On the Potential for Improving Equilibrium Thermodynamic Databases with Kinetic Simulations

In this work, the possibilities for improving the accuracy of thermodynamic databases based on kinetic simulations are explored. With a new model for the simulation of precipitation kinetics in multi-component alloys, calculations are performed with all unknown parameters of the simulation obtained from independent thermodynamic and kinetic databases. Since no fitting parameters are used, the simulations are considered as having ‘predictive character’. The corresponding methodology is outlined. Based on the comparison of the predicted precipitation kinetics and experimental information, the potential for improving the accuracy of thermodynamic databases is explored. This article was presented at the Multi-Component Alloy Thermodynamics Symposium sponsored by The Alloy Phase Committee of the joint EMPMD/SMD of the Minerals, Metals, and Materials Society (TMS), held in San Antonio, Texas, March 12-16, 2006, to honor the 2006 William Hume-Rothery Award recipient, Professor W. Alan Oates of the University of Salford, UK. The symposium was organized by Y. Austin Chang of the University of Wisconsin, Madison, WI, Patrice Turchi of the Lawrence Livermore National Laboratory, Livermore, CA, and Rainer Schmid-Fetzer of the Technische Universitat Clausthal, Clauthal-Zellerfeld, Germany.     

Alloy Thermal Physical Property Prediction Coupled Computational Thermodynamics with Back Diffusion Consideration

Simulation technologies are applied extensively in casting industries to understand the heat transfer and fluid transport phenomena and their relationships to the microstructure and the formation of defects. It is critical to have accurate thermo-physical properties as input for reliable simulations of the complex solidification and solid phase transformation processes. The thermo-physical properties can be calculated with the help of thermodynamic calculations of phase stability at given temperatures and compositions. A multicomponent alloy solidification model, coupled with a Gibbs free energy minimization engine and thermodynamic databases, has been developed. A back diffusion model is integrated so that the solidification conditions, such as cooling rate, can be taken into account. This article was presented at the Multi-Component Alloy Thermodynamics Symposium sponsored by The Alloy Phase Committee of the joint EMPMD/SMD of the Minerals, Metals, and Materials Society (TMS), held in San Antonio, Texas, USA, March 12-16, 2006, to honor the 2006 William Hume-Rothery Award recipient, Professor W. Alan Oates of the University of Salford, UK. The symposium was organized by Y. Austin Chang of the University of Wisconsin, Madison, WI, USA, Patrice Turchi of the Lawrence Livermore National Laboratory, Livermore, CA, USA, and Rainer Schmid-Fetzer of the Technische Universitat Clausthal, Clauthal-Zellerfeld, Germany.     

Thermodynamics of Hydrogen Solution and Hydride Formation in Binary Pd Alloys

Some recent thermodynamic results for the solution of H₂ and hydride formation in fcc disordered Pd-rich alloys based on a combined equilibrium-calorimetric technique are reviewed in this paper. This dual approach is more powerful than employing only one of these techniques. Some interesting thermodynamic results connected with these systems are presented, such as minima in ΔH _H and ΔS _H as a function of the H content of the alloys. This paper was presented at the Multi-Component Alloy Thermodynamics Symposium sponsored by the Alloy Phase Committee of the joint EMPMD/SMD of The Minerals, Metals, and Materials Society (TMS), held in San Antonio, Texas, March 12-16, 2006, to honor the 2006 William Hume-Rothery Award recipient, Professor W. Alan Oates of the University of Salford, UK. The symposium was organized by Y. Austin Chang of the University of Wisconsin, Madison, WI, Patrice Turchi of the Lawrence Livermore National Laboratory, Livermore, CA, and Rainer Schmid-Fetzer of the Technische Universitat Clausthal, Clauthal-Zellerfeld, Germany.     

