Thermodynamic assessment of the Fe–Mn–Si system and atomic mobility of its fcc phase

Abstract

Thermodynamic optimizations have been performed for the Mn–Si binary and Fe–Mn–Si ternary system by the CALPHAD method. Combining the experimental and ab initio calculated data on the enthalpies of formation of manganese silicides, a better description for those silicides has been obtained. Almost all the latest data on phase equilibria in the Mn–Si system were reproduced satisfactorily. Based on the new assessments of the binary sub-systems and the recent experimental data on phase equilibria including martensitic transformations, a reassessment of the Fe–Mn–Si system has been carried out. The optimized parameters of the Fe–Mn–Si system successfully reproduced phase equilibrium data, as well as the T0 temperature between the fcc and hcp phases. Apart from the thermodynamic evaluation, the interdiffusion coefficients for the fcc phase of the binary Fe–Si and ternary Fe–Mn–Si system have been determined experimentally over the temperature range from 1273K to 1473K employing the diffusion-couple technique. Subsequently, atomic mobility data for the fcc phase of the Fe–Mn–Si system have been assessed and most diffusivity data have been satisfactorily described.