Thermodynamic description of Sn-Y and Mg-Sn-Y systems

The thermodynamic optimization of the Sn-Y and Mg-Sn-Y systems was critically carried out by means of the CALPHAD (CALculation of PHAse Diagram) technique. In the Sn-Y system, the solution phases (liquid, bcc, bct and hcp) were described by the substitutional solution model. The compound Sn₃Y₅, which has a homogeneity range, was treated as the formula (Sn, Y)₃(Sn, Y)₂Y₃ by a three-sublattice model in accordance with the site occupancies. In the Mg-Sn-Y system, the liquid phase was treated as the formula (Mg, Sn, Y, Mg₂Sn) using an associated solution model, and bcc, bct and hcp were treated as the formula (Mg, Sn, Y). The compound Sn₃Y₅ was treated as the formula (Sn, Y, Mg)₃(Sn, Y, Mg)₂Y₃. The ternary compound MgSnY was treated as stoichiometric compound. A set of self-consistent thermodynamic parameters of the Mg-Sn-Y system was obtained. The projection of the liquidus surfaces and the reaction scheme of the Mg-Sn-Y system were predicted.