Probing the crystal structure and dislocation evolution in single crystal Al0.3CoCrFeNi high-entropy alloy under nanoindentation

The elastic-plastic deformation behavior of single crystal Al0.3CoCrFeNi high-entropy alloy under nanoindentation and its plastic deformation mechanisms at the atomic scale are investigated by the molecular dynamics method. The crystal structure evolution and the nucleation and evolution of dislocation in Al0.3CoCrFeNi high-entropy alloy during nanoindentation are studied. As the indentation depth increases, the elastic recovery rate decreases nonlinearly and gradually stabilizes in the plastic deformation stage, and the plastic work becomes the dominant work. The generation of stacking faults, various dislocations, and dislocation loops due to the dislocation-dislocation interactions are observed in the simulation cell. The nucleation and growth of Shockley partial dislocations and stacking faults are the main mechanisms for the plastic deformation of Al0.3CoCrFeNi high-entropy alloy. The release of dislocation loops under further dislocation reactions becomes a new mechanism of plastic deformation. The competition between material softening caused by plastic yield and strain hardening caused by Stair-rod and Hirth partial dislocations is responsible for fluctuations in force-penetration depth curves.