Zr-Y alloy material. The selfhealing pathway was investigated with advanced computations only. Beryllium was identified as a valid self-healing additive early in this work. However, all attempts to fabricate a Zr-Be alloy failed. Several avenues of fabrication were explored. ATI ultimately declined our fabrication request over health concerns associated with Be (we note that Be was not part of the original work scope and the ATI SOW). Likewise, Ames Laboratory declined our fabrication request, citing known litigation dating to the 1980s and 1990s involving the U.S. Federal government and U.S. National Laboratory employees involving the use of Be. Materion (formerly, Brush Wellman) also declined our fabrication request, citing the difficulty in working with a highly reactive Zr and Be. International fabrication options were explored in Europe and Asia, but this proved to be impractical, if not impossible. Consequently, experimental investigation of the Zr-Be binary system was dropped and exploration binary Zr-Y binary system was initiated. The motivation behind the Zr-Y system is the known thermodynamic stability of yttria over zirconia.« less

Effect of Cr contents on the diffusion behavior of Te in Ni-based alloy

NASA Astrophysics Data System (ADS)

Jia, Yanyan; Li, Zhefu; Ye, Xiangxi; Liu, Renduo; Leng, Bin; Qiu, Jie; Liu, Min; Li, Zhijun

2017-12-01

The embrittlement of Ni-based structural alloys caused by fission production Te is one of the major challenges for molten salt reactors. It has been reported that solution element Cr can prevent the situation of intergranular cracks caused by Te. However, there is no detailed mechanism explanation on this phenomenon. In this study, the effect of Cr on Te diffusion in Ni-Cr binary system was investigated by diffusion experiments at 800 °C for 100 h. Results show that Te reacts with the alloy mainly forming Ni3Te2, and strip shaped Cr3Te4 is only found on the surface of Ni-15%Cr alloy. According to the discussion of thermodynamic chemical reaction process, Cr3Te4 exhibits the best stability and preferential formation compound in Te/Ni-Cr system as its Gibbs free energy of formation is the lowest. With the increase of Cr content in the alloy, the diffusion depth of Te along grain boundaries significantly decreases. Moreover, the formation process of reaction product and diffusion process are described. The diffusion of Te can be suppressed by high content of Cr in Ni-Cr alloy due to the formation of Cr3Te4 and thus the grain boundary is protected from Te corroding.

Viscosities of Fe Ni, Fe Co and Ni Co binary melts

NASA Astrophysics Data System (ADS)

Sato, Yuzuru; Sugisawa, Koji; Aoki, Daisuke; Yamamura, Tsutomu

2005-02-01

Viscosities of three binary molten alloys consisting of the iron group elements, Fe, Ni and Co, have been measured by using an oscillating cup viscometer over the entire composition range from liquidus temperatures up to 1600 °C with high precision and excellent reproducibility. The viscosities measured showed good Arrhenius linearity for all the compositions. The viscosities of Fe, Ni and Co as a function of temperature are as follows: \\eqalign{ & \\log \\eta={-}0.6074 + 2493/T\\qquad for\\quad Fe\\\\ & \\log \\eta={-}0.5695 + 2157/T\\qquad for\\quad Ni \\\\ & \\log \\eta={-}0.6620 + 2430/T\\qquad for\\quad Co.} The isothermal viscosities of Fe-Ni and Fe-Co binary melts increase monotonically with increasing Fe content. On the other hand, in Ni-Co binary melt, the isothermal viscosity decreases slightly and then increases with increasing Co. The activation energy of Fe-Co binary melt increased slightly on mixing, and those of Fe-Ni and Ni-Co melts decreased monotonically with increasing Ni content. The above behaviour is discussed based on the thermodynamic properties of the alloys.

Nuclear fuel alloys or mixtures and method of making thereof

DOEpatents

Mariani, Robert Dominick; Porter, Douglas Lloyd

2016-04-05

Nuclear fuel alloys or mixtures and methods of making nuclear fuel mixtures are provided. Pseudo-binary actinide-M fuel mixtures form alloys and exhibit: body-centered cubic solid phases at low temperatures; high solidus temperatures; and/or minimal or no reaction or inter-diffusion with steel and other cladding materials. Methods described herein through metallurgical and thermodynamics advancements guide the selection of amounts of fuel mixture components by use of phase diagrams. Weight percentages for components of a metallic additive to an actinide fuel are selected in a solid phase region of an isothermal phase diagram taken at a temperature below an upper temperature limit for the resulting fuel mixture in reactor use. Fuel mixtures include uranium-molybdenum-tungsten, uranium-molybdenum-tantalum, molybdenum-titanium-zirconium, and uranium-molybdenum-titanium systems.

NEUTRON REACTOR FUEL ELEMENT UTILIZING ZIRCONIUM-BASE ALLOYS

DOEpatents

Saller, H.A.; Keeler, J.R.; Szumachowski, E.R.

1957-11-12

This patent relates to clad fuel elements for use in neutronic reactors and is drawn to such a fuel element which consists of a core of fissionable material, comprised of an alloy of zirconium and U/sup 235/ enriched uranium, encased in a jacket of a binary zirconium-tin alloy in which the tin content ranges between 1 and 15% by weight.

Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohno, S.; Shimakura, H.; Tahara, S.

The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquidmore » Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.« less

Improved hydrogen absorption and desorption kinetics of magnesium-based alloy via addition of yttrium

NASA Astrophysics Data System (ADS)

Yang, Tai; Li, Qiang; Liu, Ning; Liang, Chunyong; Yin, Fuxing; Zhang, Yanghuan

2018-02-01

Yttrium (Y) is selected to modify the microstructure of magnesium (Mg) to improve the hydrogen storage performance. Thereby, binary alloys with the nominal compositions of Mg24Yx (x = 1-5) are fabricated by inexpensive casting technique. Their microstructure and phase transformation during hydriding and dehydriding process are characterized by using X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy analysis. The isothermal hydrogen absorption and desorption kinetics are also measured by a Sievert's-type apparatus at various temperatures. Typical multiphase structures of binary alloy can be clearly observed. All of these alloys can reversibly absorb and desorb large amount of hydrogen at proper temperatures. The addition of Y markedly promotes the hydrogen absorption kinetics. However, it results in a reduction of reversible hydrogen storage capacity. A maximum value of dehydrogenation rate is observed with the increase of Y content. The Mg24Y3 alloy has the optimal desorption kinetic performance, and it can desorb about 5.4 wt% of hydrogen at 380 °C within 12 min. Combining Johnson-Mehl-Avrami kinetic model and Arrhenius equation, the dehydrogenation activation energy of the alloys are evaluated. The Mg24Y3 alloy also has the lowest dehydrogenation activation energy (119 kJ mol-1).

Reassessment of Atomic Mobilities in fcc Cu-Ag-Sn System Aiming at Establishment of an Atomic Mobility Database in Sn-Ag-Cu-In-Sb-Bi-Pb Solder Alloys

NASA Astrophysics Data System (ADS)

Xu, Huixia; Zhang, Lijun; Cheng, Kaiming; Chen, Weimin; Du, Yong

2017-04-01

To establish an accurate atomic mobility database in solder alloys, a reassessment of atomic mobilities in the fcc (face centered cubic) Cu-Ag-Sn system was performed as reported in the present work. The work entailed initial preparation of three fcc Cu-Sn diffusion couples, which were used to determine the composition-dependent interdiffusivities at 873 K, 923 K, and 973 K, to validate the literature data and provide new experimental data at low temperatures. Then, atomic mobilities in three boundary binaries, fcc Cu-Sn, fcc Ag-Sn, and fcc Cu-Ag, were updated based on the data for various experimental diffusivities obtained from the literature and the present work, together with the available thermodynamic database for solder alloys. Finally, based on the large number of interdiffusivities recently measured from the present authors, atomic mobilities in the fcc Cu-Ag-Sn ternary system were carefully evaluated. A comprehensive comparison between various calculated/model-predicted diffusion properties and the experimental data was used to validate the reliability of the obtained atomic mobilities in ternary fcc Cu-Ag-Sn alloys.

Analytical model of radiation-induced precipitation at the surface of dilute binary alloy

NASA Astrophysics Data System (ADS)

Pechenkin, V. A.; Stepanov, I. A.; Konobeev, Yu. V.

2002-12-01

Growth of precipitate layer at the foil surface of an undersaturated binary alloy under uniform irradiation is treated analytically. Analytical expressions for the layer growth rate, layer thickness limit and final component concentrations in the matrix are derived for coherent and incoherent precipitate-matrix interfaces. It is shown that the high temperature limit of radiation-induced precipitation is the same for both types of interfaces, whereas layer thickness limits are different. A parabolic law of the layer growth predicted for both types of interfaces is in agreement with experimental data on γ '-phase precipitation at the surface of Ni-Si dilute alloys under ion irradiation. Effect of sputtering on the precipitation rate and on the low temperature limit of precipitation under ion irradiation is discussed.

Numerical Modeling of HgCdTe Solidification: Effects of Phase Diagram, Double-Diffusion Convection and Microgravity Level

NASA Technical Reports Server (NTRS)

Bune, Andris V.; Gillies, Donald C.; Lehoczky, Sandor L.

1997-01-01

Melt convection, along with species diffusion and segregation on the solidification interface are the primary factors responsible for species redistribution during HgCdTe crystal growth from the melt. As no direct information about convection velocity is available, numerical modeling is a logical approach to estimate convection. Furthermore influence of microgravity level, double-diffusion and material properties should be taken into account. In the present study, HgCdTe is considered as a binary alloy with melting temperature available from a phase diagram. The numerical model of convection and solidification of binary alloy is based on the general equations of heat and mass transfer in two-dimensional region. Mathematical modeling of binary alloy solidification is still a challenging numericial problem. A Rigorous mathematical approach to this problem is available only when convection is not considered at all. The proposed numerical model was developed using the finite element code FIDAP. In the present study, the numerical model is used to consider thermal, solutal convection and a double diffusion source of mass transport.

Static and vibrational properties of equiatomic Na-based binary alloys

NASA Astrophysics Data System (ADS)

Vora, Aditya M.

2007-09-01

The computations of the static and vibrational properties of four equiatomic Na-based binary alloys viz. Na0.5Li0.5, Na0.5K0.5, Na0.5Rb0.5 and Na0.5Cs0.5, to second order in local model potential is discussed in terms of real-space sum of Born von Karman central force constants. The local field correlation functions due to Hartree (H), Ichimaru Utsumi (IU) and Sarkar et al. (S) are used to investigate the influence of the screening effects on the aforesaid properties. Results for the lattice constants C11, C12, C44, C12 C44, C12/C44 and bulk modulus B obtained using the H-local field correction function have higher values in comparison with the results obtained for the same properties using IU- and S-local field correction functions. The results for the Shear modulus (C‧), deviation from Cauchy's relation, Poisson's ratio σ, Young modulus Y, propagation velocity of elastic waves, phonon dispersion curves and degree of anisotropy A are highly appreciable for the four equiatomic Na-based binary alloys.

Effect of Ni +-ION bombardment on nickel and binary nickel alloys

NASA Astrophysics Data System (ADS)

Roarty, K. B.; Sprague, J. A.; Johnson, R. A.; Smidt, F. A.

1981-03-01

Pure nickel and four binary nickel alloys have been subjected to high energy Ni ion bombardment at 675, 625 and 525°C. After irradiation, each specimen was studied by transmission electron microscopy. The pure nickel control was found to swell appreciably (1 to 5%) and the Ni-Al and the Ni-Ti samples were found to swell at all temperatures, but to a lesser degree (0.01 to 0.35%). The Ni-Mo contained a significant density of voids only at 525° C, while swelling was suppressed at all temperatures in the Ni-Si alloy. The dislocation structure progressed from loops to tangles as temperature increased in all materials except the Ni-Ti, in which there was an absence of loops at all temperatures. Dislocation densities decreased as temperature increased in all samples. These results do not correlate well with the relative behavior of the same alloys observed after neutron irradiation at 455°C. The differences between these two sets of data appear to be caused by different mechanisms controlling void nucleation in ion and neutron irradiation of these alloys.

The Effect of Impurities on the Processing of Aluminum Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zi-Kui Liu; Shengjun Zhang; Qingyou Han

2007-04-23

For this Aluminum Industry of the Future (IOF) project, the effect of impurities on the processing of aluminum alloys was systematically investigated. The work was carried out as a collaborative effort between the Pennsylvania State University and Oak Ridge National Laboratory. Industrial support was provided by ALCOA and ThermoCalc, Inc. The achievements described below were made. A method that combines first-principles calculation and calculation of phase diagrams (CALPHAD) was used to develop the multicomponent database Al-Ca-K-Li-Mg-Na. This method was extensively used in this project for the development of a thermodynamic database. The first-principles approach provided some thermodynamic property data thatmore » are not available in the open literature. These calculated results were used in the thermodynamic modeling as experimental data. Some of the thermodynamic property data are difficult, if not impossible, to measure. The method developed and used in this project allows the estimation of these data for thermodynamic database development. The multicomponent database Al-Ca-K-Li-Mg-Na was developed. Elements such as Ca, Li, Na, and K are impurities that strongly affect the formability and corrosion behavior of aluminum alloys. However, these impurity elements are not included in the commercial aluminum alloy database. The process of thermodynamic modeling began from Al-Na, Ca-Li, Li-Na, K-Na, and Li-K sub-binary systems. Then ternary and higher systems were extrapolated because of the lack of experimental information. Databases for five binary alloy systems and two ternary systems were developed. Along with other existing binary and ternary databases, the full database of the multicomponent Al-Ca-K-Li-Mg-Na system was completed in this project. The methodology in integrating with commercial or other aluminum alloy databases can be developed. The mechanism of sodium-induced high-temperature embrittlement (HTE) of Al-Mg is now understood. Using the thermodynamic database developed in this project, thermodynamic simulations were carried out to investigate the effect of sodium on the HTE of Al-Mg alloys. The simulation results indicated that the liquid miscibility gap resulting from the dissolved sodium in the molten material plays an important role in HTE. A liquid phase forms from the solid face-centered cubic (fcc) phase (most likely at grain boundaries) during cooling, resulting in the occurrence of HTE. Comparison of the thermodynamic simulation results with experimental measurements on the high-temperature ductility of an Al-5Mg-Na alloy shows that HTE occurs in the temperature range at which the liquid phase exists. Based on this fundamental understanding of the HTE mechanism during processing of aluminum alloy, an HTE sensitive zone and a hot-rolling safe zone of the Al-Mg-Na alloys are defined as functions of processing temperature and alloy composition. The tendency of HTE was evaluated based on thermodynamic simulations of the fraction of the intergranular sodium-rich liquid phase. Methods of avoiding HTE during rolling/extrusion of Al-Mg-based alloys were suggested. Energy and environmental benefits from the results of this project could occur through a number of avenues: (1) energy benefits accruing from reduced rejection rates of the aluminum sheet and bar, (2) reduced dross formation during the remelting of the aluminum rejects, and (3) reduced CO2 emission related to the energy savings. The sheet and extruded bar quantities produced in the United States during 2000 were 10,822 and 4,546 million pounds, respectively. It is assumed that 50% of the sheet and 10% of the bar will be affected by implementing the results of this project. With the current process, the rejection rate of sheet and bar is estimated at 5%. Assuming that at least half of the 5% rejection of sheet and bar will be eliminated by using the results of this project and that 4% of the aluminum will be lost through dross (Al2O3) during remelting of the rejects, the full-scale industrial implementation of the project results would lead to energy savings in excess of 6.2 trillion Btu/year and cost savings of $42.7 million by 2020.« less

On Nb Silicide Based Alloys: Alloy Design and Selection.

PubMed

Tsakiropoulos, Panos

2018-05-18

The development of Nb-silicide based alloys is frustrated by the lack of composition-process-microstructure-property data for the new alloys, and by the shortage of and/or disagreement between thermodynamic data for key binary and ternary systems that are essential for designing (selecting) alloys to meet property goals. Recent publications have discussed the importance of the parameters δ (related to atomic size), Δχ (related to electronegativity) and valence electron concentration (VEC) (number of valence electrons per atom filled into the valence band) for the alloying behavior of Nb-silicide based alloys (J Alloys Compd 748 (2018) 569), their solid solutions (J Alloys Compd 708 (2017) 961), the tetragonal Nb₅Si₃ (Materials 11 (2018) 69), and hexagonal C14-NbCr₂ and cubic A15-Nb₃X phases (Materials 11 (2018) 395) and eutectics with Nb ss and Nb₅Si₃ (Materials 11 (2018) 592). The parameter values were calculated using actual compositions for alloys, their phases and eutectics. This paper is about the relationships that exist between the alloy parameters δ, Δχ and VEC, and creep rate and isothermal oxidation (weight gain) and the concentrations of solute elements in the alloys. Different approaches to alloy design (selection) that use property goals and these relationships for Nb-silicide based alloys are discussed and examples of selected alloy compositions and their predicted properties are given. The alloy design methodology, which has been called NICE (Niobium Intermetallic Composite Elaboration), enables one to design (select) new alloys and to predict their creep and oxidation properties and the macrosegregation of Si in cast alloys.

On Nb Silicide Based Alloys: Alloy Design and Selection

PubMed Central

Tsakiropoulos, Panos.

2018-01-01

The development of Nb-silicide based alloys is frustrated by the lack of composition-process-microstructure-property data for the new alloys, and by the shortage of and/or disagreement between thermodynamic data for key binary and ternary systems that are essential for designing (selecting) alloys to meet property goals. Recent publications have discussed the importance of the parameters δ (related to atomic size), Δχ (related to electronegativity) and valence electron concentration (VEC) (number of valence electrons per atom filled into the valence band) for the alloying behavior of Nb-silicide based alloys (J Alloys Compd 748 (2018) 569), their solid solutions (J Alloys Compd 708 (2017) 961), the tetragonal Nb5Si3 (Materials 11 (2018) 69), and hexagonal C14-NbCr2 and cubic A15-Nb3X phases (Materials 11 (2018) 395) and eutectics with Nbss and Nb5Si3 (Materials 11 (2018) 592). The parameter values were calculated using actual compositions for alloys, their phases and eutectics. This paper is about the relationships that exist between the alloy parameters δ, Δχ and VEC, and creep rate and isothermal oxidation (weight gain) and the concentrations of solute elements in the alloys. Different approaches to alloy design (selection) that use property goals and these relationships for Nb-silicide based alloys are discussed and examples of selected alloy compositions and their predicted properties are given. The alloy design methodology, which has been called NICE (Niobium Intermetallic Composite Elaboration), enables one to design (select) new alloys and to predict their creep and oxidation properties and the macrosegregation of Si in cast alloys. PMID:29783707

Microstructure and mechanical behavior of metal injection molded Ti-Nb binary alloys as biomedical material.

PubMed

Zhao, Dapeng; Chang, Keke; Ebel, Thomas; Qian, Ma; Willumeit, Regine; Yan, Ming; Pyczak, Florian

2013-12-01

The application of titanium (Ti) based biomedical materials which are widely used at present, such as commercially pure titanium (CP-Ti) and Ti-6Al-4V, are limited by the mismatch of Young's modulus between the implant and the bones, the high costs of products, and the difficulty of producing complex shapes of materials by conventional methods. Niobium (Nb) is a non-toxic element with strong β stabilizing effect in Ti alloys, which makes Ti-Nb based alloys attractive for implant application. Metal injection molding (MIM) is a cost-efficient near-net shape process. Thus, it attracts growing interest for the processing of Ti and Ti alloys as biomaterial. In this investigation, metal injection molding was applied to the fabrication of a series of Ti-Nb binary alloys with niobium content ranging from 10wt% to 22wt%, and CP-Ti for comparison. Specimens were characterized by melt extraction, optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Titanium carbide formation was observed in all the as-sintered Ti-Nb binary alloys but not in the as-sintered CP-Ti. Selected area electron diffraction (SAED) patterns revealed that the carbides are Ti2C. It was found that with increasing niobium content from 0% to 22%, the porosity increased from about 1.6% to 5.8%, and the carbide area fraction increased from 0% to about 1.8% in the as-sintered samples. The effects of niobium content, porosity and titanium carbides on mechanical properties have been discussed. The as-sintered Ti-Nb specimens exhibited an excellent combination of high tensile strength and low Young's modulus, but relatively low ductility. © 2013 Elsevier Ltd. All rights reserved.

Enhanced-wetting, boron-based liquid-metal ion source and method

DOEpatents

Bozack, Michael J.; Swanson, Lynwood W.; Bell, Anthony E.; Clark Jr., William M.; Utlaut, Mark W.; Storms, Edmund K.

1999-01-01

A binary, boron-based alloy as a source for field-emission-type, ion-beam generating devices, wherein boron predominates in the alloy, preferably with a presence of about 60 atomic percent. The other constituent in the alloy is selected from the group of elements consisting of nickel, palladium and platinum. Predominance of boron in these alloys, during operation, promotes combining of boron with trace impurities of carbon in the alloys to form B.sub.4 C and thus to promote wetting of an associated carbon support substrate.

Enhanced-wetting, boron-based liquid-metal ion source and method

DOEpatents

Bozack, M.J.; Swanson, L.W.; Bell, A.E.; Clark, W.M. Jr.; Utlaut, M.W.; Storms, E.K.

1999-02-16

A binary, boron-based alloy as a source for field-emission-type, ion-beam generating devices, wherein boron predominates in the alloy, preferably with a presence of about 60 atomic percent is disclosed. The other constituent in the alloy is selected from the group of elements consisting of nickel, palladium and platinum. Predominance of boron in these alloys, during operation, promotes combining of boron with trace impurities of carbon in the alloys to form B{sub 4}C and thus to promote wetting of an associated carbon support substrate. 1 fig.

Role of electron concentration in softening and hardening of ternary molybdenum alloys

NASA Technical Reports Server (NTRS)

Stephens, J. R.; Witzke, W. R.

1975-01-01

Effects of various combinations of hafnium, tantalum, rhenium, osmium, iridium, and platinum in ternary molybdenum alloys on alloy softening and hardening were determined. Hardness tests were conducted at four test temperatures over the temperature range 77 to 411 K. Results showed that hardness data for ternary molybdenum alloys could be correlated with anticipated results from binary data based upon expressions involving the number of s and d electrons contributed by the solute elements. The correlation indicated that electron concentration plays a dominant role in controlling the hardness of ternary molybdenum alloys.

The Effect of Palladium Additions on the Solidus/Liquidus Temperatures and Wetting Properties of Ag-CuO Based Air Brazes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darsell, Jens T.; Weil, K. Scott

2007-05-16

As a means of increasing the use temperature of ceramic-ceramic and ceramic-metal air brazes, palladium was investigated as possible ternary addition to the currently employed silver - copper oxide system. The silver component was directly substituted with palladium to form the following series of alloys: (100-y)[(100-z)Pd - (z)Ag] - (y)CuOx where y = 0 - 34 mol% CuOx, z = 50 - 100 mol% silver, and x = 0, 0.5, and 1, denoting copper metal, Cu2O, or CuO. From differential scanning calorimetry, it was determined that the addition of palladium causes an increase in the solidus and liquidus temperatures ofmore » the resulting Pd-Ag-CuO brazes. In general, the liquidus was found to increase by approximately 220°C for the (100-y)(25Pd - 75Ag) - (z)CuOx filler metal compositions relative to comparable Ag-CuOx alloys. Likewise, the solidus was found to increase for these alloys, respectively by 185°C and 60°C, respectively for CuOx contents of y = 0 - 1mol% and 4 - 10 mol%. For the (100-y)(50Pd - 50Ag) - (y)CuOx alloys, the solidus increased between 280 - 390°C over a copper oxide compositional range of x = 0 to 8 mol%. It was determined from sessile drop experiments conducted on alumina substrates that in all cases the palladium causes an increase in the wetting angle relative to the corresponding binary braze. Alloy compositions of (100-y)(25Pd - 75Ag) - (y)CuOx displayed increased wetting angles of 5-20° relative to comparable binary compositions. (100-y)(50Pd - 50Ag) - (y)CuOx alloys exhibited an increase in contact angle of 10-60° and compositions containing less than 10 mol% CuOx were not able to wet the substrate. Scanning electron microscopy indicated that the microstructure of the braze consists of discrete CuOx precipitates in an alloyed silver-palladium matrix. In both the binary and ternary filler metal formulations, a reaction layer consisting of CuAlO2 was observed along the interface with the alumina substrate. This reaction product appears to be beneficial in promoting wetting by the remaining braze filler metal. However the formation of this layer is hindered as the concentration of palladium in the filler metal is increased, which appears to be the primary cause of poor wettability in these compositions, as indicated by the substantial amount of porosity found along the braze/substrate interface.« less

The As-Cu-Ni System: A Chemical Thermodynamic Model for Ancient Recycling

NASA Astrophysics Data System (ADS)

Sabatini, Benjamin J.

2015-12-01

This article is the first thermodynamically reasoned ancient metal system assessment intended for use by archaeologists and archaeometallurgists to aid in the interpretation of remelted/recycled copper alloys composed of arsenic and copper, and arsenic, copper, and nickel. These models are meant to fulfill two main purposes: first, to be applied toward the identification of progressive and regressive temporal changes in artifact chemistry that would have occurred due to recycling, and second, to provide thermodynamic insight into why such metal combinations existed in antiquity. Built on well-established thermodynamics, these models were created using a combination of custom-written software and published binary thermodynamic systems data adjusted to within the boundary conditions of 1200°C and 1 atm. Using these parameters, the behavior of each element and their likelihood of loss in the binaries As-Cu, As-Ni, Cu-Ni, and ternary As-Cu-Ni, systems, under assumed ancient furnace conditions, was determined.

Processing, physical metallurgy and creep of NiAl + Ta and NiAl + Nb alloys. Ph.D. Thesis. Final Contractor Report

NASA Technical Reports Server (NTRS)

Pathare, Viren M.

1988-01-01

Powder processed NiAl + Ta alloys containing 1, 2, and 4.5 at percent tantalum and NiAl + Nb alloys containing 1 and 2 at percent niobium were developed for improved creep properties. In addition, a cast alloy with 5 at percent tantalum was also studied. Hot extrusion parameters for processing alloys with 1 and 2 at percent of tantalum or niobium were designed. The NiAl + 4.5 at percent Ta alloy could be vacuum hot pressed successfully, even though it could not be extruded. All the phases in the multiphase alloys were identified and the phase transformations studied. The Ni2AlTa in NiAl + 4.5 at percent Ta alloy transforms into a liquid phase above 1700 K. Solutionizing and annealing below this temperature gives rise to a uniform distribution of fine second phase precipitates. Compressive creep properties were evaluated at 1300 K using constant load and constant velocity tests. In the higher strain rate region single phase NiAl + 1 at percent Ta and NiAl + 1 at percent Nb alloys exhibit a stress exponent of 5 characteristic of climb controlled dislocation creep. In slower strain rate regime diffusional creep becomes important. The two phase alloys containing 2 to 5 at percent Ta and 2 at percent Nb show considerable improvement over binary NiAl and single phase alloys. Loose dislocation networks and tangles stabilized by the precipitates were found in the as crept microstructure. The cast alloy which has larger grains and a distribution of fine precipitates shows the maximum improvement over binary NiAl.

Microstructure and physical properties of bismuth-lead-tin ternary eutectic alloy

NASA Astrophysics Data System (ADS)

Kamal, M.; Moharram, B. M.; Farag, H.; El-Bediwi, A.; Abosheiasha, H. F.

2006-07-01

Using different experimental techniques, microstructure, electrical resistivity, attenuation coefficient, and mechanical and thermal properties of the quenched Bi-Pb-Sn ternary eutectic alloy have been investigated. From the X-ray analysis, Bi3Pb7 and Bi-Sn meta-stable phases are detected, in addition to rhombohedral bismuth and Sn body-centered tetragonal phases. This study also compared the physical properties of the Bi-Sn-Pb ternary eutectic alloys with the base binary Bi-Sn and Bi-Pb eutectic alloys.

Cobalt-Free Permanent Magnet Alloys.

DTIC Science & Technology

1984-10-01

carbide co- UC CbC lumbium carbide M003 Uranium carbide - tho- UC 2 25ThC rium carbide ZrO2 MgO WOs Use of this Process for MnAlC As indicated in the...cobalt. Free World Cobal Consumption Estimated Breakdown by End Uses Magnetic alloys 20% Cemented carbides - 5% 30 SuPerolloy _ 15% Other steels and...would normally result in the formation of binary alloy of TbFe 2 and preventing the formation of amorphous alloy (Fe-B) contain- ing Tb. The

Assessment of phase constitution on the Al-rich region of rapidly solidified Al-Co-Fe-Cr alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolf, W., E-mail: witorw@gmail.com

The formation of quasicrystalline approximants in rapidly solidified Al-Co-Fe-Cr alloys was investigated. Alloys of atomic composition Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8}, Al{sub 77}Co{sub 11}Fe{sub 6}Cr{sub 6} and Al{sub 76}Co{sub 19}Fe{sub 4}Cr{sub 1} were produced using melt spinning and arc melting methods and their microstructural characterization was carried out by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Up to the present there is no consensus in the literature regarding the formation of quasicrystalline phase or quasicrystalline approximants in the Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8} alloy. This work presents, for the first time, a detailed structural characterization of selected alloysmore » in the Al-Co-Fe-Cr system close to the atomic composition Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8}. The results indicated the samples to be composed, mostly, by two intermetallic phases, which are quaternary extensions of Al{sub 5}Co{sub 2} and Al{sub 13}Co{sub 4} and are quasicrystalline approximants. Although the Al{sub 5}Co{sub 2} phase has already been reported in the Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8} alloy, the presence of the monoclinic Al{sub 13}Co{sub 4} is now identified for the first time in the as cast state. In the binary Al-Co system a quasicrystalline phase is known to form in a rapidly solidified alloy with composition close to the monoclinic and orthorhombic Al{sub 13}Co{sub 4} phases. This binary quasicrystalline phase presents an average valence electron per atom (e/a) between 1.7 and 1.9; thus, in addition to the Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8} alloy, the compositions Al{sub 77}Co{sub 11}Fe{sub 6}Cr{sub 6} and Al{sub 76}Co{sub 19}Fe{sub 4}Cr{sub 1} were chosen to be within the region of formation of the quaternary extension of the Al{sub 13}Co{sub 4} phase and also within the (e/a) of 1.7 to 1.9. However, no quasicrystalline phase is present in any of the studied alloys. The Al-Co-Fe-Cr system, around the compositions studied, is composed of quaternary extensions of Al-Co intermetallic phases, which present solubility of Fe and Cr at Co atomic sites. - Highlights: •The Al rich region of the AlCoFeCr system is studied concerning phase formation on rapidly solidified alloys. •The alloys were composed mostly by quaternary extensions of Al-Co intermetallic phases. •Al{sub 5}Co{sub 2} and Al{sub 13}Co{sub 4} were the major phases observed in the alloys and are approximants of a quasicrystalline phase. •No quasicrystalline phase was observed in the Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8} composition.« less

Fabrication of biodegradable Zn-Al-Mg alloy: Mechanical properties, corrosion behavior, cytotoxicity and antibacterial activities.

PubMed

Bakhsheshi-Rad, H R; Hamzah, E; Low, H T; Kasiri-Asgarani, M; Farahany, S; Akbari, E; Cho, M H

2017-04-01

In this work, binary Zn-0.5Al and ternary Zn-0.5Al-xMg alloys with various Mg contents were investigated as biodegradable materials for implant applications. Compared with Zn-0.5Al (single phase), Zn-0.5Al-xMg alloys consisted of the α-Zn and Mg 2 (Zn, Al) 11 with a fine lamellar structure. The results also revealed that ternary Zn-Al-Mg alloys presented higher micro-hardness value, tensile strength and corrosion resistance compared to the binary Zn-Al alloy. In addition, the tensile strength and corrosion resistance increased with increasing the Mg content in ternary alloys. The immersion tests also indicated that the corrosion rates in the following order Zn-0.5Al-0.5Mg

Identification of a new pseudo-binary hydroxide during calendar corrosion of (La, Mg)2Ni7-type hydrogen storage alloys for Nickel-Metal Hydride batteries

NASA Astrophysics Data System (ADS)

Monnier, J.; Chen, H.; Joiret, S.; Bourgon, J.; Latroche, M.

2014-11-01

To improve the performances of Nickel-Metal Hydride batteries, an important step is the understanding of the corrosion processes that take place in the electrode material. In particular, the present study focuses for the first time on the model (La, Mg)2Ni7 system. The calendar corrosion in 8.7 M KOH medium was investigated from 6 h to 16 weeks immersion. By a unique combination of structural and elemental characterisations, the corrosion products are evidenced in those systems. In particular, we demonstrate that Ni and Mg combine in a pseudo-binary hydroxide Mg1-xNix(OH)2 whereas La corrodes into nanoporous La(OH)3 needles with inner hollow nanochannels.

Influence of grain boundaries on the distribution of components in binary alloys

NASA Astrophysics Data System (ADS)

L'vov, P. E.; Svetukhin, V. V.

2017-12-01

Based on the free-energy density functional method (the Cahn-Hilliard equation), a phenomenological model that describes the influence of grain boundaries on the distribution of components in binary alloys has been developed. The model is built on the assumption of the difference between the interaction parameters of solid solution components in the bulk and at the grain boundary. The difference scheme based on the spectral method is proposed to solve the Cahn-Hilliard equation with interaction parameters depending on coordinates. Depending on the ratio between the interaction parameters in the bulk and at the grain boundary, temperature, and alloy composition, the model can give rise to different types of distribution of a dissolved component, namely, either depletion or enrichment of the grain-boundary area, preferential grainboundary precipitation, competitive precipitation in the bulk and at the grain boundary, etc.

Hardware Modifications to the US Army Research Laboratory’s Metalorganic Chemical Vapor Deposition (MOCVD) System for Optimization of Complex Oxide Thin Film Fabrication

DTIC Science & Technology

2015-04-01

studies on flow and thermal fields in MOCVD reactor. Chinese Science Bulletin. 2010;55:560–566. 36. Hampdensmith MJ, Kodas TT. Chemical vapor...Chemistry. 1995;19727–750. 47. Xu CY, Hampdensmith MJ, Kodas TT. Aerosol-assisted chemical-vapor- deposition (AACVD) of binary alloy (AGXPD1-X, CUXPD1-X

Discussion Meeting on Thermodynamics of Alloys Held in Sant Feliu de Guixols, Spain on 23-26 May 1990. Abstracts

DTIC Science & Technology

1990-05-26

OFFICE OF THE U.S. ARMY EUROPEAN RESEARCH OFFICE OF THE U.S. AIR FORCE MINISTERIO DE EDUCACION Y CIENCIA I I Wednesday, May 23 8.30 Registration 9.00... especially regarding the structural but less the thermodynamic proper- ties). The third binary system Ag-Te has been investigated in detail by our group. No

Corrosion of Nickel-Based Alloys in Ultra-High Temperature Heat Transfer Fluid

NASA Astrophysics Data System (ADS)

Wang, Tao; Reddy, Ramana G.

2017-03-01

MgCl2-KCl binary system has been proposed to be used as high temperature reactor coolant. Due to its relatively low melting point, good heat capacity and excellent thermal stability, this system can also be used in high operation temperature concentrating solar power generation system as heat transfer fluid (HTF). The corrosion behaviors of nickel based alloys in MgCl2-KCl molten salt system at 1,000 °C were determined based on long-term isothermal dipping test. After 500 h exposure tests under strictly maintained high purity argon gas atmosphere, the weight loss and corrosion rate analysis were conducted. Among all the tested samples, Ni-201 demonstrated the lowest corrosion rate due to the excellent resistance of Ni to high temperature element dissolution. Detailed surface topography and corrosion mechanisms were also determined by using scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS).

Solidification of a binary alloy: Finite-element, single-domain simulation and new benchmark solutions

NASA Astrophysics Data System (ADS)

Le Bars, Michael; Worster, M. Grae

2006-07-01

A finite-element simulation of binary alloy solidification based on a single-domain formulation is presented and tested. Resolution of phase change is first checked by comparison with the analytical results of Worster [M.G. Worster, Solidification of an alloy from a cooled boundary, J. Fluid Mech. 167 (1986) 481-501] for purely diffusive solidification. Fluid dynamical processes without phase change are then tested by comparison with previous numerical studies of thermal convection in a pure fluid [G. de Vahl Davis, Natural convection of air in a square cavity: a bench mark numerical solution, Int. J. Numer. Meth. Fluids 3 (1983) 249-264; D.A. Mayne, A.S. Usmani, M. Crapper, h-adaptive finite element solution of high Rayleigh number thermally driven cavity problem, Int. J. Numer. Meth. Heat Fluid Flow 10 (2000) 598-615; D.C. Wan, B.S.V. Patnaik, G.W. Wei, A new benchmark quality solution for the buoyancy driven cavity by discrete singular convolution, Numer. Heat Transf. 40 (2001) 199-228], in a porous medium with a constant porosity [G. Lauriat, V. Prasad, Non-darcian effects on natural convection in a vertical porous enclosure, Int. J. Heat Mass Transf. 32 (1989) 2135-2148; P. Nithiarasu, K.N. Seetharamu, T. Sundararajan, Natural convective heat transfer in an enclosure filled with fluid saturated variable porosity medium, Int. J. Heat Mass Transf. 40 (1997) 3955-3967] and in a mixed liquid-porous medium with a spatially variable porosity [P. Nithiarasu, K.N. Seetharamu, T. Sundararajan, Natural convective heat transfer in an enclosure filled with fluid saturated variable porosity medium, Int. J. Heat Mass Transf. 40 (1997) 3955-3967; N. Zabaras, D. Samanta, A stabilized volume-averaging finite element method for flow in porous media and binary alloy solidification processes, Int. J. Numer. Meth. Eng. 60 (2004) 1103-1138]. Finally, new benchmark solutions for simultaneous flow through both fluid and porous domains and for convective solidification processes are presented, based on the similarity solutions in corner-flow geometries recently obtained by Le Bars and Worster [M. Le Bars, M.G. Worster, Interfacial conditions between a pure fluid and a porous medium: implications for binary alloy solidification, J. Fluid Mech. (in press)]. Good agreement is found for all tests, hence validating our physical and numerical methods. More generally, the computations presented here could now be considered as standard and reliable analytical benchmarks for numerical simulations, specifically and independently testing the different processes underlying binary alloy solidification.

Microstructural development from interdiffusion and reaction between U–Mo and AA6061 alloys annealed at 600° and 550 °C

DOE PAGES

Perez, E.; Keiser, D. D.; Sohn, Y. H.

