Thermodynamic assessment of the Cr–Si binary system

Abstract

A thermodynamic evaluation of the Cr–Si system was performed concerning the latest experimental phase diagram and with the aid of first-principles calculations. The thermodynamic parameters for the Gibbs energy of pure Cr were modified based on the new experimental value of 1861 °C for the melting point of pure Cr, which was previously reported as 1907 °C in the SGTE database. The Gibbs energy descriptions of the Cr₃Si and Cr₅Si₃ phases were revised using Cr₃(Cr,Si)- and (Cr,Si)₅Si₃-type two-sublattice models to reproduce the latest experimental results of their solubility composition ranges, that is, Cr₃Si extending toward the Cr-rich side and Cr₅Si₃ extending toward the Si-rich side from the stoichiometry. The CrSi and CrSi₂ phases were considered line compounds with no solubility range, and the solubility of Cr in the Si phase was ignored. A set of self-consistent thermodynamic parameters for the Cr–Si system was obtained using the CALPHAD technique. The phase diagrams calculated using the optimized parameters showed reasonable agreement with the latest phase equilibrium data and thermodynamic property data in the literature, including the enthalpy of mixing, formation enthalpy, and chemical potential diagrams of Cr and Si in the equilibrium phases.