Modeling on the molar volume of the Al-Cu-Mg-Si system

Molar volume is an important parameter for the microstructure evolution simulation in materials science. In this work, a comprehensive study on the temperature- and composition-dependents of the molar volume in the Al-Cu-Mg-Si system were performed using a CALPHAD (CALculation of PHAse Diagram)-type formalism. Based on the critical review of the available data on molar volume, molar volume of pure elements was described with a thermal expansion relation. Subsequently, molar volume of the binary solution phases was assessed via CALPHAD technique and the obtained description can reproduce the corresponding experimental data reasonably. Then, molar volume of ternary and higher-order solution phases was extrapolated from the binaries. Molar volumes of the stable compounds in the Al-Cu-Mg-Si system are also assessed in the similar model of the corresponding Gibbs energy expression. Using the established database for the quaternary Al-Cu-Mg-Si system, molar volume of some commercial aluminum alloys was predicted, which shows a good agreement with experimental data from literature.