Abstract
To address the insufficient strength-toughness, wear resistance, and corrosion resistance of AlCoCrNiMo_x high-entropy alloys, graphene (Gr)-reinforced AlCoCrNiMo_x (x = 0.1, 0.2, 0.3, 0.4) high-entropy alloy composites were fabricated by vacuum arc melting. The regulatory mechanisms of Mo content and graphene on the phase composition, microstructure, and comprehensive properties of the alloys were systematically revealed primarily via qualitative analysis, without quantitative separation of individual strengthening contributions. The phase structure, morphology, and elemental distribution were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Microhardness, dry sliding wear behavior, and electrochemical corrosion performance in 3.5 wt.% NaCl solution were tested. The results show that the as-cast microstructure of the composite consists of an FCC phase, a B2 ordered phase, and a minor σ phase. With increasing Mo content from 0.1 to 0.4, the fraction of the FCC phase gradually decreases, while those of the B2 and σ phases continuously increase; the grains transform from coarse equiaxed grains to fine columnar grains. Graphene is inferred to be uniformly distributed at grain boundaries and phase boundaries, which is proposed to significantly refine grains, suppress elemental segregation, and forms a sound interfacial bond with the matrix. Mechanical and corrosion tests indicate that the hardness and wear resistance of the alloy increase continuously with increasing Mo content. The composite exhibits optimal comprehensive performance at x = 0.4 with 0.5 wt.% graphene addition: a microhardness of 625 HV, a wear rate as low as 2.75 × 10^–6 mm³ N^–1 m^–1, and a corrosion current density of 3.82 × 10^–6 A cm^–2. The synergistic improvement in comprehensive properties is attributed to the combined effects of solid-solution strengthening by Mo, second-phase strengthening by B2 and σ phases, as well as grain refinement, dispersion strengthening, self-lubrication, and physical barrier effects of graphene. This study focuses on qualitative discussion of the synergistic mechanisms, and the individual contribution of each mechanism is not quantified separately. This study provides experimental evidence and theoretical support for the compositional design and engineering applications of high-performance high-entropy alloy composites.

Key words
high-entropy alloy, AlCoCrNiMo_x, graphene, microstructure, mechanical property, corrosion resistance

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