Surface modification for AlCoCrFeNi_2.1 eutectic high-entropy alloy via laser remelting technology and subsequent aging heat treatment

Eutectic high-entropy alloys (EHEAs) are a class of prospective structural material in advanced engineering applications due to their excellent mechanical properties and castability. However, few researchers focused on the surface modification of these EHEAs. This study aimed to propose an effective method combining laser remelting and heat treatment to modify the surface of classical AlCoCrFeNi_2.1 EHEA. After surface modification, the surface microhardness of the EHEA increased by 59%, and the average friction coefficient and wear rate decreased by 26% and 68%, respectively. The improved performance was mainly attributed to the decrease in lamellar spacing between face-centered cubic (FCC)/body-centered cubic (BCC) (B2) and coherent precipitation of nanoparticles in both FCC and B2 phases. A semi-empirical model was built to estimate the contribution of lamellar spacing to microhardness. The method and model might be applied to modify the surface properties of other EHEAs with lamellar structures.