Effect of Si on evolution of microstructure and wear resistance of Al_0.5CrFeNi_2.5 high-entropy alloy fabricated via laser melting deposition

Al_0.5CrFeNi_2.5 high-entropy alloy (HEA) was reinforced by the small-radius Si. Al_0.5CrFeNi_2.5Si_x (x = 0 and 0.25) HEAs were fabricated by laser melting deposition. The evolution of microstructure, nanohardness, and wear properties of Al_0.5CrFeNi_2.5Si_x (x = 0 and 0.25) HEAs were systematically investigated. Al_0.5CrFeNi_2.5 HEA exhibits a face-centered cubic (FCC) matrix with Ni₃Al-type ordered nanoprecipitates. When Si was doped, σ phase and Cr-rich nanoprecipitates existed in the B2 matrix and L1₂ in the FCC matrix. The nanohardness was increased from 4.67 to 5.45 GPa with doping of Si, which is associated with forming the new phases and improved nanohardness of L1₂/FCC phases. The coefficient of friction (COF) value was reduced from 0.75 to 0.67 by adding Si. σ phase and Cr-rich nanoprecipitates in B2 matrix support a decreased wear rate from 7.87 × 10^–4 to 6.82 × 10^–4 mm³/(N m). Furthermore, the main wear mechanism of Al_0.5CrFeNi_2.5 and Al_0.5CrFeNi_2.5Si_0.25 HEAs is abrasive wear.