Abstract: AlCr_xCuFeNi (x=0, 1.0, 2.0) high-entropy alloys, which named as Cr₀, Cr_1.0 and Cr_2.0, was prepared by using arc melting technology. The effect of Cr content on microstructure and microhardness of the as-cast high-entropy alloys and after heat treatment at 600 ℃ was studied. The results indicate that the phase structure of the as-cast Cr₀ alloy is mainly composed of (Fe, Ni)-rich FCC solid solution phase and AlCu₃ phase, while both Cr_1.0 and Cr_2.0 alloys are composed of Cu-rich FCC2 phase, (Cr, Fe)-rich BCC phase and AlNi phase. After heat treatment at 600 ℃, the phase structure of the alloy remains largely unchanged, indicating good phase stability, meanwhile, the element segregation degree of the high-entropy alloy is significantly improved. The microhardness of the as-cast Cr₀ alloy is 348 HV10, which slightly increases to 370 HV10 after heat treatment at 600 ℃. As the Cr content increases, the hardness of the high-entropy alloys also increases, and the microhardness of the as-cast Cr_2.0 alloy and after heat treatment at 600 ℃ is the highest, reaching 435 and 462 HV10, respectively. The increase in hardness of the high-entropy alloys after heat treatment is mainly related to the mechanisms of solid solution strengthening, precipitation strengthening and fine-grained strengthening.

Key words: Cr content, high-entropy alloy, heat treatment, microstructure, microhardness