Update of thermodynamic descriptions of the binary Al-Sn and ternary Mg-Al-Sn systems

Abstract

In this paper, the thermodynamic descriptions of the binary Al-Sn and ternary Mg-Al-Sn systems were updated by using the CALculation of PHAse Diagram (CALPHAD) approach. For the Al-Sn sub-binary system, the solubility of Sn in (Al)fcc, which was ignored in the previous assessment, together with the recently experimental enthalpies of mixing in the liquid phase were taken into account. The calculated phase equilibria and thermodynamic properties in the binary Al-Sn system showed better agreement with more experimental information than those in the previous assessment. As for the Mg-Al-Sn ternary system, the newly updated thermodynamic descriptions of the Al-Sn system as well as those of the Mg-Al and Mg-Sn binary systems from the literature were adopted. A set of reliable and self-consistent thermodynamic parameters for the Mg-Al-Sn ternary system were obtained by reassessing the thermodynaic parameters of the liquid and solid solutions. Better agreement between the calculated results and the experimental data was achieved in the present assessent in comparison with the previous one. Furthermore, the Scheil-Gulliver solidification simulations were performed to predict the volume fractions of Mg2Sn, (Mg)hcp and γ (Mg17Al12) phases in the 9 as-cast Mg-Al-Sn alloys. The simulation results were compared with the experiental as-cast microstructures in the literature, which further validated the presently obtained thermodynamic descriptions.