Microstructure, Mechanical and Corrosion Properties of AlCoCrFeNi High-Entropy Alloy Prepared by Spark Plasma Sintering

Abstract

AlCoCrFeNi is one of the most widely studied alloy systems in the high-entropy alloy (HEA) area due to the interesting microstructure and mechanical properties. In this study, the AlCoCrFeNi alloy was prepared using spark plasma sintering (SPS) with pre-alloy powders obtained through gas atomization. Then, the sintered samples were annealed at 700, 800 and 900 °C, and the effect of annealing temperature on the microstructure, mechanical and corrosion properties was studied. The results show that phase formation takes place during annealing process with the new phase (σ) and some nanoscale BCC precipitates formation. The size and quantity of the nanoscale precipitates increase with increasing annealing temperature. The twin is also observed after annealing at 900 °C. The annealing temperature has an obvious effect on the mechanical properties and corrosion resistance of the spark plasma sintered AlCoCrFeNi HEA. When the annealing temperature is 700 °C, the hardness, yield strength and fracture strength reach the maximum with the value of 545 HV, 1430 MPa and 2230 MPa, respectively. The compressive ratio reaches the maximum of 17.2%, with the annealing temperature increasing to 800 °C. The corrosion resistance of the samples decreases with increasing the annealing temperature.