2016-05-10

The U.S. Material Management and Minimization Reactor Conversion Program is developing low enrichment fuel systems encased in Al-alloy for use in research and test reactors. Monolithic fuel plates have local regions where the Usingle bondMo fuel plate may come into contact with the Al-alloy 6061 (AA6061) cladding. This results in the development of interdiffusion zones with complex microstructures with multiple phases. In this study, the microstructural development of diffusion couples, U–7 wt%Mo, U–10 wt%Mo, and U–12 wt%Mo vs. AA6061, annealed at 600 °C for 24 h and at 550 °C for 1, 5, and 20 h, were analyzed by scanningmore » electron microscopy with x-ray energy dispersive spectroscopy. The microstructural development and kinetics were compared to diffusion couples U–Mo vs. high purity Al and binary Al–Si alloys. As a result, the diffusion couples developed complex interaction regions where phase development was influenced by the alloying additions of the AA6061.« less

Solute effects on deformation and fracture of beta brass

NASA Technical Reports Server (NTRS)

Shea, M. M.; Stoloff, N. S.

1973-01-01

It is shown that the ductility of several ternary beta brass alloys in air and in several liquid metals can be related to the operative slip and grain boundary relaxation processes. Nickel and manganese were chosen as alloying elements because they are expected to respectively enhance and suppress cross slip in beta brass. Single-phase binary and ternary beta brass alloys were used in both polycrystalline and single crystal form.

Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr.

PubMed

Li, H F; Xie, X H; Zheng, Y F; Cong, Y; Zhou, F Y; Qiu, K J; Wang, X; Chen, S H; Huang, L; Tian, L; Qin, L

2015-05-29

Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.

Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr

PubMed Central

Li, H. F.; Xie, X. H.; Zheng, Y. F.; Cong, Y.; Zhou, F. Y.; Qiu, K. J.; Wang, X.; Chen, S. H.; Huang, L.; Tian, L.; Qin, L.

2015-01-01

Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals. PMID:26023878

Development of rapidly quenched nickel-based non-boron filler metals for brazing corrosion resistant steels

NASA Astrophysics Data System (ADS)

Ivannikov, A.; Kalin, B.; Suchkov, A.; Penyaz, M.; Yurlova, M.

2016-04-01

Corrosion-resistant steels are stably applied in modern rocket and nuclear technology. Creating of permanent joints of these steels is a difficult task that can be solved by means of welding or brazing. Recently, the use rapidly quenched boron-containing filler metals is perspective. However, the use of such alloys leads to the formation of brittle borides in brazing zone, which degrades the corrosion resistance and mechanical properties of the compounds. Therefore, the development of non-boron alloys for brazing stainless steels is important task. The study of binary systems Ni-Be and Ni-Si revealed the perspective of replacing boron in Ni-based filler metals by beryllium, so there was the objective of studying of phase equilibrium in the system Ni-Be-Si. The alloys of the Ni-Si-Be with different contents of Si and Be are considered in this paper. The presence of two low-melting components is revealed during of their studying by methods of metallography analysis and DTA. Microhardness is measured and X-ray diffraction analysis is conducted for a number of alloys of Ni-Si-Be. The compositions are developed on the basis of these data. Rapidly quenched brazing alloys can be prepared from these compositions, and they are suitable for high temperature brazing of steels.

Charge-doping and chemical composition-driven magnetocrystalline anisotropy in CoPt core-shell alloy clusters

NASA Astrophysics Data System (ADS)

Ruiz-Díaz, P.; Muñoz-Navia, M.; Dorantes-Dávila, J.

2018-03-01

Charge-doping together with 3 d-4 d alloying emerges as promising mechanisms for tailoring the magnetic properties of low-dimensional systems. Here, throughout ab initio calculations, we present a systematic overview regarding the impact of both electron(hole) charge-doping and chemical composition on the magnetocrystalline anisotropy (MA) of CoPt core-shell alloy clusters. By taking medium-sized Co n Pt m ( N = n + m = 85) octahedral-like alloy nanoparticles for some illustrative core-sizes as examples, we found enhanced MA energies and large induced spin(orbital) moments in Pt-rich clusters. Moreover, depending on the Pt-core-size, both in-plane and off-plane directions of magnetization are observed. In general, the MA of these binary compounds further stabilizes upon charge-doping. In addition, in the clusters with small MA, the doping promotes magnetization switching. Insights into the microscopical origins of the MA behavior are associated to changes in the electronic structure of the clusters. [Figure not available: see fulltext.

Effect of Inoculant Alloy Selection and Particle Size on Efficiency of Isomorphic Inoculation of Ti-Al

PubMed Central

Rouat, Bernard; Daloz, Dominique; Bouzy, Emmanuel

2018-01-01

The process of isomorphic inoculation relies on precise selection of inoculant alloys for a given system. Three alloys, Ti-10Al-25Nb, Ti-25Al-10Ta, and Ti-47Ta (at %) were selected as potential isomorphic inoculants for a Ti-46Al alloy. The binary Ti-Ta alloy selected was found to be ineffective as an inoculant due to its large density difference with the melt, causing the particles to settle. Both ternary alloys were successfully implemented as isomorphic inoculants that decreased the equiaxed grain size and increased the equiaxed fraction in their ingots. The degree of grain refinement obtained was found to be dependent on the number of particles introduced to the melt. Also, more new grains were formed than particles added to the melt. The grains/particle efficiency varied from greater than one to nearly twenty as the size of the particle increased. This is attributed to the breaking up of particles into smaller particles by dissolution in the melt. For a given particle size, Ti-Al-Ta and Ti-Al-Nb particles were found to have a roughly similar grain/particle efficiency. PMID:29693591

Study of Plastic Deformation in Binary Aluminum Alloys by Internal-Friction Methods

NASA Technical Reports Server (NTRS)

Olson, E. C.; Maringer, R. E.; Marsh, L. L.; Manning, G. K.

1959-01-01

The damping capacity of several aluminum-copper alloys has been investigated during tensile elongation. This damping is shown to depend on strain rate, strain, temperature, alloy content, and heat treatment. A tentative hypothesis, based on the acceleration of solute atom diffusion by deformation-produced vacancies, is proposed to account for the observed behavior. Internal-friction maxima are observed in deformed aluminum and aluminum-copper alloys at -70 deg and -50 deg C. The peaks appear to be relatively insensitive to frequency and alloy content, but they disappear after annealing at temperatures nearing the recrystallization temperature.

Influence of alloying elements on friction and wear of copper

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1972-01-01

The friction and wear characteristics were determined for copper binary alloys containing 10 atomic percent aluminum, silicon, indium, and tin. A ternary alloy containing 10 atomic percent aluminum and 5 atomic percent silicon was also examined. The effectiveness of each of the alloying elements aluminum and silicon were very effective in reducing friction. Silicon, however, also reduced wear appreciably. With lubrication, silicon, indium, and tin were all effective alloying elements in reducing friction and wear from values obtained for copper. Silicon was the most effective single element in reducing friction and wear in dry sliding and with lubrication.

Al and Mg Alloys for Aerospace Applications Using Rapid Solidification and Powder Metallurgy Processing.

DTIC Science & Technology

1986-11-14

5wt % Si was completely different from that of the alloy without silicon. The (X phase formed around the primary Mg2 Si crystals, and an irregular...content, and primary crystals in a binary Mg- 5wt % Si alloy did not exhibit this behavior. The surface of the rapidly solidified melt pools was rough and...Microhardness* of the laser treated alloys . Alloy As-cast Laser treated Mg- 5wt %Li 40.8 55.7 o, Mg- 5wt %Li- 5wt % Si 51.1 74.1 Mg-8wt%Li 42.8 71.2

Corrosion analysis of NiCu and PdCo thermal seed alloys used as interstitial hyperthermia implants.

PubMed

Paulus, J A; Parida, G R; Tucker, R D; Park, J B

1997-12-01

Ferromagnetic materials with low Curie temperatures are being investigated for use as interstitial implants for fractionated hyperthermia treatment of prostatic disease. Previous investigations of the system have utilized alloys, such as NiCu, with inadequate corrosion resistance, requiring the use of catheters for removal of the implants following treatment or inert surface coatings which may interfere with thermal characteristics of the implants. We are evaluating a palladium-cobalt (PdCo) binary alloy which is very similar to high palladium alloys used in dentistry. Electrochemical corrosion tests and immersion tests at 37 degrees C for both NiCu and PdCo alloy samples in mammalian Ringer's solution were performed. Long-term corrosion rates are 5.8 x 10(-5) microm per year (NiCu) and 7.7 x 10(-8) microm per year (PdCo) from average immersion test results, indicating higher corrosion resistance of PdCo (P < 0.02); immersion corrosion rates were much lower than initial corrosion rates found electrochemically. Both alloys had significantly lower corrosion rates than standard surgical implant rates of 0.04 microm per year (P < 0.001 for both alloys). Scanning electron microscopy illustrates changes in the NiCu alloy surface due to pitting corrosion; no difference is observed for PdCo. The data indicate that the PdCo alloy may be suitable as a long-term implant for use in fractionated hyperthermia.

Effect of solutes in binary columbium /Nb/ alloys on creep strength

NASA Technical Reports Server (NTRS)

Klein, M. J.; Metcalfe, A. G.

1973-01-01

The effect of seven different solutes in binary columbium (Nb) alloys on creep strength was determined from 1400 to 3400 F for solute concentrations to 20 at.%, using a new method of creep-strength measurement. The technique permits rapid determination of approximate creep strength over a large temperature span. All of the elements were found to increase the creep strength of columbium except tantalum. This element did not strengthen columbium until the concentration exceeded 10 at.%. Hafnium, zirconium, and vanadium strengthed columbium most at low temperatures and concentrations, whereas tungsten, molybdenum, and rhenium contributed more to creep strength at high temperatures and concentrations.

Enthalpies of mixing of liquid systems for lead free soldering: Al-Cu-Sn system.

PubMed

Flandorfer, Hans; Rechchach, Meryem; Elmahfoudi, A; Bencze, László; Popovič, Arkadij; Ipser, Herbert

2011-11-01

The present work refers to high-temperature drop calorimetric measurements on liquid Al-Cu, Al-Sn, and Al-Cu-Sn alloys. The binary systems have been investigated at 973 K, up to 40 at.% Cu in case of Al-Cu, and over the entire concentrational range in case of Al-Sn. Measurements in the ternary Al-Cu-Sn system were performed along the following cross-sections: x(Al)/x(Cu) = 1:1, x(Al)/x(Sn) = 1:1, x(Cu)/x(Sn) = 7:3, x(Cu)/x(Sn) = 1:1, and x(Cu)/x(Sn) = 3:7 at 1273 K. Experimental data were used to find ternary interaction parameters by applying the Redlich-Kister-Muggianu model for substitutional solutions, and a full set of parameters describing the concentration dependence of the enthalpy of mixing was derived. From these, the isoenthalpy curves were constructed for 1273 K. The ternary system shows an exothermic enthalpy minimum of approx. -18,000 J/mol in the Al-Cu binary and a maximum of approx. 4000 J/mol in the Al-Sn binary system. The Al-Cu-Sn system is characterized by considerable repulsive ternary interactions as shown by the positive ternary interaction parameters.

Primary radiation damage of Zr-0.5%Nb binary alloy: atomistic simulation by molecular dynamics method

NASA Astrophysics Data System (ADS)

Tikhonchev, M.; Svetukhin, V.; Kapustin, P.

2017-09-01

Ab initio calculations predict high positive binding energy (˜1 eV) between niobium atoms and self-interstitial configurations in hcp zirconium. It allows the expectation of increased niobium fraction in self-interstitials formed under neutron irradiation in atomic displacement cascades. In this paper, we report the results of molecular dynamics simulation of atomic displacement cascades in Zr-0.5%Nb binary alloy and pure Zr at the temperature of 300 K. Two sets of n-body interatomic potentials have been used for the Zr-Nb system. We consider a cascade energy range of 2-20 keV. Calculations show close estimations of the average number of produced Frenkel pairs in the alloy and pure Zr. A high fraction of Nb is observed in the self-interstitial configurations. Nb is mainly detected in single self-interstitial configurations, where its fraction reaches tens of percent, i.e. more than its tenfold concentration in the matrix. The basic mechanism of this phenomenon is the trapping of mobile self-interstitial configurations by niobium. The diffusion of pure zirconium and mixed zirconium-niobium self-interstitial configurations in the zirconium matrix at 300 K has been simulated. We observe a strong dependence of the estimated diffusion coefficients and fractions of Nb in self-interstitials produced in displacement cascades on the potential.

Investigation of the wett-ability of various pure metals and alloys and beryllium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilliland, Ralph Gerald

1963-06-13

Thesis submitted to University of Tennessee, Knoxville. Activities in a program to determine the wetting behavior of pure metals such as Au, Ag, Ge, Al, and Cu on solid Be are reported. Results of similar investigations of binary alloys such as Be--Ti, Be-Zr, and Be--Pd are also included. The contact angles of the molten metals on Be as a function of temperature, exposure time, and atmosphere were measured. The solid-liquid interfacial reactions occurring as a function of test temperature and atmosphere were investigated, and the liquid- vapor and internal surface tensions for those systems in which interfacial reactions did notmore » appear to occur were calculated.« less

Solid state amorphization in the Al-Fe binary system during high energy milling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urban, P., E-mail: purban@us.es; Montes, J. M.; Cintas, J.

2013-12-16

In the present study, mechanical alloying (MA) of Al75Fe25 elemental powders mixture was carried out in argon atmosphere, using a high energy attritor ball mill. The microstructure of the milled products at different stages of milling was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results showed that the amorphous phase content increased by increasing the milling time, and after 50 hours the amorphization process became complete. Heating the samples resulted in the crystallization of the synthesized amorphous alloys and the appearance of the equilibrium intermetallic compounds Al{sub 5}Fe{submore » 2}.« less

New eutectic alloys and their heats of transformation

NASA Technical Reports Server (NTRS)

Farkas, D.; Birchenall, C. E.

1985-01-01

Eutectic compositions and congruently melting intermetallic compounds in binary and multicomponent systems among common elements such as Al, Ca, Cu, Mg, P, Si, and Zn may be useful for high temperature heat storage. In this work, heats of fusion of new multicomponent eutectics and intermetallic phases are reported, some of which are competitive with molten salts in heat storage density at high temperatures. The method used to determine unknown eutectic compositions combined results of differential thermal analysis, metallography, and microprobe analysis. The method allows determination of eutectic compositions in no more than three steps. The heats of fusion of the alloys were measured using commercial calorimeters, a differential thermal analyzer, and a differential scanning calorimeter.

Antimicrobial properties of ternary eutectic aluminum alloys.

PubMed

Hahn, Claudia; Hans, Michael; Hein, Christina; Dennstedt, Anne; Mücklich, Frank; Rettberg, Petra; Hellweg, Christine Elisabeth; Leichert, Lars Ingo; Rensing, Christopher; Moeller, Ralf

2018-06-27

Several Escherichia coli deletion mutants of the Keio collection were selected for analysis to better understand which genes may play a key role in copper or silver homeostasis. Each of the selected E. coli mutants had a deletion of a single gene predicted to encode proteins for homologous recombination or contained functions directly linked to copper or silver transport or transformation. The survival of these strains on pure copper surfaces, stainless steel, and alloys of aluminum, copper and/or silver was investigated. When exposed to pure copper surfaces, E. coli ΔcueO was the most sensitive, whereas E. coli ΔcopA was the most resistant amongst the different strains tested. However, we observed a different trend in sensitivities in E. coli strains upon exposure to alloys of the system Al-Ag-Cu. While minor antimicrobial effects were detected after exposure of E. coli ΔcopA and E. coli ΔrecA to Al-Ag alloys, no effect was detected after exposure to Al-Cu alloys. The release of copper ions and cell-associated copper ion concentrations were determined for E. coli ΔcopA and the wild-type E. coli after exposure to pure copper surfaces. Altogether, compared to binary alloys, ternary eutectic alloys (Al-Ag-Cu) had the highest antimicrobial effect and thus, warrant further investigation.

Primary radiation damage of an FeCr alloy under pressure: Atomistic simulation

NASA Astrophysics Data System (ADS)

Tikhonchev, M. Yu.; Svetukhin, V. V.

2017-05-01

The primary radiation damage of a binary FeCr alloy deformed by applied mechanical loading is studied by an atomistic molecular dynamics simulation. Loading is simulated by specifying an applied pressure of 0.25, 1.0, and 2.5 GPa of both signs. Hydrostatic and uniaxial loading is considered along the [001], [111], [112], and [210] directions. The influence of loading on the energy of point defect formation and the threshold atomic displacement energy in single-component bcc iron is investigated. The 10-keV atomic displacement cascades in a "random" binary Fe-9 at % Cr alloy are simulated at an initial temperature of 300 K. The number of the point defects generated in a cascade is estimated, and the clustering of point defects and the spatial orientation of interstitial configurations are analyzed. Our results agree with the results of other researchers and supplement them.

An Investigation of the Interatomic Bonding Characteristics of a Ti - 51at.% Al Alloy by X-Ray Diffraction

DTIC Science & Technology

1991-06-01

GROUP SUBGROUP X-ray Diffraction, XRD, TiAI, titanium , aluminum, bonding characteristics, titanium aluminides , Debye-Waller temperature factor...XRD Powder Particles (575X) .............. 47 viii I. INTRODUCTION Titanium aluminides are recognized for their high specific strength, particularly at...bonding characteristics of binary titanium aluminides . Upon the introduction of a third element to the system, a rearrangement of the valence

Acoustic emission from a solidifying aluminum-lithium alloy

NASA Technical Reports Server (NTRS)

Henkel, D. P.; Wood, J. D.

1992-01-01

Physical phenomena associated with the solidification of an AA2090 Al-Li alloy have been characterized by AE methods. Repeatable patterns of AE activity as a function of solidification time are recorded and explained for ultrahigh-purity (UHP) aluminum and an Al-4.7 wt pct Cu binary alloy, in addition to the AA2090 Al-Li alloy, by the complementary utilization of thermal, AE, and metallographic methods. One result shows that the solidification of UHP aluminum produces one discrete period of high AE activity as the last 10 percent of solid forms.

First-principles studiesy of the order-disorder phase transition in FeCo using Wang-Landau Monte-Carlo method

NASA Astrophysics Data System (ADS)

Pei, Zongrui; Eisenbach, Markus; Stocks, G. Malcolm

Simulating order-disorder phase transitions in magnetic materials requires the accurate treatment of both the atomic and magnetic interactions, which span a vast configuration space. Using FeCo as a prototype system, we demonstrate that this can be addressed by combining the Locally Self-consistent Multiple Scattering (LSMS) method with the Wang-Landau (WL) Monte-Carlo algorithm. Fe-Co based materials are interesting magnetic materials but a reliable phase diagram of the binary Fe-Co system is still difficult to obtain. Using the combined WL-LSMS method we clarify the existence of the disordered A2 phase and predict the Curie temperature between it and the ordered B2 phase. The WL-LSMS method is readily applicable to the study of second-order phase transitions in other binary and multi-component alloys, thereby providing a means to the direct simulation of order-disorder phase transitions in complex alloys without need of intervening classical model Hamiltonians. We also demonstrate the capability of our method to guide the design of new magnetic materials. This research was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division and it used Oak Ridge Leadership Computing Facility resources at Oak Ridge National Laboratory.

Melting Experiments in the Fe-FeSi System at High Pressure

NASA Astrophysics Data System (ADS)

Ozawa, H.; Hirose, K.

2013-12-01

The principal light element in the Earth's core must reproduce the density jump at the inner core boundary (ICB). Silicon is thought to be a plausible light element in the core, and the melting phase relations in Fe-FeSi binary system at the ICB pressure are of great importance. Theoretical calculations on the Fe-FeSi binary system suggested that the difference in Si content between the outer core and the inner core would be too small to satisfy the observed density jump at the ICB [Alfè et al., 2002 EPSL], which requires other light elements in addition to silicon. Here we experimentally examined partitioning of silicon between liquid and solid iron up to 97 GPa. High pressure and temperature conditions were generated in a laser-heated diamond-anvil cell. Chemical compositions of co-existing quenched liquid and solid Fe-Si alloys were determined with a field-emission-type electron probe micro-analyzer. We used Fe-Si alloy containing 9 wt% Si as a starting material. Chemical analyses on the recovered samples from 39 and 49 GPa demonstrated the coexistence of quenched Si-depleted liquid and Si-enriched solid. In contrast, silicon partitions preferentially into liquid metal at 97 GPa, suggesting the starting composition (Fe-9wt% Si) lies on the iron-rich part of the eutectic. These results indicate the eutectic composition shifts toward FeSi between 49 and 97 GPa.

Electrical conductivity and phase diagram of binary alloys. 21: The system palladium-chromium

NASA Technical Reports Server (NTRS)

Grube, G.; Knabe, R.

1985-01-01

Pd-Cr alloys were investigated by thermal analysis, hardness measurements, X-ray analysis, microscopic examination of etched pieces, and temperature-resistance curves of the solid alloys. Only one compound, Pd2Cr3, m, 1389 deg, is formed. It possesses a cubic face centered lattice and forms with excess Pd a series of solid solutions with a minimum m.p. at 45 atoms% Pd. Hardness maximum appears at the Pd2Cr3 point. Pd2Cr3 forms no solid solutions with Cr but eutectic point appears at 25 atoms% Pd, m. 1320 deg. The sp. resistance of pure Cr in an atom of H, indicates no allotropic forms. Cr2O3 is solid in molten Cr. Pure Cr melts at 1890 plus or minus 10 deg but Cr contg. Cr2O3 starts to melt at 1770 to 1790 deg.

Microstructure Formations in the Two-Phase Region of the Binary Peritectic Organic System TRIS-NPG

NASA Technical Reports Server (NTRS)

Mogeritsch, Johann; Ludwig, Andreas

2012-01-01

In order to prepare for an onboard experiment on the International Space Station (ISS), systematic directional solidification experiments with transparent hypoperitectic alloys were carried out at different solidification rates around the critical velocity for morphological stability of both solid phases. The investigations were done in the peritectic region of the binary transparent organic TRIS-NPG system where the formation of layered structures is expected to occur. The transparent appearance of the liquid and solid phase enables real time observations of the dynamic of pattern formation during solidification. The investigations show that frequently occurring nucleation events govern the peritectic solidification morphology which occurs at the limit of morphological stability. As a consequence, banded structures lead to coupled growth even if the lateral growth is much faster compared to the growth in pulling direction.

Dentritic morphology and microsegregation in directionally solidified superalloy, PWA-1480, single crystal: Effect of gravity; center director's discretionary fund report

NASA Technical Reports Server (NTRS)

Tewari, S. N.; Kumar, M. Vijaya; Lee, J. E.; Curreri, P. A.

1990-01-01

Primary dendrite spacings, secondary dendrite spacings, and microsegregation have been examined in PWA-1480 single crystal specimens which were directionally solidified during parabolic maneuvers on the KC-135 aircraft. Experimentally observed growth rate and thermal gradient dependence of primary dendrite spacings are in good agreement with predictions from dendrite growth models for binary alloys. Secondary dendrite coarsening kinetics show a reasonable fit with the predictions from an analytical model proposed by Kirkwood for a binary alloy. The partition coefficients of tantalum, titanium, and aluminum are observed to be less than unity, while that for tungsten and cobalt are greater than unity. This is qualitatively similar to the nickel base binaries. Microsegregation profiles experimentally observed for PWA-1480 superalloy show a good fit with Bower, Brody, and Flemings model developed for binary alloys. Transitions in gravity levels do not appear to affect primary dendrite spacings. A trend of decreased secondary arm spacings with transition from high gravity to the low gravity period was observed at a growth speed of 0.023 cm s(exp -1). However, definite conclusions can only be drawn by experiments at lower growth speeds which make it possible to examine the side-branch coarsening kinetics over a longer duration. Such experiments, not possible due to the insufficient low-gravity time of the KC-135, may be carried out in the low-gravity environment of space.

PROCESS FOR DISSOLVING BINARY URANIUM-ZIRCONIUM OR ZIRCONIUM-BASE ALLOYS

DOEpatents

Jonke, A.A.; Barghusen, J.J.; Levitz, N.M.

1962-08-14

A process of dissolving uranium-- zirconium and zircaloy alloys, e.g. jackets of fuel elements, with an anhydrous hydrogen fluoride containing from 10 to 32% by weight of hydrogen chloride at between 400 and 450 deg C., preferably while in contact with a fluidized inert powder, such as calcium fluoride is described. (AEC)

Modeling of Disordered Binary Alloys Under Thermal Forcing: Effect of Nanocrystallite Dissociation on Thermal Expansion of AuCu3

NASA Astrophysics Data System (ADS)

Kim, Y. W.; Cress, R. P.

2016-11-01

Disordered binary alloys are modeled as a randomly close-packed assembly of nanocrystallites intermixed with randomly positioned atoms, i.e., glassy-state matter. The nanocrystallite size distribution is measured in a simulated macroscopic medium in two dimensions. We have also defined, and measured, the degree of crystallinity as the probability of a particle being a member of nanocrystallites. Both the distribution function and the degree of crystallinity are found to be determined by alloy composition. When heated, the nanocrystallites become smaller in size due to increasing thermal fluctuation. We have modeled this phenomenon as a case of thermal dissociation by means of the law of mass action. The crystallite size distribution function is computed for AuCu3 as a function of temperature by solving some 12 000 coupled algebraic equations for the alloy. The results show that linear thermal expansion of the specimen has contributions from the temperature dependence of the degree of crystallinity, in addition to respective thermal expansions of the nanocrystallites and glassy-state matter.

Growth of normally-immiscible materials (NIMs), binary alloys, and metallic fibers by hyperbaric laser chemical vapor deposition

NASA Astrophysics Data System (ADS)

Maxwell, J. L.; Black, M. R.; Chavez, C. A.; Maskaly, K. R.; Espinoza, M.; Boman, M.; Landstrom, L.

2008-06-01

This work demonstrates that two or more elements of negligible solubility (and no known phase diagram) can be co-deposited in fiber form by hyperbaric-pressure laser chemical vapor deposition (HP-LCVD). For the first time, Hg-W alloys were grown as fibers from mixtures of tungsten hexafluoride, mercury vapor, and hydrogen. This new class of materials is termed normally-immiscible materials (NIMs), and includes not only immiscible materials, but also those elemental combinations that have liquid states at exclusive temperatures. This work also demonstrates that a wide variety of other binary and ternary alloys, intermetallics, and mixtures can be grown as fibers, e.g. silicon-tungsten, aluminum-silicon, boron-carbon-silicon, and titanium-carbon-nitride. In addition, pure metallic fibers of aluminum, titanium, and tungsten were deposited, demonstrating that materials of high thermal conductivity can indeed be grown in three-dimensions, provided sufficient vapor pressures are employed. A wide variety of fiber properties and microstructures resulted depending on process conditions; for example, single crystals, fine-grained alloys, and glassy metals could be deposited.

Solid-liquid surface tensions of critical nuclei and nucleation barriers from a phase-field-crystal study of a model binary alloy using finite system sizes.

PubMed

Choudhary, Muhammad Ajmal; Kundin, Julia; Emmerich, Heike; Oettel, Martin

2014-08-01

Phase-field-crystal (PFC) modeling has emerged as a computationally efficient tool to address crystal growth phenomena on atomistic length and diffusive time scales. We use a two-dimensional phase-field-crystal model for a binary system based on Elder et al. [Phys. Rev. B 75, 064107 (2007)] to study critical nuclei and their liquid-solid phase boundaries, in particular the nucleus size dependence of the liquid-solid interface tension as well as of the nucleation barrier. Critical nuclei are stabilized in finite systems of various sizes, however, the extracted interface tension as function of the nucleus radius r is independent of system size. We suggest a phenomenological expression to describe the dependence of the extracted interface tension on the nucleus radius r for the liquid-solid system. Moreover, the numerical PFC results show that this dependency can not be fully described by the nonclassical Tolman formula.

Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation

NASA Astrophysics Data System (ADS)

Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

2016-08-01

Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance.

Characterisation of phases in nanostructured, multilayered titanium alloys by analytical and high-resolution electron microscopy.

PubMed

Czyrska-Filemonowicz, A; Buffat, P A

2009-01-01

Surface processing of a Ti-6Al-4V alloy led to a complex multilayered microstructure containing several phases of the Ni-Ti-P-Al-O system, which improves the mechanical and tribological surface properties. The microstructure, chemical and phase compositions of the hard layer formed on the surface were investigated by LM, XRD, SEM as well as analytical/high-resolution TEM, STEM, EDS, electron diffraction and FIB. Phase identification based on electron diffraction, HRTEM and EDS microanalysis revealed the presence of several binary and ternary phases in the system Ti-Ni-P, sometimes with partial substitution of Ti by Al. However some phases, mainly nanoparticles, still remain not identified satisfactorily. Electron microscopy techniques used for identification of phases present in surface multilayers and some practical limits to their routine application are reminded here.

An Investigation of the Effects of Metallurgical and/or Testing Variables on the Acoustic Emission from Crystalline Materials.

DTIC Science & Technology

1982-09-01

alloy , a number of minor phases have been reported (Thompson and Brooks, 1975). The precipitates expected after the heat treatments used in this study... precipitate or inclusion fracture, twin formation, martensite to create detectable acoustic emission. In alloy formation, dislocation motion, and... precipitate anticipated for each heat The nominal composition of 2219 is given in Table 2. It is treatment. essentially a binary aluminium- copper alloy

Development of a Knowledge Base of Ti-Alloys From First-Principles and Thermodynamic Modeling

NASA Astrophysics Data System (ADS)

Marker, Cassie

An aging population with an active lifestyle requires the development of better load-bearing implants, which have high levels of biocompatibility and a low elastic modulus. Titanium alloys, in the body centered cubic phase, are great implant candidates, due to their mechanical properties and biocompatibility. The present work aims at investigating the thermodynamic and elastic properties of bcc Tialloys, using the integrated first-principles based on Density Functional Theory (DFT) and the CALculation of PHAse Diagrams (CALPHAD) method. The use of integrated first-principles calculations based on DFT and CALPHAD modeling has greatly reduced the need for trial and error metallurgy, which is ineffective and costly. The phase stability of Ti-alloys has been shown to greatly affect their elastic properties. Traditionally, CALPHAD modeling has been used to predict the equilibrium phase formation, but in the case of Ti-alloys, predicting the formation of two metastable phases o and alpha" is of great importance as these phases also drastically effect the elastic properties. To build a knowledge base of Ti-alloys, for biomedical load-bearing implants, the Ti-Mo-Nb-Sn-Ta-Zr system was studied because of the biocompatibility and the bcc stabilizing effects of some of the elements. With the focus on bcc Ti-rich alloys, a database of thermodynamic descriptions of each phase for the pure elements, binary and Ti-rich ternary alloys was developed in the present work. Previous thermodynamic descriptions for the pure elements were adopted from the widely used SGTE database for global compatibility. The previous binary and ternary models from the literature were evaluated for accuracy and new thermodynamic descriptions were developed when necessary. The models were evaluated using available experimental data, as well as the enthalpy of formation of the bcc phase obtained from first-principles calculations based on DFT. The thermodynamic descriptions were combined into a database ensuring that the sublattice models are compatible with each other. For subsystems, such as the Sn-Ta system, where no thermodynamic description had been evaluated and minimal experimental data was available, first-principles calculations based on DFT were used. The Sn-Ta system has two intermetallic phases, TaSn2 and Ta3Sn, with three solution phases: bcc, body centered tetragonal (bct) and diamond. First-principles calculations were completed on the intermetallic and solution phases. Special quasirandom structures (SQS) were used to obtain information about the solution phases across the entire composition range. The Debye-Gruneisen approach, as well as the quasiharmonic phonon method, were used to obtain the finite-temperature data. Results from the first-principles calculations and experiments were used to complete the thermodynamic description. The resulting phase diagram reproduced the first-principles calculations and experimental data accurately. In order to determine the effect of alloying on the elastic properties, first-principles calculations based on DFT were systematically done on the pure elements, five Ti-X binary systems and Ti-X-Y ternary systems (X ≠ Y = Mo, Nb, Sn, Ta Zr) in the bcc phase. The first-principles calculations predicted the single crystal elastic stiffness constants cij 's. Correspondingly, the polycrystalline aggregate properties were also estimated from the cij's, including bulk modulus B, shear modulus G and Young's modulus E. The calculated results showed good agreement with experimental results. The CALPHAD method was then adapted to assist in the database development of the elastic properties as a function of composition. On average, the database predicted the elastic properties of higher order Ti-alloys within 5 GPa of the experimental results. Finally, the formation of the metastable phases, o and alpha" was studied in the Ti-Ta and Ti-Nb systems. The formation energy of these phases, calculated from first-principles at 0 K, showed that the phases have similar formation energies to the bcc and hcp phases. Inelastic neutron scattering was completed on four different Ti-Nb compositions to study the entropy of the phases as well as the transformations occurring when the phases form and the phase fractions. Ongoing work is being done to use the experimental information to introduce thermodynamic descriptions for these two phases in the Ti-Nb system in order to be able to predict the formation and phase fractions. DFT based first-principles were used to predict the effect these phases have on the elastic properties and a rule of mixtures was used to determine the elastic properties of multi-phase alloys. The results were compared with experiments and showed that if the ongoing modeling can predict the phase fraction, the elastic database can accurately predict the elastic properties of the o and alpha" phases. This thesis provides a knowledge base of the thermodynamic and elastic properties of Ti-alloys from computational thermodynamics. The databases created will impact research activities on Ti-alloys and specifically efforts focused on Ti-alloys for biomedical applications.

Thermosolutal convection during dendritic solidification

NASA Technical Reports Server (NTRS)

Heinrich, J. C.; Nandapurkar, P.; Poirier, D. R.; Felicelli, S.

1989-01-01

This paper presents a mathematical model for directional solidification of a binary alloy including a dendritic region underlying an all-liquid region. It is assumed initially that there exists a nonconvecting state with planar isotherms and isoconcentrates solidifying at a constant velocity. The stability of this system has been analyzed and nonlinear calculations are performed that show the effect of convection in the solidification process when the system is unstable. Results of calculations for various cases defined by the initial temperature gradient at the dendrite tips and varying strength of the gravitational field are presented for systems involving lead-tin alloys. The results show that the systems are stable for a gravitational constant of 0.0001 g(0) and that convection can be suppressed by appropriate choice of the container's size for higher values of the gravitational constant. It is also concluded that for the lead-tin systems considered, convection in the mushy zone is not significant below the upper 20 percent of the dendritic zone, if al all.

Rapid correction of electron microprobe data for multicomponent metallic systems

NASA Technical Reports Server (NTRS)

Gupta, K. P.; Sivakumar, R.

1973-01-01

This paper describes an empirical relation for the correction of electron microprobe data for multicomponent metallic systems. It evaluates the empirical correction parameter, a for each element in a binary alloy system using a modification of Colby's MAGIC III computer program and outlines a simple and quick way of correcting the probe data. This technique has been tested on a number of multicomponent metallic systems and the agreement with the results using theoretical expressions is found to be excellent. Limitations and suitability of this relation are discussed and a model calculation is also presented in the Appendix.

Phase-field-crystal study of solute trapping

NASA Astrophysics Data System (ADS)

Humadi, Harith; Hoyt, Jeffrey J.; Provatas, Nikolas

2013-02-01

In this study we have incorporated two time scales into the phase-field-crystal model of a binary alloy to explore different solute trapping properties as a function of crystal-melt interface velocity. With only diffusive dynamics, we demonstrate that the segregation coefficient, K as a function of velocity for a binary alloy is consistent with the model of Kaplan and Aziz where K approaches unity in the limit of infinite velocity. However, with the introduction of wavelike dynamics in both the density and concentration fields, the trapping follows the kinetics proposed by Sobolev [Phys. Lett. A10.1016/0375-9601(95)00084-G 199, 383 (1995)], where complete trapping occurs at a finite velocity.

Thermodynamic assessment and binary nucleation modeling of Sn-seeded InGaAs nanowires

NASA Astrophysics Data System (ADS)

Ghasemi, Masoomeh; Selleby, Malin; Johansson, Jonas

2017-11-01

We have performed a thermodynamic assessment of the As-Ga-In-Sn system based on the CALculation of PHAse Diagram (CALPHAD) method. This system is part of a comprehensive thermodynamic database that we are developing for nanowire materials. Specifically, the As-Ga-In-Sn can be used in modeling the growth of GaAs, InAs, and InxGa1-xAs nanowires assisted by Sn liquid seeds. In this work, the As-Sn binary, the As-Ga-Sn, As-In-Sn, and Ga-In-Sn ternary systems have been thermodynamically assessed using the CALPHAD method. We show the relevant phase diagrams and property diagrams. They all show good agreement with experimental data. Using our optimized description we have modeled the nucleation of InxGa1-xAs in the zinc blende phase from a Sn-based quaternary liquid alloy using binary nucleation modeling. We have linked the composition of the solid nucleus to the composition of the liquid phase. Eventually, we have predicted the critical size of the nucleus that forms from InAs and GaAs pairs under various conditions. We believe that our modeling can guide future experimental realization of Sn-seeded InxGa1-xAs nanowires.

Surface and cut-edge corrosion behavior of Zn-Mg-Al alloy-coated steel sheets as a function of the alloy coating microstructure

NASA Astrophysics Data System (ADS)

Oh, Min-Suk; Kim, Sang-Heon; Kim, Jong-Sang; Lee, Jae-Won; Shon, Je-Ha; Jin, Young-Sool

2016-01-01

The effects of Mg and Al content on the microstructure and corrosion resistance of hot-dip Zn-Mg-Al alloycoated steel sheets were investigated. Pure Zn and Zn-based alloy coatings containing Mg (0-5 wt%) and Al (0.2-55 wt%) were produced by a hot-dip galvanizing method. Mg and Al addition induced formation of intermetallic microstructures, like primary Zn, Zn/MgZn2 binary eutectic, dendric Zn/Al eutectoid, and Zn/Al/MgZn2/ternary eutectic structures in the coating layer. MgZn2-related structures (Zn/MgZn2, Zn/Al/MgZn2, MgZn2) played an important role in increasing the corrosion resistance of Zn-Mg-Al alloy-coated steel sheets. Zn-3%Mg-2.5%Al coating layer containing a large volume of lamellar-shaped Zn/MgZn2 binary eutectic structures showed the best cut-edge corrosion resistance. The analysis indicated that Mg dissolved from MgZn2 in the early stage of corrosion and migrated to the cathodic region of steel-exposed cut-edge area to form dense and ordered protective corrosion products, leading to prolonged cathodic protection of Zn-Mg-Al alloy-coated steel sheets.

Nial and Nial-Based Composites Directionally Solidified by a Containerless Zone Process. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Joslin, Steven M.

