Abstract

Thermodynamic modeling of the Mg-Al-Sb system is carried out as a part of thermodynamic database construction for Mg-Al based alloys. This system was modeled by combining the thermodynamic descriptions of the constituent binaries Mg-Al, Al-Sb, and Mg-Sb. The Mg-Al system has been already studied thoroughly and its database is readily available. Hence, only Al-Sb and Mg-Sb were modeled in the present work considering all available experimental phase diagrams and thermodynamic data in the literature. Liquid phases in both systems were described by the Redlich-Kister polynomial model. High temperature modification of the Mg 3 Sb 2 compound in the Mg-Sb system was described by the sublattice model. The constructed database provides a basis to understand the alloys in the Mg-Al-Sb system. It was used to calculate and predict thermodynamic properties, binary phase diagrams of Al-Sb and Mg-Sb, and liquidus projections of the ternary Mg-Al-Sb. The calculated phase diagrams, the thermodynamic properties such as enthalpy, entropy, and Gibbs free energy of mixing, and activity of liquid Al-Sb and Mg-Sb alloys were found to be in good agreement with the experimental data reported in the literature. Moreover, isothermal sections, vertical sections, and phase assemblage diagrams were calculated for the Mg-Al-Sb ternary system, and the invariant reaction points were predicted. The predicted critical points in the Mg-Al-Sb system were 6 ternary eutectics, 2 ternary peritectics, one saddle point and 4 plait points. Mg-Al-Sb ternary phase diagram was modeled for the first time in this work.