Improved tensile properties of Al0.5CoCrFeNi high-entropy alloy by tailoring microstructures

The effect of heat treatment on microstructure and tensile properties of as-cast AlCoCrFeNi high-entropy alloy was investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM) equipped with energy-dispersive spectroscopy(EDS), and tensile tests.The results show that heat treatment strongly affects the microstructure, particularly the morphology of bcc phases,and improves tensile properties. Microstructure analysis reveals that rod-shaped and elliptoid phases appear in the matrix after heat treatment at 1150 °C. Besides, under850 °C heat-treated condition, ultimate tensile strength increases by about 60% without sacrificing much plasticity,which can be attributed to the content of bcc phases and fine precipitates dispersed in the dendrites. For other heattreated conditions, tensile ductility increases by at least30%, especially 60% for heat treatment at 450 °C, and strength also improves. Fracture analysis indicates that the fracture mode of heat treatment at 850 °C is a mixture of quasi-cleavage and ductile fracture, while the other heattreated conditions show the mode of ductile fracture.