A thermodynamic description of the Al-Mg-Zn system

Abstract

A thermodynamic description of the Al-Mg-Zn system was developed based on critically evaluated experimental data. All binary intermetallic phases are assumed to have negligible ternary solubility except for MgZn2. Three different thermodynamic models are applied to three different types of phases in this system, i.e., disordered solution phases, stoichiometric compounds, and semistoichiometric phases. The model parameters are optimized based on the thermodynamic descriptions of the constituent binaries and experimental phase equilibrium and thermodynamic data available in the literature. The good agreement obtained between several calculated isopleths and thermodynamic values of the liquid phase and experimental data shows that the current description of this system is reasonable. The calculated phase equilibria in the Al-rich corner are believed to be reliable for practical applications, while those away from the Al-rich region are subjected to large uncertainty. Additional experimental investigations are needed to firmly establish the phase equilibrium of this system over wide ranges of composition and temperature.