Thermodynamic modeling of the Pd-X (X=Ag, Co, Fe, Ni) systems

A set of self-consistent thermodynamic model parameters is presented to describe the phase equilibria of the Ag-Pd, Co-Pd, Fe-Pd, and Ni-Pd systems. In most cases, the calculated values using the optimized model parameters agree very well with the experimental data. The FePd and FePd₃ phases with large homogeneity ranges are described by the compound energy formalism. At present, insufficient thermodynamic data are available for these two phases. Therefore, experimental data on the heat of formation and/or the first-principle calculation of cohesive energies will be very useful for further refinement of thermodynamic parameters of FePd and FePd₃ phases.     

Phase equilibria in Fe-Cu-X (X: Co, Cr, Si, V) ternary systems

Phase equilibria on the Fe-Cu side in the Fe-Cu-X (X: Co, Cr, Si, V) system were experimentally determined over the temperature range of 1073–1273 K. Based on the present results and previous works, the thermodynamic assessments of the phase equilibria in the Fe-Cu-X system were evaluated using the Calculation of Phase Diagram (CALPHAD) method. The Gibbs energies (G) of the bcc, fcc, and liquid phases are described by the subregular solution model, and a set of thermodynamic parameters enable us to calculate various isothermal and vertical sections and the miscibility gaps of the solid and liquid phases.     

Phase equilibria in Fe-Cu-X (X: Co, Cr, Si, V) ternary systems

Phase equilibria on the Fe-Cu side in the Fe-Cu-X (X: Co, Cr, Si, V) system were experimentally determined over the temperature range of 1073–1273 K. Based on the present results and previous works, the thermodynamic assessments of the phase equilibria in the Fe-Cu-X system were evaluated using the Calculation of Phase Diagram (CALPHAD) method. The Gibbs energies (G) of the bcc, fcc, and liquid phases are described by the subregular solution model, and a set of thermodynamic parameters enable us to calculate various isothermal and vertical sections and the miscibility gaps of the solid and liquid phases.     

Experimental investigation and thermodynamic calculation of binary Mg-Mn phase equilibria

The monotectic reaction L″=L′+δMn in the binary system Mg-Mn was measured at about 1200 °C using differential thermal analysis. This was possible by sealing the samples in arc welded Ta capsules, thus solving the problem of high vapor pressure of Mg at such high temperature and also suppressing any reaction of Mg with the environment. Problems associated with the reaction of Mn with the Ta crucible are discussed in detail. In addition, a thermodynamic assessment and calculation of the entire Mg-Mn phase diagram was performed, incorporating published experimental data on the Mn solubility in the Mg-rich corner.     

Thermodynamic modeling of the Pd-X (X=Ag, Co, Fe, Ni) systems

A set of self-consistent thermodynamic model parameters is presented to describe the phase equilibria of the Ag-Pd, Co-Pd, Fe-Pd, and Ni-Pd systems. In most cases, the calculated values using the optimized model parameters agree very well with the experimental data. The FePd and FePd₃ phases with large homogeneity ranges are described by the compound energy formalism. At present, insufficient thermodynamic data are available for these two phases. Therefore, experimental data on the heat of formation and/or the first-principle calculation of cohesive energies will be very useful for further refinement of thermodynamic parameters of FePd and FePd₃ phases.     

Experimental investigation and thermodynamic calculation of the phase equilibria in the Co-Nb-Ta ternary system

The isothermal sections of the Co-Nb-Ta ternary system at 900 °C, 1000 °C, 1100 °C, 1200 °C, 1300 °C have been experimentally determined by electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques on the equilibrated alloys. On the basis of the experimental data investigated in the present work, the phase equilibria in the Co-Nb-Ta system has been thermodynamically assessed by using CALPHAD (CALculation of PHAse Diagrams) method, and a consistent set of the thermodynamic parameters leading to reasonable agreement between the calculated results and experimental data was obtained.     

Thermodynamic calculation of phase equilibria of the Bi-Sn-Zn system

A thermodynamic assessment of the Bi-Sn-Zn ternary system was carried out by considering the experimental data including the phase equilibria and thermodynamic properties on the basis of the CALPHAD method. A set of optimized thermodynamic parameters has been obtained, which leads to a very good fit between calculation and experiments. In particular, the thermodynamic calculations in the Sn-rich portion are presented in view of the recent progress in Pb-free solder alloys.     

Thermodynamic calculation of phase equilibria of the Bi-Sn-Zn system

A thermodynamic assessment of the Bi-Sn-Zn ternary system was carried out by considering the experimental data including the phase equilibria and thermodynamic properties on the basis of the CALPHAD method. A set of optimized thermodynamic parameters has been obtained, which leads to a very good fit between calculation and experiments. In particular, the thermodynamic calculations in the Sn-rich portion are presented in view of the recent progress in Pb-free solder alloys.     