1995-01-01

A containerless electromagnetically levitated zone (CELZ) process has been used to directionally solidify NiAl and NiAl-based composites. The CELZ processing results in single crystal NiAl (HP-NiAl) having higher purity than commercially pure NiAl grown by a modified Bridgman process (CP-NiAl). The mechanical properties, specifically fracture toughness and creep strength, of the HP-NiAl are superior to binary CP-NiAl and are used as a base-line for comparison with the composite materials subsequently studied. Two-phase composite materials (NiAl-based eutectic alloys) show improvement in room temperature fracture toughness and 1200 to 1400 K creep strength over that of binary HP-NiAl. Metallic phase reinforcements produce the greatest improvement in fracture toughness, while intermetallic reinforcement produces the largest improvement in high temperature strength. Three-phase eutectic alloys and composite materials were identified and directionally solidified with the intent to combine the improvements observed in the two-phase alloys into one alloy. The room temperature fracture toughness and high temperature strength (in air) serve as the basis for comparison between all of the alloys. Finally, the composite materials are discussed in terms of dominant fracture mechanism observed by fractography.

Transport properties of Y1-xNdxCo2 compounds

NASA Astrophysics Data System (ADS)

Uchima, K.; Takeda, M.; Zukeran, C.; Nakamura, A.; Arakaki, N.; Komesu, S.; Takaesu, Y.; Hedo, M.; Nakama, T.; Yagasaki, K.; Uwatoko, Y.; Burkov, A. T.

2012-12-01

Electrical resistivity ρ and thermopower S of light rare earth-based pseudo-binary Y1-xNdxCo2 alloys have been measured at temperatures from 2 K to 300 K and under pressures up to 3.5 GPa. The Curie temperature of the alloys, TC, determined from characteristic features in the temperature dependences of the transport properties, decreases with decreasing Nd concentration x and vanishes around xc = 0.3. The residual resistivity has a pronounced maximum at x = xc. The temperature coefficient of thermopower dS/dT at low temperature limit shows a complex dependence on alloy composition: it changes its sign from negative to positive at x ≍ 0.2, having a maximum at x = xc, and is nearly composition independent at x > 0.5. The pressure dependences of TC and ρ0 of Yo.6Ndo.4Co2 reveal the behavior similar to that observed in the Y1-xRxHCo2 (RH = heavy rare earth) alloy systems, which implies that the magnetic state of the Co-3d electron subsystem is responsible for the transport properties in the Y1-xNdxCo2 alloys.

Features of the Percolation Scheme of Vibrational Spectrum Reconstruction in the Ga1 - x Al x P Alloy

NASA Astrophysics Data System (ADS)

Kozyrev, S. P.

2018-04-01

Specific features of the properties of Ga-P lattice vibrations have been investigated using the percolation model of a mixed Ga1 - x Al x P crystal (alloy) with zero lattice mismatch between binary components of the alloy. In contrast to other two-mode alloy systems, in Ga1 - x Al x P a percolation splitting of δ 13 cm-1 is observed for the low-frequency mode of GaP-like vibrations. An additional GaP mode (one of the percolation doublet components) split from the fundamental mode is observed for the GaP-rich alloy, which coincides in frequency with the gap corresponding to the zero density of one-phonon states of the GaP crystal. The vibrational spectrum of impurity Al in the GaP crystal has been calculated using the theory of crystal lattice dynamics. Upon substitution of lighter Al for the Ga atom, the calculated spectrum includes, along with the local mode, a singularity near the gap with the zero density of phonon states of the GaP crystal, which coincides with the mode observed experimentally at a frequency of 378 cm-1 in the Ga1 - x Al x P ( x < 0.4) alloy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briggs, Samuel A.; Edmondson, Philip D.; Littrell, Kenneth C.

Here, FeCrAl alloys are currently under consideration for accident-tolerant fuel cladding applications in light water reactors owing to their superior high-temperature oxidation and corrosion resistance compared to the Zr-based alloys currently employed. However, their performance could be limited by precipitation of a Cr-rich α' phase that tends to embrittle high-Cr ferritic Fe-based alloys. In this study, four FeCrAl model alloys with 10–18 at.% Cr and 5.8–9.3 at.% Al were neutron-irradiated to nominal damage doses up to 7.0 displacements per atom at a target temperature of 320 °C. Small angle neutron scattering techniques were coupled with atom probe tomography to assessmore » the composition and morphology of the resulting α' precipitates. It was demonstrated that Al additions partially destabilize the α' phase, generally resulting in precipitates with lower Cr contents when compared with binary Fe-Cr systems. The precipitate morphology evolution with dose exhibited a transient coarsening regime akin to previously observed behavior in aged Fe-Cr alloys. Similar behavior to predictions of the LSW/UOKV models suggests that α' precipitation in irradiated FeCrAl is a diffusion-limited process with coarsening mechanisms similar to those in thermally aged high-Cr ferritic alloys.« less

Electrical Transport Properties of Liquid Al-Cu Alloys

NASA Astrophysics Data System (ADS)

Thakore, B. Y.; Khambholja, S. G.; Suthar, P. H.; Jani, A. R.

2010-06-01

Electrical transport properties viz. electrical resistivity, thermoelectric power and thermal conductivity of liquid Al-Cu alloys as a function of Cu concentration have been studied in the present paper. Ashcroft empty core model potential has been used to incorporate the ion-electron interaction. To incorporate the exchange and correlation effects, five different forms of local field correction functions viz. Hartree, Taylor, Ichimaru et al., Farid et al. and Sarkar et al. have been used. The transport properties of binary system have been studied using Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. The computed values of electrical resistivity are compared with experimental data and for low Cu concentration, good agreement has been observed. Further, thermoelectric power and thermal conductivity have also been predicted.

Modelling of Surfaces. Part 2: Metallic Alloy Surfaces Using the BFS Method

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John; Kobistek, Robert J.

1994-01-01

Using BFS, a new semiempirical method for alloys, we study the surface structure of fcc ordered binary alloys. We concentrate on the calculation of surface energies and surface relaxations for the L1(sub 0) and L1(sub 2) ordered structures. Different terminations of the low-index faces are studied. Also, we present results for the interlayer relaxations for planes close to the surface, revealing different relaxations for atoms of different species producing a rippled surface layer.

The Role of Grain Boundary Chemistry and the Environment on Intergranular Fracture.

DTIC Science & Technology

1980-10-01

and alloys as well. Grain boundary segregation of phosphorus, for example, has been observed in thermally treated nickel-base alloys such as Inconel ...base alloys such as Inconel 600 and Hastelloy C-276. Hence, Ni-P binary glasses may be considered to be good structural and chemical analog of grain...p. 625 17. H.W. Pickering and M. Zamanzedeh: This Conference, Poster Session 18. B.J. Berkowitz, J.J. Burton, C.R. Helms and R.S. Polizzotti

A combined APT and SANS investigation of α' phase precipitation in neutron-irradiated model FeCrAl alloys

DOE PAGES

Briggs, Samuel A.; Edmondson, Philip D.; Littrell, Kenneth C.; ...

2017-03-01

Here, FeCrAl alloys are currently under consideration for accident-tolerant fuel cladding applications in light water reactors owing to their superior high-temperature oxidation and corrosion resistance compared to the Zr-based alloys currently employed. However, their performance could be limited by precipitation of a Cr-rich α' phase that tends to embrittle high-Cr ferritic Fe-based alloys. In this study, four FeCrAl model alloys with 10–18 at.% Cr and 5.8–9.3 at.% Al were neutron-irradiated to nominal damage doses up to 7.0 displacements per atom at a target temperature of 320 °C. Small angle neutron scattering techniques were coupled with atom probe tomography to assessmore » the composition and morphology of the resulting α' precipitates. It was demonstrated that Al additions partially destabilize the α' phase, generally resulting in precipitates with lower Cr contents when compared with binary Fe-Cr systems. The precipitate morphology evolution with dose exhibited a transient coarsening regime akin to previously observed behavior in aged Fe-Cr alloys. Similar behavior to predictions of the LSW/UOKV models suggests that α' precipitation in irradiated FeCrAl is a diffusion-limited process with coarsening mechanisms similar to those in thermally aged high-Cr ferritic alloys.« less

Intrinsic properties and strengthening mechanism of monocrystalline Ni-containing ternary concentrated solid solutions

DOE PAGES

Jin, K.; Gao, Y. F.; Bei, H.

2017-04-07

Ternary single-phase concentrated solid solution alloys (SP-CSAs), so-called "medium entropy alloys", not only possess notable mechanical and physical properties but also form a model system linking the relatively simple binary alloys to the complex high entropy alloys. Our knowledge of their intrinsic properties is vital to understand the material behavior and to prompt future applications. To this end, three model alloys NiCoFe, NiCoCr, and NiFe-20Cr have been selected and grown as single crystals. We measured their elastic constants using an ultrasonic method, and several key materials properties, such as shear modulus, bulk modulus, elastic anisotropy, and Debye temperatures have beenmore » derived. Furthermore, nanoindentation tests have been performed on these three alloys together with Ni, NiCo and NiFe on their (100) surface, to investigate the strengthening mechanisms. NiCoCr has the highest hardness, NiFe, NiCoFe and NiFe-20Cr share a similar hardness that is apparently lower than NiCoCr; NiCo has the lowest hardness in the alloys, which is similar to elemental Ni. The Labusch-type solid solution model has been applied to interpret the nanoindentation data, with two approaches used to calculate the lattice mismatch. Finally, by adopting an interatomic spacing matrix method, the Labusch model can reasonably predict the hardening effects for the whole set of materials.« less

Micromechanisms of Monotonic and Cyclic Subcritical Crack Growth in Advanced High Melting Point Low-Ductility Intermetallics

DTIC Science & Technology

1993-05-01

Advanced Structural Ceramics, MRS Symp. Proc., P. F. Becher et al . (eds.), MRS, Pittsburgh, PA (1986). 11) M. J. Reece, F. Guiu and M. F. R. Sammur...composites under study, listed in Table 2.1, were fabricated by phase blending -80 mesh y-TiAI (Ti-55 at.% Al , with small additions of Nb, Ta, C and 0...on phase transformations in the alloy system. In the case of the binary Nb- Al system, the peritectic reaction at 2060’C (Fig. 3.1), involving the

Influence of Dy in solid solution on the degradation behavior of binary Mg-Dy alloys in cell culture medium.

PubMed

Yang, Lei; Ma, Liangong; Huang, Yuanding; Feyerabend, Frank; Blawert, Carsten; Höche, Daniel; Willumeit-Römer, Regine; Zhang, Erlin; Kainer, Karl Ulrich; Hort, Norbert

2017-06-01

Rare earth element Dy is one of the promising alloying elements for magnesium alloy as biodegradable implants. To understand the effect of Dy in solid solution on the degradation of Mg-Dy alloys in simulated physiological conditions, the present work studied the microstructure and degradation behavior of Mg-Dy alloys in cell culture medium. It is found the corrosion resistance enhances with the increase of Dy content in solid solution in Mg. This can be attributed to the formation of a relatively more corrosion resistant Dy-enriched film which decreases the anodic dissolution of Mg. Copyright © 2017 Elsevier B.V. All rights reserved.

First-principles study of amorphous Ga4Sb6Te3 phase-change alloys

NASA Astrophysics Data System (ADS)

Bouzid, Assil; Gabardi, Silvia; Massobrio, Carlo; Boero, Mauro; Bernasconi, Marco

2015-05-01

First-principles molecular dynamics simulations within the density functional theory framework were performed to generate amorphous models of the Ga4Sb6Te3 phase change alloy by quenching from the melt. We find that Ga-Sb and Ga-Te are the most abundant bonds with only a minor amount of Sb-Te bonds participating to the alloy network. Ga and four-coordinated Sb atoms present a tetrahedral-like geometry, whereas three-coordinated Sb atoms are in a pyramidal configuration. The tetrahedral-like geometries are similar to those of the crystalline phase of the two binary compounds GaTe and GaSb. A sizable fraction of Sb-Sb bonds is also present, indicating a partial nanoscale segregation of Sb. Despite the fact that the composition Ga4Sb6Te3 lies on the pseudobinary Ga Sb -Sb2Te3 tie line, the amorphous network can be seen as a mixture of the two binary compounds GaTe and GaSb with intertwined elemental Sb.

Morphological instabilities of rapidly solidified binary alloys under weak flow

NASA Astrophysics Data System (ADS)

Kowal, Katarzyna; Davis, Stephen

2017-11-01

Additive manufacturing, or three-dimensional printing, offers promising advantages over existing manufacturing techniques. However, it is still subject to a range of undesirable effects. One of these involves the onset of flow resulting from sharp thermal gradients within the laser melt pool, affecting the morphological stability of the solidified alloys. We examine the linear stability of the interface of a rapidly solidifying binary alloy under weak boundary-layer flow by performing an asymptotic analysis for a singular perturbation problem that arises as a result of departures from the equilibrium phase diagram. Under no flow, the problem involves cellular and pulsatile instabilities, stabilised by surface tension and attachment kinetics. We find that travelling waves appear as a result of flow and we map out the effect of flow on two absolute stability boundaries as well as on the cells and solute bands that have been observed in experiments under no flow. This work is supported by the National Institute of Standards and Technology [Grant Number 70NANB14H012].

GPU-accelerated phase-field simulation of dendritic solidification in a binary alloy

NASA Astrophysics Data System (ADS)

Yamanaka, Akinori; Aoki, Takayuki; Ogawa, Satoi; Takaki, Tomohiro

2011-03-01

The phase-field simulation for dendritic solidification of a binary alloy has been accelerated by using a graphic processing unit (GPU). To perform the phase-field simulation of the alloy solidification on GPU, a program code was developed with computer unified device architecture (CUDA). In this paper, the implementation technique of the phase-field model on GPU is presented. Also, we evaluated the acceleration performance of the three-dimensional solidification simulation by using a single NVIDIA TESLA C1060 GPU and the developed program code. The results showed that the GPU calculation for 5763 computational grids achieved the performance of 170 GFLOPS by utilizing the shared memory as a software-managed cache. Furthermore, it can be demonstrated that the computation with the GPU is 100 times faster than that with a single CPU core. From the obtained results, we confirmed the feasibility of realizing a real-time full three-dimensional phase-field simulation of microstructure evolution on a personal desktop computer.

Magnetic, structural and magnetocaloric properties of Ni-Si and Ni-Al thermoseeds for self-controlled hyperthermia.

PubMed

Pandey, Sudip; Quetz, Abdiel; Aryal, Anil; Dubenko, Igor; Mazumdar, Dipanjan; Stadler, Shane; Ali, Naushad

2017-11-01

Self-controlled hyperthermia is a non-invasive technique used to kill or destroy cancer cells while preserving normal surrounding tissues. We have explored bulk magnetic Ni-Si and Ni-Al alloys as a potential thermoseeds. The structural, magnetic and magnetocaloric properties of the samples were investigated, including saturation magnetisation, Curie temperature (T C ), and magnetic and thermal hysteresis, using room temperature X-ray diffraction and magnetometry. The annealing time, temperature and the effects of homogenising the thermoseeds were studied to determine the functional hyperthermia applications. The bulk Ni-Si and Ni-Al binary alloys have Curie temperatures in the desired range, 316 K-319 K (43 °C-46 °C), which is suitable for magnetic hyperthermia applications. We have found that T C strictly follows a linear trend with doping concentration over a wide range of temperature. The magnetic ordering temperature and the magnetic properties can be controlled through substitution in these binary alloys.

Mechanism of abnormally slow crystal growth of CuZr alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, X. Q.; Lü, Y. J., E-mail: yongjunlv@bit.edu.cn; State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027

2015-10-28

Crystal growth of the glass-forming CuZr alloy is shown to be abnormally slow, which suggests a new method to identify the good glass-forming alloys. The crystal growth of elemental Cu, Pd and binary NiAl, CuZr alloys is systematically studied with the aid of molecular dynamics simulations. The temperature dependence of the growth velocity indicates the different growth mechanisms between the elemental and the alloy systems. The high-speed growth featuring the elemental metals is dominated by the non-activated collision between liquid-like atoms and interface, and the low-speed growth for NiAl and CuZr is determined by the diffusion across the interface. Wemore » find that, in contrast to Cu, Pd, and NiAl, a strong stress layering arisen from the density and the local order layering forms in front of the liquid-crystal interface of CuZr alloy, which causes a slow diffusion zone. The formation of the slow diffusion zone suppresses the interface moving, resulting in much small growth velocity of CuZr alloy. We provide a direct evidence of this explanation by applying the compressive stress normal to the interface. The compression is shown to boost the stress layering in CuZr significantly, correspondingly enhancing the slow diffusion zone, and eventually slowing down the crystal growth of CuZr alloy immediately. In contrast, the growth of Cu, Pd, and NiAl is increased by the compression because the low diffusion zones in them are never well developed.« less

Continuous composition-spread thin films of transition metal oxides by pulsed-laser deposition

NASA Astrophysics Data System (ADS)

Ohkubo, I.; Christen, H. M.; Khalifah, P.; Sathyamurthy, S.; Zhai, H. Y.; Rouleau, C. M.; Mandrus, D. G.; Lowndes, D. H.

2004-02-01

We have designed an improved pulsed-laser deposition-continuous composition-spread (PLD-CCS) system that overcomes the difficulties associated with earlier related techniques. Our new PLD-CCS system is based on a precisely controlled synchronization between the laser firing, target exchange, and substrate translation/rotation, and offers more flexibility and control than earlier PLD-based approaches. Most importantly, the deposition energetics and the film thickness are kept constant across the entire composition range, and the resulting samples are sufficiently large to allow characterization by conventional techniques. We fabricated binary alloy composition-spread films composed of SrRuO 3 and CaRuO 3. Alternating ablation from two different ceramic targets leads to in situ alloy formation, and the value of x in Sr xCa x-1 RuO 3 can be changed linearly from 0 to 1 (or over any arbitrarily smaller range) along one direction of the substrate.

Silver-hafnium braze alloy

DOEpatents

Stephens, Jr., John J.; Hosking, F. Michael; Yost, Frederick G.

2003-12-16

A binary allow braze composition has been prepared and used in a bonded article of ceramic-ceramic and ceramic-metal materials. The braze composition comprises greater than approximately 95 wt % silver, greater than approximately 2 wt % hafnium and less than approximately 4.1 wt % hafnium, and less than approximately 0.2 wt % trace elements. The binary braze alloy is used to join a ceramic material to another ceramic material or a ceramic material, such as alumina, quartz, aluminum nitride, silicon nitride, silicon carbide, and mullite, to a metal material, such as iron-based metals, cobalt-based metals, nickel-based metals, molybdenum-based metals, tungsten-based metals, niobium-based metals, and tantalum-based metals. A hermetic bonded article is obtained with a strength greater than 10,000 psi.

Shape selection criterion for cellular array during constrained growth of binary alloys - Need for low gravity experiment

NASA Technical Reports Server (NTRS)

Tewari, Surendra N.; Trivedi, Rohit

1991-01-01

Development of steady-state periodic cellular array is one of the critical problems in the study of nonlinear pattern formation during directional solidification of binary alloys. The criterion which establishes the values of cell tip radius and spacing under given growth condition is not known. Theoretical models, such as marginal stability and microscopic solvability, have been developed for purely diffusive regime. However, the experimental conditions where cellular structures are stable are precisely the ones where the convection effects are predominant. Thus, the critical data for meaningful evaluation of cellular array growth models can only be obtained by partial directional solidification and quenching experiments carried out in the low gravity environment of space.

Estimation of the viscosities of liquid binary alloys

NASA Astrophysics Data System (ADS)

Wu, Min; Su, Xiang-Yu

2018-01-01

As one of the most important physical and chemical properties, viscosity plays a critical role in physics and materials as a key parameter to quantitatively understanding the fluid transport process and reaction kinetics in metallurgical process design. Experimental and theoretical studies on liquid metals are problematic. Today, there are many empirical and semi-empirical models available with which to evaluate the viscosity of liquid metals and alloys. However, the parameter of mixed energy in these models is not easily determined, and most predictive models have been poorly applied. In the present study, a new thermodynamic parameter Δ G is proposed to predict liquid alloy viscosity. The prediction equation depends on basic physical and thermodynamic parameters, namely density, melting temperature, absolute atomic mass, electro-negativity, electron density, molar volume, Pauling radius, and mixing enthalpy. Our results show that the liquid alloy viscosity predicted using the proposed model is closely in line with the experimental values. In addition, if the component radius difference is greater than 0.03 nm at a certain temperature, the atomic size factor has a significant effect on the interaction of the binary liquid metal atoms. The proposed thermodynamic parameter Δ G also facilitates the study of other physical properties of liquid metals.

Surface tension estimation of high temperature melts of the binary alloys Ag-Au

NASA Astrophysics Data System (ADS)

Dogan, Ali; Arslan, Hüseyin

2017-11-01

Surface tension calculation of the binary alloys Ag-Au at the temperature of 1381 K, where Ag and Au have similar electronic structures and their atomic radii are comparable, are carried out in this study using several equations over entire composition range of Au. Apparently, the deviations from ideality of the bulk solutions, such as activities of Ag and Au are small and the maximum excess Gibbs free energy of mixing of the liquid phase is for instance -4500 J/mol at XAu = 0.5. Besides, the results obtained in Ag-Au alloys that at a constant temperature the surface tension increases with increasing composition while the surface tension decreases as the temperature increases for entire composition range of Au. Although data about surface tension of the Ag-Au alloy are limited, it was possible to make a comparison for the calculated results for the surface tension in this study with the available experimental data. Taken together, the average standard error analysis that especially the improved Guggenheim model in the other models gives the best agreement along with the experimental results at temperature 1383 K although almost all models are mutually in agreement with the other one.

Criteria for predicting the formation of single-phase high-entropy alloys

DOE PAGES

Troparevsky, M Claudia; Morris, James R..; Kent, Paul R.; ...

2015-03-15

High entropy alloys constitute a new class of materials whose very existence poses fundamental questions. Originally thought to be stabilized by the large entropy of mixing, these alloys have attracted attention due to their potential applications, yet no model capable of robustly predicting which combinations of elements will form a single-phase currently exists. Here we propose a model that, through the use of high-throughput computation of the enthalpies of formation of binary compounds, is able to confirm all known high-entropy alloys while rejecting similar alloys that are known to form multiple phases. Despite the increasing entropy, our model predicts thatmore » the number of potential single-phase multicomponent alloys decreases with an increasing number of components: out of more than two million possible 7-component alloys considered, fewer than twenty single-phase alloys are likely.« less

Characterization of microstructural, mechanical and thermophysical properties of Th-52U alloy

NASA Astrophysics Data System (ADS)

Das, Santanu; Kaity, S.; Kumar, R.; Banerjee, J.; Roy, S. B.; Chaudhari, G. P.; Daniel, B. S. S.

2016-11-01

Th-52 wt.% U alloy has a microstructure featuring interspersed networks of uranium rich and thorium rich phases. Room temperature hardness of the alloy is more than twice that of unalloyed thorium. The alloy age hardens (550 °C) only slightly (peak hardness/hardness of solution heated and quenched = 1.05). Room temperature thermal conductivity (25.6 W m-1 °C-1) is close to that of uranium and most of the binary and ternary metallic alloy fuel materials. Average linear coefficient of thermal expansion (CTE) of Th-52 wt.% U alloy [11.2 × 10-06 °C-1 (27-290 °C) and 16.75 × 10-06 °C-1 (27-600 °C)] are comparable with that of many metallic alloy fuel candidates. Th-52 wt.% U alloy with non-age hardenable microstructure, appreciable thermal conductivity, moderate thermal expansion may find metallic fuel applications in nuclear reactors.

Structural, microstructural and thermal analysis of U-(6-x)Zr-xNb alloys (x = 0, 2, 4, 6)

NASA Astrophysics Data System (ADS)

Kaity, Santu; Banerjee, Joydipta; Parida, S. C.; Bhasin, Vivek

2018-06-01

Uranium-rich U-Zr-Nb alloy is considered as a good alternative fuel for fast reactors from the perspective of excellent dimensional stability and desired thermo-physical properties to achieve higher burnup. Detailed investigations related to the structural and microstructural characterization, thermal expansion, phase transformation, microhardness were carried out on U-6Zr, U-4Zr-2Nb, U-2Zr-4Nb and U-6Nb alloys (composition in wt%) where the total amount of alloying elements was restricted to 6 wt%. Structural, microstructural and thermal analysis studies revealed that these alloys undergo a series of transformations from high temperature bcc γ-phase to a variety of equilibrium and intermediate phases depending upon alloy composition, cooling rate and quenching. The structural analysis was carried out by Rietveld refinement. The data of U-Nb and U-Zr-Nb alloys have been highlighted and compared with binary U-Zr alloy.

Heteroepitaxial growth of 3-5 semiconductor compounds by metal-organic chemical vapor deposition for device applications

NASA Technical Reports Server (NTRS)

Collis, Ward J.; Abul-Fadl, Ali

1988-01-01

The purpose of this research is to design, install and operate a metal-organic chemical vapor deposition system which is to be used for the epitaxial growth of 3-5 semiconductor binary compounds, and ternary and quaternary alloys. The long-term goal is to utilize this vapor phase deposition in conjunction with existing current controlled liquid phase epitaxy facilities to perform hybrid growth sequences for fabricating integrated optoelectronic devices.

Acceptable aluminum additions for minimal environmental effect in iron-aluminum alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikka, V.K.; Viswanathan, S.; Vyas, S.

A systematic study of iron-aluminum alloys has shown that Fe-16 at. % Al alloys are not very sensitive to environmental embrittlement. The Fe-22 and -28 at. % Al alloys are sensitive to environmental embrittlement, and the effect can be reduced by the addition of chromium and through the control of grain size by additions of zirconium and carbon. The Fe-16 at. % Al binary, and alloys based on it, yielded over 20% room-temperature (RT) elongation even after high-temperature annealing treatments at 1100[degree]C. The best values for the Fe-22 and -28 at. % Al-base alloys after similar annealing treatments were 5more » and 10%, respectively. A multicomponent alloy, FAP, based on Fe- 16 at. % Al was designed, which gave an RT ductility of over 25%.« less

Acceptable aluminum additions for minimal environmental effect in iron-aluminum alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikka, V.K.; Viswanathan, S.; Vyas, S.

A systematic study of iron-aluminum alloys has shown that Fe-16 at. % Al alloys are not very sensitive to environmental embrittlement. The Fe-22 and -28 at. % Al alloys are sensitive to environmental embrittlement, and the effect can be reduced by the addition of chromium and through the control of grain size by additions of zirconium and carbon. The Fe-16 at. % Al binary, and alloys based on it, yielded over 20% room-temperature (RT) elongation even after high-temperature annealing treatments at 1100{degree}C. The best values for the Fe-22 and -28 at. % Al-base alloys after similar annealing treatments were 5more » and 10%, respectively. A multicomponent alloy, FAP, based on Fe- 16 at. % Al was designed, which gave an RT ductility of over 25%.« less

Modification of band gaps and optoelectronic properties of binary calcium chalcogenides by means of doping of magnesium atom(s) in rock-salt phase- a first principle based theoretical initiative

NASA Astrophysics Data System (ADS)

Debnath, Bimal; Sarkar, Utpal; Debbarma, Manish; Bhattacharjee, Rahul; Chattopadhyaya, Surya

2018-02-01

The band gaps and optoelectronic properties of binary calcium chalcogenide semiconductors have been modified theoretically by doping magnesium atom(s) into their respective rock-salt unit cells at some specific concentrations x = 0.0, 0.25, 0.50, 0.75 and 1.0 and confirmed such modifications by studying their structural, electronic and optical properties using DFT based FP-LAPW approach. The WC-GGA functional is used to calculate structural properties, while mBJ, B3LYP and WC-GGA are used for calculating electronic and optical properties. The concentration dependences of lattice parameter, bulk modulus and fundamental band gap for each alloy system exhibit nonlinearity. The atomic and orbital origin of different electronic states in the band structure of each compound are explored from its density of states (DOS). The microscopic origin of band gap bowing for each of the alloy systems is explored in terms of volume deformation, charge exchange and structural relaxation. The chemical bonds between the constituent atoms in each compound are found as ionic in nature. Optical properties of each specimen are calculated from its computed spectra of dielectric function, refractive index, extinction coefficient, normal incidence reflectivity, optical conductivity, optical absorption and energy loss function. Several calculated results have been compared with available experimental and other theoretical data.

Tailoring Morphology and Size of Microstructure and Tensile Properties of Sn-5.5 wt.%Sb-1 wt.%(Cu,Ag) Solder Alloys

NASA Astrophysics Data System (ADS)

Dias, Marcelino; Costa, Thiago A.; Soares, Thiago; Silva, Bismarck L.; Cheung, Noé; Spinelli, José E.; Garcia, Amauri

2018-02-01

Transient directional solidification experiments, and further optical and scanning electron microscopy analyses and tensile tests, allowed the dependence of tensile properties on the micromorphology and length scale of the dendritic/cellular matrix of ternary Sn-5.5Sb-1Ag and Sn-5.5Sb-1Cu alloys to be determined. Extensive ranges of cooling rates were obtained, which permitted specific values of cooling rate for each sample examined along the length of the casting to be attributed. Very broad microstructural length scales were revealed as well as the presence of either cells or dendrites for the Ag-containing alloy. Hereafter, microstructural spacing values such as the cellular spacing, λ c, and the primary dendritic spacing, λ 1, may be correlated with thermal solidification parameters, that is, the cooling rate and the growth rate. While, for the Cu-containing Sn-Sb alloy, the β-Sn matrix is characterized only by the presence of dendritic arrangements, the Ag-containing Sn-Sb alloy is shown to have high-velocity β-Sn cells associated with high cooling rate regions, i.e., positions closer to the bottom of the alloy casting, with the remaining positions being characterized by a complex growth of β-Sn dendrites. Minor additions of Cu and Ag increase both the yield and ultimate tensile strengths when compared with the corresponding values of the binary Sn-5.5Sb alloy, with a small reduction in ductility. This has been attributed to the homogeneous distribution of the Ag3Sn and Cu6Sn5 intermetallic particles related to smaller λ 1 characterizing the dendritic zones of the ternary Sn-Sb-(Cu,Ag) alloys. In addition, the Ag-modified Sn-Sb alloy exhibited an initial wetting angle consistent with that characterizing the binary Sn-5.5Sb alloy.

Microstructure Analysis of Ti-xPt Alloys and the Effect of Pt Content on the Mechanical Properties and Corrosion Behavior of Ti Alloys

PubMed Central

Song, Ho-Jun; Han, Mi-Kyung; Jeong, Hyeon-Gyeong; Lee, Yong-Tai; Park, Yeong-Joon

2014-01-01

The microstructure, mechanical properties, and corrosion behavior of binary Ti-xPt alloys containing 5, 10, 15 and 20 wt% Pt were investigated in order to develop new Ti-based dental materials possessing superior properties than those of commercially pure titanium (cp-Ti). All of the Ti-xPt (x = 5, 10, 15, 20) alloys showed hexagonal α-Ti structure with cubic Ti3Pt intermetallic phase. The mechanical properties and corrosion behavior of Ti-xPt alloys were sensitive to the Pt content. The addition of Pt contributed to hardening of cp-Ti and to improving its oxidation resistance. Electrochemical results showed that the Ti-xPt alloys exhibited superior corrosion resistance than that of cp-Ti. PMID:28788660

Effect of zone size on the convergence of exact solutions for diffusion in single phase systems with planar, cylindrical or spherical geometry

NASA Technical Reports Server (NTRS)

Unnam, J.; Tenney, D. R.

1981-01-01

Exact solutions for diffusion in single phase binary alloy systems with constant diffusion coefficient and zero-flux boundary condition have been evaluated to establish the optimum zone size of applicability. Planar, cylindrical and spherical interface geometry, and finite, singly infinite, and doubly infinite systems are treated. Two solutions are presented for each geometry, one well suited to short diffusion times, and one to long times. The effect of zone-size on the convergence of these solutions is discussed. A generalized form of the diffusion solution for doubly infinite systems is proposed.

Macrosegregation in aluminum alloy ingot cast by the semicontinuous direct chill method

NASA Technical Reports Server (NTRS)

Yu, H.; Granger, D. A.

1984-01-01

A theoretical model of the semicontinuous DC casting method is developed to predict the positive segregation observed at the subsurface and the negative segregation commonly found at the center of large commercial-size aluminum alloy ingot. Qualitative analysis of commercial-size aluminum alloy semicontinuous cast direct chill (DC) ingot is carried out. In the analysis, both positive segregation in the ingot subsurface and negative segregation at the center of the ingot are examined. Ingot subsurface macrosegregation is investigated by considering steady state casting of a circular cross-section binary alloy ingot. Nonequilibrium solidification is assumed with no solid diffusion, constant equilibrium partition ratio, and constant solid density.

Evaluation of damage induced by high irradiation levels on α-Ni-Ni3Si eutectic structure

NASA Astrophysics Data System (ADS)

Camacho Olguin, Carlos Alberto; Garcia-Borquez, Arturo; González-Rodríguez, Carlos Alberto; Loran-Juanico, Jose Antonio; Cruz-Mejía, Hector

2015-06-01

Diluted alloys of the binary system Ni-Si have been used as target of beam of ions, electrons, neutrons and so on because in this kind of alloy occurs transformations order-disorder, when the temperature is raised. This fact has permitted to evaluate the phenomena associated with the damage induced by irradiation (DII). The results of these works have been employed to understand the behavior under irradiation of complex alloys and to evaluate the reliability of the results of mathematical simulation of the evolution of the DII. The interest in the alloy system Ni-Si has been reborn due to the necessity of developing materials, which have better resistance against the corrosion on more aggressive environments such as those generated on the nuclear power plants or those that exist out of the Earth's atmosphere. Now, a growing interest to use concentrated alloys of this binary system on diverse fields of the materials science has been taking place because up to determined concentration of silicon, a regular eutectic is formed, and this fact opens the possibility to develop lamellar composite material by directional solidification. However, nowadays, there is a lack of fundamental knowledge about the behavior of this type of lamellar structure under aggressive environments, like those mentioned before. Hence, the task of this work is to evaluate the effect that has the irradiation over the microstructure of the concentrated alloy Ni22at%Si. The dendritic region of the hypereutectic alloy consists of an intermetallic phase Ni3Si, whereas the interdendritic region is formed by the alternation of lamellas of solid solution α-Ni and intermetallic phase Ni3Si. Such kind of microstructure has the advantage to get information of the DII over different phases individually, and at the same time, about of the microstructure influence over the global damage in the alloy. The hypereutectic Ni22at%Si alloy was irradiated perpendicularly to its surface, with 3.66 MeV - Ni ions up to 380 dpa at 650°C in a Tandetron linear accelerator. The level of irradiation dose was chosen similar to the irradiation conditions of the next-generation nuclear reactors. The theoretical maximum depth of the DII (maximum depth of damage (MDD)) was calculated as 1.35 µm using the SRIM-2013 program; the laminar microstructure of the eutectic was simulated using the lattice parameters of the eutectic before irradiation. The experimental MDD was 1.47 µm, as determined through transmission electron microscope (TEM) images and the DII was characterized using µX-ray diffraction and TEM. The elimination of cubic phase of the intermetallic Ni3Si, the suppression of lamellae of the α-Ni phase, the generation of dislocation loops and lines, all of these changes generated by the irradiation are clear evidences that the DII was severe. Based on theoretical and experimental evidence, we propose that the amount of phases, alternate of lamellae with different chemical concentrations of silicon and lamellae spatial distribution have a direct relation with the severe evolution of the DII.

Forming a single layer of a composite powder based on the Ti-Nb system via selective laser melting (SLM)

NASA Astrophysics Data System (ADS)

Saprykin, A. A.; Sharkeev, Yu P.; Ibragimov, E. A.; Babakova, E. V.; Dudikhin, D. V.

2016-07-01

Alloys based on the titanium-niobium system are widely used in implant production. It is conditional, first of all, on the low modulus of elasticity and bio-inert properties of an alloy. These alloys are especially important for tooth replacement and orthopedic surgery. At present alloys based on the titanium-niobium system are produced mainly using conventional metallurgical methods. The further subtractive manufacturing an end product results in a lot of wastes, increasing, therefore, its cost. The alternative of these processes is additive manufacturing. Selective laser melting is a technology, which makes it possible to synthesize products of metal powders and their blends. The point of this technology is laser melting a layer of a powdered material; then a sintered layer is coated with the next layer of powder etc. Complex products and working prototypes are made on the base of this technology. The authors of this paper address to the issue of applying selective laser melting in order to synthesize a binary alloy of a composite powder based on the titanium-niobium system. A set of 10x10 mm samples is made in various process conditions. The samples are made by an experimental selective laser synthesis machine «VARISKAF-100MB». The machine provides adjustment of the following process variables: laser emission power, scanning rate and pitch, temperature of powder pre-heating, thickness of the layer to be sprinkled, and diameter of laser spot focusing. All samples are made in the preliminary vacuumized shielding atmosphere of argon. The porosity and thickness of the sintered layer related to the laser emission power are shown at various scanning rates. It is revealed that scanning rate and laser emission power are adjustable process variables, having the greatest effect on forming the sintered layer.

Ultrasmall PdmMn1-mOx binary alloyed nanoparticles on graphene catalysts for ethanol oxidation in alkaline media

NASA Astrophysics Data System (ADS)

Ahmed, Mohammad Shamsuddin; Park, Dongchul; Jeon, Seungwon

2016-03-01

A rare combination of graphene (G)-supported palladium and manganese in mixed-oxides binary alloyed catalysts (BACs) have been synthesized with the addition of Pd and Mn metals in various ratios (G/PdmMn1-mOx) through a facile wet-chemical method and employed as an efficient anode catalyst for ethanol oxidation reaction (EOR) in alkaline fuel cells. The as prepared G/PdmMn1-mOx BACs have been characterized by several instrumental techniques; the transmission electron microscopy images show that the ultrafine alloyed nanoparticles (NPs) are excellently monodispersed onto the G. The Pd and Mn in G/PdmMn1-mOx BACs have been alloyed homogeneously, and Mn presents in mixed-oxidized form that resulted by X-ray diffraction. The electrochemical performances, kinetics and stability of these catalysts toward EOR have been evaluated using cyclic voltammetry in 1 M KOH electrolyte. Among all G/PdmMn1-mOx BACs, the G/Pd0.5Mn0.5Ox catalyst has shown much superior mass activity and incredible stability than that of pure Pd catalysts (G/Pd1Mn0Ox, Pd/C and Pt/C). The well dispersion, ultrafine size of NPs and higher degree of alloying are the key factor for enhanced and stable EOR electrocatalysis on G/Pd0.5Mn0.5Ox.