Modeling of Microstructure and Microsegregation in Solidification of Multi-Component Alloys

Driven by industrial demand, extensive efforts have been made to investigate microstructure evolution and microsegregation development during solidification of multicomponent alloys. This paper briefly reviews the recent progress in modeling of microstructures and microsegregation in solidification of multicomponent alloys using various models including micromodel, phase field, front tracking, and cellular automaton approaches. A two-dimensional modified cellular automaton (MCA) model coupled with phase diagram software PanEngine is presented for the prediction of microstructures and microsegregation in the solidification of ternary alloys. The model adopts MCA technique to simulate dendritic growth. The thermodynamic data needed for determining the dynamics of dendritic growth are calculated with PanEngine. After validating the model by comparing the simulated values with the prediction of the Scheil model for solute profiles in the primary dendrites as a function of solid fraction, the model was applied to simulate the microstructure and microsegregation in the solidification of Al-rich ternary alloys. The simulation results demonstrate the capabilities of the present model not only to simulate realistic dendrite morphologies, but also to predict quantitatively the microsegregation profiles in the solidification of multi-component alloys. This article was presented at the Multi-Component Alloy Thermodynamics Symposium sponsored by the Alloy Phase Committee of the joint EMPMD/SMD of The Minerals, Metals, and Materials Society (TMS), held in San Antonio, Texas, March 12-16, 2006, to honor the 2006 William Hume-Rothery Award recipient, Professor W. Alan Oates of the University of Salford, UK. The symposium was organized by Y. Austin Chang of the University of Wisconsin, Madison, WI, Patrice Turchi of the Lawrence Livermore National Laboratory, Livermore, CA, and Rainer Schmid-Fetzer of the Technische Universitat Clausthal, Clauthal-Zellerfeld, Germany.     

Theoretical Investigation of Phase Equilibria for Metal-Hydrogen Alloy

Cluster variation method (CVM) was applied to calculate phase equilibria of metal-hydrogen systems. Two subjects are introduced in the present report. One is the summary of previous studies on the Pd-H system, and it is demonstrated that a single CVM free energy formula can systematically derive information of phase equilibria, intrinsic stability, and short range order diffuse intensities. The second subject is the theoretical calculations of superabundant vacancy (SAV) formation. Within the square approximation of the CVM, it is shown that abundant vacancies are introduced with the absorption of hydrogen when the interaction between vacancy and hydrogen is considered. This article was presented at the Multi-Component Alloy Thermodynamics Symposium sponsored by the Alloy Phase Committee of the joint EMPMD/SMD of The Minerals, Metals, and Materials Society (TMS), held in San Antonio, Texas, March 12-16, 2006, to honor the 2006 William Hume-Rothery Award recipient, Professor W. Alan Oates of the University of Salford, UK. The symposium was organized by Y. Austin Chang of the University of Wisconsin, Madison, WI, Patrice Turchi of the Lawrence Livermore National Laboratory, Livermore, CA, and Rainer Schmid-Fetzer of the Technische Universitat Clausthal, Clauthal-Zellerfeld, Germany.     

Configurational Entropies of Mixing in Solid Alloys

Entropy becomes an increasingly important contributor to the Gibbs energy at high temperatures with both non-configurational and configurational contributions to be considered. Some examples of where configurational entropies alone are important in determining the domain of phase stability of a solution phase are given. In phenomenological calculations, the modeling of configurational entropy should allow for short range order and be readily applicable to multicomponent systems. The use of Fowler-Yang-Li transforms is important in this regard by providing the opportunity for changing the functional variables in cluster calculations of the Gibbs energy from cluster probabilities or correlation functions to the considerably fewer point probabilities, just as in the Bragg-Williams approximation. This article was presented at the Multi-Component Alloy Thermodynamics Symposium sponsored by The Alloy Phase Committee of the joint EMPMD/SMD of The Minerals, Metals, and Materials Society (TMS), held in San Antonio, Texas, March 12-16, 2006, to honor the 2006 William Hume-Rothery Award recipient, Professor W. Alan Oates of the University of Salford, UK. The symposium was organized by Y. Austin Chang of the University of Wisconsin, Madison, WI. Patrice Turchi of the Lawrence Livermore National Laboratory, Livermore, CA, and Rainer Schmid-Fetzer of the Technische Universitat Clausthal, Clauthal-Zellerfeld, Germany.     

