Thermodynamic assessment of La–Si and Mg–La–Si systems

Based on available phase equilibria and thermodynamic data, thermodynamic assessment has been carried out for La–Si binary system using CALPHAD approach. A set of self-consistent thermodynamic model parameters was obtained. The solution phases including Liquid, BCC, FCC, DHCP and Diamond_A4 were modeled as substitutional phases, of which the excess Gibbs energies being formulated with the Redlich–Kister polynomial function. And six intermediate compounds were treated as stoichiometric phases. Incorporated with thermodynamic parameters of Mg–La and Mg–Si binary systems cited from literatures, an isothermal section at 773 K of Mg–La–Si ternary system was thermodynamically optimized, including four ternary stoichiometric compounds (τ2, τ3, τ4 and τ5) and one semi-stoichiometric compound (τ1). The calculated phase equilibria and thermodynamic properties agreed well with experimental data.