Preparation and Thermoelectric Properties of IR(sub x)Co(sub 1-x)Sb(sub 2) Alloys

NASA Technical Reports Server (NTRS)

Caillat, Thierry

1995-01-01

The preparation and characterization of the binary arsenopyrite compounds CoSb2 and IrSb2 and IrxCo1-xSb2 alloys is reported. Single crystals of CoSb2 were grown by the vertical gradient freeze technique from solution rich in antimony. Polycrystalline samples of IrSb2 and IrxCo1-xSb2 alloys were prepared by hot-pressing of prereacted elemental powders. Samples were investigated by X-ray diffractometry, microprobe analysis and density measurements. It was found that a range of solid solution exist in the system IrxCo1-xSb2 for 0.1

Atom Probe Tomography Analysis of the Distribution of Rhenium in Nickel Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mottura, A.; Warnken, N; Miller, Michael K

2010-01-01

Atom probe tomography (APT) is used to characterise the distributions of rhenium in a binary Ni-Re alloy and the nickel-based single-crystal CMSX-4 superalloy. A purpose-built algorithm is developed to quantify the size distribution of solute clusters, and applied to the APT datasets to critique the hypothesis that rhenium is prone to the formation of clusters in these systems. No evidence is found to indicate that rhenium forms solute clusters above the level expected from random fluctuations. In CMSX-4, enrichment of Re is detected in the matrix phase close to the matrix/precipitate ({gamma}/{gamma}{prime}) phase boundaries. Phase field modelling indicates that thismore » is due to the migration of the {gamma}/{gamma}{prime} interface during cooling from the temperature of operation. Thus, neither clustering of rhenium nor interface enrichments can be the cause of the enhancement in high temperature mechanical properties conferred by rhenium alloying.« less

Co(x)Ni(4-x)Sb(12-y)Sn(y) Ternary Skutterudites: Processing and Thermoelectric Properties

NASA Technical Reports Server (NTRS)

Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

2014-01-01

Skutterudites have proven to be a useful thermoelectric system as a result of their high figure of merit, favorable mechanical properties, and good thermal stability. Binary skutterudites have received the majority of interest in recent years, as a result of successful double and triple filling schemes. Ternary skutterudites, such as Ni4Sb7Sn5, also demonstrate good thermoelectric performance, with high power factor and low thermal conductivity. Ternary skutterudites, as contrasted to binary systems, provide more possibility for tuning electronic structure as substitutions can be studied on three elements. The Co(x)Ni(4-x)Sb(12-y)Sn(y) system has been investigated as both a p- and n-type thermoelectric material, stable up to 200 C. The system is processed through a combination of solidification, mechanical alloying, and hot pressing steps. Rietveld structure refinement has revealed an interesting occupancy of Sn on both the 24g Wyckoff position with Sb as well as the 2a position as a rattler. In addition to thermoelectric properties, detailed processing routes have been investigated on the system.

In-Vitro Corrosion Studies of Bioabsorbable Alloys

NASA Astrophysics Data System (ADS)

Gill, P.; Munroe, N.

Magnesium alloys have inspired a significant amount of attention from researchers all over the world for cardiovascular and orthopedic applications due to their light weight, mechanical integrity and degradation behavior. In this investigation, cast manufactured binary, ternary and quaternary magnesium alloys were studied for their degradation behavior by potentiodynamic polarization tests in phosphate buffer saline solution (PBS) and PBS containing amino acids (cysteine, C and tryptophan, W) at 37 °C. Electrochemical impedance spectroscopy (EIS) tests were performed to determine the charge transfer resistance and immersion tests were performed to assess corrosion rate and hydrogen evolution from the alloys. Furthermore, the surface morphology and surface chemistry of the alloys were observed by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Stable biomimetic super-hydrophobic engineering materials.

PubMed

Guo, Zhiguang; Zhou, Feng; Hao, Jingcheng; Liu, Weimin

2005-11-16

We describe a simple and inexpensive method to produce super-hydrophobic surfaces on aluminum and its alloy by oxidation and chemical modification. Water or aqueous solutions (pH = 1-14) have contact angles of 168 +/- 2 and 161 +/- 2 degrees on the treated surfaces of Al and Al alloy, respectively. The super-hydrophobic surfaces are produced by the cooperation of binary structures at micro- and nanometer scales, thus reducing the energies of the surfaces. Such super-hydrophobic properties will greatly extend the applications of aluminum and its alloy as lubricating materials.

PROCESS OF DISSOLVING ZIRCONIUM ALLOYS

DOEpatents

Shor, R.S.; Vogler, S.

1958-01-21

A process is described for dissolving binary zirconium-uranium alloys where the uranium content is about 2%. In prior dissolution procedures for these alloys, an oxidizing agent was added to prevent the precipitation of uranium tetrafluoride. In the present method complete dissolution is accomplished without the use of the oxidizing agent by using only the stoichiometric amount or slight excess of HF required by the zirconium. The concentration of the acid may range from 2M to 10M and the dissolution is advatageously carried out at a temperature of 80 deg C.

TERNARY ALLOY-CONTAINING PLUTONIUM

DOEpatents

Waber, J.T.

1960-02-23

Ternary alloys of uranium and plutonium containing as the third element either molybdenum or zirconium are reported. Such alloys are particularly useful as reactor fuels in fast breeder reactors. The alloy contains from 2 to 25 at.% of molybdenum or zirconium, the balance being a combination of uranium and plutonium in the ratio of from 1 to 9 atoms of uranlum for each atom of plutonium. These alloys are prepared by melting the constituent elements, treating them at an elevated temperature for homogenization, and cooling them to room temperature, the rate of cooling varying with the oomposition and the desired phase structure. The preferred embodiment contains 12 to 25 at.% of molybdenum and is treated by quenching to obtain a body centered cubic crystal structure. The most important advantage of these alloys over prior binary alloys of both plutonium and uranium is the lack of cracking during casting and their ready machinability.

The Effect of CO2 Pressure on Chromia Scale Microstructure at 750°C

NASA Astrophysics Data System (ADS)

Pint, B. A.; Unocic, K. A.

2018-06-01

To understand and model performance in supercritical CO2 (sCO2) for high-efficiency, concentrating solar power (CSP) and fossil energy power cycles, reaction rates are compared at 750°C in 0.1 MPa CO2 and 30 MPa sCO2 as well as laboratory air as a baseline on structural materials such as Ni-based alloy 625. Due to the thin reaction products formed even after 5000 h, scanning transmission electron microscopy was used to study the Cr-rich surface oxide scale. The scales formed in CO2 and sCO2 had a much finer grain size with more voids observed in CO2. However, the observations on alloy 625 were complicated by Mo and Nb-rich precipitates in the adjacent substrate and Al internal oxidation. To simplify the system, a binary Ni-22Cr alloy was exposed for 1000 h in similar environments. After exposure in sCO2, there was an indication of carbon segregation detected on the Cr2O3 grain boundaries. After exposure in air, metallic Ni precipitates were observed in the scale that were not observed in the scale formed on alloy 625. The scale formed in air on a second Ni-22Cr model alloy with Mn and Si additions did not contain Ni precipitates, suggesting caution when drawing conclusions from model alloys.

Extended vapor-liquid-solid growth of silicon carbide nanowires.

PubMed

Rajesh, John Anthuvan; Pandurangan, Arumugam

2014-04-01

We developed an alloy catalytic method to explain extended vapor-liquid-solid (VLS) growth of silicon carbide nanowires (SiC NWs) by a simple thermal evaporation of silicon and activated carbon mixture using lanthanum nickel (LaNi5) alloy as catalyst in a chemical vapor deposition process. The LaNi5 alloy binary phase diagram and the phase relationships in the La-Ni-Si ternary system were play a key role to determine the growth parameters in this VLS mechanism. Different reaction temperatures (1300, 1350 and 1400 degrees C) were applied to prove the established growth process by experimentally. Scanning electron microscopy and transmission electron microscopy studies show that the crystalline quality of the SiC NWs increases with the temperature at which they have been synthesized. La-Ni alloyed catalyst particles observed on the top of the SiC NWs confirms that the growth process follows this extended VLS mechanism. The X-ray diffraction and confocal Raman spectroscopy analyses demonstrate that the crystalline structure of the SiC NWs was zinc blende 3C-SiC. Optical property of the SiC NWs was investigated by photoluminescence technique at room temperature. Such a new alloy catalytic method may be extended to synthesis other one-dimensional nanostructures.

Alloying effect on bright-dark exciton states in ternary monolayer Mo x W1-x Se2

NASA Astrophysics Data System (ADS)

Liu, Yanping; Tom, Kyle; Zhang, Xiaowei; Lou, Shuai; Liu, Yin; Yao, Jie

2017-07-01

Binary transition metal dichalcogenides (TMDCs) in the class MX2 (M = Mo, W; X = S, Se) have been widely investigated for potential applications in optoelectronics and nanoelectronics. Recently, alloy-based monolayers of TMDCs have provided a stable and versatile technique to tune the physical properties and optimize them for potential applications. Here, we present experimental evidence for the existence of an intermediate alloy state between the MoSe2-like and the WSe2-like behavior of the neutral exciton (X 0) using temperature-dependent photoluminescence (PL) of the monolayer Mo x W1-x Se2 alloy. The existence of a maximum PL intensity around 120 K can be explained by the competition between the thermally activated bright states and the non-radiative quenching of the bright states. Moreover, we also measured localized exciton (XB ) PL peak in the alloy and the observed behavior agrees well with a model previously proposed for the 3D case, which indicates the theory also applies to 2D systems. Our results not only shed light on bright-dark states and localized exciton physics of 2D semiconductors, but also offer a new route toward the control of the bright-dark transition and tailoring optical properties of 2D semiconductors through defect engineering.

Half-metallic Co-based quaternary Heusler alloys for spintronics: Defect- and pressure-induced transitions and properties

DOE PAGES

Enamullah, .; Johnson, D. D.; Suresh, K. G.; ...

2016-11-07

Heusler compounds offer potential as spintronic devices due to their spin polarization and half-metallicity properties, where electron spin-majority (minority) manifold exhibits states (band gap) at the electronic chemical potential, yielding full spin polarization in a single manifold. Yet, Heuslers often exhibit intrinsic disorder that degrades its half-metallicity and spin polarization. Using density-functional theory, we analyze the electronic and magnetic properties of equiatomic Heusler (L2 1) CoMnCrAl and CoFeCrGe alloys for effects of hydrostatic pressure and intrinsic disorder (thermal antisites, binary swaps, and vacancies). Under pressure, CoMnCrAl undergoes a metallic transition, while half-metallicity in CoFeCrGe is retained for a limited range.more » Antisite disorder between Cr-Al pair in CoMnCrAl alloy is energetically the most favorable, and retains half-metallic character in Cr-excess regime. However, Co-deficient samples in both alloys undergo a transition from half-metallic to metallic, with a discontinuity in the saturation magnetization. For binary swaps, configurations that compete with the ground state are identified and show no loss of half-metallicity; however, the minority-spin band gap and magnetic moments vary depending on the atoms swapped. For single binary swaps, there is a significant energy cost in CoMnCrAl but with no loss of half-metallicity. Although a few configurations in CoFeCrGe energetically compete with the ground state, the minority-spin band gap and magnetic moments vary depending on the atoms swapped. Furthermore, this information should help in controlling these potential spintronic materials.« less

Half-metallic Co-based quaternary Heusler alloys for spintronics: Defect- and pressure-induced transitions and properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Enamullah, .; Johnson, D. D.; Suresh, K. G.

Heusler compounds offer potential as spintronic devices due to their spin polarization and half-metallicity properties, where electron spin-majority (minority) manifold exhibits states (band gap) at the electronic chemical potential, yielding full spin polarization in a single manifold. Yet, Heuslers often exhibit intrinsic disorder that degrades its half-metallicity and spin polarization. Using density-functional theory, we analyze the electronic and magnetic properties of equiatomic Heusler (L2 1) CoMnCrAl and CoFeCrGe alloys for effects of hydrostatic pressure and intrinsic disorder (thermal antisites, binary swaps, and vacancies). Under pressure, CoMnCrAl undergoes a metallic transition, while half-metallicity in CoFeCrGe is retained for a limited range.more » Antisite disorder between Cr-Al pair in CoMnCrAl alloy is energetically the most favorable, and retains half-metallic character in Cr-excess regime. However, Co-deficient samples in both alloys undergo a transition from half-metallic to metallic, with a discontinuity in the saturation magnetization. For binary swaps, configurations that compete with the ground state are identified and show no loss of half-metallicity; however, the minority-spin band gap and magnetic moments vary depending on the atoms swapped. For single binary swaps, there is a significant energy cost in CoMnCrAl but with no loss of half-metallicity. Although a few configurations in CoFeCrGe energetically compete with the ground state, the minority-spin band gap and magnetic moments vary depending on the atoms swapped. Furthermore, this information should help in controlling these potential spintronic materials.« less

High pressure study of Pu(0.92)Am(0.08) binary alloy.

PubMed

Klosek, V; Griveau, J C; Faure, P; Genestier, C; Baclet, N; Wastin, F

2008-07-09

The phase transitions (by means of x-ray diffraction) and electrical resistivity of a Pu(0.92)Am(0.08) binary alloy were determined under pressure (up to 2 GPa). The evolution of atomic volume with pressure gives detailed information concerning the degree of localization of 5f electronic states and their delocalization process. A quasi-linear V = f(P) dependence reflects subtle modifications of the electronic structure when P increases. The electrical resistivity measurements reveal the very high stability of the δ phase for pressures less than 0.7 GPa, since no martensitic-like transformation occurs at low temperature. Remarkable electronic behaviours have also been observed. Finally, resistivity curves have shown the temperature dependence of the phase transformations together with unexpected kinetic effects.

An experimental study of energy dependence of saturation thickness of multiply scattered gamma rays in binary alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Gurvinderjit; Singh, Bhajan, E-mail: bhajan2k1@yahoo.co.in; Sandhu, B. S.

2015-08-28

The present measurements are carried out to investigate the multiple scattering of 662 keV gamma photons emerging from targets of binary alloys (brass and soldering material). The scattered photons are detected by 51 mm × 51 mm NaI(Tl) scintillation detector whose response unscrambling converting the observed pulse–height distribution to a true photon energy spectrum, is obtained with the help of 10 × 10 inverse response matrix. The numbers of multiply scattered events, having same energy as in the singly scattered distribution, first increases with target thickness and then saturate. The application of response function of scintillation detector does not result in anymore » change of measured saturation thickness. Monte Carlo calculation supports the present experimental results.« less

Thermal conductivity of disordered two-dimensional binary alloys.

PubMed

Zhou, Yang; Guo, Zhi-Xin; Cao, Hai-Yuan; Chen, Shi-You; Xiang, Hong-Jun; Gong, Xin-Gao

2016-10-20

Using non-equilibrium molecular dynamics simulations, we have studied the effect of disorder on the thermal conductivity of two-dimensional (2D) C 1-x N x alloys. We find that the thermal conductivity not only depends on the substitution concentration of nitrogen, but also strongly depends on the disorder distribution. A general linear relationship is revealed between the thermal conductivity and the participation ratio of phonons in 2D alloys. Localization mode analysis further indicates that the thermal conductivity variation in the ordered alloys can be attributed to the number of inequivalent atoms. As for the disordered alloys, we find that the thermal conductivity variation can be described by a simple linear formula with the disorder degree and the substitution concentration. The present study suggests some general guidance for phonon manipulation and thermal engineering in low dimensional alloys.

Computer-Based Methods for Thermodynamic Analysis of Materials Processing.

DTIC Science & Technology

1983-11-30

metallic alloys (12,13), silicides (14),and oxynitride * . systems (15). - . 2. Thermochemical System Employed to Characterize Binary Ill-V Phase Diagrams The...reference to Figure I shows that the stable form of RbF is the sodium chloride S form. Table I shows that OGH -oS -RFRFLS-RFRFLM-12866-.381T J/g.at. (5...KF, BF=(I/3)8aF LF-(I/4)LaF3V PF-(113)PbF 2 S- Sodium Chloride Structures Stable form of NF, KE, RE and (;F L-Liquid, M-Stable form of ZF, KeStable form

BCAT Setup

NASA Image and Video Library

2011-10-24

ISS029-E-032412 (24 Oct. 2011) --- NASA Mike Fossum, Expedition 29 commander, conducts a session with the Binary Colloidal Alloy Test-6 (BCAT-6) experiment in the Kibo laboratory of the International Space Station.

BCAT Setup

NASA Image and Video Library

2011-10-24

ISS029-E-032414 (24 Oct. 2011) --- NASA Mike Fossum, Expedition 29 commander, conducts a session with the Binary Colloidal Alloy Test-6 (BCAT-6) experiment in the Kibo laboratory of the International Space Station.

BCAT Setup

NASA Image and Video Library

2011-10-24

ISS029-E-032422 (24 Oct. 2011) --- NASA Mike Fossum, Expedition 29 commander, conducts a session with the Binary Colloidal Alloy Test-6 (BCAT-6) experiment in the Kibo laboratory of the International Space Station.

BCAT Setup

NASA Image and Video Library

2011-10-24

ISS029-E-032410 (24 Oct. 2011) --- NASA Mike Fossum, Expedition 29 commander, conducts a session with the Binary Colloidal Alloy Test-6 (BCAT-6) experiment in the Kibo laboratory of the International Space Station.

Mechanical property, biocorrosion and in vitro biocompatibility evaluations of Mg-Li-(Al)-(RE) alloys for future cardiovascular stent application.

PubMed

Zhou, W R; Zheng, Y F; Leeflang, M A; Zhou, J

2013-11-01

Mg-Li-based alloys were investigated for future cardiovascular stent application as they possess excellent ductility. However, Mg-Li binary alloys exhibited reduced mechanical strengths due to the presence of lithium. To improve the mechanical strengths of Mg-Li binary alloys, aluminum and rare earth (RE) elements were added to form Mg-Li-Al ternary and Mg-Li-Al-RE quarternary alloys. In the present study, six Mg-Li-(Al)-(RE) alloys were fabricated. Their microstructures, mechanical properties and biocorrosion behavior were evaluated by using optical microscopy, X-ray diffraction, scanning electronic microscopy, tensile tests, immersion tests and electrochemical measurements. Microstructure characterization indicated that grain sizes were moderately refined by the addition of rare earth elements. Tensile testing showed that enhanced mechanical strengths were obtained, while electrochemical and immersion tests showed reduced corrosion resistance caused by intermetallic compounds distributed throughout the magnesium matrix in the rare-earth-containing Mg-Li alloys. Cytotoxicity assays, hemolysis tests as well as platelet adhesion tests were performed to evaluate in vitro biocompatibilities of the Mg-Li-based alloys. The results of cytotoxicity assays clearly showed that the Mg-3.5Li-2Al-2RE, Mg-3.5Li-4Al-2RE and Mg-8.5Li-2Al-2RE alloys suppressed vascular smooth muscle cell proliferation after 5day incubation, while the Mg-3.5Li, Mg-8.5Li and Mg-8.5Li-1Al alloys were proven to be tolerated. In the case of human umbilical vein endothelial cells, the Mg-Li-based alloys showed no significantly reduced cell viabilities except for the Mg-8.5Li-2Al-2RE alloy, with no obvious differences in cell viability between different culture periods. With the exception of Mg-8.5Li-2Al-2RE, all of the other Mg-Li-(Al)-(RE) alloys exhibited acceptable hemolysis ratios, and no sign of thrombogenicity was found. These in vitro experimental results indicate the potential of Mg-Li-(Al)-(RE) alloys as biomaterials for future cardiovascular stent application and the worthiness of investigating their biodegradation behaviors in vivo. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Biomimetic hydrophobic surface fabricated by chemical etching method from hierarchically structured magnesium alloy substrate

NASA Astrophysics Data System (ADS)

Liu, Yan; Yin, Xiaoming; Zhang, Jijia; Wang, Yaming; Han, Zhiwu; Ren, Luquan

2013-09-01

As one of the lightest metal materials, magnesium alloy plays an important role in industry such as automobile, airplane and electronic product. However, magnesium alloy is hindered due to its high chemical activity and easily corroded. Here, inspired by typical plant surfaces such as lotus leaves and petals of red rose with super-hydrophobic character, the new hydrophobic surface is fabricated on magnesium alloy to improve anti-corrosion by two-step methodology. The procedure is that the samples are processed by laser first and then immersed and etched in the aqueous AgNO3 solution concentrations of 0.1 mol/L, 0.3 mol/L and 0.5 mol/L for different times of 15 s, 40 s and 60 s, respectively, finally modified by DTS (CH3(CH2)11Si(OCH3)3). The microstructure, chemical composition, wettability and anti-corrosion are characterized by means of SEM, XPS, water contact angle measurement and electrochemical method. The hydrophobic surfaces with microscale crater-like and nanoscale flower-like binary structure are obtained. The low-energy material is contained in surface after DTS treatment. The contact angles could reach up to 138.4 ± 2°, which hydrophobic property is both related to the micro-nano binary structure and chemical composition. The results of electrochemical measurements show that anti-corrosion property of magnesium alloy is improved. Furthermore, our research is expected to create some ideas from natural enlightenment to improve anti-corrosion property of magnesium alloy while this method can be easily extended to other metal materials.

Structural Characteristics and In Vitro Biodegradation of a Novel Zn-Li Alloy Prepared by Induction Melting and Hot Rolling

NASA Astrophysics Data System (ADS)

Zhao, Shan; McNamara, Cameron T.; Bowen, Patrick K.; Verhun, Nicholas; Braykovich, Jacob P.; Goldman, Jeremy; Drelich, Jaroslaw W.

2017-03-01

Zinc shows great promise as a bioabsorbable metal; however, the low tensile strength of pure zinc limits its application for endovascular stent purposes. In this study, a new Zn- xLi alloy (with x = 2, 4, 6 at. pct) was prepared by induction melting in an argon atmosphere and processed through hot rolling. Structures of the formulated binary alloys were characterized by X-ray diffraction and optical microscopy. Mechanical testing showed that the incorporation of Li into Zn increased ultimate tensile strength from <120 MPa (pure Zn) to >560 MPa ( x = 6 at. pct). In vitro corrosion behavior was evaluated by immersion tests in simulated body fluid. The Zn-2Li and Zn-4Li corrosion study demonstrated that corrosion rates and products resemble those observed for pure Zn in vivo, and in addition, the Zn-4Li alloy exhibits higher resistance to corrosion as compared to Zn-2Li. The findings herein encourage further exploration of Zn-Li systems for structural use in biomedical vascular support applications with the ultimate goal of simplifying stent procedures, thereby reducing stent-related complications.

Phase stability in nanoscale material systems: extension from bulk phase diagrams

NASA Astrophysics Data System (ADS)

Bajaj, Saurabh; Haverty, Michael G.; Arróyave, Raymundo; Goddard Frsc, William A., III; Shankar, Sadasivan

2015-05-01

Phase diagrams of multi-component systems are critical for the development and engineering of material alloys for all technological applications. At nano dimensions, surfaces (and interfaces) play a significant role in changing equilibrium thermodynamics and phase stability. In this work, it is shown that these surfaces at small dimensions affect the relative equilibrium thermodynamics of the different phases. The CALPHAD approach for material surfaces (also termed ``nano-CALPHAD'') is employed to investigate these changes in three binary systems by calculating their phase diagrams at nano dimensions and comparing them with their bulk counterparts. The surface energy contribution, which is the dominant factor in causing these changes, is evaluated using the spherical particle approximation. It is first validated with the Au-Si system for which experimental data on phase stability of spherical nano-sized particles is available, and then extended to calculate phase diagrams of similarly sized particles of Ge-Si and Al-Cu. Additionally, the surface energies of the associated compounds are calculated using DFT, and integrated into the thermodynamic model of the respective binary systems. In this work we found changes in miscibilities, reaction compositions of about 5 at%, and solubility temperatures ranging from 100-200 K for particles of sizes 5 nm, indicating the importance of phase equilibrium analysis at nano dimensions.Phase diagrams of multi-component systems are critical for the development and engineering of material alloys for all technological applications. At nano dimensions, surfaces (and interfaces) play a significant role in changing equilibrium thermodynamics and phase stability. In this work, it is shown that these surfaces at small dimensions affect the relative equilibrium thermodynamics of the different phases. The CALPHAD approach for material surfaces (also termed ``nano-CALPHAD'') is employed to investigate these changes in three binary systems by calculating their phase diagrams at nano dimensions and comparing them with their bulk counterparts. The surface energy contribution, which is the dominant factor in causing these changes, is evaluated using the spherical particle approximation. It is first validated with the Au-Si system for which experimental data on phase stability of spherical nano-sized particles is available, and then extended to calculate phase diagrams of similarly sized particles of Ge-Si and Al-Cu. Additionally, the surface energies of the associated compounds are calculated using DFT, and integrated into the thermodynamic model of the respective binary systems. In this work we found changes in miscibilities, reaction compositions of about 5 at%, and solubility temperatures ranging from 100-200 K for particles of sizes 5 nm, indicating the importance of phase equilibrium analysis at nano dimensions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01535a

Three-dimensional nanometer scale analyses of precipitate structures and local compositions in titanium aluminide engineering alloys

NASA Astrophysics Data System (ADS)

Gerstl, Stephan S. A.

Titanium aluminide (TiAl) alloys are among the fastest developing class of materials for use in high temperature structural applications. Their low density and high strength make them excellent candidates for both engine and airframe applications. Creep properties of TiAl alloys, however, have been a limiting factor in applying the material to a larger commercial market. In this research, nanometer scale compositional and structural analyses of several TiAl alloys, ranging from model Ti-Al-C ternary alloys to putative commercial alloys with 10 components are investigated utilizing three dimensional atom probe (3DAP) and transmission electron microscopies. Nanometer sized borides, silicides, and carbide precipitates are involved in strengthening TiAl alloys, however, chemical partitioning measurements reveal oxygen concentrations up to 14 at. % within the precipitate phases, resulting in the realization of oxycarbide formation contributing to the precipitation strengthening of TiAl alloys. The local compositions of lamellar microstructures and a variety of precipitates in the TiAl system, including boride, silicide, binary carbides, and intermetallic carbides are investigated. Chemical partitioning of the microalloying elements between the alpha2/gamma lamellar phases, and the precipitate/gamma-matrix phases are determined. Both W and Hf have been shown to exhibit a near interfacial excess of 0.26 and 0.35 atoms nm-2 respectively within ca. 7 nm of lamellar interfaces in a complex TiAl alloy. In the case of needle-shaped perovskite Ti3AlC carbide precipitates, periodic domain boundaries are observed 5.3+/-0.8 nm apart along their growth axis parallel to the TiAl[001] crystallographic direction with concomitant composition variations after 24 hrs. at 800°C.

Thermodynamic assessment of the Sn-Co lead-free solder system

NASA Astrophysics Data System (ADS)

Liu, Libin; Andersson, Cristina; Liu, Johan

2004-09-01

The Sn-Co-Cu eutectic alloy can be a less expensive alternative for the Sn-Ag-Cu alloy. In order to find the eutectic solder composition of the Sn-Co-Cu system, the Sn-Co binary system has been thoroughly assessed with the calculation of phase diagram (CALPHAD) method. The liquid phase, the FCC and HCP Co-rich solid solution, and the BCT Sn-rich solid solution have been described by the Redlich-Kister model. The Hillert-Jarl-Inden model has been used to describe the magnetic contributions to Gibbs energy in FCC and HCP. The CoSn2, CoSn, Co3Sn2_β, and Co3Sn2_α phases have been treated as stoichiometric phases. A series of thermodynamic parameters have been obtained. The calculated phase diagram and thermodynamic properties are in good agreement with the experimental data. The obtained thermodynamic data was used to extrapolate the ternary Sn-Co-Cu phase diagram. The composition of the Sn-rich eutectic point of the Sn-Co-Cu system was found to be 224°C, 0.4% Co, and 0.7% Cu.

BCAT setup in Kibo

NASA Image and Video Library

2014-06-03

ISS040-E-006891 (3 June 2014) --- NASA astronaut Reid Wiseman, Expedition 40 flight engineer, conducts a session with the Binary Colloidal Alloy Test (BCAT) experiment in the Kibo laboratory of the International Space Station.

Formation of the Fe-Containing Intermetallic Compounds during Solidification of Al-5Mg-2Si-0.7Mn-1.1Fe Alloy

NASA Astrophysics Data System (ADS)

Que, Zhongping; Wang, Yun; Fan, Zhongyun

2018-06-01

Iron (Fe) is the most common and the most detrimental impurity element in Al alloys due to the formation of Fe-containing intermetallic compounds (IMCs), which are harmful to mechanical performance of the Al-alloy components. In this paper we investigate the formation of Fe-containing IMCs during solidification of an Al-5Mg-2Si-0.7Mn-1.1Fe alloy under varied solidification conditions. We found that the primary Fe-containing intermetallic compound (P-IMC) in the alloy is the BCC α-Al15(Fe,Mn)3Si2 phase and has a polyhedral morphology with {1 1 0} surface termination. The formation of the P-IMCs can be easily suppressed by increasing the melt superheat and/or cooling rate, suggesting that the nucleation of the α-Al15(Fe,Mn)3Si2 phase is difficult. In addition, we found that the IMCs with a Chinese script morphology is initiated on the {1 0 0} surfaces of the P-IMCs during the binary eutectic reaction with the α-Al phase. Both the binary and ternary eutectic IMCs are also identified as the BCC α-Al15(Fe,Mn)3Si2 phase. Furthermore, we found that the Fe content increases and the Mn content decreases in the Fe-containing intermetallic compounds with the decrease of the formation temperature, although the sum of the Fe and Mn contents in all of the IMCs is constant.

Band gap characterization of ternary BBi1-xNx (0≤x≤1) alloys using modified Becke-Johnson (mBJ) potential

NASA Astrophysics Data System (ADS)

Yalcin, Battal G.

2015-04-01

The semi-local Becke-Johnson (BJ) exchange-correlation potential and its modified form proposed by Tran and Blaha have attracted a lot of interest recently because of the surprisingly accurate band gaps they can deliver for many semiconductors and insulators (e.g., sp semiconductors, noble-gas solids, and transition-metal oxides). The structural and electronic properties of ternary alloys BBi1-xNx (0≤x≤1) in zinc-blende phase have been reported in this study. The results of the studied binary compounds (BN and BBi) and ternary alloys BBi1-xNx structures are presented by means of density functional theory. The exchange and correlation effects are taken into account by using the generalized gradient approximation (GGA) functional of Wu and Cohen (WC) which is an improved form of the most popular Perdew-Burke-Ernzerhof (PBE). For electronic properties the modified Becke-Johnson (mBJ) potential, which is more accurate than standard semi-local LDA and PBE calculations, has been chosen. Geometric optimization has been implemented before the volume optimization calculations for all the studied alloys structure. The obtained equilibrium lattice constants of the studied binary compounds are in coincidence with experimental works. And, the variation of the lattice parameter of ternary alloys BBi1-xNx almost perfectly matches with Vegard's law. The spin-orbit interaction (SOI) has been also considered for structural and electronic calculations and the results are compared to those of non-SOI calculations.

Molten Chloride Salts for Heat Transfer in Nuclear Systems

NASA Astrophysics Data System (ADS)

Ambrosek, James Wallace

2011-12-01

A forced convection loop was designed and constructed to examine the thermal-hydraulic performance of molten KCl-MgCl2 (68-32 at %) salt for use in nuclear co-generation facilities. As part of this research, methods for prediction of the thermo-physical properties of salt mixtures for selection of the coolant salt were studied. In addition, corrosion studies of 10 different alloys were exposed to the KCl-MgCl2 to determine a suitable construction material for the loop. Using experimental data found in literature for unary and binary salt systems, models were found, or developed to extrapolate the available experimental data to unstudied salt systems. These property models were then used to investigate the thermo-physical properties of the LINO3-NaNO3-KNO 3-Ca(NO3), system used in solar energy applications. Using these models, the density, viscosity, adiabatic compressibility, thermal conductivity, heat capacity, and melting temperatures of higher order systems can be approximated. These models may be applied to other molten salt systems. Coupons of 10 different alloys were exposed to the chloride salt for 100 hours at 850°C was undertaken to help determine with which alloy to construct the loop. Of the alloys exposed, Haynes 230 had the least amount of weight loss per area. Nickel and Hastelloy N performed best based on maximum depth of attack. Inconel 625 and 718 had a nearly uniform depletion of Cr from the surface of the sample. All other alloys tested had depletion of Cr along the grain boundaries. The Nb in Inconel 625 and 718 changed the way the Cr is depleted in these alloys. Grain-boundary engineering (GBE) of Incoloy 800H improved the corrosion resistance (weight loss and maximum depth of attack) by nearly 50% as compared to the as-received Incoloy 800H sample. A high temperature pump, thermal flow meter, and pressure differential device was designed, constructed and tested for use in the loop, The heat transfer of the molten chloride salt was found to follow general correlations used to estimate the Nusselt number for water in both the forced convection laminar regime and in the mixed convection regime.

Biocompatibility of austenite and martensite phases in NiTi-based alloys

NASA Astrophysics Data System (ADS)

Danilov, A.; Kapanen, A.; Kujala, S.; Saaranen, J.; Ryhänen, J.; Pramila, A.; Jämsä, T.; Tuukkanen, J.

2003-10-01

The effect of surface phase composition on the biocompatibility of NiTi-based shape memory alloys was studied. The biocompatibility characteristics of parent β-phase (austenite) in binary NiTi and of martensite in ternary NiTiCu alloys after similar surface mechanical treatment were compared. The martensitic phase as a result of surface mechanical treatment (strain-induced martensite) was shown to decrease the biocompatibility of material in comparison to fully austenite state. The cytotoxicity (amount of dead cells / 1000 cells) and cell attachent (paxillin count / frame) were found to be linear functions of structural stresses in austenite.

Effect of heat treatment on the corrosion resistance of modified aluminum-magnesium alloys in seawater

NASA Astrophysics Data System (ADS)

Ahmad, Z.; Aleem, A.

1993-10-01

Study of modified Al-2.5Mg alloys containing chromium, silica, iron, and manganese in various tempers (O, H-18, T-4, T-6, T-18, and H-34) has shown that their corrosion resistance is significantly altered by thermomechanical treatment and the beneficial effect of chromium on microstructural changes. Modified binary Al-2.5Mg alloys in the T-6 and T-4 tempers exhibit a higher resistance to corrosion in Arabian Gulf water than H-34 tempers due to the beneficial effect of chromium on microstructural changes.

Performance of ethanol electro-oxidation on Ni-Cu alloy nanowires through composition modulation.

PubMed

Tian, Xi-Ke; Zhao, Xiao-Yu; Zhang, Li-de; Yang, Chao; Pi, Zhen-Bang; Zhang, Su-Xin

2008-05-28

To reduce the cost of the catalyst for direct ethanol fuel cells and improve its catalytic activity, highly ordered Ni-Cu alloy nanowire arrays have been fabricated successfully by differential pulse current electro-deposition into the pores of a porous anodic alumina membrane (AAMs). The energy dispersion spectrum, scanning and transmission electron microscopy were utilized to characterize the composition and morphology of the Ni-Cu alloy nanowire arrays. The results reveal that the nanowires in the array are uniform, well isolated and parallel to each other. The catalytic activity of the nanowire electrode arrays for ethanol oxidation was tested and the binary alloy nanowire array possesses good catalytic activity for the electro-oxidation of ethanol. The performance of ethanol electro-oxidation was controlled by varying the Cu content in the Ni-Cu alloy and the Ni-Cu alloy nanowire electrode shows much better stability than the pure Ni one.

iss028e036517

NASA Image and Video Library

2011-09-02

ISS028-E-036517 (2 Sept. 2011) --- NASA astronaut Mike Fossum, Expedition 28 flight engineer, conducts a session with the Binary Colloidal Alloy Test-5 (BCAT-5) in the Kibo laboratory of the International Space Station.

Reid BCAT Experiment

NASA Image and Video Library

2014-06-17

ISS040-E-013856 (17 June 2014) --- NASA astronaut Reid Wiseman, Expedition 40 flight engineer, conducts a session with the Binary Colloidal Alloy Test (BCAT) experiment at a workstation in the Harmony node of the International Space Station.

iss028e036580

NASA Image and Video Library

2011-09-02

ISS028-E-036580 (2 Sept. 2011) --- NASA astronaut Mike Fossum, Expedition 28 flight engineer, conducts a session with the Binary Colloidal Alloy Test-5 (BCAT-5) in the Kibo laboratory of the International Space Station.

A quasi two-dimensional benchmark experiment for the solidification of a tin lead binary alloy

NASA Astrophysics Data System (ADS)

Wang, Xiao Dong; Petitpas, Patrick; Garnier, Christian; Paulin, Jean-Pierre; Fautrelle, Yves

2007-05-01

A horizontal solidification benchmark experiment with pure tin and a binary alloy of Sn-10 wt.%Pb is proposed. The experiment consists in solidifying a rectangular sample using two lateral heat exchangers which allow the application a controlled horizontal temperature difference. An array of fifty thermocouples placed on the lateral wall permits the determination of the instantaneous temperature distribution. The cases with the temperature gradient G=0, and the cooling rates equal to 0.02 and 0.04 K/s are studied. The time evolution of the interfacial total heat flux and the temperature field are recorded and analyzed. This allows us to evaluate heat transfer evolution due to natural convection, as well as its influence on the solidification macrostructure. To cite this article: X.D. Wang et al., C. R. Mecanique 335 (2007).

Effect of boundary heat flux on columnar formation in binary alloys: A phase-field study

NASA Astrophysics Data System (ADS)

Du, Lifei; Zhang, Peng; Yang, Shaomei; Chen, Jie; Du, Huiling

2018-02-01

A non-isothermal phase-field model was employed to simulate the columnar formation during rapid solidification in binary Ni-Cu alloy. Heat flux at different boundaries was applied to investigate the temperature gradient effect on the morphology, concentration and temperature distributions during directional solidifications. With the heat flux input/extraction from boundaries, coupling with latent heat release and initial temperature gradient, temperature distributions are significantly changed, leading to solute diffusion changes during the phase-transition. Thus, irregular columnar structures are formed during the directional solidification, and the concentration distribution in solid columnar arms could also be changed due to the different growing speeds and temperature distributions at the solid-liquid interfaces. Therefore, applying specific heat conditions at the solidifying boundaries could be an efficient way to control the microstructure during solidifications.

