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High-entropy alloys exhibit great potential for cryogenic applications. This study investigates the nano-scratching behavior of CuCoCrFeNi high-entropy alloy at a cryogenic temperature (77 K) using molecular dynamics. Results show that compared with the single-grain model, the average friction coefficient (AFC) increases for all three polycrystalline models with different grain sizes d, but the anti-wear property can be improved by 28.5%, when grain size d = 10.7 nm. The smaller friction on the scratching surface of the single-grain model (AFC is 15.5% less than that of the model with d = 8.2 nm), which makes the overall temperature rise lower compared to that of the polycrystalline models. However, due to the stress concentration released when a complete stacking fault tetrahedron is produced, the single-grain model cannot significantly harden the surface and subsurface to a greater degree. In the polycrystalline models, dislocations are blocked at grain boundaries (GBs). However, the introduction of GBs changes the von Mises stress distribution. Finally, an attempt was made to reveal the role of yield pressure H3/ E2 ( H—hardness, E—elastic modulus) in friction-reducing and anti-wear properties.

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Aluminum matrix composites (AMCs) reinforced by 1.5 and 3 wt% FeCoCrNi high-entropy alloy particles (HEAp) were obtained by a stir casting process. The AMCs strip was further prepared by room temperature rolling (RTR, 298 K) and cryorolling (CR, 77 K). The mechanical properties of the AMCs produced by RTR and CR were studied. The effect of a microstructure on mechanical properties of composites was analyzed by scanning electron microscopy (SEM). The results show that CR can greatly improve the mechanical properties of the HEAp/AMCs. Under 30% rolling reduction, the ultimate tensile strength (UTS) of the RTR 1.5 wt% HEAp/AMCs was 120.3 MPa, but it increased to 139.7 MPa in CR composites. Due to the volume shrinkage effect, the bonding ability of CR HEAp/AMCs reinforcement with Al matrix was stronger, exhibiting higher mechanical properties.