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 modified cluster-site approximation (CSA) model has been used to model the f.c.c. phases (ordered L12 and disordered A1) in the Ni-Al system. The CSA model has the advantage over the cluster variation method (CVM) in that the independent variables in the free energy functional are the site probabilities and not the cluster probabilities. Unlike the zeroth approximation, however, the CSA takes short-range order into consideration, an essential requirement for describing phases that undergo an order/disorder transition, as does the f.c.c. phase in the Ni-Al system. By using the modified CSA model, we have been able to obtain an improved phenomenological description of this system with the use of fewer model parameters than used in previous descriptions. The topology of the calculated metastable f.c.c. phase diagram is similar to the one obtained using a 'first-principles'-CVM approach, whereas the f.c.c. phase diagrams based on the previous phenomenological descriptions are unsatisfactory.

The Al-Be system is investigated via three steps. In the first step, all of the experimentally measured phase diagram and thermodynamic data available in the literature are critically reviewed. On the basis of the assessed phase diagram, in the second step, eight decisive samples are prepared by arc melting of Al and Be pieces and annealing at 600℃ for eight days. Water-quenched samples are analyzed using differential thermal analysis (DTA), X-ray diffraction (XRD), optical microscopy, and scanning electron microscopy (SEM) techniques. In the last step, an optimal thermodynamic data set for the Al-Be system has been obtained by considering the present experimental data and the reliable literature data. The calculated phase diagram and thermodynamic properties agree well with the accurate experimental values.

The isothermal section at 950℃ of the Co-Nb-Ti system was investigated using diffusion couples and six ternary alloys. The specimens were examined by means of optical microscopy, scanning electron microscopy and electron probe microanalysis. No ternary compound was found. Nine three-phase equilibria were observed. The binary intermediate phases NbCo3 and Nb2Co7, the existence of which is still controversial in the literature, were observed at 950℃. The solubilities of Ti in Nb2Co7, NbCo3, γ-NbCo2 and μ-Nb6Co7 were determined to be 1.9, 16.4, 14.4 and 17.4 at.%, respectively. The solubilities of Nb in TiCo3, TiCo2(h), TiCo2(c), TiCo and Ti2Co were determined to be about 5.7, 11.0, 2.6, 13.6 and 3.1 at.%, respectively.

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.