FCRD Advanced Reactor (Transmutation) Fuels Handbook

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janney, Dawn Elizabeth; Papesch, Cynthia Ann

2016-09-01

Transmutation of minor actinides such as Np, Am, and Cm in spent nuclear fuel is of international interest because of its potential for reducing the long-term health and safety hazards caused by the radioactivity of the spent fuel. One important approach to transmutation (currently being pursued by the DOE Fuel Cycle Research & Development Advanced Fuels Campaign) involves incorporating the minor actinides into U-Pu-Zr alloys, which can be used as fuel in fast reactors. U-Pu-Zr alloys are well suited for electrolytic refining, which leads to incorporation rare-earth fission products such as La, Ce, Pr, and Nd. It is, therefore, importantmore » to understand not only the properties of U-Pu-Zr alloys but also those of U-Pu-Zr alloys with concentrations of minor actinides (Np, Am) and rare-earth elements (La, Ce, Pr, and Nd) similar to those in reprocessed fuel. In addition to requiring extensive safety precautions, alloys containing U, Pu, and minor actinides (Np and Am) are difficult to study for numerous reasons, including their complex phase transformations, characteristically sluggish phasetransformation kinetics, tendency to produce experimental results that vary depending on the histories of individual samples, rapid oxidation, and sensitivity to contaminants such as oxygen in concentrations below a hundred parts per million. Although less toxic, rare-earth elements such as La, Ce, Pr, and Nd are also difficult to study for similar reasons. Many of the experimental measurements were made before 1980, and the level of documentation for experimental methods and results varies widely. It is, therefore, not surprising that little is known with certainty about U-Pu-Zr alloys, particularly those that also contain minor actinides and rare-earth elements. General acceptance of results commonly indicates that there is only a single measurement for a particular property. This handbook summarizes currently available information about U, Pu, Zr, Np, Am, La, Ce, Pr, and Nd and alloys of two or three of these elements. It contains information about phase diagrams and related information (including phases and phase transformations); heat capacity, entropy, and enthalpy; thermal expansion; and thermal conductivity and diffusivity. In addition to presenting information about materials properties, the handbook attempts to provide information about how well the property is known and how much variation exists between measurements. Although it includes some results from models, its primary focus is experimental data. The Handbook is organized in two sections: one with information about the U-Pu-Zr ternary and one with information about other elements and binary and vi ternary alloys in the U-Np-Pu-Am-La-Ce-Pr-Nd-Zr system. Within each section, information about elements is presented first, followed by information about binary alloys, then information about ternary alloys. The order in which the elements in each alloy are mentioned follows the order in the first sentence of this paragraph. Much of the information on the U-Pu-Zr system repeats information from the FCRD Transmutation Fuels Handbook 2015. Most of the other data has been published elsewhere (although scattered throughout numerous references, some quite obscure); however, some data from Idaho National Laboratory is presented here for the first time. As the FCRD programmatic mission evolves, future editions of this handbook will begin to include other advanced reactor fuel designs and compositions. Hence, the title of the handbook will transition to the Advanced Reactor Fuels Handbook.« less

Influence of carbon on the formation of the surface layer in the process of electroerosion alloying of steel with tungsten

NASA Astrophysics Data System (ADS)

Vasil'eva, E. V.; Bochkov, V. E.; Mikheev, É. A.; Lyakishev, V. A.; Afanas'eva, T. N.

1983-10-01

With an increase in carbon content in the steel being treated, the thickness of the alloyed layer increases and its microhardness also increases. The carbon exerts a deoxidizing action on the layer being formed and promotes a reduction in the threshold of deerosion and also additional strengthening of the layer as the result of the formation of binary η-carbides.

Structural and dynamical properties of liquid Al-Au alloys

NASA Astrophysics Data System (ADS)

Peng, H. L.; Voigtmann, Th.; Kolland, G.; Kobatake, H.; Brillo, J.

2015-11-01

We investigate temperature- and composition-dependent structural and dynamical properties of Al-Au melts. Experiments are performed to obtain accurate density and viscosity data. The system shows a strong negative excess volume, similar to other Al-based binary alloys. We develop a molecular-dynamics (MD) model of the melt based on the embedded-atom method (EAM), gauged against the available experimental liquid-state data. A rescaling of previous EAM potentials for solid-state Au and Al improves the quantitative agreement with experimental data in the melt. In the MD simulation, the admixture of Au to Al can be interpreted as causing a local compression of the less dense Al system, driven by less soft Au-Au interactions. This local compression provides a microscopic mechanism explaining the strong negative excess volume of the melt. We further discuss the concentration dependence of self- and interdiffusion and viscosity in the MD model. Al atoms are more mobile than Au, and their increased mobility is linked to a lower viscosity of the melt.

A quantitative study of factors influencing lamellar eutectic morphology during solidification

NASA Technical Reports Server (NTRS)

Kaukler, W. F. S.

1981-01-01

The factors that influence the shape of the solid-liquid interface of a lamellar binary eutectic alloy are evaluated. Alloys of carbon tetrabromide and hexachloroethane which serve as a transparent analogue of lamellar metallic eutectics are used. The observed interface shapes are analyzed by computer-aided methods. The solid-liquid interfacial free energies of each of the individual phases comprising the eutectic system are measured as a function of composition using a 'grain boundary groove' technique. The solid-liquid interfacial free energy of the two phases are evaluated directly from the eutectic interface. The phase diagram for the system, the heat of fusion as a function of composition, and the density as a function of composition are measured. The shape of the eutectic interface is controlled mainly by the solid-liquid and solid-solid interfacial free energy relationships at the interface and by the temperature gradient present, rather than by interlamellar diffusion in the liquid at the interface, over the range of growth rates studied.

Model for the Prediction of the Hydriding Thermodynamics of Pd-Rh-Co Ternary Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teter, D.F.; Thoma, D.J.

1999-03-01

A dilute solution model (with respect to the substitutional alloying elements) has been developed, which accurately predicts the hydride formation and decomposition thermodynamics and the storage capacities of dilute ternary Pd-Rh-Co alloys. The effect of varying the rhodium and cobalt compositions on the thermodynamics of hydride formation and decomposition and hydrogen capacity of several palladium-rhodium-cobalt ternary alloys has been investigated using pressure-composition (PC) isotherms. Alloying in the dilute regime (<10 at.%) causes the enthalpy for hydride formation to linearly decrease with increasing alloying content. Cobalt has a stronger effect on the reduction in enthalpy than rhodium for equivalent alloying amounts.more » Also, cobalt reduces the hydrogen storage capacity with increasing alloying content. The plateau thermodynamics are strongly linked to the lattice parameters of the alloys. A near-linear dependence of the enthalpy of hydride formation on the lattice parameter was observed for both the binary Pd-Rh and Pd-Co alloys, as well as for the ternary Pd-Rh-Co alloys. The Pd-5Rh-3Co (at. %) alloy was found to have similar plateau thermodynamics as a Pd-10Rh alloy, however, this ternary alloy had a diminished hydrogen storage capacity relative to Pd-10Rh.« less

Magnetic cluster expansion model for random and ordered magnetic face-centered cubic Fe-Ni-Cr alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavrentiev, M. Yu., E-mail: Mikhail.Lavrentiev@ukaea.uk; Nguyen-Manh, D.; Dudarev, S. L.

A Magnetic Cluster Expansion model for ternary face-centered cubic Fe-Ni-Cr alloys has been developed, using DFT data spanning binary and ternary alloy configurations. Using this Magnetic Cluster Expansion model Hamiltonian, we perform Monte Carlo simulations and explore magnetic structures of alloys over the entire range of compositions, considering both random and ordered alloy structures. In random alloys, the removal of magnetic collinearity constraint reduces the total magnetic moment but does not affect the predicted range of compositions where the alloys adopt low-temperature ferromagnetic configurations. During alloying of ordered fcc Fe-Ni compounds with Cr, chromium atoms tend to replace nickel rathermore » than iron atoms. Replacement of Ni by Cr in ordered alloys with high iron content increases the Curie temperature of the alloys. This can be explained by strong antiferromagnetic Fe-Cr coupling, similar to that found in bcc Fe-Cr solutions, where the Curie temperature increase, predicted by simulations as a function of Cr concentration, is confirmed by experimental observations. In random alloys, both magnetization and the Curie temperature decrease abruptly with increasing chromium content, in agreement with experiment.« less

Theoretical calculation of the melting curve of Cu-Zr binary alloys

DOE PAGES

Gunawardana, K. G.S.H.; Wilson, S. R.; Mendelev, M. I.; ...

2014-11-14

Helmholtz free energies of the dominant binary crystalline solids found in the Cu-Zr system at high temperatures close to the melting curve are calculated. This theoretical approach combines fundamental measure density functional theory (applied to the hard-sphere reference system) and a perturbative approach to include the attractive interactions. The studied crystalline solids are Cu(fcc), Cu 51Zr 14(β), CuZr(B 2), CuZr 2(C11b), Zr(hcp), and Zr(bcc). The calculated Helmholtz free energies of crystalline solids are in good agreement with results from molecular-dynamics (MD) simulations. Using the same perturbation approach, the liquid phase free energies are calculated as a function of composition andmore » temperature, from which the melting curve of the entire composition range of this system can be obtained. Phase diagrams are determined in this way for two leading embedded atom method potentials, and the results are compared with experimental data. Furthermore, theoretical melting temperatures are compared both with experimental values and with values obtained directly from MD simulations at several compositions.« less

High-Strength Nanotwinned Al Alloys with 9R Phase.

PubMed

Li, Qiang; Xue, Sichuang; Wang, Jian; Shao, Shuai; Kwong, Anthony H; Giwa, Adenike; Fan, Zhe; Liu, Yue; Qi, Zhimin; Ding, Jie; Wang, Han; Greer, Julia R; Wang, Haiyan; Zhang, Xinghang

2018-03-01

Light-weight aluminum (Al) alloys have widespread applications. However, most Al alloys have inherently low mechanical strength. Nanotwins can induce high strength and ductility in metallic materials. Yet, introducing high-density growth twins into Al remains difficult due to its ultrahigh stacking-fault energy. In this study, it is shown that incorporating merely several atomic percent of Fe solutes into Al enables the formation of nanotwinned (nt) columnar grains with high-density 9R phase in Al(Fe) solid solutions. The nt Al-Fe alloy coatings reach a maximum hardness of ≈5.5 GPa, one of the strongest binary Al alloys ever created. In situ uniaxial compressions show that the nt Al-Fe alloys populated with 9R phase have flow stress exceeding 1.5 GPa, comparable to high-strength steels. Molecular dynamics simulations reveal that high strength and hardening ability of Al-Fe alloys arise mainly from the high-density 9R phase and nanoscale grain sizes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microstructure, Tensile Properties, and Corrosion Behavior of Die-Cast Mg-7Al-1Ca- xSn Alloys

NASA Astrophysics Data System (ADS)

Wang, Feng; Dong, Haikuo; Sun, Shijie; Wang, Zhi; Mao, Pingli; Liu, Zheng

2018-02-01

The microstructure, tensile properties, and corrosion behavior of die-cast Mg-7Al-1Ca- xSn ( x = 0, 0.5, 1.0, and 2.0 wt.%) alloys were studied using OM, SEM/EDS, tensile test, weight loss test, and electrochemical test. The experimental results showed that Sn addition effectively refined grains and intermetallic phases and increased the amount of intermetallic phases. Meanwhile, Sn addition to the alloys suppressed the formation of the (Mg,Al)2Ca phase and resulted in the formation of the ternary CaMgSn phase and the binary Mg2Sn phase. The Mg-7Al-1Ca-0.5Sn alloy exhibited best tensile properties at room temperature, while Mg-7Al-1Ca-1.0Sn alloy exhibited best tensile properties at elevated temperature. The corrosion resistance of studied alloys was improved by the Sn addition, and the Mg-7Al-1Ca-0.5Sn alloy presented the best corrosion resistance.

Prediction of as-cast grain size of inoculated aluminum alloys melt solidified under non-isothermal conditions

NASA Astrophysics Data System (ADS)

Du, Qiang; Li, Yanjun

2015-06-01

In this paper, a multi-scale as-cast grain size prediction model is proposed to predict as-cast grain size of inoculated aluminum alloys melt solidified under non-isothermal condition, i.e., the existence of temperature gradient. Given melt composition, inoculation and heat extraction boundary conditions, the model is able to predict maximum nucleation undercooling, cooling curve, primary phase solidification path and final as-cast grain size of binary alloys. The proposed model has been applied to two Al-Mg alloys, and comparison with laboratory and industrial solidification experimental results have been carried out. The preliminary conclusion is that the proposed model is a promising suitable microscopic model used within the multi-scale casting simulation modelling framework.

Electrical and mechanical properties of Sn-5wt.%Sb alloy with annealing temperature

NASA Astrophysics Data System (ADS)

Said Gouda, El; Ahmed, E. M.; Saad Allah, F. A.

2009-01-01

A binary Sn-5wt.%Sb solder alloy was chosen as a potential alternative to Sn-Pb solder alloy to be subjected to many studies. It was casted from the liquid state, cold drawn into wires of 1 mm diameters. The study includes the structure, electrical resistivity, tensile strength, hardness and indentation creep behavior using XRD, four probes electrical circuit, conventional tensile testing machine, Vickers microhardness tester, respectively. These properties were carried out for the cold worked alloy and after annealing at 393 and 473 K for 60 min. It was found that annealed samples exhibit more precipitations of the intermetallic compounds SnSb, higher lattice parameters and higher crystallite size, while have lower lattice-strain induced due to the cold working process. These structural changes greatly affect the electrical resistivity and mechanical properties of this alloy.

Ultrathin Pt xSn 1–x Nanowires for Methanol and Ethanol Oxidation Reactions: Tuning Performance by Varying Chemical Composition

DOE PAGES

Li, Luyao; Liu, Haiqing; Qin, Chao; ...

2018-02-28

Pt-based alloys denote promising catalysts for the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR), due to their enhanced activity toward alcohol-oxidation reactions and reduced cost as compared with Pt alone. Among all of these binary systems, PtSn has been reported to exhibit superior methanol/ethanol oxidation activity. In this paper, we deliberatively tailor chemical composition, reduce size, and optimize morphology of the catalyst in an effort to understand structure–property correlations that can be used to improve upon the electrocatalytic activity of these systems. Previous work performed by our group suggested that Pt-based catalysts, possessing an ultrathin one-dimensional (1D)more » structure, dramatically promote both cathodic and anodic reactions with respect to their zero-dimensional (0D) counterparts. Herein, a novel set of ultrathin binary Pt–Sn 1D nanowire (NW) catalysts with rationally controlled chemical compositions, i.e., Pt 9Sn 1, Pt 8Sn 2, and Pt 7Sn 3, has been synthesized using a facile, room-temperature, wet-solution-based method. The crystallinity and chemical composition of these as-prepared samples were initially characterized using XRD, XPS, and EDX. Results revealed that this synthetic protocol could successfully generate PtSn alloys with purposely tunable chemical compositions. TEM and HRTEM verified the structural integrity of our ultrathin 1D NW morphology for our Pt 9Sn 1, Pt 8Sn 2, and Pt 7Sn 3 samples. The effects of varying Sn content within these alloy samples toward the electro-oxidation reaction of methanol and ethanol were probed using cyclic voltammetry (CV) in acidic media. Finally, within this series, we find that the optimized chemical composition for both the MOR and the EOR is Pt 7Sn 3.« less

Ultrathin Pt xSn 1–x Nanowires for Methanol and Ethanol Oxidation Reactions: Tuning Performance by Varying Chemical Composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Luyao; Liu, Haiqing; Qin, Chao

Pt-based alloys denote promising catalysts for the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR), due to their enhanced activity toward alcohol-oxidation reactions and reduced cost as compared with Pt alone. Among all of these binary systems, PtSn has been reported to exhibit superior methanol/ethanol oxidation activity. In this paper, we deliberatively tailor chemical composition, reduce size, and optimize morphology of the catalyst in an effort to understand structure–property correlations that can be used to improve upon the electrocatalytic activity of these systems. Previous work performed by our group suggested that Pt-based catalysts, possessing an ultrathin one-dimensional (1D)more » structure, dramatically promote both cathodic and anodic reactions with respect to their zero-dimensional (0D) counterparts. Herein, a novel set of ultrathin binary Pt–Sn 1D nanowire (NW) catalysts with rationally controlled chemical compositions, i.e., Pt 9Sn 1, Pt 8Sn 2, and Pt 7Sn 3, has been synthesized using a facile, room-temperature, wet-solution-based method. The crystallinity and chemical composition of these as-prepared samples were initially characterized using XRD, XPS, and EDX. Results revealed that this synthetic protocol could successfully generate PtSn alloys with purposely tunable chemical compositions. TEM and HRTEM verified the structural integrity of our ultrathin 1D NW morphology for our Pt 9Sn 1, Pt 8Sn 2, and Pt 7Sn 3 samples. The effects of varying Sn content within these alloy samples toward the electro-oxidation reaction of methanol and ethanol were probed using cyclic voltammetry (CV) in acidic media. Finally, within this series, we find that the optimized chemical composition for both the MOR and the EOR is Pt 7Sn 3.« less

Combinatorial assessment of the influence of composition and exposure time on the oxidation behavior and concurrent oxygeninduced phase transformations of binary Ti-x systems

NASA Astrophysics Data System (ADS)

Samimi, Peyman

The relatively low oxidation resistance and subsequent surface embrittlement have often limited the use of titanium alloys in elevated temperature structural applications. Although extensive effort is spent to investigate the high temperature oxidation performance of titanium alloys, the studies are often constrained to complex technical titanium alloys and neither the mechanisms associated with evolution of the oxide scale nor the effect of oxygen ingress on the microstructure of the base metal are well-understood. In addition lack of systematic oxidation studies across a wider domain of the alloy composition has complicated the determination of composition-mechanism-property relationships. Clearly, it would be ideal to assess the influence of composition and exposure time on the oxidation resistance, independent of experimental variabilities regarding time, temperature and atmosphere as the potential source of error. Such studies might also provide a series of metrics (e.g., hardness, scale, etc) that could be interpreted together and related to the alloy composition. In this thesis a novel combinatorial approach was adopted whereby a series of compositionally graded specimens, (Ti-xMo, Ti-xCr, Ti-xAl and Ti-xW) were prepared using Laser Engineered Net Shaping (LENS(TM)) technology and exposed to still-air at 650 °C. (Abstract shortened by ProQuest.).

Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

PubMed Central

Mukundan, Vineetha; Yin, Jun; Joseph, Pharrah; Luo, Jin; Shan, Shiyao; Zakharov, Dmitri N; Zhong, Chuan-Jian; Malis, Oana

2014-01-01

Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2) alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C). The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering. PMID:27877663

Thermodynamic criteria for the removal of impurities from end-of-life magnesium alloys by evaporation and flux treatment

NASA Astrophysics Data System (ADS)

Hiraki, Takehito; Takeda, Osamu; Nakajima, Kenichi; Matsubae, Kazuyo; Nakamura, Shinichiro; Nagasaka, Tetsuya

2011-06-01

In this paper, the possibility of removing impurities during magnesium recycling with pyrometallurgical techniques has been evaluated by using a thermodynamic analysis. For 25 different elements that are likely to be contained in industrial magnesium alloys, the equilibrium distribution ratios between the metal, slag and gas phases in the magnesium remelting process were calculated assuming binary systems of magnesium and an impurity element. It was found that calcium, gadolinium, lithium, ytterbium and yttrium can be removed from the remelted end-of-life (EoL) magnesium products by oxidization. Calcium, cerium, gadolinium, lanthanum, lithium, plutonium, sodium, strontium and yttrium can be removed by chlorination with a salt flux. However, the other elements contained in magnesium alloy scrap are scarcely removed and this may contribute toward future contamination problems. The third technological option for the recycling of EoL magnesium products is magnesium recovery by a distillation process. Based on thermodynamic considerations, it is predicted that high-purity magnesium can be recovered through distillation because of its high vapor pressure, yet there is a limit on recoverability that depends on the equilibrium vapor pressure of the alloying elements and the large energy consumption. Therefore, the sustainable recycling of EoL magnesium products should be an important consideration in the design of advanced magnesium alloys or the development of new refining processes.

Thermodynamic criteria for the removal of impurities from end-of-life magnesium alloys by evaporation and flux treatment

PubMed Central

Hiraki, Takehito; Takeda, Osamu; Nakajima, Kenichi; Matsubae, Kazuyo; Nakamura, Shinichiro; Nagasaka, Tetsuya

2011-01-01

In this paper, the possibility of removing impurities during magnesium recycling with pyrometallurgical techniques has been evaluated by using a thermodynamic analysis. For 25 different elements that are likely to be contained in industrial magnesium alloys, the equilibrium distribution ratios between the metal, slag and gas phases in the magnesium remelting process were calculated assuming binary systems of magnesium and an impurity element. It was found that calcium, gadolinium, lithium, ytterbium and yttrium can be removed from the remelted end-of-life (EoL) magnesium products by oxidization. Calcium, cerium, gadolinium, lanthanum, lithium, plutonium, sodium, strontium and yttrium can be removed by chlorination with a salt flux. However, the other elements contained in magnesium alloy scrap are scarcely removed and this may contribute toward future contamination problems. The third technological option for the recycling of EoL magnesium products is magnesium recovery by a distillation process. Based on thermodynamic considerations, it is predicted that high-purity magnesium can be recovered through distillation because of its high vapor pressure, yet there is a limit on recoverability that depends on the equilibrium vapor pressure of the alloying elements and the large energy consumption. Therefore, the sustainable recycling of EoL magnesium products should be an important consideration in the design of advanced magnesium alloys or the development of new refining processes. PMID:27877407

Influence of alloying elements on the oxidation behavior of NbAl3

NASA Technical Reports Server (NTRS)

Hebsur, M. G.; Stephens, J. R.; Smialek, J. L.; Barrett, C. A.; Fox, D. S.

1988-01-01

NbAL3 is one candidate material for advanced aeropropulsion systems because of its high melting point, low density, and good oxidation resistance. Although NbAl3 has the lowest oxidation rate among the binary Nb-Al alloys, it does not form exclusive layers of protective Al2O3 scales. Recently Perkin et al., have shown the feasibility of forming alumina scales on Nb-Al alloys at greatly reduced Al contents. However, the objective was to maintain the high Al content, and hence low density, while achieving the capability of growing protective alumina scales. Alloy development followed approaches similar to those used successfully for superalloys and oxidation resistant MCrAlY coatings. Among the three elements examined (Ti, Si, and Cr) as ternary additions to Nb-Al3, Cr was the most effective in favoring the selective oxidation of Al. Nb-41Al-8Cr formed exclusive layers of alumina and had a k sub p value of 0.22 mg squared/cm (sup 4)/hr at 1200 C. The addition of 1 wt percent Y to this alloy was also beneficial, resulting in nearly an order of magnitude decrease in K sub p at 1200 C. Further improvements were achieved by adding about 1 wt percent Si to the quaternary alloy. The k sub p value of 0.012 mg squared/cm (sup 4)/hr for Nb-40Al-8Cr-1Y-1Si at 1200 C was identical to the best NiAl + Zr alloys. These NbAl3 alloys also exhibited excellent cyclic oxidation resistance for 100 hr at 1200 C, being nearly equivalent to NiAl + Zr.

Influence of alloying elements on the oxidation behavior of NbAl3

NASA Technical Reports Server (NTRS)

Hebsur, M. G.; Stephens, J. R.; Smialek, J. L.; Barrett, C. A.; Fox, D. S.

1989-01-01

NbAl3 is one candidate material for advanced aeropropulsion systems because of its high melting point, low density, and good oxidation resistance. Although NbAl3 has the lowest oxidation rate among the binary Nb-Al alloys, it does not form exclusive layers of protective Al203 scales. Recently Perkin et al., have shown the feasibility of forming alumina scales on Nb-Al alloys at greatly reduced Al contents. However, the objective was to maintain the high Al content, and hence low density, while achieving the capability of growing protective alumina scales. Alloy development followed approaches similar to those used successfully for superalloys and oxidation resistant MCrAly coatings. Among the three elements examined (Ti, Si, and Cr) as ternary additions to Nb-Al3, Cr was the most effective in favoring the selective oxidation of Al. Nb-41Al-8Cr formed exclusive layers of alumina and had a k sub p value of 0.22 mg squared/cm (sup 4)/hr at 1200 C. The addition of 1 wt percent Y to this alloy was also beneficial, resulting in nearly an order of magnitude decrease in K sub p at 1200 C. Further improvements were achieved by adding about 1 wt percent Si to the quaternary alloy. The k sub p value of 0.012 mg squared/cm (sup 4)/hr for Nb-40Al-8Cr-1Y-1Si at 1200 C was identical to the best NiAl + Zr alloys. These NbAl3 alloys also exhibited excellent cyclic oxidation resistance for 100 hr at 1200 C, being nearly equivalent to NiAl + Zr.

Phase Equilibria of Sn-Co-Cu Ternary System

NASA Astrophysics Data System (ADS)

Chen, Yu-Kai; Hsu, Chia-Ming; Chen, Sinn-Wen; Chen, Chih-Ming; Huang, Yu-Chih

2012-10-01

Sn-Co-Cu ternary alloys are promising lead-free solders, and isothermal sections of Sn-Co-Cu phase equilibria are fundamentally important for the alloys' development and applications. Sn-Co-Cu ternary alloys were prepared and equilibrated at 523 K, 1073 K, and 1273 K (250 °C, 800 °C, and 1000 °C), and the equilibrium phases were experimentally determined. In addition to the terminal solid solutions and binary intermetallic compounds, a new ternary compound, Sn3Co2Cu8, was found. The solubilities of Cu in the α-CoSn3 and CoSn2 phases at 523 K (250 °C) are 4.2 and 1.6 at. pct, respectively, while the Cu solubility in the α-Co3Sn2 phase is as high as 20.0 at. pct. The Cu solubility increases with temperature and is around 30.0 at. pct in the β-Co3Sn2 at 1073 K (800 °C). The Co solubility in the η-Cu6Sn5 phase is also significant and is 15.5 at. pct at 523 K (250 °C).

On the effect of stress on nucleation and growth of precipitates in an Al-Cu-Mg-Ag alloy

NASA Astrophysics Data System (ADS)

Skrotzki, B.; Shiflet, G. J.; Starke, E. A.

1996-11-01

A study has been made of the effect of an externally applied tensile stress on Ω and Θ' precipitate nucleation and growth in an Al-Cu-Mg-Ag alloy and a binary Al-Cu alloy which was used as a model system. Both solutionized and solutionized and aged conditions were studied. The mechanical properties have been measured and the microstructures have been characterized by transmission electron microscopy (TEM). The volume fraction and number density, as well as the precipitate size, have been experimentally determined. It was found that for as-solutionized samples aged under stress, precipitation occurs preferentially parallel to the stress axis. A threshold stress has to be exceeded before this effect can be observed. The critical stress for influencing the precipitate habit plane is between 120 and 140 MPa for Ω and between 16 and 19 MPa for Θ' for the aging temperature of 160 °C. The major effect of the applied stress is on the nucleation process. The results are discussed in terms of the role of the lattice misfit between the matrix and the precipitate nucleus.

Disorder trapping by rapidly moving phase interface in an undercooled liquid

NASA Astrophysics Data System (ADS)

Galenko, Peter; Danilov, Denis; Nizovtseva, Irina; Reuther, Klemens; Rettenmayr, Markus

2017-08-01

Non-equilibrium phenomena such as the disappearance of solute drag, the origin of solute trapping and evolution of disorder trapping occur during fast transformations with originating metastable phases [D.M. Herlach, P.K. Galenko, D. Holland-Moritz, Metastable solids from undrercooled melts (Elsevier, Amsterdam, 2007)]. In the present work, a theoretical investigation of disorder trapping by a rapidly moving phase interface is presented. Using a model of fast phase transformations, a system of governing equations for the diffusion of atoms, and the evolution of both long-range order parameter and phase field variable is formulated. First numerical solutions are carried out for a congruently melting binary alloy system.

First principles study on structural, electronic and optical properties of Ga1-xBxP ternary alloys (x = 0, 0.25, 0.5, 0.75 and 1)

NASA Astrophysics Data System (ADS)

Hoat, D. M.; Rivas Silva, J. F.; Méndez Blas, A.

2018-07-01

The structural, electronic and optical properties of GaP, BP binary compounds and their ternary alloys Ga1-xBxP (x = 0.25, 0.5 and 0.75) have been studied by full-potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT) as implemented in WIEN2k package. Local density approximation (LDA) and generalized gradient approximation (GGA) as proposed by Perdew-Burke-Ernzerhof (PBE), Wu-Cohen (WC) and PBE for solid (PBESol) were used for treatment of exchange-correlation effect in calculations. Additionally, the Tran-Blaha modified Becke-Johnson (mBJ) potential was also employed for electronic and optical calculations due to that it gives very accurate band gap of solids. As B concentration increases, the lattice constant reduces and the energy band gap firstly decreases for small composition x and then it shows increasing trend until pure BP. Our results show that the indirect-direct band gap transition can be reached from x = 0.33. The linear optical properties, such as reflectivity, absorption coefficient, refractive index and optical conductivity of binary compounds and ternary alloys were derived from their calculated complex dielectric function in wide energy range up to 30 eV, and the alloying effect on these properties was also analyzed in detail.

Structural Stabilities of β-Ti Alloys Studied Using a New Mo Equivalent Derived from [ β/( α + β)] Phase-Boundary Slopes

NASA Astrophysics Data System (ADS)

Wang, Qing; Dong, Chuang; Liaw, Peter K.

2015-08-01

Structural stabilities of β-Ti alloys are generally investigated by an empirical Mo equivalent, which quantifies the stability contribution of each alloying element, M, in comparison to that of the major β-Ti stabilizer, Mo. In the present work, a new Mo equivalent (Moeq)Q is proposed, which uses the slopes of the boundary lines between the β and ( α + β) phase zones in binary Ti-M phase diagrams. This (Moeq)Q reflects a simple fact that the β-Ti stability is enhanced, when the β phase zone is enlarged by a β-Ti stabilizer. It is expressed as (Moeq)Q = 1.0 Mo + 0.74 V + 1.01 W + 0.23 Nb + 0.30 Ta + 1.23 Fe + 1.10 Cr + 1.09 Cu + 1.67 Ni + 1.81 Co + 1.42 Mn + 0.38 Sn + 0.34 Zr + 0.99 Si - 0.57 Al (at. pct), where the equivalent coefficient of each element is the slope ratio of the [ β/( α + β)] boundary line of the binary Ti-M phase diagram to that of the Ti-Mo. This (Moeq)Q is shown to reliably characterize the critical stability limit of multi-component β-Ti alloys with low Young's moduli, where the critical lower limit for β stabilization is (Moeq)Q = 6.25 at. pct or 11.8 wt pct Mo.

In Situ Synchrotron Radiation X-ray Diffraction Study on Phase and Oxide Growth during a High Temperature Cycle of a NiTi-20 at.% Zr High Temperature Shape Memory Alloy

NASA Astrophysics Data System (ADS)

Carl, Matthew; Van Doren, Brian; Young, Marcus L.

2018-03-01

Ternary additions to binary NiTi shape memory alloys are known to significantly affect the characteristic martensite-to-austenite phase transformation, i.e., decrease or increase transformation temperatures. High temperature shape memory alloys can be created by adding Au, Pt, Pd, Hf, or Zr to binary NiTi in appropriate amounts; however, the majority of these ternary additions are exceedingly expensive, unfortunately making them impractical for most commercial applications. Zr is the exception of the group, but it is often disregarded because of its poor workability and thermal stability. In an effort to find a temperature range that allows for the potential workability of NiTiZr alloys in normal atmosphere environments and to gain understanding as to the cause of failure during processing, a NiTi-20 at.% Zr was subjected to a thermal cycle ranging from RT to 1000 °C with short 15 min holds at select temperatures during both heating and cooling while simultaneously collecting high-energy synchrotron radiation X-ray diffraction measurements. This study provides valuable insight into the kinetics of precipitation and oxide formation and its relationship to processing. In addition, scanning electron microscopy was performed on five samples, each isothermally held to examine precipitation and oxide structure and growth.

In Situ Synchrotron Radiation X-ray Diffraction Study on Phase and Oxide Growth during a High Temperature Cycle of a NiTi-20 at.% Zr High Temperature Shape Memory Alloy

NASA Astrophysics Data System (ADS)

Carl, Matthew; Van Doren, Brian; Young, Marcus L.

2018-02-01

Ternary additions to binary NiTi shape memory alloys are known to significantly affect the characteristic martensite-to-austenite phase transformation, i.e., decrease or increase transformation temperatures. High temperature shape memory alloys can be created by adding Au, Pt, Pd, Hf, or Zr to binary NiTi in appropriate amounts; however, the majority of these ternary additions are exceedingly expensive, unfortunately making them impractical for most commercial applications. Zr is the exception of the group, but it is often disregarded because of its poor workability and thermal stability. In an effort to find a temperature range that allows for the potential workability of NiTiZr alloys in normal atmosphere environments and to gain understanding as to the cause of failure during processing, a NiTi-20 at.% Zr was subjected to a thermal cycle ranging from RT to 1000 °C with short 15 min holds at select temperatures during both heating and cooling while simultaneously collecting high-energy synchrotron radiation X-ray diffraction measurements. This study provides valuable insight into the kinetics of precipitation and oxide formation and its relationship to processing. In addition, scanning electron microscopy was performed on five samples, each isothermally held to examine precipitation and oxide structure and growth.

Suppression of vacancy cluster growth in concentrated solid solution alloys

DOE PAGES

Zhao, Shijun; Velisa, Gihan; Xue, Haizhou; ...

2016-12-13

Large vacancy clusters, such as stacking-fault tetrahedra, are detrimental vacancy-type defects in ion-irradiated structural alloys. Suppression of vacancy cluster formation and growth is highly desirable to improve the irradiation tolerance of these materials. In this paper, we demonstrate that vacancy cluster growth can be inhibited in concentrated solid solution alloys by modifying cluster migration pathways and diffusion kinetics. The alloying effects of Fe and Cr on the migration of vacancy clusters in Ni concentrated alloys are investigated by molecular dynamics simulations and ion irradiation experiment. While the diffusion coefficients of small vacancy clusters in Ni-based binary and ternary solid solutionmore » alloys are higher than in pure Ni, they become lower for large clusters. This observation suggests that large clusters can easily migrate and grow to very large sizes in pure Ni. In contrast, cluster growth is suppressed in solid solution alloys owing to the limited mobility of large vacancy clusters. Finally, the differences in cluster sizes and mobilities in Ni and in solid solution alloys are consistent with the results from ion irradiation experiments.« less

Investigation of the dependence of deformation mechanisms on solute content in polycrystalline Mg–Al magnesium alloys by neutron diffraction and acoustic emission

DOE PAGES

Mathis, Kristian; Capek, J.; Clausen, Bjorn; ...

2015-04-20

Influence of aluminium content on the deformation mechanisms in Mg–Al binary alloys has been studied using in-situ neutron diffraction and acoustic emission technique. Here, it is shown that the addition of the solute increases the critical resolved shear stress for twinning. Further, the role of aluminium on the solid solution hardening of the basal plane and softening of non-basal planes are discussed using results of the convolutional multiple peak profile analysis of diffraction patterns. In conclusion, the results indicate that the density of both prismatic and pyramidal dislocations increases with increasing alloying content.

Martensitic transformation and phase diagram in ternary Co-V-Ga Heusler alloys

NASA Astrophysics Data System (ADS)

Xu, Xiao; Nagashima, Akihide; Nagasako, Makoto; Omori, Toshihiro; Kanomata, Takeshi; Kainuma, Ryosuke

2017-03-01

We report the martensitic transformation behavior in Co-V-Ga Heusler alloys. Thermoanalysis and thermomagnetization measurements were conducted to observe the martensitic transformation. By using a transmission electron microscope and an in situ X-ray diffractometer, martensitic transformation was found to occur from the L21 Heusler parent phase to the D022 martensite phase. Phase diagrams were determined for two pseudo-binary sections where martensitic transformation was detected. Magnetic properties, including the Curie temperatures and spontaneous magnetization of the parent phase, were also investigated. The magnetic properties showing behaviors different from those of NiMn-based alloys were found.

BCAT-C1 Session in the JPM

NASA Image and Video Library

2012-08-08

ISS032-E-014593 (6 Aug. 2012) --- NASA astronaut Joe Acaba, Expedition 32 flight engineer, conducts a session with the Binary Colloidal Alloy Test-6 (BCAT-6) experiment in the Kibo laboratory of the International Space Station.

The effect of an electric field on the morphological stability of the crystal-melt interface of a binary alloy. III - Weakly nonlinear theory

NASA Technical Reports Server (NTRS)

Wheeler, A. A.; Mcfadden, G. B.; Coriell, S. R.; Hurle, D. T. J.

1990-01-01

The effect of a constant electric current on the crystal-melt interface morphology during directional solidification at constant velocity of a binary alloy is considered. A linear temperature field is assumed, and thermoelectric effects and Joule heating are neglected; electromigration and differing electrical conductivities of crystal and melt are taken into account. A two-dimensional weakly nonlinear analysis is carried out to third order in the interface amplitude, resulting in a cubic amplitude equation that describes whether the bifurcation from the planar state is supercritical or subcritical. For wavelengths corresponding to the most dangerous mode of linear theory, the demarcation between supercritical and subcritical behavior is calculated as a function of processing conditions and material parameters. The bifurcation behavior is a sensitive function of the magnitude and direction of the electric current and of the electrical conductivity ratio.

A canonical stability-elasticity relationship verified for one million face-centred-cubic structures.

PubMed

Maisel, Sascha B; Höfler, Michaela; Müller, Stefan

2012-11-29

Any thermodynamically stable or metastable phase corresponds to a local minimum of a potentially very complicated energy landscape. But however complex the crystal might be, this energy landscape is of parabolic shape near its minima. Roughly speaking, the depth of this energy well with respect to some reference level determines the thermodynamic stability of the system, and the steepness of the parabola near its minimum determines the system's elastic properties. Although changing alloying elements and their concentrations in a given material to enhance certain properties dates back to the Bronze Age, the systematic search for desirable properties in metastable atomic configurations at a fixed stoichiometry is a very recent tool in materials design. Here we demonstrate, using first-principles studies of four binary alloy systems, that the elastic properties of face-centred-cubic intermetallic compounds obey certain rules. We reach two conclusions based on calculations on a huge subset of the face-centred-cubic configuration space. First, the stiffness and the heat of formation are negatively correlated with a nearly constant Spearman correlation for all concentrations. Second, the averaged stiffness of metastable configurations at a fixed concentration decays linearly with their distance to the ground-state line (the phase diagram of an alloy at zero Kelvin). We hope that our methods will help to simplify the quest for new materials with optimal properties from the vast configuration space available.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cable, J.W.

The diffuse scattering of neutrons from magnetic materials provides unique and important information regarding the spatial correlations of the atoms and the spins. Such measurements have been extensively applied to magnetically ordered systems, such as the ferromagnetic binary alloys, for which the observed correlations describe the magnetic moment fluctuations associated with local environment effects. With the advent of polarization analysis, these techniques are increasingly being applied to study disordered paramagnetic systems such as the spin-glasses and the diluted magnetic semiconductors. The spin-pair correlations obtained are essential in understanding the exchange interactions of such systems. In this paper, we describe recentmore » neutron diffuse scattering results on the atom-pair and spin-pair correlations in some of these disordered magnetic systems. 56 refs.« less

Comparative study of local atomic structures in Zr2CuxNi1-x (x = 0, 0.5, 1) metallic glasses

NASA Astrophysics Data System (ADS)

Huang, Yuxiang; Huang, Li; Wang, C. Z.; Kramer, M. J.; Ho, K. M.

