This paper provides a consistent thermodynamic data set for the whole Cr-Nb-Ni ternary system via thermodynamic modeling. All of the experimental phase diagram data available from the literature are critically reviewed and assessed using thermodynamic models for the Gibbs energies of individual phases. The ternary liquid and (Ni) phases are described with a regular solution model. The two-sublattice model is used to model the binary phases NbCr2(HT), NbCr2(LT), NbNi3, and Nb6Ni7. In order to reproduce the measured solid solubilities in the ternary system and to reduce the number of adjustable parameters, the third element is assumed to be anti-site atoms in only one sublattice. Optimal thermodynamic parameters are obtained by considering reliable literature data. Comprehensive comparisons between calculated and measured phase diagrams show that all the accurate experimental information is satisfactorily accounted for by the present thermodynamic description. The thermodynamic parameters obtained can also describe the diffusion paths observed for the diffusion couples between Nb and several Cr-Ni alloys annealed at 1002℃

The phase equilibria of the Co-Cu-Ti system at 850℃ are investigated using a high-efficiency diffusion couple and six key ternary alloys. The samples are examined by means of optical microscopy, scanning electron microscopy, and electron probe microanalysis. At 850℃, no ternary compound is found. The Ti3Cu phase is a metastable phase. The solubilities of Cu in Ti2Co, TiCo, TiCo2 (c) and TiCo3 were determined to be 8.7, 36, 2 and 5.4, respectively. And the solubilities of Co in Ti2Cu, TiCu, Ti3Cu4, and TiCu2 were measured to be 6.6, 0.7, 2.4, and 10.2, respectively. The following 9 three-phase equilibria are observed: (Ti)+Ti2Co+Ti2Cu, Ti2Co+Ti2Cu+TiCo, Ti2Cu+TiCu+TiCo, TiCu+Ti3Cu4+TiCo, Ti3Cu4+TiCu2+TiCo, TiCu2+TiCo+(Cu), TiCo+TiCo2(c)+(Cu), TiCo2(h)+TiCo3+(Cu), and TiCo3+(Co)+(Cu).

A method to estimate the thermodynamic properties of ternary alloys from those of constitutive binary alloys was proposed. The thermodynamic data of binaries were calculated by Miedema's theory. The asymmetry of constitutive binary alloys in the ternary system was considered in the present extrapolating procedure. The dependence of asymmetric constituent on the choice in Toop's model was overcome. The present method was used to calculate the formation enthalpies of Fe-Ni-V alloys. The agreement between the calculation and experiment is reasonable. So the formation enthalpies of Fe-Al-RE (RE=lanthanide metal) ternary alloys were calculated with the present method. The relative stability of RE(Fe1-xAlx)13, RE2(Fe1-xAlx)17 and RE5(Fe1-xAlx)17 were also studied with the present method.

The Nb-Ni system is reassessed on the basis of a critical literature review involving recent experimental data. These newly published experimental data include the phase relation associated with the NbNi8 phase, phase transition temperatures resulting from selected alloys, all invariant reaction temperatures, and enthalpies of mixing of liquid, as well as the crystallographic data on the μ(Nb7Ni6) phase. A consistent thermodynamic data set for the Nb-Ni system is obtained by optimization of the selected experimental values. The calculated phase diagram, crystallographic properties and thermodynamic properties agree reasonably with the experimental data. Noticeable improvements have been made, compared with the previous thermodynamic optimizations.

The Al-Y system is reassessed based on a critical literature review involving recently measured phase diagram and thermodynamic data. In the thermodynamic optimization, the liquid phase is described by using a substitutional solution model. Al3Y, AlY, Al2Y3 and AlY2 are modeled as stoichiometric ones. A two-sublattice model (Al,Y)2(Al,Y)1 has been used to describe Al2Y. A set of self-consistent thermodynamic parameters for the Al-Y binary system has been obtained by means of a CALPHAD approach applied to the selected experimental data. The reliable experimental phase diagram data and thermodynamic properties are well reproduced with the optimal thermodynamic parameters. The observed solidification paths for as-cast alloys can also be described reasonably using the present parameters. Significant improvement has been made, compared with previous assessments.