Relative crystal stability of AlxFeNiCrCo high entropy alloys from XRD analysis and formation energy calculation

Abstract

Electronic structure of AlxFeNiCrCo (x ≤ 3) high-entropy alloys (HEAs) was calculated using the Korringa–Kohn–Rostoker method combined with the coherent potential approximation (KKR-CPA). Total energy minimization was performed for bcc and fcc structures in each alloy composition. The phase stability was investigated from the total energy analysis, which finally allowed to determine the bcc–fcc phase transition for aluminium concentration close to 13 at%. It inspired us to synthesize AlxFeNiCrCo (0 ≤ x ≤ 1.5) using two procedures based on arc melting and sintering to allow for observation of entropy effect on phase formation. The XRD measurements evidently proved an occurence of fcc or bcc structure and their coexistence, depending on Al concentration and temperature. This finding remains in good agreement with theoretical results from free energy analysis, when accounting for KKR-CPA total energy as well as entropy terms. Furthermore, the structure preference, from fcc to bcc HEAs, with increasing Al content was discussed in view of total and atomic-dependent density of states computed in non-magnetic and paramagnetic-like states.