Thermodynamic modeling of the Mg-Mn-(Al, Zn) systems

A self-consistent thermodynamic model of the Mg-Mn, Al-Mn, Mn-Zn binary systems as well as the Mg-Al-Mn and Mg-Mn-Zn ternary systems has been developed. The major difference between this work and the already existing assessments of these systems is the application of the modified quasichemical model for the liquid phase in each system while most of the existing descriptions use the random mixing model. Further, this model is also used to describe one intermediate solid solution phase in the Mn-Zn system. In the absence of key experimental data for the Mg-Mn system, the calculated thermodynamic quantities from the model have been found comparable with other similar systems. The critical temperature of the Mg-Mn liquid miscibility gap has been estimated with the available empirical equation and found to be in acceptable agreement with the calculated value. A comparison between the current work and the most recent work on the Al-Mn system that uses the same model for the liquid phase reveals that better agreement with the experimental data with less number of model parameters has been achieved in the current work. The Mn-Zn system has been modeled for the entire compositon range and wide temperature range starting from room temperature. The accepted experimental data are well reproduced with the current description of the Mn-Zn system. Kohler symmetric extrapolation model has been used to calculate both Mg-Al-Mn and Mg-Mn-Zn systems. The thermodynamic description of the Mg-Al-Mn system has been verified by extensive comparison with the available experimental data from numerous independent experiments. However, the calculated Mg-Mn-Zn system could not be thoroughly verified due to the lack of experimental data. The model can satisfactorily reproduce all the invariant points and the key phase diagram and thermodynamic features of the Mg-Al-Mn, Mg-Mn-Zn ternary systems and the binary sub-systems