Cooling-Rate Effect on Microstructure and Mechanical Properties of Al0.5CoCrFeNi High-Entropy Alloy

Al0.5CoCrFeNi high-entropy alloy (HEA) was prepared by spark plasma sintering (SPS) using Al0.5CoCrFeNi gas atomized powder and was treated with different cooling rates (furnace cooling, air cooling, water quenching). The phase composition, microstructure, tensile properties, Vickers hardness, compactness, and fracture morphology of the alloy were systematically studied. The results show that the cooling rate can change the phase composition and phase shape of Al0.5CoCrFeNi HEA from BCC + FCC phase to BCC + FCC + B2 phase, and the BCC phase coarsens. The ultimate tensile strength and yield strength of the heat-treated Al0.5CoCrFeNi HEA decreased with increasing cooling rate, but elongation and Vickers hardness increased with increasing cooling rate. The ultimate tensile strength and yield strength of the furnace cooling (FC) samples reached the maximum value of 985.2 MPa and 524.1 MPa, respectively. The elongation and hardness of the water quenching (WQ) samples reached a maximum value of 43.1% and 547.3 HV, respectively, and the compactness of the alloy is higher than 98.8%. Therefore, the properties of Al0.5CoCrFeNi HEAs can be greatly improved by treatment with different cooling rates.