Microstructural Transition of (CuFeMnNi)1−xCrx (x = 0-0.25) High-Entropy Alloys

The influence of Cr on the microstructure and hardness of the cast and annealed (CuFeMnNi)1−xCrx (x = 0, 0.05, 0.1, 0.15, 0.2 and 0.25) high-entropy alloys were investigated systematically. The results revealed that the microstructures of (CuFeMnNi)1−xCrx (x = 0, 0.05 and 0.1) alloys were composed of (Fe, Ni and Cr)-rich FCC1 and (Cu, Mn)-rich FCC2 phases. No obvious change in the dendritic size was detected between cast and related annealed alloys, indicating the excellent thermal structure stability of the studied alloys. The microstructures of the cast (CuFeMnNi)1−xCrx (x = 0.15, 0.2 and 0.25) alloys contained FCC1, FCC2 and (Cr, Fe)-rich BCC phases, while those of the annealed alloys were composed of FCC1, FCC2 and ρ phases. The significant transition from BCC phase to ρ phase was detected. Moreover, the hardness of both cast and annealed (CuFeMnNi)1−xCrx alloys increased with the increasing Cr content. The hardness of annealed (CuFeMnNi)1−xCrx (x = 0, 0.05 and 0.10) alloys reduced slightly as compared to corresponding cast alloys, whereas the hardness of the annealed (CuFeMnNi)1−xCrx (x = 0.15, 0.2 and 0.25) alloys increased.