Reversible plasticity under nanoindentation of atomically flat and stepped surfaces of fcc metals

Using atomistic simulation, the indentation of single-crystalline Cu is investigated for both an ideal and a stepped (111) surface. Both systems exhibit an intermediate regime of reversible plasticity, characterized by the formation of extended stacking faults, which heal entirely upon withdrawal of the indenter. This regime can be employed to clarify the role of pure stacking fault generation and cross-slip in plasticity. Its existence reveals that, on the atomistic scale, plastic deformation is characterized by material transport rather than by the nucleation of stacking faults. Finally, we establish a criterion–based on the total displacement of particles–to determine after which indentation depth plasticity is generated irreversibly in the material.