Experimental study of ternary Pd-Zn-Se phase equilibria and Pd/ZnSe bulk diffusion

The ternary system Pd-Zn-Se was investigated at 340°C. A complete isothermal phase diagram is given, containing the formerly known ternary phase Pd₅ZnSe (τ₁) as well as a newly discovered ternary phase τ₂ of approximate composition Pd₆₂Zn₃₂Se₆. The reaction diffusion between Pd and ZnSe was investigated at 340°C with bulk diffusion couples Pd/ZnSe, annealed from 6 to 192 h, and the diffusion path is described. For the investigation x-ray powder diffraction, scanning electron microscopy, and energy dispersive x-ray analysis was used. Implications for the application of Pd as metallic contact to semiconducting ZnSe are outlined.     

Experimental investigation of phase equilibria in the Co-W-V ternary system

The phase equilibria in the Co-W-V ternary system were experimentally investigated by optical microscopy (OM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) on the equilibrated alloys. Three isothermal sections of the Co-W-V ternary system at 1100 °C, 1200 °C and 1300 °C were determined, and no ternary compound was found in this system. In addition, a novel phenomena induced by the liquid phase separation in the Co-W-V alloys was firstly discovered, suggesting that a stable liquid miscibility gap exists in the Co-W-V ternary system. The newly determined phase equilibria and firstly discovered phase separation phenomena in the Co-W-V system will provide important information for the development of Co-W based alloys.     

Reinvestigation of Ni-solid solution/liquid equilibria in Ni-Al binary and Ni-Al-Zr ternary systems

The present work reports the results of a reinvestigation of the γ liquidus and solidus temperatures of the Ni-Al system and the γ/Ni₅Zr eutectic reaction temperatures in the Ni-Al-Zr system. In the Ni-Al binary system, it is found that the stability of the Ni-rich γ solid solution phase is enhanced by small additions of Al with the melting temperature of the γ phase and that the melting temperature reaches a congruent maximum at a few at.% Al. The temperature of the eutectic reaction L→γ+Ni₅Zr in the Ni-Zr binary edge is confirmed to be 1196 °C by differential thermal analysis (DTA), rather higher than the value reported previously. The reaction temperature increases with Al addition to reach or exceed 1206 °C, forming a “saddle point,” then decreasing to reach 1187 °C or below by flowing into a ternary invariant reaction. These findings can be explained by γ/liquid equilibrium in the Ni-Al binary system.     

Reinvestigation of Ni-solid solution/liquid equilibria in Ni-Al binary and Ni-Al-Zr ternary systems

The present work reports the results of a reinvestigation of the γ liquidus and solidus temperatures of the Ni-Al system and the γ/Ni₅Zr eutectic reaction temperatures in the Ni-Al-Zr system. In the Ni-Al binary system, it is found that the stability of the Ni-rich γ solid solution phase is enhanced by small additions of Al with the melting temperature of the γ phase and that the melting temperature reaches a congruent maximum at a few at.% Al. The temperature of the eutectic reaction L→γ+Ni₅Zr in the Ni-Zr binary edge is confirmed to be 1196 °C by differential thermal analysis (DTA), rather higher than the value reported previously. The reaction temperature increases with Al addition to reach or exceed 1206 °C, forming a “saddle point,” then decreasing to reach 1187 °C or below by flowing into a ternary invariant reaction. These findings can be explained by γ/liquid equilibrium in the Ni-Al binary system.     

Experimental investigation and thermodynamic calculation of the phase equilibria in the Co–Mo–W system

The isothermal sections in the Co–Mo–W ternary system at 600 °C, 800 °C, 1000 °C, 1100 °C, 1200 °C and 1300 °C have been determined using the Electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD) techniques. A thermodynamic assessment of the Co–Mo–W ternary system was carried out by the CALPHAD (Calculation of Phase Diagrams) method. The Gibbs free energies of the liquid and solution phases were described by the subregular solution models, and those of intermetallic compounds were described by the sublattice model. A consistent set of thermodynamic parameters has been derived for describing the Gibbs free energies of each solution phase and intermetallic compound in the Co–Mo–W ternary system. The calculated phase diagrams and thermodynamic properties in the Co–Mo–W ternary system are in good agreement with experimental data.     

