Effects of the Replacement of Co with Ni on the Microstructure, Mechanical Properties, and Age Hardening of AlCo(1−x)CrFeNi(1+x) High-Entropy Alloys

In this study, effects of the replacement of Co with Ni on the microstructure, mechanical properties, and age hardening of high-entropy alloys of AlCo(1−x)CrFeNi(1+x) (x = molar ratio; x = 0, 0.5, 1, denoted as X(0), X(0.5), and X(1), respectively) were investigated. These three alloys exhibited a dendritic structure comprising an ordered BCC matrix, a BCC phase, and an FCC or an ordered FCC phase. From X(0) to X(1) alloys, the yield stress and compressive stress decreased from 1202 and 1790 MPa to 693 and 1537 MPa, respectively. However, fracture strain increased from 0.15 to 0.42. Peak age hardening at 600 °C for the X(0) alloy was due to the precipitation of the (Cr,Fe)-rich σ phase. Peak age hardening for the X(0.5) and X(1) alloys was observed at 500 °C because of the precipitation of the σ phase and BCC phase, respectively.