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

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 T-0 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 1273 K to 1473 K 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. (C) 2015 Elsevier B.V. All rights reserved.