Microstructure and Mechanical Properties of a New Al_0.5CrFeMnCo₂ High Entropy Alloy

In this study, a new Al_0.5CrFeMnCo₂ (molar ratio) high entropy alloy was designed. The microstructure and mechanical properties of as-cast and annealed Al_0.5CrFeMnCo₂ high entropy alloy were investigated. FCC+BCC duplex-phase structure is formed in as-cast Al_0.5CrFeMnCo₂ high entropy alloy. Dendritic FCC phase is the predominant constituent phase, and BCC/B2 coherent structure is formed in the inter-dendritic BCC phase. A large number of short-rod small-sized BCC phases are precipitated within FCC dendrites after annealing at 1000 °C for 6 h but unobserved after annealing at 1100 °C and 1200 °C for 6 h. The as-cast Al_0.5CrFeMnCo₂ high entropy alloy exhibits favorable comprehensive mechanical properties, with a compressive fracture strength of 1493 MPa and a plastic strain of 28.3%. After annealing at 1000 °C for 6 h, the compressive fracture strength and plastic strain reached are improved to 1676 MPa and 32.6%, respectively. However, further increase in annealing temperature results in gradual decrease in mechanical properties.