A re-evaluation of the Al---Ge system

Abstract

The Al---Ge phase diagram has been reassessed in the light of more recent information on phase equilibria and SGTE data for the phase stabilities of pure elements. A Redlich-Kister equation was used for the thermodynamic description of the liquid and solid solution phases. The assessment was carried out by simultaneously optimising the thermodynamic and phase diagram data using a nonlinear least squares optimisation technique developed for this purpose. It was based on a modified conjugate gradient method. The evaluated coefficients for the solid phase differ significantly from that reported in the earlier assessment by McAlister and Murray. The calculated phase diagram and thermodynamic properties of the liquid phase are in very good agreement with the literature. In view of the importance of metastable phase formations in these alloys, the equal Gibbs energy curve (T0 curve) and metastable extensions of liquidus and solidus are also calculated from the optimised thermodynamic data for the liquid and solid phases.