Investigation of alumina reinforcement effects on microstructure, hardness, and tribological behavior of AlCoCrFeNi high entropy alloy

This study examines the effect of alumina (Al₂O₃) reinforcement on the microstructure, hardness, and wear behavior of AlCoCrFeNi high-entropy alloy (HEA). Al₂O₃ particles (0–15 wt%) were incorporated into the HEA matrix using mechanical alloying (MA) and the prepared powder mixtures were consolidated by spark plasma sintering (SPS) method. The microstructural examination showed that the base alloy displayed a dual-phase structure comprising BCC and FCC phases, with alumina addition stabilizing the BCC phase at higher concentrations (15 wt%). Microhardness tests indicated that the incorporation of up to 10 wt% Al₂O₃ had minimal impact on hardness, whereas 15 wt% Al₂O₃ significantly increased it from approximately 600 HV to 999 HV. Tribological investigations demonstrated that the wear resistance improved with increasing alumina content and HEA-15 wt% Al₂O₃ composite exhibited the lowest wear width (1892 μm) and the best wear performance. The primary wear mechanisms consisted of abrasion, delamination, adhesion, and oxidation. These findings highlight the potential of alumina-reinforced HEAs for applications requiring enhanced mechanical strength and wear resistance.