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 (tau(2), tau(3), tau(4) and tau(5)) and one semi-stoichiometric compound (tau(1)). The calculated phase equilibria and thermodynamic properties agreed well with experimental data. (C) 2009 Elsevier B.V. All rights reserved.