Effects of the Replacement of Co with Ni on the Microstructure,Mechanical Properties,and Age Hardening of AlCo1−xCrFeNi1+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−xCrFeNi_1+x (x = molar ratio; x = 0, 0.5, 1, denoted as X₀, X_0.5, and X₁, 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 X₀ to X₁ 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 X₀ alloy was due to the precipitation of the (Cr,Fe)-rich σ phase. Peak age hardening for the X_0.5 and X₁ alloys was observed at 500 °C because of the precipitation of the σ phase and BCC phase, respectively.