Phase separation and its effect on atomic interactions in CoCrNiCu medium-entropy alloys

Abstract Herein, the phase separation phenomenon and its effect on the atomic interactions of CoCrNiCux (x = 0, 0.33, 0.66, 1 in molar ratio) medium-entropy alloys were investigated. Phase alteration from single solid-solution face-centered cubic (FCC) phase to Cu-lean FCC1 and Cu-rich FCC2 structures was observed when Cu was added. This occurred due to the positive mixing enthalpy of Cu with other constituents, causing higher Gibbs free energy of mixing with increasing Cu content. This phase separation also affected the atomic interactions in the CoCrNiCux, as demonstrated by an atomic size misfit modelling. The tendency of the atomic interactions was also reflected in the mechanical properties, as displayed by Vickers microhardness result.