2015-11-01

Extensive analysis has been performed to understand the key structural motifs accounting for the difference in glass forming ability in the Zr-Cu and Zr-Ni binary alloy systems. Here, the reliable atomic structure models of Zr2CuxNi1-x (x = 0, 0.5, 1) are constructed using the combination of X-ray diffraction experiments, ab initio molecular dynamics simulations and a constrained reverse Monte Carlo method. We observe a systematic variation of the interatomic distance of different atomic pairs with respect to the alloy composition. The ideal icosahedral content in all samples is limited, despite the high content of five-fold symmetry motifs. We also demonstrate that the population of Z-clusters in Zr2Cu glass is much higher than that in the Zr2Ni and Zr2Cu0.5Ni0.5 samples. And Z12 ⟨0, 0, 12, 0⟩ Voronoi polyhedra clusters prefer to form around Cu atoms, while Ni-centered clusters are more like Z11 ⟨0, 2, 8, 1⟩ clusters, which is less energetically stable compared to Z12 clusters. These two different structural properties may account for the higher glass forming ability of Zr2Cu alloy than that of Zr2Ni alloy.

Process for preparing schottky diode contacts with predetermined barrier heights

DOEpatents

Chang, Y. Austin; Jan, Chia-Hong; Chen, Chia-Ping

1996-01-01

A process is provided for producing a Schottky diode having a preselected barrier height .phi..sub.Bn. The substrate is preferably n-GaAs, the metallic contact is derived from a starting alloy of the Formula [.SIGMA.M.sub..delta. ](Al.sub.x Ga.sub.1-x) wherein: .SIGMA.M is a moiety which consists of at least one M, and when more than one M is present, each M is different, M is a Group VIII metal selected from the group consisting of nickel, cobalt, ruthenium, rhodium, indium and platinum, .delta. is a stoichiometric coefficient whose total value in any given .SIGMA.M moiety is 1, and x is a positive number between 0 and 1 (that is, x ranges from greater than 0 to less than 1). Also, the starting alloy is capable of forming with the substrate a two phase equilibrium reciprocal system of the binary alloy mixture [.SIGMA.M.sub..delta. ]Ga-[.SIGMA.M.sub..delta. ]Al-AlAs-GaAs. When members of an alloy subclass within this Formula are each preliminarily correlated with the barrier height .phi..sub.Bn of a contact producable therewith, then Schottky diodes of predetermined barrier heights are producable by sputtering and annealing. Further provided are the product Schottky diodes that are produced according to this process.

Microstructure and mechanical properties of a single crystal NiAl alloy with Zr or Hf rich G-phase precipitates

NASA Technical Reports Server (NTRS)

Locci, I. E.; Noebe, R. D.; Bowman, R. R.; Miner, R. V.; Nathal, M. V.; Darolia, R.

1991-01-01

The possibility of producing NiAl reinforced with the G-phase (Ni16X6Si7), where X is Zr or Hf, has been investigated. The microstructure of these NiAl alloys have been characterized in the as-cast and annealed conditions. The G-phases are present as fine cuboidal precipitates (10 to 40 nm) and have lattice parameters almost four times that of NiAl. They are coherent with the matrix and fairly resistant to coarsening during annealing heat treatments. Segregation and nonuniform precipitate distribution observed in as-cast materials were eliminated by homogenization at temperatures near 1600 K. Slow cooling from these temperatures resulted in large plate shaped precipitates, denuded zones, and a loss of coherency in some of the large particles. Faster cooling produced a homogeneous fine distribution of cuboidal G-phase particles in the matrix. Preliminary mechanical properties for the Zr-doped alloy are presented and compared to binary single crystal NiAl. The presence of these precipitates appears to have an important strengthening effect at temperatures not less than 1000 K compared to binary NiAl single crystals.

Crystal Nucleation and Growth in Undercooled Melts of Pure Zr, Binary Zr-Based and Ternary Zr-Ni-Cu Glass-Forming Alloys

NASA Astrophysics Data System (ADS)

Herlach, Dieter M.; Kobold, Raphael; Klein, Stefan

2018-03-01

Glass formation of a liquid undercooled below its melting temperature requires the complete avoidance of crystal nucleation and subsequent crystal growth. Even though they are not part of the glass formation process, a detailed knowledge of both processes involved in crystallization is mandatory to determine the glass-forming ability of metals and metallic alloys. In the present work, methods of containerless processing of drops by electrostatic and electromagnetic levitation are applied to undercool metallic melts prior to solidification. Heterogeneous nucleation on crucible walls is completely avoided giving access to large undercoolings. A freely suspended drop offers the additional benefit of showing the rapid crystallization process of an undercooled melt in situ by proper diagnostic means. As a reference, crystal nucleation and dendrite growth in the undercooled melt of pure Zr are experimentally investigated. Equivalently, binary Zr-Cu, Zr-Ni and Zr-Pd and ternary Zr-Ni-Cu alloys are studied, whose glass-forming abilities differ. The experimental results are analyzed within classical nucleation theory and models of dendrite growth. The findings give detailed knowledge about the nucleation-undercooling statistics and the growth kinetics over a large range of undercooling.

An exact solution for the solidification of a liquid slab of binary mixture

NASA Technical Reports Server (NTRS)

Antar, B. N.; Collins, F. G.; Aumalia, A. E.

1986-01-01

The time dependent temperature and concentration profiles of a one dimensional finite slab of a binary liquid alloy is investigated during solidification. The governing equations are reduced to a set of coupled, nonlinear initial value problems using the method outlined by Meyer. Two methods will be used to solve these equations. The first method uses a Runge-Kutta-Fehlberg integrator to solve the equations numerically. The second method comprises of finding closed form solutions of the equations.

Segregation effects during solidification in weightless melts. [effects of evaporation and solidification on crystalization

NASA Technical Reports Server (NTRS)

Li, C.

1975-01-01

Computer programs are developed and used in the study of the combined effects of evaporation and solidification in space processing. The temperature and solute concentration profiles during directional solidification of binary alloys with surface evaporation were mathematically formulated. Computer results are included along with an econotechnical model of crystal growth. This model allows: prediction of crystal size, quality, and cost; systematic selection of the best growth equipment or alloy system; optimization of growth or material parameters; and a maximization of zero-gravity effects. Segregation in GaAs crystals was examined along with vibration effects on GaAs crystal growth. It was found that a unique segregation pattern and strong convention currents exist in GaAs crystal growth. Some beneficial effects from vibration during GaAs growth were discovered. The implications of the results in space processing are indicated.

Modeling and Characterization of Cyclic Shape Memory Behaviors of the Binary Ni49.9Ti50.1 Material System

NASA Astrophysics Data System (ADS)

Saleeb, A. F.; Natsheh, S. H.; Owusu-Danquah, J. S.; Dhakal, B.

2017-05-01

In this work, we address two of the main challenges encountered in constitutive modeling of the thermomechanical behaviors of actuation-based shape memory alloys. Firstly, the complexity of behavior under cyclic thermomechanical loading is properly handled, particularly with regard to assessing the long-term dimensional stability. Secondly, we consider the marked differences in behavior distinguishing virgin-versus-trained SMA material. To this end, we utilize a set of experimental data comprehensive in scope to cover all the anticipated operational conditions for one and same SMA alloy, having a specific chemical composition with fixed heat treatment. More specifically, this includes twenty-four different tests from the recent SMA experimental literature for the Ni49.9Ti50.1 material having austenite finish temperature above 100 °C. Under all the different conditions investigated, the model results were found to be in very good agreement with the experimental measurements.

Solute segregation kinetics and dislocation depinning in a binary alloy

NASA Astrophysics Data System (ADS)

Dontsova, E.; Rottler, J.; Sinclair, C. W.

2015-06-01

Static strain aging, a phenomenon caused by diffusion of solute atoms to dislocations, is an important contributor to the strength of substitutional alloys. Accurate modeling of this complex process requires both atomic spatial resolution and diffusional time scales, which is very challenging to achieve with commonly used atomistic computational methods. In this paper, we use the recently developed "diffusive molecular dynamics" (DMD) method that is capable of describing the kinetics of the solute segregation process at the atomic level while operating on diffusive time scales in a computationally efficient way. We study static strain aging in the Al-Mg system and calculate the depinning shear stress between edge and screw dislocations and their solute atmospheres formed for various waiting times with different solute content and for a range of temperatures. A simple phenomenological model is also proposed that describes the observed behavior of the critical shear stress as a function of segregation level.

Solute-defect interactions in Al-Mg alloys from diffusive variational Gaussian calculations

NASA Astrophysics Data System (ADS)

Dontsova, E.; Rottler, J.; Sinclair, C. W.

2014-11-01

Resolving atomic-scale defect topologies and energetics with accurate atomistic interaction models provides access to the nonlinear phenomena inherent at atomic length and time scales. Coarse graining the dynamics of such simulations to look at the migration of, e.g., solute atoms, while retaining the rich atomic-scale detail required to properly describe defects, is a particular challenge. In this paper, we present an adaptation of the recently developed "diffusive molecular dynamics" model to describe the energetics and kinetics of binary alloys on diffusive time scales. The potential of the technique is illustrated by applying it to the classic problems of solute segregation to a planar boundary (stacking fault) and edge dislocation in the Al-Mg system. Our approach provides fully dynamical solutions in situations with an evolving energy landscape in a computationally efficient way, where atomistic kinetic Monte Carlo simulations are difficult or impractical to perform.

Theoretical study of the density of states and magnetic properties of LaCoO3

NASA Astrophysics Data System (ADS)

Zhuang, Min; Zhang, Weiyi; Hu, Cheng; Ming, Naiben

1998-05-01

The density of states and magnetic properties of low-spin, high-spin, and mixing states of LaCoO3 have been studied within the unrestricted Hartree-Fock approximation. The real-space recursion method is adopted for computing the electronic structure of the disordered system. The paramagnetic high-spin state is dealt with using the usual binary alloy coherent potential approximation (CPA); an extended trinary alloy CPA approximation is developed to describe the mixing state. In agreement with experiments, our results show that the main features of the quasiparticle spectra in the mixing state are not a sensitive function of the high-spin component, but the spectrum does get broadened due to spin scattering. The increasing of the high-spin component also results in a pileup of the density of states at the Fermi energy which indicates an insulator to metal phase transition. Some limitations of the present approach are also discussed.

The development of binary Mg-Ca alloys for use as biodegradable materials within bone.

PubMed

Li, Zijian; Gu, Xunan; Lou, Siquan; Zheng, Yufeng

2008-04-01

Binary Mg-Ca alloys with various Ca contents were fabricated under different working conditions. X-ray diffraction (XRD) analysis and optical microscopy observations showed that Mg-xCa (x=1-3 wt%) alloys were composed of two phases, alpha (Mg) and Mg2Ca. The results of tensile tests and in vitro corrosion tests indicated that the mechanical properties could be adjusted by controlling the Ca content and processing treatment. The yield strength (YS), ultimate tensile strength (UTS) and elongation decreased with increasing Ca content. The UTS and elongation of as-cast Mg-1Ca alloy (71.38+/-3.01 MPa and 1.87+/-0.14%) were largely improved after hot rolling (166.7+/-3.01 MPa and 3+/-0.78%) and hot extrusion (239.63+/-7.21 MPa and 10.63+/-0.64%). The in vitro corrosion test in simulated body fluid (SBF) indicated that the microstructure and working history of Mg-xCa alloys strongly affected their corrosion behaviors. An increasing content of Mg2Ca phase led to a higher corrosion rate whereas hot rolling and hot extrusion could reduce it. The cytotoxicity evaluation using L-929 cells revealed that Mg-1Ca alloy did not induce toxicity to cells, and the viability of cells for Mg-1Ca alloy extraction medium was better than that of control. Moreover, Mg-1Ca alloy pins, with commercial pure Ti pins as control, were implanted into the left and right rabbit femoral shafts, respectively, and observed for 1, 2 and 3 months. High activity of osteoblast and osteocytes were observed around the Mg-1Ca alloy pins as shown by hematoxylin and eosin stained tissue sections. Radiographic examination revealed that the Mg-1Ca alloy pins gradually degraded in vivo within 90 days and the newly formed bone was clearly seen at month 3. Both the in vitro and in vivo corrosion suggested that a mixture of Mg(OH)2 and hydroxyapatite formed on the surface of Mg-1Ca alloy with the extension of immersion/implantation time. In addition, no significant difference (p>0.05) of serum magnesium was detected at different degradation stages. All these results revealed that Mg-1Ca alloy had the acceptable biocompatibility as a new kind of biodegradable implant material. Based on the above results, a solid alloy/liquid solution interface model was also proposed to interpret the biocorrosion process and the associated hydroxyapatite mineralization.

High temperature properties of non-critical Fe-Al alloys doped by non critical or “slightly–critical” elements

NASA Astrophysics Data System (ADS)

Vodičková, Věra; Hanus, Pavel; Vlasák, Tomáš; Švec, Martin

2018-03-01

Iron aluminides were developed as an alternative to stainless steels after World War II. The main intended impact was to save strategic elements (chromium or nickel). The result of these investigations was development of registered alloys as Pyroferal (Czechoslovak Republic), Thugal (Soviet Union) or Thermagal (France). The investigation of these type alloys continued in the nineties thanks to technological progress. In this time iron aluminides seems to be promising material with very good corrosive and environment resistivity. The mechanical properties of binary iron aluminides (Fe-Al) are average at higher temperatures but strengthening effect of alloying elements is significant. The aim of the article is to show influence of non-critical additives (such as C, Ti, Zr) and also “slightly critical” elements as e.g. Ce, Nb on high temperature creep properties of alloys.

Vertical solidification of dendritic binary alloys

NASA Technical Reports Server (NTRS)

Heinrich, J. C.; Felicelli, S.; Poirier, D. R.

1991-01-01

Three numerical techniques are employed to analyze the influence of thermosolutal convection on defect formation in directionally solidified (DS) alloys. The finite-element models are based on the Boussinesq approximation and include the plane-front model and two plane-front models incorporating special dendritic regions. In the second model the dendritic region has a time-independent volume fraction of liquid, and in the last model the dendritic region evolves as local conditions dictate. The finite-element models permit the description of nonlinear thermosolutal convection by treating the dendritic regions as porous media with variable porosities. The models are applied to lead-tin alloys including DS alloys, and severe segregation phenomena such as freckles and channels are found to develop in the DS alloys. The present calculations and the permeability functions selected are shown to predict behavior in the dendritic regions that qualitatively matches that observed experimentally.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, L. L.; Wang, Y. D.; Ren, Y.

Microstructure evolution, mechanical behaviors of cold rolled Ti-Nb alloys with different Nb contents subjected to different heat treatments were investigated. Here, optical microstructure and phase compositions of Ti-Nb alloys were characterized using optical microscopy and X-ray diffractometre, while mechanical behaviors of Ti-Nb alloys were examined by using tension tests. Stress-induced martensitic transformation in a Ti-30. at%Nb binary alloy was in-situ explored by synchrotron-based high-energy X-ray diffraction (HE-XRD). The results obtained suggested that mechanical behavior of Ti-Nb alloys, especially Young's modulus was directly dependent on chemical compositions and heat treatment process. According to the results of HE-XRD, α"-V1 martensite generated priormore » to the formation of α"-V2 during loading and a partial reversible transformation from α"-V1 to β phase was detected while α"-V2 tranformed to β completely during unloading.« less

Structural and electronic transport properties of compound forming HgPb liquid alloy using ab-initio pseudopotential

NASA Astrophysics Data System (ADS)

Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

2013-02-01

The electrical resistivity of compound forming liquid alloy HgPb is studied as a function of concentration. Hard sphere diameters of Hg and Pb are obtained through the inter-ionic pair potential evaluated using Troullier and Martins ab initio pseudopotential, which have been used to calculate partial structure factors. Considering the liquid alloy to be a ternary mixture Ziman's formula for calculating the resistivity of binary liquid alloys, modified for complex formation, has been used. The concentration dependence in resistivity occurs due to preferential ordering of unlike atoms as nearest neighbours with help of complex formation model. Though the compound HgiPbi as per structure peaks is found to be less stable. However it contributes significantly to resistivity as compared to bare ions.

Effect of atomic size on undercoolability of binary solid solution alloy liquids with Zr, Ti, and Hf using electrostatic levitation

NASA Astrophysics Data System (ADS)

Jeon, S.; Kang, D.-H.; Lee, Y. H.; Lee, S.; Lee, G. W.

2016-11-01

We investigate the relationship between the excess volume and undercoolability of Zr-Ti and Zr-Hf alloy liquids by using electrostatic levitation. Unlike in the case of Zr-Hf alloy liquids in which sizes of the constituent atoms are matched, a remarkable increase of undercoolability and negative excess volumes are observed in Zr-Ti alloy liquids as a function of their compositional ratios. In this work, size mismatch entropies for the liquids were obtained by calculating their hard sphere diameters, number densities, and packing fractions. We also show that the size mismatch entropy, which arises from the differences in atomic sizes of the constituent elements, plays an important role in determining the stabilities of metallic liquids.

Irradiation-enhanced α' precipitation in model FeCrAl alloys

DOE PAGES

Edmondson, Philip D.; Briggs, Samuel A.; Yamamoto, Yukinori; ...

2016-02-17

We have irradiated the model FeCrAl alloys with varying compositions (Fe(10–18)Cr(10–6)Al at.%) with a neutron at ~ 320 to damage levels of ~ 7 displacements per atom (dpa) to investigate the compositional influence on the formation of irradiation-induced Cr-rich α' precipitates using atom probe tomography. In all alloys, significant number densities of these precipitates were observed. Cluster compositions were investigated and it was found that the average cluster Cr content ranged between 51.1 and 62.5 at.% dependent on initial compositions. Furthermore, this is significantly lower than the Cr-content of α' in binary FeCr alloys. As a result, significant partitioning ofmore » the Al from the α' precipitates was also observed.« less

Spin-diffusions and diffusive molecular dynamics

NASA Astrophysics Data System (ADS)

Farmer, Brittan; Luskin, Mitchell; Plecháč, Petr; Simpson, Gideon

2017-12-01

Metastable configurations in condensed matter typically fluctuate about local energy minima at the femtosecond time scale before transitioning between local minima after nanoseconds or microseconds. This vast scale separation limits the applicability of classical molecular dynamics (MD) methods and has spurned the development of a host of approximate algorithms. One recently proposed method is diffusive MD which aims at integrating a system of ordinary differential equations describing the likelihood of occupancy by one of two species, in the case of a binary alloy, while quasistatically evolving the locations of the atoms. While diffusive MD has shown itself to be efficient and provide agreement with observations, it is fundamentally a model, with unclear connections to classical MD. In this work, we formulate a spin-diffusion stochastic process and show how it can be connected to diffusive MD. The spin-diffusion model couples a classical overdamped Langevin equation to a kinetic Monte Carlo model for exchange amongst the species of a binary alloy. Under suitable assumptions and approximations, spin-diffusion can be shown to lead to diffusive MD type models. The key assumptions and approximations include a well-defined time scale separation, a choice of spin-exchange rates, a low temperature approximation, and a mean field type approximation. We derive several models from different assumptions and show their relationship to diffusive MD. Differences and similarities amongst the models are explored in a simple test problem.

BCAT5 Video Setup In JEM

NASA Image and Video Library

2011-09-21

ISS029-E-010998 (21 Sept. 2011) --- NASA astronaut Mike Fossum, Expedition 29 commander, prepares a camcorder for recording documentary video of the Binary Colloidal Alloy Test-5 (BCAT-5) payload operations in the Kibo laboratory of the International Space Station.

Burbank during session with BCAT-6 Experiment in the JPM

NASA Image and Video Library

2012-02-08

ISS030-E-063961 (8 Feb. 2012) --- NASA astronaut Dan Burbank, Expedition 30 commander, conducts a session with the Binary Colloidal Alloy Test-6 (BCAT-6) experiment in the Kibo laboratory of the International Space Station.

Burbank during session with BCAT-6 Experiment in the JPM

NASA Image and Video Library

2012-02-08

ISS030-E-063957 (8 Feb. 2012) --- NASA astronaut Dan Burbank, Expedition 30 commander, conducts a session with the Binary Colloidal Alloy Test-6 (BCAT-6) experiment in the Kibo laboratory of the International Space Station.

BCAT5 Video Setup In JEM

NASA Image and Video Library

2011-09-21

ISS029-E-010999 (21 Sept. 2011) --- NASA astronaut Mike Fossum, Expedition 29 commander, prepares a camcorder for recording documentary video of the Binary Colloidal Alloy Test-5 (BCAT-5) payload operations in the Kibo laboratory of the International Space Station.

DFT study of hydrogen production from formic acid decomposition on Pd-Au alloy nanoclusters

NASA Astrophysics Data System (ADS)

Liu, D.; Gao, Z. Y.; Wang, X. C.; Zeng, J.; Li, Y. M.

2017-12-01

Recently, it has been reported that the hydrogen production rate of formic acid decomposition can be significantly increased using Pd-Au binary alloy nano-catalysts [Wang et al. J. Mater. Chem. A 1 (2013) 12721-12725]. To explain the reaction mechanism of this alloy catalysis method, formic acid decomposition reactions on pure Pd and Pd-Au alloy nanoclusters are studied via density functional theory simulations. The simulation results indicate that the addition of inert element Au would not influence formic acid decomposition on Pd surface sites of Pd-Au alloy nanoclusters. On the other hand, the existence of Au surface sites brings relative weak hydrogen atom adsorption. On Pd-Au alloy nanoclusters, the dissociated hydrogen atoms from formic acid are easier to combine as hydrogen molecules than that on pure Pd clusters. Via the synergetic effect between Pd and Au, both formic acid decomposition and hydrogen production are events with large probability, which eventually results in high hydrogen production rate.

Enhanced Oxygen Diffusion Within the Internal Oxidation Zone of Alloy 617 in Controlled Impurity Helium Environments from 1023 K to 1123 K (750 °C to 850 °C)

NASA Astrophysics Data System (ADS)

Gulsoy, Gokce; Was, Gary S.

2015-04-01

Alloy 617 was exposed to He-CO-CO2 environments with of either 9 or 1320 at temperatures from 1023 K to 1123 K (750 °C to 850 °C) to determine the oxygen diffusion coefficients within the internal oxidation zone of the alloy. The oxygen diffusion coefficients determined based on both intergranular and transgranular oxidation rates were several orders of magnitude greater than those reported in pure nickel and in nickel-based binary alloys, indicating that the rapid internal aluminum oxidation of Alloy 617 was primarily due to enhanced oxygen diffusion along the incoherent Al2O3-alloy interfaces. The range of activation energy values determined for oxygen diffusion associated with the intergranular aluminum oxidation was from 149.6 to 154.7 kJ/mol, and that associated with the transgranular aluminum oxidation was from 244.7 to 283.5 kJ/mol.

Perpendicular Magnetic Anisotropy in Heusler Alloy Films and Their Magnetoresistive Junctions

PubMed Central

Frost, William; Samiepour, Marjan

2018-01-01

For the sustainable development of spintronic devices, a half-metallic ferromagnetic film needs to be developed as a spin source with exhibiting 100% spin polarisation at its Fermi level at room temperature. One of the most promising candidates for such a film is a Heusler-alloy film, which has already been proven to achieve the half-metallicity in the bulk region of the film. The Heusler alloys have predominantly cubic crystalline structures with small magnetocrystalline anisotropy. In order to use these alloys in perpendicularly magnetised devices, which are advantageous over in-plane devices due to their scalability, lattice distortion is required by introducing atomic substitution and interfacial lattice mismatch. In this review, recent development in perpendicularly-magnetised Heusler-alloy films is overviewed and their magnetoresistive junctions are discussed. Especially, focus is given to binary Heusler alloys by replacing the second element in the ternary Heusler alloys with the third one, e.g., MnGa and MnGe, and to interfacially-induced anisotropy by attaching oxides and metals with different lattice constants to the Heusler alloys. These alloys can improve the performance of spintronic devices with higher recording capacity. PMID:29324709

Study of Ni-Mo electrodeposition in direct and pulse-reverse current

NASA Astrophysics Data System (ADS)

Stryuchkova, Yu M.; Rybin, N. B.; Suvorov, D. V.; Gololobov, G. P.; Tolstoguzov, A. B.; Tarabrin, D. Yu; Serpova, M. A.; Korotchenko, V. A.; Slivkin, E. V.

2017-05-01

Process of electrochemical deposition of the coating based on a binary nickel-molybdenum alloy onto a nickel substrate under pulse mode with current reverse within the range of current density change from 2 to 9 A/dm2 has been researched. Coating structure and its surface morphology have been studied. Method of X-ray energy dispersive spectroscopy has determined a percentage ratio of alloy components in the coating. Mode to obtain the densest and smoothest deposits has been identified under considered terms.

Prediction of Formation of Amorphous Alloys During Annealing of Ti-binary Alloys and Validation of the Same

DTIC Science & Technology

2009-11-22

The authors argued that the occurrence of the reversible step in the specific heat reflected “the freezing and unfreezing of some degree of freedom...of steel, the austenite phase is sometimes formed in a composition range where ferrite and liquid are the equilibrium phases. The formation of the...austenite is explained by the construction of a meta-stable extension of the (austenite+liquid) field into the ( ferrite +liquid) region. The

An Assessment of Binary Metallic Glasses: Correlations Between Structure, Glass Forming Ability and Stability (Preprint)

DTIC Science & Technology

2009-04-01

Cu, germanium and tellurium ," J. Mat. Sci., vol. 9, pp. 707-717, 1974. [29] A. Inoue, T. Zhang, K. Kita, and T. Masumoto, "Mechanical strengths...Toribuchi, K. Aoki, and T. Masumoto, "Formation of La-M- Cu (M=Ca, Sr or Ba) amorphous alloys and their oxidization and superconductivity," Trans. JIM...structure of Pd- Ge alloys glasses by pulsed neutron total scattering," presented at Proc. 4 th International Conference on Rapidly Quenched Metals

Metastable Polymeric Nitrogen From N2H2 Alloys

DTIC Science & Technology

2008-12-01

dioxide [Iota et al., 2oo7J and oxygen [MililZer and Hemley, 2006] and rich phase diagrams have been derived for each. However, the r~overy of the... oxygen , may lead to the stabilization of ordered extended molecular solid phases [Vos et aI., 1992; Loubeyre et a!., 1993; Somayazulu et al., 1996...and SlI7.hemechny, M.A., 2007: Structure of quench condensed nl·lz-Nl binary alloys: isotope effect, Low Temp. Phys. 33, 499 - 503. Goncharov, A.F

Investigation of High Temperature Ductility Losses in Alpha-Beta Titanium Alloys

DTIC Science & Technology

1988-04-01

Gleeble simulation of GTAW thermal _ cycles, Figure 1.1 (6). They found that Ti-6AI-4V (Ti-64), Ti-6A1-2Nb-lTa-0.8Mo (Ti-6211), and Ti-6AI suffered...or weak beta stabilizers depending on the other alloying elements present. Vanadium, molybdenum, tantalum, niobium, chromium , silicon, copper...elements. Chromium , - silicon, copper, manganese, cobalt, iron, and hydrogen are all eutectic formers. A schematic binary phase diagram of a 0 beta

Development of an inter-atomic potential for the Pd-H binary system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zimmerman, Jonathan A.; Hoyt, Jeffrey John; Leonard, Francois Leonard

2007-09-01

Ongoing research at Sandia National Laboratories has been in the area of developing models and simulation methods that can be used to uncover and illuminate the material defects created during He bubble growth in aging bulk metal tritides. Previous efforts have used molecular dynamics calculations to examine the physical mechanisms by which growing He bubbles in a Pd metal lattice create material defects. However, these efforts focused only on the growth of He bubbles in pure Pd and not on bubble growth in the material of interest, palladium tritide (PdT), or its non-radioactive isotope palladium hydride (PdH). The reason formore » this is that existing inter-atomic potentials do not adequately describe the thermodynamics of the Pd-H system, which includes a miscibility gap that leads to phase separation of the dilute (alpha) and concentrated (beta) alloys of H in Pd at room temperature. This document will report the results of research to either find or develop inter-atomic potentials for the Pd-H and Pd-T systems, including our efforts to use experimental data and density functional theory calculations to create an inter-atomic potential for this unique metal alloy system.« less

Beyond Atomic Sizes and Hume-Rothery Rules: Understanding and Predicting High-Entropy Alloys

DOE PAGES

Troparevsky, M. Claudia; Morris, James R.; Daene, Markus; ...

2015-09-03

High-entropy alloys constitute a new class of materials that provide an excellent combination of strength, ductility, thermal stability, and oxidation resistance. Although they have attracted extensive attention due to their potential applications, little is known about why these compounds are stable or how to predict which combination of elements will form a single phase. Here, we present a review of the latest research done on these alloys focusing on the theoretical models devised during the last decade. We discuss semiempirical methods based on the Hume-Rothery rules and stability criteria based on enthalpies of mixing and size mismatch. To provide insightsmore » into the electronic and magnetic properties of high-entropy alloys, we show the results of first-principles calculations of the electronic structure of the disordered solid-solution phase based on both Korringa Kohn Rostoker coherent potential approximation and large supercell models of example face-centered cubic and body-centered cubic systems. Furthermore, we discuss in detail a model based on enthalpy considerations that can predict which elemental combinations are most likely to form a single-phase high-entropy alloy. The enthalpies are evaluated via first-principles high-throughput density functional theory calculations of the energies of formation of binary compounds, and therefore it requires no experimental or empirically derived input. Finally, the model correctly accounts for the specific combinations of metallic elements that are known to form single-phase alloys while rejecting similar combinations that have been tried and shown not to be single phase.« less

The Effects of Adding Elements of Zinc and Magnesium on Ag-Cu Eutectic Alloy for Warming Acupuncture

PubMed Central

Park, Il Song; Kim, Keun Sik; Lee, Min Ho

2013-01-01

The warming acupuncture for hyperthermia therapy is made of STS304. However, its needle point cannot be reached to a desirable temperature due to heat loss caused by low thermal conductivity, and the quantification of stimulation condition and the effective standard establishment of warming acupuncture are required as a heat source. Accordingly, in this study, after Ag-Cu alloys with different composition ratios were casted and then mixed with additives to improve their physical and mechanical properties, the thermal conductivity and biocompatibility of the alloy specimens were evaluated for selecting suitable material. Ag-Cu binary alloys and ternary alloys added 5 wt% Zn or 2 wt% Mg were casted and then cold drawn to manufacture needles for acupuncture, and their physical properties, thermal conductivity, and biocompatibility were evaluated for their potential use in warming acupuncture. The results of this study showed that the physical and mechanical properties of the Ag-Cu alloys were improved by additives and that the thermal conductivity, machinability, and biocompatibility of the Ag-Cu alloys were improved by Mg addition. PMID:24078827

The effects of adding elements of zinc and magnesium on ag-cu eutectic alloy for warming acupuncture.

PubMed

Kim, Yu Kyoung; Park, Il Song; Kim, Keun Sik; Lee, Min Ho

2013-01-01

The warming acupuncture for hyperthermia therapy is made of STS304. However, its needle point cannot be reached to a desirable temperature due to heat loss caused by low thermal conductivity, and the quantification of stimulation condition and the effective standard establishment of warming acupuncture are required as a heat source. Accordingly, in this study, after Ag-Cu alloys with different composition ratios were casted and then mixed with additives to improve their physical and mechanical properties, the thermal conductivity and biocompatibility of the alloy specimens were evaluated for selecting suitable material. Ag-Cu binary alloys and ternary alloys added 5 wt% Zn or 2 wt% Mg were casted and then cold drawn to manufacture needles for acupuncture, and their physical properties, thermal conductivity, and biocompatibility were evaluated for their potential use in warming acupuncture. The results of this study showed that the physical and mechanical properties of the Ag-Cu alloys were improved by additives and that the thermal conductivity, machinability, and biocompatibility of the Ag-Cu alloys were improved by Mg addition.

Microstructure and properties of Ti-Fe-Y alloy fabricated by laser-aided direct metal deposition

NASA Astrophysics Data System (ADS)

Wang, Cunshan; Han, Liying

2018-04-01

Ti-Fe-Y alloys were designed using a "cluster-plus-glue-atom" model and then were prepared by laser-aided direct metal deposition (LDMD) on a pure titanium substrate. The influence of the Y addition on the microstructure and properties of the alloys were investigated. The results show that the alloys are composed of β-Ti solid solution and FeTi compound. The addition of Y not only suppresses the formation of Ti4Fe2O oxide but also increases the supercooling degree of the melt, leading to the grain refinement and the increase in the solid solution of the β-Ti. Meanwhile, the microstructure changes sequentially from eutectic to hypereutectic to hypoeutectic with the increasing of the Y addition. The strengest Ti-Fe-Y alloy has a dispersed eutectic structure and exhibits a good combination of mechanical, tribological, and forming properties, which is superior to that obtained for the binary Ti70.6Fe29.4 eutectic alloy. This makes the alloy a promising candidate as a LDMD material.

First-principles screening of structural properties of intermetallic compounds on martensitic transformation

NASA Astrophysics Data System (ADS)

Lee, Joohwi; Ikeda, Yuji; Tanaka, Isao

2017-11-01

Martensitic transformation with good structural compatibility between parent and martensitic phases are required for shape memory alloys (SMAs) in terms of functional stability. In this study, first-principles-based materials screening is systematically performed to investigate the intermetallic compounds with the martensitic phases by focusing on energetic and dynamical stabilities as well as structural compatibility with the parent phase. The B2, D03, and L21 crystal structures are considered as the parent phases, and the 2H and 6M structures are considered as the martensitic phases. In total, 3384 binary and 3243 ternary alloys with stoichiometric composition ratios are investigated. It is found that 187 alloys survive after the screening. Some of the surviving alloys are constituted by the chemical elements already widely used in SMAs, but other various metallic elements are also found in the surviving alloys. The energetic stability of the surviving alloys is further analyzed by comparison with the data in Materials Project Database (MPD) to examine the alloys whose martensitic structures may cause further phase separation or transition to the other structures.

Hydrogen storage as a hydride. Citations from the International Aerospace Abstracts data base

NASA Technical Reports Server (NTRS)

Zollars, G. F.

1980-01-01

These citations from the international literature concern the storage of hydrogen in various metal hydrides. Binary and intermetallic hydrides are considered. Specific alloys discussed are iron titanium, lanthanium nickel, magnesium copper and magnesium nickel among others.

Kelly takes photo of BCAT-5 Payload Setup

NASA Image and Video Library

2011-02-23

ISS026-E-028666 (23 Feb. 2011) --- NASA astronaut Scott Kelly, Expedition 26 commander, uses a digital still camera to photograph the Binary Colloidal Alloy Test-5 (BCAT-5) payload setup in the Kibo laboratory of the International Space Station.

Thermodynamic properties of calcium-bismuth alloys determined by emf measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, H; Boysen, DA; Bradwell, DJ

2012-01-15

The thermodynamic properties of Ca-Bi alloys were determined by electromotive force (emf) measurements to assess the suitability of Ca-Bi electrodes for electrochemical energy storage applications. Emf was measured at ambient pressure as a function of temperature between 723 K and 1173 K using a Ca(s)vertical bar CaF2(s)vertical bar Ca(in Bi) cell for twenty different Ca-Bi alloys spanning the entire range of composition from chi(Ca) = 0 to 1. Reported are the temperature-independent partial molar entropy and enthalpy of calcium for each Ca-Bi alloy. Also given are the measured activities of calcium, the excess partial molar Gibbs energy of bismuth estimatedmore » from the Gibbs-Duhem equation, and the integral change in Gibbs energy for each Ca-Bi alloy at 873 K, 973 K, and 1073 K. Calcium activities at 973 K were found to be nearly constant at a value a(Ca) = 1 x 10(-8) over the composition range chi(Ca) = 0.32-0.56, yielding an emf of similar to 0.77 V. Above chi(Ca) = 0.62 and coincident with Ca5Bi3 formation, the calcium activity approached unity. The Ca-Bi system was also characterized by differential scanning calorimetry over the entire range of composition. Based upon these data along with the emf measurements, a revised Ca-Bi binary phase diagram is proposed. (C) 2011 Elsevier Ltd. All rights reserved.« less

Improvement of Corrosion Resistance of Binary Mg-Ca Alloys Using Duplex Aluminum-Chromium Coatings

NASA Astrophysics Data System (ADS)

Daroonparvar, Mohammadreza; Yajid, Muhamad Azizi Mat; Yusof, Noordin Mohd; Bakhsheshi-Rad, Hamid Reza; Adabi, Mohsen; Hamzah, Esah; Kamali, Hussein Ali

2015-07-01

Al-AlCr was coated on Mg-Ca and Mg-Zn-Ce-La alloys using physical vapor deposition method. The surface morphology of the specimens was characterized by x-ray diffraction, scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and atomic force microscopy (AFM). The AFM results indicated that the average surface roughness of Al-AlCr coating on the Mg-Ca alloy is much lower than that of Al-AlCr coating on the Mg-Zn-Ce-La alloy. However, Al-AlCr coating on the Mg-Ca alloy presented a more compact structure with fewer pores, pinholes, and cracks than Al-AlCr coating on the Mg-Zn-Ce-La alloy. Electrochemical studies revealed that the novel coating (Al-AlCr) can remarkably reduce the corrosion rate of the Mg-Ca alloy in 3.5 wt.% NaCl solution. It was seen that the anodic current density of the Al-AlCr-coated Mg-Ca alloy was very small when compared to the Al-AlCr-coated Mg-Zn-Ce-La and uncoated alloys. Impedance modulus ( Z) of the Al-AlCr-coated samples was higher than that of the bare Mg alloys. Z of Al-AlCr-coated Mg-Ca alloy was higher than that of the Al-AlCr-coated Mg-Zn-Ce-La alloy at low frequency.

A comparative study of the microstructures observed in statically cast and continuously cast Bi-In-Sn ternary eutectic alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengupta, S.; Soda, H.; McLean, A.

