Effect of Al content on structure and wear behavior of AlCoCrFeMoNi high entropy alloys

High-entropy AlxCoCrFeMo0.5Ni (x=0-2) alloys are prepared by the vacuum arc melting and casting method. The effects of Al content on the microstructure, hardness and wear resistance of the high-entropy alloys (HEAs) are investigated. The HEAs were characterized for phase content by X-ray diffractometer (XRD) and morphology by scanning electron microscope (SEM). Wear tests were performed under dry friction conditions with WC balls at a 5 N normal load and sliding speed of 5 cm·s-1 in a ball-on-disc geometry. The worn surfaces of the samples were also examined by SEM to identify the wear mechanism. The hardness starts from 328 HV, at x=0, reach to the maximum, 710 HV, at x=1.0 and then declines to 684 HV, at x=2.0. On the other hand, the wear resistance of HEAs gradually increases with the increasing aluminum content. The correlation between composition, microstructure, hardness and wear properties of these alloys is detailed discussed with in this study.