Thermodynamic optimization of La–Zn and La–Mg–Zn systems

The La–Zn and La–Mg–Zn systems are optimized by means of CALPHAD (CALculation of PHase Diagrams) approach based on available experimental data in terms of thermodynamic properties and phase equilibria. Parameters for the thermodynamic models of the La–Mg and Mg–Zn systems are adopted from the literature. Solution phases are all described with the substitutional solution model. To taken into account the order/disorder transition between the couple of phases Bcc_B2/Bcc_A2, a single Gibbs energy function is applied for both the ordered and the disordered state. Isoplethic and isothermal sections as well as the liquidus projection are calculated using the obtained thermodynamic descriptions. They show good agreement with reported experimental data.