Ab Initio Calculations of Phase Stabilities in the Fe-Al-C System and CALPHAD-Type Assessment of the Iron-Rich Corner

Abstract

The goal of this article is to improve the description of the Fe-Al-C phase diagram through the density-functional theory (DFT) calculation of the Fe3AlC compound. Several binary stoichiometric compounds in the iron-rich part of the ternary Fe-Al-C system and the ternary stoichiometric carbide Fe3AlC are studied ab initio. The results in terms of lattice parameter, bulk modulus, magnetization, and enthalpy of formation are compared with the calculated values available in the literature. Via a fitted entropy of formation of the ternary carbide, the Gibbs energy of formation of this compound is evaluated as a function of temperature. A CALPHAD-type procedure is then used to calculate ternary Gibbs isotherms at 800 °C, 1000 °C, and 1200 °C. The isotherms are compared with the experimental data of the literature.