Microstructure and mechanical properties of Al_xSi_0.2CrFeCoNiCu_1-x high-entropy alloys

Al_xSi_0.2CrFeCoNiCu_1-x (x=0.2, 0.4, 0.5, 0.6, 0.8, 0.9) high-entropy alloys (HEAs) were prepared using vacuum arc melting and injection casting. The microstructures, detailed phases, and strain rate-related mechanical properties of the alloys were investigated. The alloys changed gradually from FCC to coexisting FCC and BCC and then to a BCC solid solution with an increase in the Al content and a decrease in the Cu content. With the Al content increase, the alloys with FCC structures exhibited an increased yield stress but a decreased plasticity. However, the alloys with the BCC structure exhibited both increased strength and plasticity. The improved mechanical properties of alloys are attributed to the combined action of solid-solution strengthening, a decrease in compositional segregation, and fine-grain strengthening.