Thermodynamic Assessment and Determination of Spinodal Lines for Al-Zn Binary System

Abstract

Calphad type thermodynamic assessment of Al-Zn binary system was performed to calculate the metastable phase diagram including not only miscibility gap but also spinodal lines. The Gibbs free energy for liquid, fcc and hcp phases was evaluated by taking into account available experimental data, and most of them were satisfactorily reproduced by our thermodynamic descriptions. Furthermore, the Gibbs free energy for GP zones was also expressed by combining the chemical energy for solid solution of fcc-Al with appropriate elastic strain energy, in good agreement with experimentally reported solubility limits. Therefore, the spinodal lines derived from the differential of the Gibbs free energy could be also reasonably estimated, although those are quite difficult to be measured experimentally.