Composition Stability of Single Fcc Phase in Cr-Fe-Mn-Ni Alloys: First-Principles Prediction and Experimental Validation

Abstract

The relative phase stability of face-centered cubic (fcc) and body-centered cubic (bcc) Cr-Fe-Mn-Ni alloys has been investigated using a combination of density functional theory (DFT), cluster expansion (CE) and Monte Carlo (MC) simulations. The MC simulations for bcc and fcc Cr-Fe-Mn-Ni alloys performed using the CE models described in this work and in our previous paper, respectively, have enabled to compute the difference between Gibbs free energies of 1767 fcc and bcc alloys in the whole composition range with a 5% composition step as a function of temperature. By applying a common tangent construction procedure and averaging over six pseudobinary sets, the regions of stability of fcc and bcc phases have been identified as well as the region of coexistence of both phases. For the latter, the fractions of fcc and bcc phases have been calculated using a lever rule. The results of MC simulations are in agreement with the available experimental data from the literature and the experiments performed within this work for the samples of [CrFeMn] 100-x Ni x (x = 20, 25 and 35 at.%) alloys synthesized using arc-melting and annealed at 1273 K for 48 hours. In particular, the fcc fractions obtained using the electron backscatter diffraction (EBSD) method for the as-cast and annealed samples are in line with the values from MC simulations. The analysis of fcc fractions of the near-equiatomic alloy compositions has enabled the identification of the best candidates that are predicted to be single fcc phase for a wide range of temperatures with 95% confidence.

Keywords: High Entropy Alloys, phase composition, density functional theory (DFT), Monte Carlo simulations, Electron backscatter diffraction (EBSD)