Third generation Calphad: A case study of the Fe–Cr–Ni system and its binary subsystems

Abstract

Thermodynamic descriptions of the binary Fe–Cr, Cr–Ni and Fe–Ni systems are evaluated in the present work using the most recent third generation Calphad models. The assessment incorporates formation energies of ordered fcc and bcc and σ compounds obtained from Density Functional Theory (DFT), where the formation energies of the ordered bcc and fcc phases were calculated in this study. The revised Inden–Hillert–Jarl model is applied to account for magnetic contributions to the thermodynamic properties. The Gibbs energies of the ordered end-members of the bcc, fcc and σ phases are formulated using the Effective Bond Energy Formalism (EBEF). This formalism provides reliable binary extrapolation for the fcc and bcc phases, whereas additional ternary interaction parameters remain necessary for the σ phase to reproduce the experimentally observed homogeneity and temperature ranges. EBEF significantly reduces the number of parameters required for the descriptions of binary and higher-order systems compared with the Compound Energy Formalism (CEF), where explicit treatment of end-members typically necessitates a larger parameter set.