Thermodynamic Description of the Mg-Mn, Al-Mn and Mg-Al-Mn Systems Using the Modified Quasichemical Model for the Liquid Phases

Abstract

A self-consistent thermodynamic model of the Mg-Mn, Al-Mn and Mg-Al-Mn 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. In the absence of key data for the Mg-Mn system, the calculated thermodynamic properties from the model have been found comparable to other similar systems and the estimated critical temperature of the Mg-Mn liquid miscibility gap using the available empirical equation has been 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. Kohler symmetric extrapolation model with only one ternary interaction parameter has been used to calculate the ternary Mg-Al-Mn system. The thermodynamic description of the Mg-Al-Mn system has been verified by extensive comparison with the available experimental data from numerous independent experiments. The model can satisfactorily reproduce all the invariant points and the key phase diagram and thermodynamic features of the ternary as well as the constituent binary systems.