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.