Understanding mechanical properties of small volume materials has attracted much interest in recent years. We perform atomistic simulations to understand the mechanisms involved in nanoscale deformation during nanoindentation. Nanoindentation simulations performed at low temperatures suggest that dislocation nucleation and subsequent dislocation propagation and multiplication processes dominate the deformation mechanisms. However, at finite temperatures point defect formation and migration can become important. The stress field of the indenter results in a stress gradient inside the material which creates a mass transport channel by vacancy migration through surface diffusion and bulk diffusion pathways. Although this leads to enhanced long range transport of vacancies towards the indented region, we find it is not sufficient to dominate the deformation process. Using high temperature molecular dynamics simulations, we find localized sources such as vacancy-adatom pair formation and adatom cluster formation play an important role during nanoindentation. Our results suggest the existence of different regimes of deformation mechanisms in temperature, strain rate and indenter size parameter space.
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