2000-01-01

A ternary eutectic alloy with a composition of 57.2 pct Bi, 24.8 pct In, and 18 pct Sn was continuously cast into wire of 2 mm diameter with casting speeds of 14 and 79 mm/min using the Ohno Continuous Casting (OCC) process. The microstructures obtained were compared with those of statically cast specimens. Extensive segregation of massive Bi blocks, Bi complex structures, and tin-rich dendrites was found in specimens that were statically cast. Decomposition of {radical}Sn by a eutectoid reaction was confirmed based on microstructural evidence. Ternary eutectic alloy with a cooling rate of approximately 1 C/min formed a doublemore » binary eutectic. The double binary eutectic consisted of regions of BiIn and decomposed {radical}Sn in the form of a dendrite cell structure and regions of Bi and decomposed {radical}Sn in the form of a complex-regular cell. The Bi complex-regular cells, which are a ternary eutectic constituent, existed either along the boundaries of the BiIn-decomposed {radical}Sn dendrite cells or at the front of elongated dendrite cell structures. In the continuously cast wires, primary Sn dendrites coupled with a small Bi phase were uniformly distributed within the Bi-In alloy matrix. Neither massive Bi phase, Bi complex-regular cells, no BiIn eutectic dendrite cells were observed, resulting in a more uniform microstructure in contrast to the heavily segregated structures of the statically cast specimens.« less

Float processing of high-temperature complex silicate glasses and float baths used for same

NASA Technical Reports Server (NTRS)

Cooper, Reid Franklin (Inventor); Cook, Glen Bennett (Inventor)

2000-01-01

A float glass process for production of high melting temperature glasses utilizes a binary metal alloy bath having the combined properties of a low melting point, low reactivity with oxygen, low vapor pressure, and minimal reactivity with the silicate glasses being formed. The metal alloy of the float medium is exothermic with a solvent metal that does not readily form an oxide. The vapor pressure of both components in the alloy is low enough to prevent deleterious vapor deposition, and there is minimal chemical and interdiffusive interaction of either component with silicate glasses under the float processing conditions. Alloys having the desired combination of properties include compositions in which gold, silver or copper is the solvent metal and silicon, germanium or tin is the solute, preferably in eutectic or near-eutectic compositions.

Suzuki segregation in a binary Cu-Si alloy.

PubMed

Mendis, Budhika G; Jones, Ian P; Smallman, Raymond E

2004-01-01

Suzuki segregation to stacking faults and coherent twin boundaries has been investigated in a Cu-7.15 at.% Si alloy, heat-treated at temperatures of 275, 400 and 550 degrees C, using field-emission gun transmission electron microscopy. Silicon enrichment was observed at the stacking fault plane and decreased monotonically with increasing annealing temperature. This increase in the concentration of solute at the fault is due to the stacking fault energy being lowered at higher values of the electron-to-atom ratio of the alloy. From a McLean isotherm, the binding energy for segregation was calculated to be -0.021 +/- 0.019 eV atom(-1). Hardly any segregation was observed to coherent twin boundaries in the same alloy. This is because a twin has a lower interfacial energy than a stacking fault, so that the driving force for segregation is diminished.

Mössbauer study of oxide films of Fe-, Sn-, Cr- doped zirconium alloys during corrosion in autoclave

NASA Astrophysics Data System (ADS)

Filippov, V. P.; Bateev, A. B.; Lauer, Yu. A.

2016-12-01

Mössbauer investigations were used to compare iron atom states in oxide films of binary Zr-Fe, ternary Zr-Fe-Cu and quaternary Zr-Fe-Cr-Sn alloys. Oxide films are received in an autoclave at a temperature of 350-360 °C and at pressure of 16.8 MPa. The corrosion process decomposes the intermetallic precipitates in alloys and forms metallic iron with inclusions of chromium atoms α-Fe(Cr), α-Fe(Cu), α-Fe 2O3 and Fe 3O4 compounds. Some iron ions are formed in divalent and in trivalent paramagnetic states. The additional doping influences on corrosion kinetics and concentration of iron compounds and phases formed in oxide films. It was shown the correlation between concentration of iron in different chemical states and corrosion resistance of alloys.

McArthur photographs BCAT-3 samples during Expedition 12

NASA Image and Video Library

2005-11-11

ISS012-E-07685 (11 Nov. 2005) --- Astronaut William S. (Bill) McArthur Jr., Expedition 12 commander and NASA space station science officer, photographs Binary Colloidal Alloy Test-3 (BCAT-3) experiment samples in the Destiny laboratory of the international space station.

Coleman takes photo of BCAT-5 Payload Setup

NASA Image and Video Library

2011-02-23

ISS026-E-028660 (23 Feb. 2011) --- NASA astronaut Catherine (Cady) Coleman, Expedition 26 flight engineer, uses a digital still camera to photograph the Binary Colloidal Alloy Test-5 (BCAT-5) payload setup in the Kibo laboratory of the International Space Station.

Optical Studies of model binary miscibility gap system

NASA Technical Reports Server (NTRS)

Lacy, L. L.; Witherow, W. K.; Facemire, B. R.; Nishioka, G. M.

1982-01-01

In order to develop a better understanding of separation processes in binary miscibility gap metal alloys, model transparent fluid systems were studied. The system selected was diethylene glycol-ethyl salicylate which has convenient working temperatures (288 to 350 K), low toxicity, and is relatively easy to purify. The system is well characterized with respect to its phase diagram, density, surface and interfacial tensions, viscosity and other pertinent physical properties. Studies of migration of the dispersed phase in a thermal gradient were performed using conventional photomicroscopy. Velocities of the droplets of the dispersed phase were measured and compared to calculated rates which included both Stokes and thermal components. A holographic microscopy system was used to study growth, coalescence, and particle motions. Sequential holograms allowed determination of particle size distribution changes with respect to time and temperature. Holographic microscopy is capable of recording particle densities up to 10 to the 7th power particles/cu cm and is able to resolve particles of the order of 2 to 3 microns in diameter throughout the entire volume of the test cell. The reconstructed hologram produces a wavefront that is identical to the original wavefront as it existed when the hologram was made. The reconstructed wavefront is analyzed using a variety of conventional optical methods.

Prediction and characterization of heat-affected zone formation in tin-bismuth alloys due to nickel-aluminum multilayer foil reaction

DOE PAGES

Hooper, R. J.; Davis, C. G.; Johns, P. M.; ...

2015-06-26

Reactive multilayer foils have the potential to be used as local high intensity heat sources for a variety of applications. In this study, most of the past research effort concerning these materials have focused on understanding the structure-property relationships of the foils that govern the energy released during a reaction. To improve the ability of researchers to more rapidly develop technologies based on reactive multilayer foils, a deeper and more predictive understanding of the relationship between the heat released from the foil and microstructural evolution in the neighboring materials is needed. This work describes the development of a numerical modelmore » for the purpose of predicting heat affected zone size in substrate materials. The model is experimentally validated using a commercially available Ni-Al multilayer foils and alloys from the Sn-Bi binary system. To accomplish this, phenomenological models for predicting the variation of physical properties (i.e., thermal conductivity, density, and heat capacity) with temperature and composition in the Sn-Bi system were utilized using literature data.« less

Formation of amorphous materials

DOEpatents

Johnson, William L.; Schwarz, Ricardo B.

1986-01-01

Metastable amorphous or fine crystalline materials are formed by solid state reactions by diffusion of a metallic component into a solid compound or by diffusion of a gas into an intermetallic compound. The invention can be practiced on layers of metals deposited on an amorphous substrate or by intermixing powders with nucleating seed granules. All that is required is that the diffusion of the first component into the second component be much faster than the self-diffusion of the first component. The method is practiced at a temperature below the temperature at which the amorphous phase transforms into one or more crystalline phases and near or below the temperature at which the ratio of the rate of diffusion of the first component to the rate of self-diffusion is at least 10.sup.4. This anomalous diffusion criteria is found in many binary, tertiary and higher ordered systems of alloys and appears to be found in all alloy systems that form amorphous materials by rapid quenching. The method of the invention can totally convert much larger dimensional materials to amorphous materials in practical periods of several hours or less.

Metastable phase in binary and ternary 12-carat gold alloys at low temperature

NASA Astrophysics Data System (ADS)

Lamiri, Imene; Abdelbaky, Mohammed S. M.; Hamana, Djamel; García-Granda, Santiago

2018-04-01

Low temperature phase transitions in 12-carat gold alloys have been investigated for binary Au-Cu and ternary Au-Cu-Ag compositions. The thermal analyses investigations using differential scanning calorimetry (DSC) and the dilatometry were performed in the 50–300 °C temperature range in order to detect the structural transformations. The thermal analyses were carried out on annealed samples at 700 °C for two hour followed by water quenching. They reveal an important new reaction for both used compositions and both thermal techniques confirm each other. This reaction has been assessed as pre-ordering reaction. SEM and STM imaging were performed on annealed samples at 700 °C for two hours and water quenched followed by a heating from room temperature up to the temperature of the new peaks obtained in the thermal study. The imaging reveals the relationship between the pre-ordering reaction and the surface aspect presented in the fact of dendrite precipitates. A series of SEM observation have been performed in order to follow the kinetic of the observed precipitates by the way of several series of heating up, from 140 to 220 °C for the binary composition and from 100 to 180 °C for the ternary composition. Furthermore, this study shows that the silver accelerates the ordering reaction.

Lattice misfits in four binary Ni-Base γ/γ1 alloys at ambient and elevated temperatures

NASA Astrophysics Data System (ADS)

Kamara, A. B.; Ardell, A. J.; Wagner, C. N. J.

1996-10-01

High-temperature X-ray diffractometry was used to determine the in situlattice parameters, a γ and a γ', and lattice misfits, δ = ( a γ', - a γ)/ a γ, of the matrix (γ) and dispersed γ'-type (Ni3X) phases in polycrystalline binary Ni-Al, Ni-Ga, Ni-Ge, and Ni-Si alloys as functions of temperature, up to about 680 °C. Concentrated alloys containing large volume fractions of the γ' phase (˜0.40 to 0.50) were aged at 700 °C to produce large, elastically unconstrained precipitates. The room-temperature misfits are 0.00474 (Ni-Al), 0.01005 (Ni-Ga), 0.00626 (Ni-Ge), and -0.00226 (Ni-Si), with an estimated error of ± 4 pct. The absolute values of the lattice constants of the γ and γ' phases, at compositions corresponding to thermodynamic equilibrium at about 700 °C, are in excellent agreement with data from the literature, with the exception of Ni3Ga, the lattice constant of which is much larger than expected. In Ni-Ge alloys, δ decreases to 0.00612 at 679 °C, and in Ni-Ga alloys, the decrease is to 0.0097. In Ni-Si and Ni-Al alloys, δ exhibits a stronger temperature dependence, changing to-0.00285 at 683 °C (Ni-Si) and to 0.00424 at 680 °C (Ni-Al). Since the times required to complete the high-temperature X-ray diffraction (XRD) scans were relatively short (2.5 hours at most), we believe that the changes in δ observed are attributable to differences between the thermal expansion coefficients of the γ and γ' phases, because the compositions of the phases in question reflect the equilibrium compositions at 700 δC. Empirical equations are presented that accurately describe the temperature dependences of a γ, a γ', and δ over the range of temperatures of this investigation.

Investigations on Laser Beam Welding of Different Dissimilar Joints of Steel and Aluminum Alloys for Automotive Lightweight Construction

NASA Astrophysics Data System (ADS)

Seffer, Oliver; Pfeifer, Ronny; Springer, André; Kaierle, Stefan

Due to the enormous potential of weight saving, and the consequential reduction of pollutant emissions, the use of hybrid components made of steel and aluminum alloys is increasing steadily, especially concerning automotive lightweight construction. However, thermal joining of steel and aluminum is still being researched, due to a limited solubility of the binary system of iron and aluminum causing the formation of hard and brittle intermetallic phases, which decrease the strength and the formability of the dissimilar seam. The presented results show the investigation of laser beam welding for joining different dissimilar hybrid components of the steel materials HX220LAD+Z100, 22MnB5+AS150 and 1.4301, as well as the aluminum alloy AA6016-T4 as a lap joint. Among other things, the influences of the energy per unit length, the material grade, the sheet thickness t, the weld type (lap weld, fillet weld) and the arrangement of the base materials in a lap joint (aluminum-sided irradiation, steel-sided irradiation) on the achievable strengths are analyzed. The characterization of the dissimilar joints includes tensile shear tests and metallographic analyses, depending on the energy per unit length.

Controlling Surface Chemistry of Gallium Liquid Metal Alloys to Enhance their Fluidic Properties

NASA Astrophysics Data System (ADS)

Ilyas, Nahid; Cumby, Brad; Cook, Alexander; Durstock, Michael; Tabor, Christopher; Materials; Manufacturing Directorate Team

Gallium liquid metal alloys (GaLMAs) are one of the key components of emerging technologies in reconfigurable electronics, such as tunable radio frequency antennas and electronic switches. Reversible flow of GaLMA in microchannels of these types of devices is hindered by the instantaneous formation of its oxide skin in ambient environment. The oxide film sticks to most surfaces leaving unwanted metallic residues that can cause undesired electronic properties. In this report, residue-free reversible flow of a binary alloy of gallium (eutectic gallium indium) is demonstrated via two types of surface modifications where the oxide film is either protected by an organic thin film or chemically removed. An interface modification layer (alkyl phosphonic acids) was introduced into the microfluidic system to modify the liquid metal surface and protect its oxide layer. Alternatively, an ion exchange membrane was utilized as a 'sponge-like' channel material to store and slowly release small amounts of HCl to react with the surface oxide of the liquid metal. Characterization of these interfaces at molecular level by surface spectroscopy and microscopy provided with mechanistic details for the interfacial interactions between the liquid metal surface and the channel materials.

Structure of dental gallium alloys.

PubMed

Herø, H; Simensen, C J; Jørgensen, R B

1996-07-01

The interest in gallium alloys as a replacement for amalgam has increased in recent years due to the risk of environmental pollution from amalgam. Alloy powders with compositions close to those for alloys of amalgam are mixed with a liquid gallium alloy. The mix is condensed into a prepared cavity in much the same way as for amalgam. The aim of the present work was to study the structure of: (1) two commercial alloy powders containing mainly silver, tin and copper, and (2) the phases formed by mixing these powders with a liquid alloy of gallium, indium and tin. One of the alloy powders contained 9 wt% palladium. Cross-sections of cylindrical specimens made by these gallium mixes were investigated by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Discrete grains of the following phases were found to be present in both gallium alloys: hexagonal Ag2Ga, tetragonal Cu(Pd)Ga2, cubic Ag9In4 and tetragonal beta-Sn. Indications of hexagonal or orthorhombic Ag2Sn were found in the remaining, unreacted alloy particles. In the palladium-containing alloy the X-ray reflections indicate a minor fraction of cubic Cu9Ga4 in addition to the Cu(Pd)Ga2 phase. Particles of beta-Sn are probably precipitated because Sn-Ga phases cannot be formed according to the binary phase diagram.

The use of computational thermodynamics for the determination of surface tension and Gibbs-Thomson coefficient of multicomponent alloys

NASA Astrophysics Data System (ADS)

Ferreira, D. J. S.; Bezerra, B. N.; Collyer, M. N.; Garcia, A.; Ferreira, I. L.

2018-04-01

The simulation of casting processes demands accurate information on the thermophysical properties of the alloy; however, such information is scarce in the literature for multicomponent alloys. Generally, metallic alloys applied in industry have more than three solute components. In the present study, a general solution of Butler's formulation for surface tension is presented for multicomponent alloys and is applied in quaternary Al-Cu-Si-Fe alloys, thus permitting the Gibbs-Thomson coefficient to be determined. Such coefficient is a determining factor to the reliability of predictions furnished by microstructure growth models and by numerical computations of solidification thermal parameters, which will depend on the thermophysical properties assumed in the calculations. The Gibbs-Thomson coefficient for ternary and quaternary alloys is seldom reported in the literature. A numerical model based on Powell's hybrid algorithm and a finite difference Jacobian approximation has been coupled to a Thermo-Calc TCAPI interface to assess the excess Gibbs energy of the liquid phase, permitting liquidus temperature, latent heat, alloy density, surface tension and Gibbs-Thomson coefficient for Al-Cu-Si-Fe hypoeutectic alloys to be calculated, as an example of calculation capabilities for multicomponent alloys of the proposed method. The computed results are compared with thermophysical properties of binary Al-Cu and ternary Al-Cu-Si alloys found in the literature and presented as a function of the Cu solute composition.

Kinetics and Equilibrium of Age-Induced Precipitation in Cu-4 At. Pct Ti Binary Alloy

NASA Astrophysics Data System (ADS)

Semboshi, Satoshi; Amano, Shintaro; Fu, Jie; Iwase, Akihiro; Takasugi, Takayuki

2017-03-01

Transformation kinetics and phase equilibrium of metastable and stable precipitates in age-hardenable Cu-4 at. pct Ti binary alloy have been investigated by monitoring the microstructural evolution during isothermal aging at temperatures between 693 K (420 °C) and 973 K (700 °C). The microstructure of the supersaturated solid solution evolves in four stages: compositional modulation due to spinodal decomposition, continuous precipitation of the needle-shaped metastable β'-Cu4Ti with a tetragonal structure, discontinuous precipitation of cellular components containing stable β-Cu4Ti lamellae with an orthorhombic structure, and eventually precipitation saturation at equilibrium. In specimens aged below 923 K (650 °C), the stable β-Cu4Ti phase is produced only due to the cellular reaction, whereas it can be also directly obtained from the intergranular needle-shaped β'-Cu4Ti precipitates in specimens aged at 973 K (700 °C). The precipitation kinetics and phase equilibrium observed for the specimens aged between 693 K (420 °C) and 973 K (700 °C) were characterized in accordance with a time-temperature-transformation (TTT) diagram and a Cu-Ti partial phase diagram, which were utilized to determine the alloy microstructure, strength, and electrical conductivity.

Numerical Study of Variation of Mechanical Properties of a Binary Aluminum Alloy with Respect to Its Grain Shapes †

PubMed Central

Sharifi, Hamid; Larouche, Daniel

2014-01-01

To study the variation of the mechanical behavior of binary aluminum copper alloys with respect to their microstructure, a numerical simulation of their granular structure was carried out. The microstructures are created by a repeated inclusion of some predefined basic grain shapes into a representative volume element until reaching a given volume percentage of the α-phase. Depending on the grain orientations, the coalescence of the grains can be performed. Different granular microstructures are created by using different basic grain shapes. Selecting a suitable set of basic grain shapes, the modeled microstructure exhibits a realistic aluminum alloy microstructure which can be adapted to a particular cooling condition. Our granular models are automatically converted to a finite element model. The effect of grain shapes and sizes on the variation of elastic modulus and plasticity of such a heterogeneous domain was investigated. Our results show that for a given α-phase fraction having different grain shapes and sizes, the elastic moduli and yield stresses are almost the same but the ultimate stress and elongation are more affected. Besides, we realized that the distribution of the θ phases inside the α phases is more important than the grain shape itself. PMID:28788607

Formation enthalpies for transition metal alloys using machine learning

NASA Astrophysics Data System (ADS)

Ubaru, Shashanka; Miedlar, Agnieszka; Saad, Yousef; Chelikowsky, James R.

2017-06-01

The enthalpy of formation is an important thermodynamic property. Developing fast and accurate methods for its prediction is of practical interest in a variety of applications. Material informatics techniques based on machine learning have recently been introduced in the literature as an inexpensive means of exploiting materials data, and can be used to examine a variety of thermodynamics properties. We investigate the use of such machine learning tools for predicting the formation enthalpies of binary intermetallic compounds that contain at least one transition metal. We consider certain easily available properties of the constituting elements complemented by some basic properties of the compounds, to predict the formation enthalpies. We show how choosing these properties (input features) based on a literature study (using prior physics knowledge) seems to outperform machine learning based feature selection methods such as sensitivity analysis and LASSO (least absolute shrinkage and selection operator) based methods. A nonlinear kernel based support vector regression method is employed to perform the predictions. The predictive ability of our model is illustrated via several experiments on a dataset containing 648 binary alloys. We train and validate the model using the formation enthalpies calculated using a model by Miedema, which is a popular semiempirical model used for the prediction of formation enthalpies of metal alloys.

Electrical properties of materials for high temperature strain gage applications

NASA Technical Reports Server (NTRS)

Brittain, John O.

1989-01-01

A study was done on the electrical resistance of materials that are potentially useful as resistance strain gages at high temperatures under static strain conditions. Initially a number of binary alloys were investigated. Later, third elements were added to these alloys, all of which were prepared by arc melting. Several transition metals were selected for experimentation, most prepared as thin films. Difficulties with electrical contacts thwarted efforts to extend measurements to the targeted 1000 C, but results obtained did suggest ways of improving the electrical resistance characteristics of certain materials.

Fraction eutectic measurements in slowly cooled Pb - 15 wt percent Sn alloys

NASA Technical Reports Server (NTRS)

Studer, Anthony C.; Laxmanan, V.

1988-01-01

A space shuttle experiment employing the General Purpose Furnace in its isothermal mode of operation is currently manifested for flight circa 1989. The aim of this experiment was to investigate the role of gravity in a slowly, and isothermally, cooled sample of a binary Pb - 15 wt percent Sn alloy. Ground based work in support of the microgravity experiment is discussed. In particular, it is shown that fraction eutectic measurements using an image analyzer, can be used to satisfactorily describe macrosegregation occurring in these slowly cooled ingots.

Some properties of low-vapor-pressure braze alloys for thermionic converters

NASA Technical Reports Server (NTRS)

Bair, V. L.

1978-01-01

Property measurements were made for arc-melted, rod-shaped specimens. Density and dc electrical resistivity at 296 K were measured for various binary eutectic alloys. Thermal conductivity was inferred from the electrical conductivity using the Wiedemann, Franz, Lorenz relation. Linear thermal expansion from 293 K to two-thirds melting point, under a helium atmosphere, was measured for Zr, 21.7-wt percent Ru; Zr, 13-wt percent W; Zr, 22.3-wt percent Nb; Nb, 66.9-wt percent Ru; and Zr, 25.7-wt percent Ta.

Spectroscopic Studies of Semiconductor Materials for Aggressive-scaled Micro- and Opto-electronic Devices: nc-SiO2, GeO2; ng-Si, Ge and ng-Transition metal (TM) oxides

NASA Astrophysics Data System (ADS)

Cheng, Cheng

Non-crystalline thin film materials are widely used in the semiconductor industry (micro- and optoelectronics) and in green energy, e.g., photovolatic applications. This dissertation under-pins these device application with studies of their electronic structures using derivative X-ray Absorption Spectroscopy (XAS) and derivative Spectroscopic Ellipsometry (SE) for the first time to experimentally determine electronic and intrinsic defect structures. Differences between electron and hole mobilities in c- (and ng-Si) and c- (and ng- Ge), make Ge channels superior to Si channels in for aggressively scaled CMOS field effect transistors (FETs). Bonding between Si and Ge substrates and gate dielectric oxides is the focus this dissertation. The primary objective of this research is to measure and interpret by ab-initio theory the electronic and intrinsic electronic defect structures mirco-electronic thin film materials. This is accomplished for the first time by combining (i) derivative XAS TEY data obtained at the Stanford Synchrotron Radiation Light Source (SSRL) with (ii) derivative Spectroscopic Ellipsometry results obtained at the J.A. Woollam Co. laboratory. All the oxides were deposited in RPECVD system with in-line AES and RHEED. Thins films and gate stacks were annealed in RTA system in Ar to determine temperature dependent changes. 2nd derivative analysis is applied on XAS and SE spectra emphasizing the conduction band (CB) and virtual bound state (VBS) regimes. 2nd derivative SE spectra for ng-Si and ng-Ge each have 3 distinct regimes: (i) 3 excitons, (ii) 2 features in the CB edge region, and (iii) 3 additional exciton features above the IP. Excitonic spectral width provides conductivity electron masses (em0*) and hence electron mobilities. The wider the energy range, the higher the electron mobility in that CB. Spectra of high-K dielectrics have an additional energy regime between the CB edge regime, and the higher eV excitons. This regime has 4 intra-d state transitions. Intra-d states are observed in all high-K dielectrics regardless of morphology, e.g. ng-TiO2, nc- Ti silicate , c-LaTiO3, nc-HfSiON334. This dissertation also discussed spectroscopic studies of: (i) nc-SiO 2, nc-GeO2 and (ii) nc-(SiO2)x(GeO2) 1-x pseudo-binary alloys. These studies, and the interpretation of these spectra and those in Chapter 3 in the This dissertation also discussed spectroscopic studies of: (i) nc-SiO2, nc-GeO2 and (ii) nc-(SiO 2)x(GeO2)1-x pseudo-binary alloys. These studies, and the interpretation of these spectra and those in Chapter 3 in the context of ab-initio theory provide a science base for the implementation of nc-oxides onto Germaniumsubstrates for aggressively scaled CMOS FETs, imaging devices as well as photovoltaics. X-Ray photoelectron spectroscopy(XPS) and Auger electron spectroscopy(AES) were used to determine SiO2 and GeO2 concentration in (SiO2)x(GeO2)1-x alloys. A linear trend in chemical shifts with compositions is observed and explained with charge-potential model, which incorporates the results of calculated partial charge from an empirical model for ionicity. The compositional linear relationships between binding energies nc-SiO 2, nc-GeO2, and (SiO2)x(GeO2)1-x alloy concentration agrees with the calculated results in charge potential model. SE and XAS spectral results show relatively strong O-vacancy in nc-GeO 2. O-vacancy defects in c-SiO2 are weaker. This is due to differences between Ge-O and Si-O bond (657.5kJ/mol and 799.6kJ/mol respectively). SE data shows a strong defect feature in GeO2, while SiO2 has no significant and distinct defect signature. Percolation theory describes the interconnection of bonds, e.g. Si-O and Ge-O in an otherwise nc-material, a (SiO2)x(GeO2)1-x pseudo-binary alloy. Changes in the band-gap energy of binary Si-Ge alloys occur at 0%Si (or 100% Ge), and the band gap energy increases from ˜ 0.6 eV to ˜0.87 eV as the Si concentration increases. A inflection point is at the percolation threshold˜16 %. For larger %Si there are increases to Si CB gap threshold energy of 1.1eV discussed in Chapter 3. The pseudo-binary system, (GeO2)x(SiO2) 1-x has been designated as a confluent double percolation phenomenon. Distinct changes are at percolation thresholds concentrations of: 16% and 84% SiO2, or equivalently at 84% and 16% Ge.

Transient Effects in Planar Solidification of Dilute Binary Alloys

NASA Technical Reports Server (NTRS)

Mazuruk, Konstantin; Volz, Martin P.

2008-01-01

The initial transient during planar solidification of dilute binary alloys is studied in the framework of the boundary integral method that leads to the non-linear Volterra integral governing equation. An analytical solution of this equation is obtained for the case of a constant growth rate which constitutes the well-known Tiller's formula for the solute transient. The more physically relevant, constant ramping down temperature case has been studied both numerically and analytically. In particular, an asymptotic analytical solution is obtained for the initial transient behavior. A numerical technique to solve the non-linear Volterra equation is developed and the solution is obtained for a family of the governing parameters. For the rapid solidification condition, growth rate spikes have been observed even for the infinite kinetics model. When recirculating fluid flow is included into the analysis, the spike feature is dramatically diminished. Finally, we have investigated planar solidification with a fluctuating temperature field as a possible mechanism for frequently observed solute trapping bands.

Simulation studies of GST phase change alloys

NASA Astrophysics Data System (ADS)

Martyna, Glenn

2008-03-01

In order to help drive post-Moore's Law technology development, switching processes involving novel materials, in particular, GeSbTe (GST) alloys are being investigated for use in memory and eFuse applications. An anneal/quench thermal process crystallizes/amorphosizes a GST alloy which then has a low/high resistance and thereby forms a readable/writeable bit; for example, a ``one'' might be the low resistance, conducting crystalline state and a ``zero'' might be the high resistance, glassy state. There are many open questions about the precise nature of the structural transitions and the coupling to electronic structure changes. Computational and experimental studies of the effect of pressure on the GST materials were initiated in order to probe the physics behind the thermal switching process. A new pathway to reversible phase change involving pressure-induced structural metal insulator transitions was discovered. In a binary GS system, a room-temperature, direct, pressure-induced transformation from the high resistance amorphous phase to the low resistance crystalline phase was observed experimentally while the reverse process under tensile load was demonstrated via ab initio MD simulations performed on IBM's Blue Gene/L enabled by massively parallel software. Pressure induced transformations of the ternary material GST-225 (Ge2Sb2Te5) were, also, examined In the talk, the behavior of the two systems will be compared and insight into the nature of the phase change given.

Trace element control in binary Ni-25Cr and ternary Ni-30Co-30Cr master alloy castings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Detrois, Martin; Jablonski, Paul D.

Electro-slag remelting (ESR) is used for control of unwanted elements in commercial alloys. This study focuses on master alloys of Ni-25Cr and Ni-30Co-30Cr, processed through a combination of vacuum induction melting (VIM) and electro-slag remelting (ESR). Minor additions were made to control tramp element levels and modify the melting characteristics. Nitrogen and sulfur levels below 10 ppm and oxygen levels below 100 ppm were obtained in the final products. The role of the alloy additions in lowering the tramp element content, the resulting residual inclusions and the melting characteristics were determined computationally and confirmed experimentally. Additions of titanium were beneficialmore » to the control of oxygen levels during VIM and nitrogen levels during ESR. Aluminum additions helped to control oxygen levels during remelting, however, aluminum pickup occurred when excess titanium was present during ESR. The usefulness of these master alloys for use as experimental remelt stock will also be discussed.« less

Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

DOE PAGES

Zhang, Yanwen; Stocks, George Malcolm; Jin, Ke; ...

2015-10-28

A long-standing objective in materials research is to understand how energy is dissipated in both the electronic and atomic subsystems in irradiated materials, and how related non-equilibrium processes may affect defect dynamics and microstructure evolution. Here we show that alloy complexity in concentrated solid solution alloys having both an increasing number of principal elements and altered concentrations of specific elements can lead to substantial reduction in the electron mean free path and thermal conductivity, which has a significant impact on energy dissipation and consequentially on defect evolution during ion irradiation. Enhanced radiation resistance with increasing complexity from pure nickel tomore » binary and to more complex quaternary solid solutions is observed under ion irradiation up to an average damage level of 1 displacement per atom. Understanding how materials properties can be tailored by alloy complexity and their influence on defect dynamics may pave the way for new principles for the design of radiation tolerant structural alloys.« less

Generalized stacking fault energies of alloys.

PubMed

Li, Wei; Lu, Song; Hu, Qing-Miao; Kwon, Se Kyun; Johansson, Börje; Vitos, Levente

2014-07-02

The generalized stacking fault energy (γ surface) provides fundamental physics for understanding the plastic deformation mechanisms. Using the ab initio exact muffin-tin orbitals method in combination with the coherent potential approximation, we calculate the γ surface for the disordered Cu-Al, Cu-Zn, Cu-Ga, Cu-Ni, Pd-Ag and Pd-Au alloys. Studying the effect of segregation of the solute to the stacking fault planes shows that only the local chemical composition affects the γ surface. The calculated alloying trends are discussed using the electronic band structure of the base and distorted alloys.Based on our γ surface results, we demonstrate that the previous revealed 'universal scaling law' between the intrinsic energy barriers (IEBs) is well obeyed in random solid solutions. This greatly simplifies the calculations of the twinning measure parameters or the critical twinning stress. Adopting two twinnability measure parameters derived from the IEBs, we find that in binary Cu alloys, Al, Zn and Ga increase the twinnability, while Ni decreases it. Aluminum and gallium yield similar effects on the twinnability.

Short and Medium-Range Order in Liquid Ternary Al80Co10Ni10, Al72.5Co14.5Ni13, and Al65Co17.5Ni17.5 Alloys

NASA Astrophysics Data System (ADS)

Roik, Oleksandr S.; Samsonnikov, Oleksiy; Kazimirov, Volodymyr; Sokolskii, Volodymyr

2010-01-01

A local short-to-intermediate range order of liquid Al80Co10Ni10, Al72.5Co14.5Ni13, and Al65Co17.5Ni17.5 alloys was examined by X-ray diffraction and the reverse Monte Carlo modelling. The comprehensive analysis of three-dimensional models of the liquid ternary alloys was performed by means of the Voronoi-Delaunay method. The existence of a prepeak on the S(Q) function of the liquid alloys is caused by medium range ordering of 3d-transition metal atoms in dense-packed polytetrahedral clusters at temperatures close to the liquidus. The non-crystalline clusters, represented by aggregates of pentagons that consist of good tetrahedra, and chemical short-range order lead to the formation of the medium range order in the liquid binary Al-Ni, Al-Co and ternary Al-Ni-Co alloys.

Effects of Some Light Alloying Elements on the Oxidation Behavior of Fe and Ni-Cr Based Alloys During Air Plasma Spraying

NASA Astrophysics Data System (ADS)

Zeng, Zhensu; Kuroda, Seiji; Kawakita, Jin; Komatsu, Masayuki; Era, Hidenori

2010-01-01

The oxidation behavior of iron binary powders with addition of Si (1, 4 wt.%) and B (1, 3 wt.%) and that of a Ni-Cr based alloy powder with Si (4.3 wt.%), B (3.0 wt.%), and C (0.8 wt.%) additions during atmosphere plasma spray (APS) have been investigated. Analysis of the chemical composition and phases of oxides in the captured in-flight particles and deposited coatings was carried out. The results show that the addition of Si and B to iron effectively reduced the oxygen contents in the coatings, especially during the in-flight period at higher particles temperature. Ni-Cr based alloy powder with Si, B, and C additions reduced the oxidation of the base alloys significantly. Preferential oxidation and subsequent vaporization of Si, B, and C from the surface of the sprayed particles are believed to play a major role in controlling oxidation in the APS process.

The kinetics of composite particle formation during mechanical alloying

NASA Technical Reports Server (NTRS)

Aikin, B. J. M.; Courtney, T. H.

1993-01-01

The kinetics of composite particle formation during attritor milling of insoluble binary elemental powders have been examined. The effects of processing conditions (i.e., mill power, temperature, and charge ratio) on these kinetics were studied. Particle size distributions and fractions of elemental and composite particles were determined as functions of milling time and processing conditions. This allowed the deduction of phenomenological rate constants describing the propensity for fracture and welding during processing. For the mill-operating conditions investigated, the number of particles in the mill generally decreased with milling time, indicating a greater tendency for particle welding than fracture. Moreover, a bimodal size distribution is often obtained as a result of preferential welding. Copper and chromium 'alloy' primarily by encapsulation of Cr particles within Cu. This form of alloying also occurs in Cu-Nb alloys processed at low mill power and/or for short milling times. For other conditions, however, Cu-Nb alloys develop a lamellar morphology characteristic of mechanically alloyed two-phase ductile metals. Increasing mill power or charge (ball-to-powder weight) ratio (CR) increases the rate of composite particle formation.

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

DOE PAGES

Sims, Zachary C.; Weiss, David; McCall, S. K.; ...

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

TA [B] Predicting Microstructure-Creep Resistance Correlation in High Temperature Alloys over Multiple Time Scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomar, Vikas

2017-03-06

DoE-NETL partnered with Purdue University to predict the creep and associated microstructure evolution of tungsten-based refractory alloys. Researchers use grain boundary (GB) diagrams, a new concept, to establish time-dependent creep resistance and associated microstructure evolution of grain boundaries/intergranular films GB/IGF controlled creep as a function of load, environment, and temperature. The goal was to conduct a systematic study that includes the development of a theoretical framework, multiscale modeling, and experimental validation using W-based body-centered-cubic alloys, doped/alloyed with one or two of the following elements: nickel, palladium, cobalt, iron, and copper—typical refractory alloys. Prior work has already established and validated amore » basic theory for W-based binary and ternary alloys; the study conducted under this project extended this proven work. Based on interface diagrams phase field models were developed to predict long term microstructural evolution. In order to validate the models nanoindentation creep data was used to elucidate the role played by the interface properties in predicting long term creep strength and microstructure evolution.« less

Ion irradiation induced defect evolution in Ni and Ni-based FCC equiatomic binary alloys

DOE PAGES

Jin, Ke; Zhang, Yanwen; Bei, Hongbin

2015-09-09

In order to explore the chemical effects on radiation response of alloys with multi-principal elements, defect evolution under Au ion irradiation was investigated in the elemental Ni, equiatomic NiCo and NiFe alloys. Single crystals were successfully grown in an optical floating zone furnace and their (100) surfaces were irradiated with 3 MeV Au ions at fluences ranging from 1 × 10 13 to 5 × 10 15 ions cm –2 at room temperature. The irradiation-induced defect evolution was analyzed by using ion channeling technique. Experiment shows that NiFe is more irradiation-resistant than NiCo and pure Ni at low fluences. Withmore » continuously increasing the ion fluences, damage level is eventually saturated for all materials but at different dose levels. The saturation level in pure Ni appears at relatively lower irradiation fluence than the alloys, suggesting that damage accumulation slows down in the alloys. Here, under high-fluence irradiations, pure Ni has wider damage ranges than the alloys, indicating that defects in pure Ni have high mobility.« less

Investigating the Thermal and Phase Stability of Nanocrystalline Ni-W Produced by Electrodeposition, Sputtering, and Mechanical Alloying

NASA Astrophysics Data System (ADS)

Marvel, Christopher Jonathan

The development of nanocrystalline materials has been increasingly pursued over the last few decades. They have been shown to exhibit superior properties compared to their coarse-grain counterparts, and thus present a tremendous opportunity to revolutionize the performance of nanoscale devices or bulk structural materials. However, nanocrystalline materials are highly prone to grain growth, and if the nanocrystalline grains coarsen, the beneficial properties are lost. There is a strong effort to determine the most effective thermal stability mechanisms to avoid grain growth, but the physical nature of nanocrystalline grain growth is still unclear due to a lack of detailed understanding of nanocrystalline microstructures. Furthermore, the influence of contamination has scarcely been explored with advanced transmission electron microscopy techniques, nor has there been a direct comparison of alloys fabricated with different bulk processes. Therefore, this research has applied aberration-corrected scanning transmission electron microscopy to characterize nanocrystalline Ni-W on the atomic scale and elucidate the physical grain growth behavior. Three primary objectives were pursued: (1) explore the thermal stability mechanisms of nanocrystalline Ni-W, (2) evaluate the phase stability of Ni-W and link any findings to grain growth behavior, and (3) compare the influences of bulk fabrication processing, including electrodeposition, DC magnetron sputtering, and mechanical alloying, on the thermal stability and phase stability of Ni-W. Several thermal stability mechanisms were identified throughout the course of this research. First and foremost, W-segregation was scarcely observed to grain boundaries, and it is unclear if W-segregation improves thermal stability contrary to most reports in the 2 literature. Long-range Ni4W chemical ordering was observed in alloys with more than 20 at.% W, and it is likely Ni4W domains reduce grain boundary mobility. In addition, lattice diffusivity calculations conceptually suggested that increasing W alloying concentrations can decrease the grain growth rate. The strongest evidence of grain growth stagnation was via nanoscale oxide particle drag in highly contaminated electrodeposited alloys. Interestingly, W-segregation was also detected to the oxide phase boundaries and revealed a potential indirect mechanism of thermal stability. The phase stability of pure and contaminated Ni-W alloys was investigated with density functional theory. Primarily, the calculations suggested that the intermetallic phases NiW and NiW2 are thermodynamically unstable, meaning the binary phase diagram is incorrect, but the ternary carbides Ni 6W6C and Ni2W4C are stable. Several Ni-W binary and Ni-W-C ternary phase diagrams were constructed using a simplified CALPHAD approach to improve the understanding of Ni-W phase stability. Lastly, it was determined that the fabrication process greatly influences the impurity types and concentrations of the alloys, and therefore greatly dictate which thermal stability mechanisms are active. Mechanically alloyed samples were found to be the most resistant to grain growth. The findings of this research will hopefully guide future efforts to design more thermally stable nanocrystalline alloys. The link between phase stability and grain growth behavior of Ni-W was thoroughly discussed, as well as the dependence of bulk fabrication processing on the contamination found in the alloys. Ultimately, this research has greatly expanded the general understanding of nanocrystalline Ni-W microstructures, and it is likely that similar phenomena occur in other nanocrystalline systems.

