Thermodynamic assessment of the Ce-Fe-Sb system

Abstract

Abstract The Ce-Fe-Sb ternary system is thermodynamically evaluated, based on all the presently available investigations of the isothermal sections and the liquidus projection. For all of the phases in the system, the expressions of Gibbs energies are proposed and the related parameters are optimized, after the systematic integration of the literature reported descriptions of the Ce-Fe and the Fe-Sb binary subsystems together with the present thermodynamic re-optimization of the Ce-Sb binary subsystem. The special attention is paid to the expression of the Gibbs energy of the liquid phase so as to get convergent the liquidus miscibility gap in the Fe-rich corner of the Ce-Fe-Sb ternary system at extraordinarily high temperature, which is easily caused by the very big difference between the values of the Gibbs energies of the terminal components Fe and CeSb. Using the Kaptay model to describe the interaction parameter between Ce and Sb, the excess Gibbs energy value approaches zero with increasing temperature, rather than decreases all the way down like using the polynomial expression, so that the difference of the Gibbs energy values between the terminal components Fe and CeSb can not become too big and the calculated liquid solution de-stabilization at extraordinarily high temperature can be avoided. For the isothermal sections, the liquidus projection and the liquidus mixing enthalpies, the comparisons between the results of computations with the data of experiments indicate that the present proposed modeling can finely reproduce the phase equilibria and the thermochemical properties of the Ce-Fe-Sb ternary system. The microstructure evolutions from high to low temperature for typical as-cast ternary alloys can be simulated by Scheil model for solidification analyses.