The diffusion coefficients of several transition elements (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) and a few non-transition elements (Mg, Si, Ga, and Ge) in fcc and liquid Al are critically reviewed and assessed by means of the least-squares method and semi-empirical correlations. Inconsistent experimental data are identified and ruled out. In the case of the elements, for which plentiful experimental data are available in the literature, the least-squares analysis gives rise to the activation energies and pre-exponential factors in an Arrhenius equation. For the elements with limited experimental data or no data at all, the diffusion parameters are estimated from two semi-empirical correlations. In one correlation, the logarithmic pre-exponential factors are plotted against the activation energies for various elements in Al. In the other correlation, the activation energies are shown as a function of valences relative to Al. The diffusion coefficients calculated by using the evaluated diffusion parameters agree reasonably with the reliable experimental data. The proposed semi-empirical correlations are used to predict the diffusion coefficients of a few elements in liquid Al. A satisfactory agreement between the predicted and measured diffusion coefficients is obtained.

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.

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.

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 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.