Microstructural evolution and mechanical characterization for the AlCoCrFeNi 2.1 eutectic high‐entropy alloy under different temperatures

Recently, there has been a lot of interest in the AlCoCrFeNi 2.1 eutectic high‐entropy alloys (EHEAs), which can achieve a good balance of strength and ductility. The relationship between the microstructure and mechanical properties of the alloy was established in this study by examining the microstructural evolution during heat treatment of 500–1000°C. The results show that the alloy's microstructure remained unchanged when the heat treatment temperature was lower than 700°C. With further rise above 800°C, the B2 II precipitates were inspected in the L1 2 matrix. Besides, L1 2II started to be precipitated from the B2 matrix at 900°C. The tensile test results conducted at 20–1000°C showed that both the yield strength and ultimate tensile strength decreased as the temperature rose. As for the elongation, however, it increased dramatically when the testing temperature was over 800°C, being attributed to the dynamic recrystallization. The results obtained provided a fundamental understanding of high‐temperature properties for duplex HEAs. The B2 II precipitates were precipitated from the L1 2 at 800°C. The B2 II and L1 2II were precipitated from the L1 2 and B2 over 900°C. The yield and tensile strength decreased sharply at 20–700°C and slowly at 800–1000°C. The elongation first remained stable at 20–700°C and then increased sharply at 800–1000°C.