Oxidation-chlorination of binary Ni-Cr alloys in flowing Ar-O2-Cl2 gas mixtures at 1200 K

NASA Technical Reports Server (NTRS)

Mcnallan, M. J.; Lee, Y. Y.; Chang, Y. W.; Jacobson, N. S.; Doychak, J.

1991-01-01

Nickel-chromium alloys are resistant to oxidation because of the selective oxidation of chromium to form a protective Cr2O3 scale. In chlorine-containing environments, volatile corrosion products can also be formed. The mixed oxidation-chlorination of Ni-4.5Cr, Ni-13.8Cr, and Ni-26.5Cr (by weight) alloys in Ar-O2-Cl2 gas mixtures is investigated using thermogravimetric analysis and atmospheric-pressure-sampling mass spectrometry, followed by examination of the corrosion products using scanning electron microscopy and X-ray diffraction analysis. The overall kinetics of the corrosion are affected by the relative amounts of oxides and chlorides formed and the composition of the oxide corrosion products.

Influence of Surface Energy on Organic Alloy Formation in Ternary Blend Solar Cells Based on Two Donor Polymers.

PubMed

Gobalasingham, Nemal S; Noh, Sangtaik; Howard, Jenna B; Thompson, Barry C

2016-10-05

The compositional dependence of the open-circuit voltage (V oc ) in ternary blend bulk heterojunction (BHJ) solar cells is correlated with the miscibility of polymers, which may be influenced by a number of attributes, including crystallinity, the random copolymer effect, or surface energy. Four ternary blend systems featuring poly(3-hexylthiophene-co-3-(2-ethylhexyl)thiophene) (P3HT 75 -co-EHT 25 ), poly(3-hexylthiophene-co-(hexyl-3-carboxylate)), herein referred to as poly(3-hexylthiophene-co-3-hexylesterthiophene) (P3HT 50 -co-3HET 50 ), poly(3-hexylthiophene-thiophene-diketopyrrolopyrrole) (P3HTT-DPP-10%), and an analog of P3HTT-DPP-10% with 40% of 3-hexylthiophene exchanged for 2-(2-methoxyethoxy)ethylthiophen-2-yl (3MEO-T) (featuring an electronically decoupled oligoether side-chain), referred to as P3HTTDPP-MEO40%, are explored in this work. All four polymers are semicrystalline and rich in rr-P3HT content and perform well in binary devices with PC 61 BM. Except for P3HTTDPP-MEO40%, all polymers exhibit similar surface energies (∼21-22 mN/m). P3HTTDPP-MEO40% exhibits an elevated surface energy of around 26 mN/m. As a result, despite the similar optoelectronic properties and binary solar cell performance of P3HTTDPP-MEO40% compared to P3HTT-DPP-10%, the former exhibits a pinned V oc in two different sets of ternary blend devices. This is a stark contrast to previous rr-P3HT-based systems and demonstrates that surface energy, and its influence on miscibility, plays a critical role in the formation of organic alloys and can supersede the influence of crystallinity, the random copolymer effect, similar backbone structures, and HOMO/LUMO considerations. Therefore, we confirm surface energy compatibility as a figure-of-merit for predicting the compositional dependence of the V oc in ternary blend solar cells and highlight the importance of polymer miscibility in organic alloy formation.

Real-time synchrotron x-ray observations of equiaxed solidification of aluminium alloys and implications for modelling

NASA Astrophysics Data System (ADS)

Prasad, A.; Liotti, E.; McDonald, S. D.; Nogita, K.; Yasuda, H.; Grant, P. S.; StJohn, D. H.

2015-06-01

Recently, in-situ observations were carried out by synchrotron X-ray radiography to observe the nucleation and growth in Al alloys during solidification. The nucleation and grain formation of a range of Al-Si and Al-Cu binary alloys were studied. When grain refiner was added to the alloys, the location of the nucleation events was readily observed. Once nucleation began it continued to occur in a wave of events with the movement of the temperature gradient across the field of view due to cooling. Other features observed were the settling of the primary phase grains in the Al-Si alloys and floating in the Al-Cu alloys, the effects of convection with marked fluctuation of the growth rate of the solid-liquid interface in the Al-Si alloys, and an absence of fragmentation. The microstructures are typical of those produced in the equiaxed zone of actual castings. These observations are compared with predictions arising from the Interdependence model. The results from this comparison have implications for further refinement of the model and simulation and modelling approaches in general. These implications will be discussed.

Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

PubMed Central

Zhang, Yanwen; Stocks, G. Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C.; Wang, Lumin; Béland, Laurent K.; Stoller, Roger E.; Samolyuk, German D.; Caro, Magdalena; Caro, Alfredo; Weber, William J.

2015-01-01

A grand challenge in materials research is to understand complex electronic correlation and non-equilibrium atomic interactions, and how such intrinsic properties and dynamic processes affect energy transfer and defect evolution in irradiated materials. Here we report that chemical disorder, with an increasing number of principal elements and/or altered concentrations of specific elements, in single-phase concentrated solid solution alloys can lead to substantial reduction in electron mean free path and orders of magnitude decrease in electrical and thermal conductivity. The subsequently slow energy dissipation affects defect dynamics at the early stages, and consequentially may result in less deleterious defects. Suppressed damage accumulation with increasing chemical disorder from pure nickel to binary and to more complex quaternary solid solutions is observed. Understanding and controlling energy dissipation and defect dynamics by altering alloy complexity may pave the way for new design principles of radiation-tolerant structural alloys for energy applications. PMID:26507943

Recent progress in GeSn growth and GeSn-based photonic devices

NASA Astrophysics Data System (ADS)

Zheng, Jun; Liu, Zhi; Xue, Chunlai; Li, Chuanbo; Zuo, Yuhua; Cheng, Buwen; Wang, Qiming

2018-06-01

The GeSn binary alloy is a new group IV material that exhibits a direct bandgap when the Sn content exceeds 6%. It shows great potential for laser use in optoelectronic integration circuits (OEIC) on account of its low light emission efficiency arising from the indirect bandgap characteristics of Si and Ge. The bandgap of GeSn can be tuned from 0.6 to 0 eV by varying the Sn content, thus making this alloy suitable for use in near-infrared and mid-infrared detectors. In this paper, the growth of the GeSn alloy is first reviewed. Subsequently, GeSn photodetectors, light emitting diodes, and lasers are discussed. The GeSn alloy presents a promising pathway for the monolithic integration of Si photonic circuits by the complementary metal–oxide–semiconductor (CMOS) technology. Project supported by the Beijing Natural Science Foundation (No. 4162063) and the Youth Innovation Promotion Association of CAS (No. 2015091).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seema, K., E-mail: s-phy@yahoo.co.in; Department of Physics, PGGC, Sector 11, Chandigarh, India-160011; Kumar, Ranjan, E-mail: ranjan@pu.ac.in

This paper presents the effect of disorder on electronic, magnetic and half-metallic properties of Co{sub 2}VGa Heusler alloy using density functional theory. Binary mixing is the most common form of atomic disorder in these compounds. We have considered three types of disorders: DO{sub 3}, A2 and B2 disorder which corresponds to X-Y, X-Z and Y-Z mixing respectively. After structural optimization, we found that A2 disorder has high formation energy and is most unlikely to occur. The half-metallic nature of the alloy is destroyed in presence of DO{sub 3} and A2 disorder. The destruction of half-metallicity is due to reconstruction ofmore » energy states. Also the loss of half-metallicity is accompanied by reversal of spin-polarization at the Fermi level. B2 disorder retains the half-metallic nature of the alloy but spin-polarization value is reduced as compared to the ordered alloy.« less

Cold crucible levitation melting of biomedical Ti-30 wt%Ta alloy.

PubMed

Fukui, H; Yang, W; Yamada, S; Fujishiro, Y; Morita, A; Niinomi, M

2001-06-01

Recently, titanium-tantalum alloys have been studied as implant materials for dental and orthopedic surgery. However, titanium and tantalum are difficult to mix by common arc melting and induction melting, because of their high melting point and the marked difference between their densities (Ti: 1,680 degrees C, 4.5 g/cm3, Ta: 2,990 degrees C, 16.6 g/cm3). Thus, the Cold Crucible Levitation Melting (CCLM) method was chosen to produce a Ti-30 wt%Ta binary alloy in the present study. The CCLM furnace, with 1 kg capacity, consisted of a water-cooled crucible comprising oxygen-free high purity copper segments and coils wrapped around the crucible and connected to a frequency inverter power supply. A qualified ingot of 1.0 kg of Ti-30 wt%Ta alloy was obtained. The ingot was characterized from the surface quality, chemical composition distribution and microstructure, and finally the melting process was discussed.

Electron Dispersion in Liquid Alkali and Their Alloys

NASA Astrophysics Data System (ADS)

Vora, Aditya M.

2010-07-01

Ashcroft's local empty core (EMC) model pseudopotential in the second-order perturbation theory is used to study the electron dispersion relation, the Fermi energy, and deviation in the Fermi energy from free electron value for the liquid alkali metals and their equiatomic binary alloys for the first time. In the present computation, the use of pseudo-alloy-atom model (PAA) is proposed and found successful. The influence of the six different forms of the local field correction functions proposed by Hartree (H), Vashishta-Singwi (VS), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F), and Sarkar et al. (S) on the aforesaid electronic properties is examined explicitly, which reflects the varying effects of screening. The depth of the negative hump in the electron dispersion of liquid alkalis decreases in the order Li → K, except for Rb and Cs, it increases. The results of alloys are in predictive nature.

Cellular and dendritic growth in a binary melt - A marginal stability approach

NASA Technical Reports Server (NTRS)

Laxmanan, V.

1986-01-01

A simple model for the constrained growth of an array of cells or dendrites in a binary alloy in the presence of an imposed positive temperature gradient in the liquid is proposed, with the dendritic or cell tip radius calculated using the marginal stability criterion of Langer and Muller-Krumbhaar (1977). This approach, an approach adopting the ad hoc assumption of minimum undercooling at the cell or dendrite tip, and an approach based on the stability criterion of Trivedi (1980) all predict tip radii to within 30 percent of each other, and yield a simple relationship between the tip radius and the growth conditions. Good agreement is found between predictions and data obtained in a succinonitrile-acetone system, and under the present experimental conditions, the dendritic tip stability parameter value is found to be twice that obtained previously, possibly due to a transition in morphology from a cellular structure with just a few side branches, to a more fully developed dendritic structure.

Effect of Alloying Elements on Nano-ordered Wear Property of Magnesium Alloys

NASA Astrophysics Data System (ADS)

Yagi, Takahiro; Hirayama, Tomoko; Matsuoka, Takashi; Somekawa, Hidetoshi

2017-03-01

The effect of alloying elements on nano-ordered wear properties was investigated using fine-grained pure magnesium and several types of 0.3 at. pct X (X = Ag, Al, Ca, Li, Mn, Y, and Zn) binary alloys. They had an average grain size of 3 to 5 μm and a basal texture due to their production by the extrusion process. The specific wear rate was influenced by the alloying element; the Mg-Ca and Mg-Mn alloys showed the best and worst wear property, respectively, among the present alloying elements, which was the same trend as that for indentation hardness. Deformed microstructural observations revealed no formation of deformation twins, because of the high activation of grain boundary-induced plasticity. On the contrary, according to scratched surface observations, when grain boundary sliding partially contributed to deformation, these alloys had large specific wear rates. These results revealed that the wear property of magnesium alloys was closely related to the plastic deformation mechanism. The prevention of grain boundary sliding is important to improve the wear property, which is the same as that of a large-scale wearing configuration. One of the influential factors is the change in the lattice parameter with the chemical composition, i.e., ∂( c/ a)/∂ C. An alloying element that has a large value of ∂( c/ a)/∂ C effectively enhances the wear property.

Elastic moduli of cast Ti-Au, Ti-Ag, and Ti-Cu alloys.

PubMed

Kikuchi, Masafumi; Takahashi, Masatoshi; Okuno, Osamu

2006-07-01

This study investigated the effect of alloying titanium with gold, silver, or copper on the elastic properties of the alloys. A series of binary titanium alloys was made with four concentrations of gold, silver, or copper (5, 10, 20, and 30 mass%) in an argon-arc melting furnace. The Young's moduli and Poisson's ratios of the alloy castings were determined with an ultrasonic-pulse method. The density of each alloy was previously measured by the Archimedes' principle. Results were analyzed using one-way ANOVA and the Scheffé's test. The densities of Ti-Au, Ti-Ag, and Ti-Cu alloys monotonically increased as the concentration of alloying elements increased. As the concentration of gold or silver increased to 20%, the Young's modulus significantly decreased, followed by a subsequent increase in value. As the concentration of copper increased, the Young's modulus monotonically increased. The Young's moduli of all the Ti-Cu alloys were significantly higher than that of the titanium. The density of all the experimental alloys was virtually independent of the alloy phases, while the Young's moduli and Poisson's ratios of the alloys were dependent. The addition of gold or silver slightly reduced the Young's modulus of the titanium when the alloy phase was single alpha. The increase in the Young's modulus of the Ti-Cu alloys is probably due to the precipitation of intermetallic compound Ti2Cu. Copper turned out to be a moderate stiffener that gains a Young's modulus of titanium up to 20% at the copper concentration of 30 mass%.

Prediction of dendrite arm spacings in unsteady-and steady-state heat flow of unidirectionally solidified binary alloys

NASA Astrophysics Data System (ADS)

Bouchard, Dominique; Kirkaldy, John S.

1997-08-01

Various theoretical dendrite and cell spacing formulas have been tested against experimental data obtained in unsteady- and steady-state heat flow conditions. An iterative assessment strategy satisfactorily overcomes the circumstances that certain constitutive parameters are inadequately established and/or highly variable and that many of the data sets, in terms of gradients, velocities, and/or cooling rates, are unreliable. The accessed unsteady- and steady-state observations on near-terminal binary alloys for primary and secondary spacings were first examined within conventional power law representations, the deduced exponents and confidence limits for each alloy being tabularly recorded. Through this analysis, it became clear that to achieve predictive generality the many constitutive parameters must be included in a rational way, this being achievable only through extant or new theoretical formulations. However, in the case of primary spacings, all formulas, including our own, failed within the unsteady heat flow algorithm while performing adequately within their steady-state context. An earlier untested, heuristically derived steady-state formula after modification, λ _1 = 120 ( {{16X_0^{{1/2}} G_0 (\\varepsilon σ )T_M D}/{(1 - k)mΔ H G R}} )^{{1/2}} ultimately proved its utility in the unsteady regime, and so it is recommended for purposes of predictions for general terminal alloys. For secondary spacings, a Mullins and Sekerka type formula proved from the start to be adequate in both unsteady- and steady-state heat flows, and so it recommends itself in calibrated form, λ _2 = 12π ( {{4σ }/{X_0 (1 - k)^2 Δ H}( {D/R} )^2 } )^{{1/3}}

Liquid-liquid phase separation and solidification behavior of Al55Bi36Cu9 monotectic alloy with different cooling rates

NASA Astrophysics Data System (ADS)

Bo, Lin; Li, Shanshan; Wang, Lin; Wu, Di; Zuo, Min; Zhao, Degang

2018-03-01

The cooling rate has a significant effect on the solidification behavior and microstructure of monotectic alloy. In this study, different cooling rate was designed through casting in the copper mold with different bore diameters. The effects of different cooling rate on the solidification behavior of Al55Bi36Cu9 (at.%) immiscible alloy have been investigated. The liquid-liquid phase separation of Al55Bi36Cu9 immiscible alloy melt was investigated by resistivity test. The solidification microstructure and phase analysis of Al55Bi36Cu9 immiscible alloy were performed by the SEM and XRD, respectively. The results showed that the liquid-liquid phase separation occurred in the solidification of Al55Bi36Cu9 monotectic melt from 917 °C to 653 °C. The monotectic temperature, liquid phase separation temperature and immiscibility zone of Al55Bi36Cu9 monotectic alloy was lower than those of Al-Bi binary monotectic alloy. The solidification morphology of Al55Bi36Cu9 monotectic alloy was very sensitive to the cooling rate. The Al/Bi core-shell structure formed when Al55Bi36Cu9 melt was cast in the copper mold with a 8 mm bore diameter.

Two-dimensional time-resolved X-ray diffraction study of liquid/solid fraction and solid particle size in Fe-C binary system with an electrostatic levitator furnace

NASA Astrophysics Data System (ADS)

Yonemura, M.; Okada, J.; Watanabe, Y.; Ishikawa, T.; Nanao, S.; Shobu, T.; Toyokawa, H.

2013-03-01

Liquid state provides functions such as matter transport or a reaction field and plays an important role in manufacturing processes such as refining, forging or welding. However, experimental procedures are significantly difficult for an observation of solidification process of iron and iron-based alloys in order to identify rapid transformations subjected to fast temperature evolution. Therefore, in order to study the solidification in iron and iron-based alloys, we considered a combination of high energy X-ray diffraction measurements and an electrostatic levitation method (ESL). In order to analyze the liquid/solid fraction, the solidification of melted spherical specimens was measured at a time resolution of 0.1 seconds during rapid cooling using the two-dimensional time-resolved X-ray diffraction. Furthermore, the observation of particle sizes and phase identification was performed on a trial basis using X-ray small angle scattering with X-ray diffraction.

A high-resolution analytical scanning transmission electron microscopy study of the early stages of spinodal decomposition in binary Fe–Cr

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westraadt, J.E., E-mail: johan.westraadt@nmmu.ac.za; Olivier, E.J.; Neethling, J.H.

2015-11-15

Spinodal decomposition (SD) is an important phenomenon in materials science and engineering. For example, it is considered to be responsible for the 475 °C embrittlement of stainless steels comprising the bcc (ferrite) or bct (martensite) phases. Structural characterization of the evolving minute nano-scale concentration fluctuations during SD in the Fe–Cr system is, however, a notable challenge, and has mainly been considered accessible via atom probe tomography (APT) and small-angle neutron scattering. The standard tool for nanostructure characterization, viz. transmission electron microscopy (TEM), has only been successfully applied to late stages of SD when embrittlement is already severe. However, we heremore » demonstrate that the structural evolution in the early stages of SD in binary Fe–Cr, and alloys based on the binary, are accessible via analytical scanning TEM. An Fe–36 wt% Cr alloy aged at 500 °C for 1, 10 and 100 h is investigated using an aberration-corrected microscope and it is found that highly coherent and interconnected Cr-rich regions develop. The wavelength of decomposition is rather insensitive to the sample thickness and it is quantified to 2, 3 and 6 nm after ageing for 1, 10 and 100 h, which is in reasonable agreement with prior APT analysis. The concentration amplitude is more sensitive to the sample thickness and acquisition parameters but the TEM analysis is in good agreement with APT analysis for the longest ageing time. These findings open up for combinatorial TEM studies where both local crystallography and chemistry is required. - Highlights: • STEM-EELS analysis was successfully applied to resolve early stage SD in Fe–Cr. • Compositional wavelength measured with STEM-EELS compares well to previous ATP studies. • Compositional amplitude measured with STEM-EELS is a function of experimental parameters. • STEM-EELS allows for combinatorial studies of SD using complementary techniques.« less

High Temperature Characteristics of Pt/TaSi2/Pt/W and Pt/Ti/W Diffusion Barrier Systems for Ohmic Contacts to 4H-SiC

NASA Technical Reports Server (NTRS)

Okojie, Robert S.; Lukco, Dorothy

2017-01-01

The degradation of ohmic contacts to 4H-SiC pressure sensors over time at high temperature is primarily due to two failure mechanisms: migrating bond pad Au and atmospheric O toward the ohmic contact SiC interface and the inter-metallic mixing between diffusion barrier systems (DBS) and the underlying ohmic contact metallization. We investigated the effectiveness of Pt/TaSi2/Pt/W (DBS-A) and Pt/Ti/W (DBS-B) in preventing Au and O diffusion through the underlying binary Ti/W or alloyed W50:Ni50 ohmic contacts to 4H-SiC and the DBS ohmic contact intermixing at temperature up to 700 C.

Electrical conductivity optimization of the Na3AlF6-Al2O3-Sm2O3 molten salts system for Al-Sm intermediate binary alloy production

NASA Astrophysics Data System (ADS)

Liao, Chun-fa; Jiao, Yun-fen; Wang, Xu; Cai, Bo-qing; Sun, Qiang-chao; Tang, Hao

2017-09-01

Metal Sm has been widely used in making Al-Sm magnet alloy materials. Conventional distillation technology to produce Sm has the disadvantages of low productivity, high costs, and pollution generation. The objective of this study was to develop a molten salt electrolyte system to produce Al-Sm alloy directly, with focus on the electrical conductivity and optimal operating conditions to minimize the energy consumption. The continuously varying cell constant (CVCC) technique was used to measure the conductivity for the Na3AlF6-AlF3-LiF-MgF2-Al2O3-Sm2O3 electrolysis medium in the temperature range from 905 to 1055°C. The temperature ( t) and the addition of Al2O3 ( W(Al2O3)), Sm2O3 ( W(Sm2O3)), and a combination of Al2O3 and Sm2O3 into the basic fluoride system were examined with respect to their effects on the conductivity ( κ) and activation energy. The experimental results showed that the molten electrolyte conductivity increases with increasing temperature ( t) and decreases with the addition of Al2O3 or Sm2O3 or both. We concluded that the optimal operation conditions for Al-Sm intermediate alloy production in the Na3AlF6-AlF3-LiF-MgF2-Al2O3-Sm2O3 system are W(Al2O3) + W(Sm2O3) = 3wt%, W(Al2O3): W(Sm2O3) = 7:3, and a temperature of 965 to 995°C, which results in satisfactory conductivity, low fluoride evaporation losses, and low energy consumption.

Empirical Study of the Multiaxial, Thermomechanical Behavior of NiTiHf Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Shukla, Dhwanil; Noebe, Ronald D.; Stebner Aaron P.

2013-01-01

An empirical study was conducted to characterize the multiaxial, thermomechanical responses of new high temperature NiTiHf alloys. The experimentation included loading thin walled tube Ni(sub 50.3)Ti(sub 29.7)Hf(sub 20) alloy samples along both proportional and nonproportional axial-torsion paths at different temperatures while measuring surface strains using stereo digital image correlation. A Ni(sub 50.3)Ti(sub 33.7)Hf(sub 16) alloy was also studied in tension and compression to document the effect of slightly depleting the Hf content on the constitutive responses of NiTiHf alloys. Samples of both alloys were made from nearly texture free polycrystalline material processed by hot extrusion. Analysis of the data shows that very small changes in composition significantly alter NiTiHf alloy properties, as the austenite finish (Af) temperature of the 16-at Hf alloy was found to be approximately 60 C less than the 20-at Hf alloy (approximately 120 C vs. 180 C). In addition, the 16-at Hf alloy exhibited smaller compressive transformation strains (2 vs. 2.5 percent). Multi-axial characterization of the 20-at % Hf alloy showed that while the random polycrystal transformation strains in tension (4 percent) and compression (2.5 percent) are modest in comparison with binary NiTi (6 percent, 4 percent), the torsion performance is superior (7 vs. 4 shear strain width to the pseudoelastic plateau).

Theoretical studies of aluminum and aluminide alloys using CALPHAD and first-principles approach

NASA Astrophysics Data System (ADS)

Jiang, Chao

Heat-treatable aluminum alloys have been widely used in the automobile and aerospace industries as structural materials due to their light weight and high strength. To study the age-hardening process in heat-treatable aluminum alloys, the Gibbs energies of the strengthening metastable phases, e.g. theta ' and theta″, are critical. However, those data are not included in the existing thermodynamic databases for aluminum alloys due to the semi-empirical nature of the CALPHAD approach. In the present study, the thermodynamics of the Al-Cu system, the pivotal age-hardening system, is remodeled using a combined CALPHAD and first-principles approach. The formation enthalpies and vibrational formation entropies of the stable and metastable phases in the Al-Cu system are provided by first-principles calculations. Special Quasirandom Structures (SQS's) are applied to model the substitutionally random fee and bee alloys. SQS's for binary bee alloys are developed and tested in the present study. Finally, a self-consistent thermodynamic description of the Al-Cu system including the two metastable theta″ and theta' phases is obtained. During welding of heat-treatable aluminum alloys, a detrimental phenomenon called constitutional liquation, i.e. the local eutectic melting of second-phase particles in a matrix at temperatures above the eutectic temperature but below the solidus of the alloy, may occur in the heat-affected zone (HAZ). In the present study, diffusion code DICTRA coupled with realistic thermodynamic and kinetic databases is used to simulate the constitutional liquation in the model Al-Cu system. The simulated results are in quantitative agreement with experiments. The critical heating rate to avoid constitutional liquation is also determined through computer simulations. Besides the heat-treatable aluminum alloys, intermetallic compounds based on transition metal aluminides, e.g. NiAl and FeAl, are also promising candidates for the next-generation of high-temperature structural materials for aerospace applications due to their high melting temperature and good oxidation resistance. Many important properties of B2 aluminides are governed by the existences of point defects. In the present study, Special Quasirandom Structures (SQS's) are developed to model non-stoichiometric B2 compounds containing large concentrations of constitutional point defects. The SQS's are then applied to study B2 NiAl. The first-principles SQS results provide formation enthalpies, equilibrium lattice parameters and elastic constants of B2 NiAl which agree satisfactorily with the existing experimental data in the literature. It is unambiguously shown that, at T = 0K and zero pressure, Ni vacancies and antisite Ni atoms are the energetically favorable point defects in Al-rich and Ni-rich B2 NiAl, respectively. Remarkably, it is predicted that high defect concentrations can lead to structural instability of B2 NiAl, which explains well the martensitic transformation observed in this compound at high Ni concentrations.

Modelling the growth of feather crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, H.J.; Hunt, J.D.; Evans, P.V.

1997-02-01

An existing numerical model of dendritic growth has been adapted to model the growth of twinned columnar dendrites (feather crystals) in a binary aluminium alloy, Examination of the effect of dendrite tip angle on growth has led to an hypothesis regarding the stability of a pointed tip morphology in these crystals.

Monosilicide-disilicide-silicon phase equilibria in the nickel-platinum-silicon and nickel-palladium-silicon systems

NASA Astrophysics Data System (ADS)

Loomans, M. E.; Chi, D. Z.; Chua, S. J.

2004-10-01

Bulk-phase equilibria in Ni-rich/Si-rich alloys of the Ni-Pt-Si and Ni-Pd-Si systems were investigated. Results suggest that a bulk monosilicide solid solution, containing up to at least 11 at. pct Pt, exists in the Ni-Pt-Si system. Monosilicides containing more than 11 at. pct Pt were not examined. Results from both ternary systems point convincingly to the existence of a NiSi+Si↔NiSi2 eutectoid reaction near 700 °C in the Ni-Si binary system; data from the Ni-Pt-Si system, which yield the more accurate determination of the eutectoid temperature, place it at roughly 710 °C. The Pt and Pd concentrations of monosilicide in equilibrium with disilicide and Si were measured using energy-dispersive spectrometry (EDS) and were found to increase with temperature.

Quantitative decoding of the response a ceramic mixed potential sensor array for engine emissions control and diagnostics

DOE PAGES

Tsui, Lok-kun; Benavidez, Angelica; Palanisamy, Ponnusamy; ...

2017-04-13

The development of on-board sensors for emissions monitoring is necessary for continuous monitoring of the performance of catalytic systems in automobiles. We have fabricated mixed potential electrochemical gas sensing devices with Pt, La 0.8Sr 0.2CrO 3 (LSCO), and Au/Pd alloy electrodes and a porous yttria-stabilized zirconia electrolyte. The three-electrode design takes advantage of the preferential selectivity of the Pt + Au/Pd and Pt + LSCO pairs towards different species of gases and has additional tunable selectivity achieved by applying a current bias to the latter pair. Voltages were recorded in single, binary, and ternary gas streams of NO, NO 2,more » C 3H 8, and CO. We have also trained artificial neural networks to examine the voltage output from sensors in biased and unbiased modes to both identify which single test gas or binary mixture of two test gases is present in a gas stream as well as extract concentration values. We were then able to identify single and binary mixtures of these gases with accuracy of at least 98%. For determining concentration, the peak in the error distribution for binary mixtures was 5% and 80% of test data fell under <12% error. The sensor stability was also evaluated over the course of over 100 days and the ability to retrain ANNs with a small dataset was demonstrated.« less

Quantitative decoding of the response a ceramic mixed potential sensor array for engine emissions control and diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsui, Lok-kun; Benavidez, Angelica; Palanisamy, Ponnusamy

The development of on-board sensors for emissions monitoring is necessary for continuous monitoring of the performance of catalytic systems in automobiles. We have fabricated mixed potential electrochemical gas sensing devices with Pt, La 0.8Sr 0.2CrO 3 (LSCO), and Au/Pd alloy electrodes and a porous yttria-stabilized zirconia electrolyte. The three-electrode design takes advantage of the preferential selectivity of the Pt + Au/Pd and Pt + LSCO pairs towards different species of gases and has additional tunable selectivity achieved by applying a current bias to the latter pair. Voltages were recorded in single, binary, and ternary gas streams of NO, NO 2,more » C 3H 8, and CO. We have also trained artificial neural networks to examine the voltage output from sensors in biased and unbiased modes to both identify which single test gas or binary mixture of two test gases is present in a gas stream as well as extract concentration values. We were then able to identify single and binary mixtures of these gases with accuracy of at least 98%. For determining concentration, the peak in the error distribution for binary mixtures was 5% and 80% of test data fell under <12% error. The sensor stability was also evaluated over the course of over 100 days and the ability to retrain ANNs with a small dataset was demonstrated.« less

Heat of mixing and morphological stability

NASA Technical Reports Server (NTRS)

Nandapurkar, P.; Poirier, D. R.

1988-01-01

A mathematical model, which incorporates heat of mixing in the energy balance, has been developed to analyze the morphological stability of a planar solid-liquid interface during the directional solidification of a binary alloy. It is observed that the stability behavior is almost that predicted by the analysis of Mullins and Sekerka (1963) at low growth velocities, while deviations in the critical concentration of about 20-25 percent are observed under rapid solidification conditions for certain systems. The calculations indicate that a positive heat of mixing makes the planar interface more unstable, whereas a negative heat of mixing makes it more stable, in terms of the critical concentration.

Effective cluster interactions at alloy surfaces and charge self-consistency: Surface segregation in Ni-10 at. % Al and Cu-Ni

NASA Astrophysics Data System (ADS)

Schulthess, T.; Monnier, R.; Crampin, S.

1994-12-01

First-principles results are presented for the effective cluster interactions at the surface of a random Ni-10 at. % Al alloy. The derivation is based on an extension of the generalized perturbation method to semi-infinite inhomogeneous binary alloys, using a layer version of the Korringa-Kohn-Rostocker multiple-scattering approach in conjunction with the single-site coherent potential approximation to compute the self-consistent electronic structure of the system. When applied to the bulk, the method yields effective pair interactions that have the full point-group symmetry of the lattice to a very high level of numerical accuracy, despite the fact that intra- and interlayer couplings (scattering-path operators) are treated differently, and which are in perfect agreement with those of a recent three-dimensional treatment. Besides the pair terms, a selected class of triplet and quadruplet interactions are calculated, as well as the point interactions induced by the presence of the surface. The value of the latter in the first lattice plane is strongly exaggerated in our approach, leading to a complete segregation of the minority species to the surface. Using a value corresponding to the difference in the surface energies of the pure components for this term leads to the observed Al concentration of ~=25% at the surface. Possible reasons for the shortcomings of the theory are analyzed, and test calculations for the well studied Cu-Ni system show that the free energy of the semi-infinite alloy cannot be approximated by the sum over the single-particle band energies, once charge self-consistency is enforced at the surface.

Theoretical modelling of AFM for bimetallic tip-substrate interactions

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John

1991-01-01

Recently, a new technique for calculating the defect energetics of alloys based on Equivalent Crystal Theory was developed. This new technique successfully predicts the bulk properties for binary alloys as well as segregation energies in the dilute limit. The authors apply this limit for the calculation of energy and force as a function of separation of an atomic force microscope (AFM) tip and substrate. The study was done for different combinations of tip and sample materials. The validity of the universality discovered for the same metal interfaces is examined for the case of different metal interactions.

Dry silver electromigration process for optical glass waveguide fabrication and fluxless bonding technology for photonics and MEMS packaging

NASA Astrophysics Data System (ADS)

Chuang, Ricky Wenkuei

2001-07-01

An effectively simple dry silver electromigration technology without the need of evaporating separate gold or aluminum film electrodes onto both sides of glass is reported to fabricate low-loss deep multimode planar and channel waveguides on BK7 and BF450 glass substrates. A relatively high electrical field ranging from 440 to 545 V/mm was applied to the glass to speed up the migration, while at the same time preventing silver ions that were driven into the glass from reducing into silver atom; a major contributor to waveguide loss. The deep planar and channel waveguides thus fabricated showed no discolors or cracks, of which the attenuation losses of less than 2dB/cm and 0.1dB/cm were later measured from channel waveguides constructed on the BK7 and BF450 glass substrates, respectively, using our 0.6328mum He-Ne laser edge-coupling setup. To complete the waveguide studies, the scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDX) detector was adopted to obtain the concentration profiles of silver and sodium ions distributed in a waveguiding region after the exchange. The EDX measurements acquired hereafter were then utilized along with the Gladstone-Dale relation altogether to deduce the refractive index profile; of which a nearly step-like profile was consistently deduced from every deep planar and channel waveguides fabricated. Finally, a numerical model utilizing the space charge approach was devised to explain the nonlinear current effect often observed during the actual waveguide fabrication. The simulation results have confirmed that the nonlinear current-versus-time profile obtained is mainly attributed to the inhomogeneous distribution of the electric field in the glass substrate due to a space charge region created by the separation between silver- and sodium-ion migration fronts as a result of their unequal mobilities; a phenomenon which is ultimately responsible for the eventual slow down in the ion exchange rate as monitored during the actual electromigration process. A fluxless oxidation-free bonding technology using multilayer composite solders based on the non eutectic binary alloys of indium-tin (In-Sn), silver-indium (Ag-In), gold-tin (Au-Sn), and bismuth-tin (Bi-Sn) has been established and studied to determine its applicability to photonics and MEMS packaging. The scanning acoustic microscopy (SAM) conducted on these solder samples has consistently shown that a nearly void-free joint fabricated from each non-eutectic binary alloy system can be reliably achieved. In addition, the scanning electron microscopy (SEM) equipped with the energy dispersive X-ray (EDX) detector was also performed on the cross section of each sample to determine its joint composition, especially of any sign of intermetallic compounds. These results will demonstrate that any intermetallic compound or phase present in a joint fabricated with a pre-determined multilayer composition based on a specific binary alloy system can be well understood and fully justified by correlating the experimental outcome with its respective binary phase diagram.

The effect of solute on the homogeneous crystal nucleation frequency in metallic melts

NASA Technical Reports Server (NTRS)

Thompson, C. V.; Spaepen, F.

1982-01-01

A complete calculation that extends the classical theory for crystal nucleation in pure melts to binary alloys has been made. Using a regular solution model, approximate expressions have been developed for the free energy change upon crystallization as a function of solute concentration. They are used, together with model-based estimates of the interfacial tension, to calculate the nucleation frequency. The predictions of the theory for the maximum attainable undercooling are compared with existing experimental results for non-glass forming alloys. The theory is also applied to several easy glass-forming alloys (Pd-Si, Au-Si, Fe-B) for qualitative comparison with the present experimental experience on the ease of glass formation, and for assessment of the potential for formation of the glass in bulk.

Mossbauer effect in dilute iron alloys

NASA Technical Reports Server (NTRS)

Singh, J. J.

1975-01-01

The effects of variable concentration, x, of Aluminum, Germanium, and Lanthanum atoms in Iron lattice on various Mossbauer parameters was studied. Dilute binary alloys of (Fe-Al), (Fe-Ge), (Fe-Al) containing up to x = 2 a/o of the dilute constituent were prepared in the form of ingots and rolled to a thickness of 0.001 in. Mossbauer spectra of these targets were then studied in transmission geometry to measure changes in the hyperfine field, peak widths isomer shifts as well as the ratio of the intensities of peaks (1,6) to the intensities of peaks (2,5). It was shown that the concept of effective hyperfine structure field in very dilute alloys provides a useful means of studying the effects of progressively increasing the solute concentration on host lattice properties.

Preparation and some properties of Cu-Li alloys containing up to 20 at. % Li

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mendelsohn, M.; Krauss, A.R.; Gruen, D.M.

1985-01-01

Lithium strongly segregates to the surface of Cu-Li alloys, thus substantially lowering the Cu sputtering yield relative to pure Cu. Use of Cu-Li limiters or divertors in tokamaks can therefore be expected to be beneficial in limiting high-Z plasma impurity influx. A large scale (100-200g) method for the preparation of Cu-Li alloys is described. Analysis reveals that on solidification from the melt stratification occurs which leads to compositional inhomogeneity. The results are discussed in the light of the Cu-Li binary phase diagram and rationalized on the basis of large density differences between Cu and Cu-Li solid solutions. It is concludedmore » that obtaining homogeneous Cu-Li solid solutions is a nontrivial task.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Pei; Fang, Z. Zak; Koopman, Mark

Hydrogen has been investigated for decades as a temporary alloying element to refine the microstructure of Ti-6Al-4V, and is now being used in a novel powder metallurgy method known as "hydrogen sintering and phase transformation". Pseudo-binary phase diagrams of (Ti-6Al-4V)-xH have been studied and developed, but are not well established due to methodological limitations. In this paper, in situ studies of phase transformations during hydrogenation and dehydrogenation of (Ti-6Al-4V)-xH alloys were conducted using high-energy synchrotron X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The eutectoid phase transformation of β ↔ α + δ was observed in themore » (Ti-6Al-4V)-xH alloy via in situ synchrotron XRD at 211 °C with a hydrogen concentration of 37.5 at.% (measured using TGA-DSC). The relationships of hydrogen composition to partial pressure and temperature were investigated in the temperature range 450-900°C. Based on these results, a partial pseudo-binary phase diagram of (Ti-6Al-4V)-xH is proposed for hydrogen compositions up to 60 at.% in the temperature range 100-900°C. Using the data collected in real time under controlled parameters of temperature, composition and hydrogen partial pressure, this work characterizes relevant phase transformations and microstructural evolution for practical titanium-hydrogen technologies of Ti-6Al-4V.« less