扩散偶实验研究Pd-M(M=Pt,Co,Ni)二元系的物相

以Pd-M(M=Pt,Co,Ni)体系为研究对象,概述了各二元体系相图的研究现状,采用扩散偶技术研究了700℃时Pd-M(M=Pt,Co,Ni)体系各元素的扩散行为及平衡物相.结果表明,700℃时Pd-Pt体系发生了调幅分解反应,生成了富Pd相和富Pt相;Pd-Co扩散偶形成了摩尔分数约Pd7.4Co92.6的合金;P...     

Analyses of HCP/D019 and D019/L10 phase boundaries in Ti-Al-X (X=V, Mn, Nb, Cr, Mo, Ni, and Co) systems by the cluster variation method

The cluster variation method (CVM) based on the octahedron and tetrahedron approximation was applied to the calculation of γ(TiAl, L1₀)/α ₂(Ti₃Al, D0₁₉) phase equilibrium in the Ti-Al-X (X=V, Mn, Nb, Cr, Mo, Ni, and Co) systems. The antiphase boundary (APB) energy, the long-range order (LRO) parameter, and the substitution behavior of the γ(TiAl, L1₀) were calculated. The results of calculations were in good agreement with the data determined experimentally.     

Analyses of HCP/D019 and D019/L10 phase boundaries in Ti-Al-X (X=V, Mn, Nb, Cr, Mo, Ni, and Co) systems by the cluster variation method

The cluster variation method (CVM) based on the octahedron and tetrahedron approximation was applied to the calculation of γ(TiAl, L1₀)/α ₂(Ti₃Al, D0₁₉) phase equilibrium in the Ti-Al-X (X=V, Mn, Nb, Cr, Mo, Ni, and Co) systems. The antiphase boundary (APB) energy, the long-range order (LRO) parameter, and the substitution behavior of the γ(TiAl, L1₀) were calculated. The results of calculations were in good agreement with the data determined experimentally.     

Thermodynamic analysis and phase equilibria calculations of pb-zn, sn-zn, and pb-sn-zn systems

Thermodynamic properties of liquid and solid phases in the Pb-Zn, Sn-Zn, and Pb-Sn-Zn systems were assessed using a quasi sub-subregular solution model. The model parameters for different phases were obtained by simultaneous optimization with respect to the available thermodynamic and phase equilibrium data. Phase diagrams and thermodynamic data were then calculated and compared with the experimental/assessed data.     

Thermodynamic study of the phase equilibria in the Sn−Ti−Zn ternary system

The Sn−Ti−Zn ternary phase diagram has been constructed using the CALPHAD technique. The Ti−Zn binary system phase boundaries were determined using differential scanning calorimetry and the solid-liquid diffusion couples method. In addition, the formation energy of some stoichiometric compounds was obtained using first-principle band energy calculations. For the ternary system, some alloys were prepared by equilibration at 600 or 700 °C, and the compositions of the precipitates were analyzed using electron probe microanalysis. Thermodynamic assessment of the Ti−Zn and Sn−Ti−Zn systems was performed based on the experimental information and by adopting reported values of the thermodynamic properties of the Sn−Zn and Sn−Ti binary systems. Microstructural observation showed that Sn₃Ti₅Zn₁₂ exists in the ternary system. Seven types of invariant reaction on the Sn-rich liquidus surface of the ternary system are predicted by the phase diagram calculations. The ternary eutectic point falls at 0,0009 mass% Ti and 8.69 mass% Zn, at T=192.40°C, which is slightly lower than the calculated eutectic point of Sn−Zn binary alloy (T=192.41°C). Based on these results, a nonequilibrium solidification process using the Scheil model was simulated. This paper was presented at the International Symposium on User Aspects of Phase Diagrams, Materials Solutions Conference and Exposition, Columbus, Ohio, 18–20 October, 2004.     

Thermodynamic database of the phase diagrams in Cu-Fe base ternary systems

A thermodynamic database of the Cu-Fe-X [X: aluminum (Al), cobalt (Co), chromium (Cr), manganese (Mn), molybdenum (Mo), niobium (Nb), nickel (Ni), vanadium (V)] systems was developed by the CALPHAD (Calculation of Phase Diagrams) method, where the Gibbs energies of solution phases such as the liquid, face-centered-cubic (fcc), body-centered-cubic (bcc), and hexagonal-close-packed (hcp) phases are described by the subregular solution model, while the those of the bcc phase in the Cu-Fe-Al system and of all compounds are described by the sublattice model. The thermodynamic parameters describing Gibbs energies of the different phases in this database were evaluated by fitting the experimental data for phase equilibria and thermodynamic properties. On the basis of this database, much information concerning stable and metastable phase equilibria of isothermal and vertical sections, molar fractions of constituent phases, the liquidus projection, etc., can be predicted. This database is expected to play an important role in the design of Cu-Fe base alloys.