Enhanced wear resistance of a multi-phase reinforced Al0.5CrFeNi2.5Si0.25 high-entropy alloy via annealing

In this work, a multiphase reinforced non-equiatomic Al0.5CrFeNi2.5Si0.25 high-entropy alloy (HEA) was prepared by vacuum induction melting. The effect of heat-treatment temperature (1023, 1123, 1323, and 1473 K) on the microstructure, mechanical properties, and wear behavior are systematically investigated. The results indicate that the as-cast and annealed alloys are composed of face-centered cubic (FCC) and body-centered cubic (BCC) structures accompanied by microscale and nanoscale precipitated phases. To be specific, the FCC matrix is enriched in the L12 phase, and BCC particles and σ phases are observed in the B2 matrix. The microstructure of Al0.5CrFeNi2.5Si0.25 HEAs consists of dendritic region (DR) and inter-dendritic (ID) region before and after annealing. The phases and microstructure did not change. After annealing, the size of the Cr-rich BCC particles is reduced. The L12 phase has a density per unit area that first increases and then decreases, reaching its highest density at 1123 K. With the annealing temperature rising, the nanohardness increases slightly and then decreases, reaching a peak value of about 6.29 GPa at 1123 K. The Al0.5CrFeNi2.5Si0.25 HEA annealed at 1123 K also exhibits the lowest specific wear rate of 2.43 × 10−4 mm3/Nm, which is decreased by 23.5% compared to the as-cast one.