Atomistic Modeling of Multicomponent Systems

The need to accelerate materials design programs based on economical and efficient modeling techniques provides the framework for the introduction of approximations in otherwise rigorous theoretical schemes. Several quantum approximate methods have been introduced through the years, bringing new opportunities for the efficient understanding of complex multicomponent alloys at the atomic level. As a promising example of the role that these methods might have in the development of complex systems, in this work we discuss the Bozzolo-Ferrante-Smith (BFS) method for alloys and its application to a variety of multicomponent systems for a detailed analysis of their defect and phase structure and their properties. Examples include the study of the phase structure of new Ru-rich Ni-base superalloys, the role of multiple alloying additions in high temperature intermetallic alloys, and interfacial phenomena in nuclear materials, highlighting the benefits that can be obtained from introducing simple modeling techniques to the investigation of complex systems. This article was presented at the Multi-Component Alloy Thermodynamics Symposium sponsored by the Alloy Phase Committee of the joint EMPMD/SMD of The Minerals, Metals, and Materials Society (TMS), held in San Antonio, Texas, March 12-16, 2006, to honor the 2006 William Hume-Rothery Award recipient, Professor W. Alan Oates of the University of Salford, UK. The symposium was organized by Y. Austin Chang of the University of Wisconsin, Madison, WI, Patrice Turchi of the Lawrence Livermore National Laboratory, Livermore, CA, and Rainer Schmid-Fetzer of the Technische Universitat Clausthal, Clauthal-Zellerfeld, Germany.     

First-Principles Phase Stability Calculations of Pseudobinary Alloys of (Al,Zn)3Ti with L 12, D 022, and D 023 Structures

The thermodynamic and mechanical stability of intermetallic phases in the Al₃Ti-Zn₃Ti pseudobinary alloy system is investigated from first-principles total energy calculations through electronic density-functional theory within the generalized gradient approximation. Both supercell calculations and sublattice-cluster-expansion methods are used to demonstrate that the addition of Zn to the Al sublattice of Al₃Ti stabilizes the cubic L1₂ structure relative to the tetragonal D0₂₂ and D0₂₃ structures. This trend can be understood in terms of a simple rigid-band picture in which the addition of Zn modifies the effective number of valence electrons that populate bonding and anti-bonding states. The calculated zero-temperature elastic constants show that the binary end members are mechanically stable in all three ordered phases. These results point to a promising way to cost effectively achieve the stabilization of L1₂ precipitates in order to favor the formation of a microstructure associated with desirable mechanical properties. This article was presented at the Multi-Component Alloy Thermodynamics Symposium sponsored by The Alloy Phase Committee of the joint EMPMD/SMD of The Minerals, Metals, and Materials Society (TMS), held in San Antonio, TX, March 12-16, 2006, to honor the 2006 William Hume-Rothery Award recipient, Professor W. Alan Oates of the University of Salford, UK. The symposium was organized by Y. Austin Chang of the University of Wisconsin, Madison, WI, Patrice Turchi of the Lawrence Livermore National Laboratory, Livermore, CA, and Rainer Schmid-Fetzer of the Technische Universitat Clausthal, Clauthal-Zellerfeld, Germany.     

The influence of solution-model complexity on phase diagram prediction

In the derivation of phase diagrams using solid- and liquid-solution thermodynamic equilibria, thermodynamic models are used to extrapolate experimental data to a broader range of compositions and temperatures. Such models have historically increased in complexity from the regular-solution formalism, with regard to both temperature and composition dependence of parameters. The regular, quasi-regular, subsubregular, and quasi-subsubregular models have been applied to existing thermodynamic data for four“simple” metallic systems of differing types (Cu-Ni, Pb-Ag, Sn-Zn, and Ge-Mg) to illustrate the effect of more accurate thermodynamic modeling on the resulting predicted phase diagrams. Comparison with the actual phase diagrams demonstrates the relative importance of“nonregularity” in the solution with regard to both composition and temperature in the accuracy of phase diagram prediction. This paper was presented at the International Phase Diagram Prediction Symposium sponsored by the ASM/MSD Thermodynamics and Phase Equilibria Committee at Materials Week, October 21-23,1991, in Cincinnati, OH. The symposium was organized by John Morral, University of Connecticut, and Philip Nash, Illinois Institute of Technology.     

