Critical assessment and thermodynamic modeling of Mg-Ca-Zn system supported by key experiments

A self-consistent thermodynamic description of the Mg-Ca-Zn ternary system has been obtained in this work. Four ternary intermetallic compounds (IM1, IM2, IM3 and IM4) and binary compounds with extended ternary solubility have been included in the modeling. Binary compounds, CaZn11 and CaZn13 in the Ca-Zn system have been re-modeled by compound energy formalism (CEF) to accommodate recently reported ternary solubility ranges. Also Mg2Ca in the Mg-Ca system has been re-optimized. Among the ternary intermetallic compounds, IM1 and IM3 having complex solubility ranges have also been modeled using compound energy formalism, whereas IM2 and IM4 have been considered as stoichiometric phases. Modified quasi-chemical model (MQM) has been used to model the liquid phase in the system. To investigate the behavior of the system and to verify the consistency of the thermodynamic model with experimental results, key samples with 4 at% and 6 at% Ca concentration were prepared and characterized with differential scanning calorimeter (DSC). Various vertical sections, liquidus projection and isothermal section at 608 K, in the Mg-Ca-Zn system have been calculated and found to be in good agreement with the experimental data.