CALCULATION OF THE TITANIUM-ALUMINUM PHASE DIAGRAM.

The Ti-Al phase diagram has been calculated by optimization of Gibbs energies with respect to phase diagram and thermochemical data. T//0 curves, the locus of compositions and temperatures where the Gibbs energies of the liquid and one of the solid phases are equal, have been calculated over the entire composition range. In order to assure physically reasonable extrapolations of the T//0 curves of the ordered phases far from their equilibrium stability ranges, the Bragg-Williams approximation was used to provide start values for the empirical optimizations. This approximation led to good convergence of the optimizations. Only small deviations from the Bragg-Williams Gibbs energies were needed to obtain excellent agreement with experimental data.