Phase equilibria and thermal analysis of Si–C–N ceramics

The phase reactions, crystallization behaviour and thermal degradation of two Si–C–N ceramics derived from precursors VT50 and NCP200, respectively, were studied by means of CALPHAD type thermodynamic calculations and experimental investigations by DTA/TG, XRD and SEM/EDX. The phase reaction Si₃N₄+3C=3SiC+2N₂ proceeds during the thermal degradation of both ceramics. Additionally, the phase reaction Si₃N₄=3Si+2N₂ occurs during the thermal degradation of the NCP200 ceramic. To explain quantitatively the high temperature behaviour of Si–C–N ceramics, thermodynamic functions, the reaction scheme, isothermal sections, isopleths, phase fraction diagrams and phase composition diagrams (for gas partial pressures) were calculated. The computer simulations were confirmed by the experiments for both ceramics.     

Phase diagram imaging by means of temperature-gradient diffusion couples

Phase diagram imaging is an experimental procedure for determining portions of binary phase diagrams in the solid state by means of isothermal and temperature- gradient diffusion couples (TGDCs). With this technique,it is possible to study phase reactions as a function of both composition and temperature simultaneously even if the temperatures of competing nonvariant phase reactions differ by no more than a few degrees. In metallographic cross sections of diffusion couples that were annealed in a temperature gradient,the phase sequence can be made visible. The phases present can be identified by X- ray diffraction (XRD), and they are accessible for electron probe microanalysis (EPMA) as well. The benefits of this technique are discussed for a portion of the Ti- N system. Results are presented and compared to results from differential thermal analysis (DTA). This paper was presented at the International Phase Diagram Prediction Symposium sponsored by the ASM/MSD Thermodynamics and Phase Equilibria Committee at Materials Week, October 21–23,1991, in Cincinnati, Ohio. The symposium was organized by John Morral, University of Connecticut, and Philip Nash, Illinois Institute of Technology.     

Comment on As-Cu (Arsenic-Copper)

This Section is intended to provide the most current phase diagram data. Guidelines for the inclusion of new information in this section are (1) systems for which no phase diagrams are given in Binary Alloy Phase Diagrams, second edition; (2) complete diagrams that are substantially different from earlier versions published in Binary Alloy Phase Diagrams, second edition, the Bulletin of Alloy Phase Diagrams, or single-topic monographs; (3) partial diagrams that alter or clarify earlier versions in the above-mentioned publications; and (4) relevant new literature of interest Thermodynamic consistency of the new phase diagrams was checked based on phase rules, and the diagrams were modified if necessary. However, the diagrams and texts have not gone through the ordinary reviewing process, and the final evaluations may be carried out by relevant category editors of the Alloy Phase Diagram Program. For convenience, reaction tables and crystal structure data are added when new information is available.     

Survey of current literature

This Section is intended to provide the most current phase diagram data. Guidelines for the inclusion of new information in this section are (1) systems for which no phase diagrams are given in Binary Alloy Phase Diagrams, second edition; (2) complete diagrams that are substantially different from earlier versions published in Binary Alloy Phase Diagrams, second edition, the Bulletin of Alloy Phase Diagrams, or single-topic monographs; (3) partial diagrams that alter or clarify earlier versions in the above-mentioned publications; and (4) relevant new literature of interest Thermodynamic consistency of the new phase diagrams was checked based on phase rules, and the diagrams were modified if necessary. However, the diagrams and texts have not gone through the ordinary reviewing process, and the final evaluations may be carried out by relevant category editors of the Alloy Phase Diagram Program. For convenience, reaction tables and crystal structure data are added when new information is available.     

