Atomic-Scale Mechanisms of Nanoscale Material Removal in FeCrNiCoCu High-Entropy Alloys: Coupled Effects of Crystallography, Grain Size, and Composition

High-entropy alloys, due to their excellent mechanical properties and service stability, hold broad application prospects under extreme working conditions. However, their high strength and complex multi-component characteristics also pose significant processing challenges. This study investigates the nanoscale material removal mechanisms of single-crystal and polycrystalline FeCrNiCoCu high-entropy alloys (HEAs) under abrasive scratching using molecular dynamics simulations. In single-crystal HEAs, dislocations preferentially nucleate along directions, with significant lattice self-healing and elastic recovery. Crystallographic orientation strongly affects dislocation density, phase transformation, and residual plastic deformation, with the (100) plane exhibiting the most favorable machining performance. For polycrystalline HEAs, subsurface deformation is dominated by dislocation migration, grain boundary rupture, and dislocation entanglement, leading to higher dislocation density, larger residual plastic deformation, and increased phase transformation compared with single crystals. Elemental composition significantly modulates these behaviors: higher Cu and Cr contents suppress dislocation motion and reduce subsurface defects, improving surface quality, whereas higher Fe content slightly increases plastic deformation but mitigates phase transformation and amorphization. Grain size effects are also pronounced, with smaller grains showing higher dislocation density and residual deformation. These findings provide atomic-scale insights into the combined effects of crystallography, grain size, and elemental composition on the machining response of FeCrNiCoCu HEAs, offering guidance for precision machining and alloy design.