Enhancement of Mechanical Properties of Cu–Fe–Ni–Co Medium‐Entropy Alloys Reinforced With Tungsten Carbide and Graphene Nanosheets

This study investigates the enhancement of Cu–Fe–Ni–Co medium‐entropy alloy (MEA) composites reinforced with 20 wt. % tungsten carbide (WC) and graphene nanosheets (GNs) at 1.0, 1.2, and 1.4 wt. %. Powders were ball‐milled, cold‐pressed, and sintered at 1250°C under vacuum conditions involving liquid phase–assisted sintering due to the partial melting of Cu, which promoted densification and chemical homogenization. The baseline alloy exhibits a dominant FCC solid‐solution structure with a crystallite size of 96.34 nm and a hardness of ∼200 HV. The addition of WC refined the crystallite size to 75 nm and increased the hardness to 221 HV, accompanied by the formation of secondary carbide phases (Co 2 W 4 C‐ and WC‐related phases). Incorporating GNs further enhanced hardness progressively to ∼240, ∼300, and ∼400 HV at 1.0, 1.2, and 1.4 wt. % GNs, respectively, due to synergistic strengthening mechanisms including dislocation hindrance, grain‐boundary strengthening, load transfer, and in situ formation of W‐ and Co‐based carbides. The compressive yield and ultimate strengths of the base alloy (806 MPa and 874 MPa) increased to 1140 MPa and 1340 MPa for the 1.4 wt. % GN composite. Wear resistance also improved significantly, with the wear rate decreasing from 0.031 mg/min for the base alloy to 0.017 mg/min for composites containing 1.2–1.4 wt. % GNs, attributed to grain refinement, graphene lubricity, and stable tribolayer formation. Overall, these results demonstrate the synergistic effect of WC and GNs in substantially enhancing the mechanical and tribological performance of Cu–Fe–Ni–Co MEAs through coupled microstructural refinement and phase evolution.