Survey of current literature

This Section is intended to provide the most current phase diagram data. Guidelines for the inclusion of new information in this section are (1) systems for which no phase diagrams are given inBinary Alloy Phase Diagrams, second edition; (2) complete diagrams that are substantially different from earlier versions published inBinary Alloy Phase Diagrams, second edition, theBulletin of Alloy Phase Diagrams, or single-topic monographs; (3) partial diagrams that alter or clarify earlier versions in the above-mentioned publications; and (4) relevant new literature of interest. Thermodynamic consistency of the new phase diagrams was checked based on phase rules, and the diagrams were modified if necessary. However, the diagrams and texts have not gone through the ordinary reviewing process, and the final evaluations may be carried out by relevant category editors of the Alloy Phase Diagram Program. For convenience, reaction tables and crystal structure data are added when new information is available.     

Survey of current literature

This Section is intended to provide the most current phase diagram data. Guidelines for the inclusion of new information in this section are (1) systems for which no phase diagrams are given inBinary Alloy Phase Diagrams, second edition; (2) complete diagrams that are substantially different from earlier versions published inBinary Alloy Phase Diagrams, second edition, theBulletin of Alloy Phase Diagrams, or single-topic monographs; (3) partial diagrams that alter or clarify earlier versions in the above-mentioned publications; and (4) relevant new literature of interest. Thermodynamic consistency of the new phase diagrams was checked based on phase rules, and the diagrams were modified if necessary. However, the diagrams and texts have not gone through the ordinary reviewing process, and the final evaluations may be carried out by relevant category editors of the Alloy Phase Diagram Program. For convenience, reaction tables and crystal structure data are added when new information is available.     

Thermodynamic assessments of the Cu–Th and Mo–Th systems

The thermodynamic assessments of the Cu–Th and Mo–Th binary systems were carried out by using Calculation of Phase Diagrams (CALPHAD) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, bcc, and fcc phases are described by the subregular solution model with the Redlich–Kister equation and those of the four intermetallic compounds Cu₆Th, Cu_3.6Th, Cu₂Th and CuTh₂ in the Cu–Th binary system were described by the sublattice model. A set of self-consistent thermodynamic parameters are obtained, and the calculated phase diagrams and thermodynamic properties are presented and compared with the experimental data from literatures. The calculated thermodynamic properties as well as phase diagrams are in good agreement with the experimental data.     

粉末中C抑制FeAl熔滴氧化机制及其对等离子喷涂层组织与性能的影响*

大气等离子喷涂（APS）金属时,熔滴不可避免地发生氧化是难以获得粒子间结合充分的致密涂层的主要原因。以FeAl金属间化合物为例,提出一种在粉末中添加亚微米金刚石颗粒引入碳源,以期利用碳在高温下优先氧化的特性抑制等离子喷涂飞行粒子中Fe、Al元素的氧化,获得无氧化物的高温熔滴从而制备低氧含量（质量分数）、粒子间充分结合的FeAl金属间化合物涂层的新方法。采用APS制备Fe Al涂层,研究金刚石的添加对涂层氧含量、碳含量、涂层内粒子间结合质量与硬度的影响规律,探讨FeAl熔滴飞行中的氧化行为。采用商用热喷涂粒子诊断系统测量APS喷涂中的粒子温度,通过SEM与XRD表征了涂层的组织结构,并表征涂层的结合强度与硬度。结果表明,在等离子射流的加热和Fe、Al元素放热反应的联合作用下,飞行中FeAl熔滴的表面温度可达2 000℃以上,满足C原位脱氧的热力学条件。与不含碳的传统Fe Al涂层中的氧含量随喷涂距离的增加而显著增加的规律完全不同,用Fe/Al/2.5C粉末喷涂时涂层中的氧含量随距离的增加而减小,表明飞行中熔滴的氧化得到抑制,实现了C原位脱氧抑制金属元素氧化的自清洁氧化物的效应。FeAl/...