Thermodynamic modeling of the Mg–Sn–Zn ternary system

Mg-based alloys have been investigated widely due to the great potential for high performance structural applications. In the present work, the Mg–Sn binary system was re-optimized using the CALPHAD method through Thermo-calc® software package on the basis of available experimental information. Combined with the previous assessments of the Mg–Zn and Sn–Zn binary systems, the thermodynamic modeling of the Mg–Sn–Zn ternary system was performed. The liquid phase is described by the associated solution model with an associate Mg2Sn, while the solid solution phases, hcp(Mg), bct(Sn) and hcp(Zn), are modeled by the substitutional solution model. The intermetallic compound Mg2Sn is treated as a stoichiometric compound and its Gibbs energy was assessed considering the experimental heat capacity and heat content. The solubility of Sn in the Mg–Zn intermetallic compounds, Mg7Zn3, MgZn, Mg2Zn3, MgZn2 and Mg2Zn11, is not taken into account. Liquidus projection and many vertical sections of this ternary system were calculated. The calculated results are in good agreement with the reported experimental data.

Research highlights▶ The re-optimization of the Mg–Sn binary system is in much better agreement with the experimental results. ▶ Thermodynamic modeling of the Mg–Sn–Zn ternary system was performed in combination with the present and previous assessments of the binary sub-systems. ▶ The calculated liquidus projection and many vertical sections of this ternary system agree well with the experimental results.