Molecular dynamics simulation of nanoindentation of cubic yttria-stabilized zirconia single crystal

Molecular dynamics simulations of nanoindentation for the [001], [110], and [111] orientations of cubic yttria-stabilized zirconia single crystals were performed to investigate the crystal orientation dependency of the plastic deformation behavior, including the atomic-scale dynamics of dislocation nucleation and evolution during nanoindentation, with the aim of elucidating the onset of plasticity. The load–depth curves obtained for each indentation revealed plateau regions where the load increase slowed or stagnated. Observing the evolution of dislocation density confirmed that load plateaus occurred after an increase in dislocation density, indicating that they arose from the collective migration of dislocations after their intermittent multiplication. An analysis of the von Mises shear strain distribution and dislocation behavior directly beneath the indenter suggested that the plasticity of the nanoindentation in cubic yttria-stabilized zirconia is dependent on the crystal orientation. Regarding the activity levels of each type of dislocation, mixed dislocations were predominant. Atomic-scale analyses revealed a trend for dislocations to be pinned by solute yttrium Y 3+ ions (and possibly by oxygen vacancies), suggesting that the interaction between dislocations and point defects results in the intermittent plasticity of cubic zirconia. To the best of our knowledge, this study is the first to conduct molecular dynamics simulations of nanoindentation with three different crystallographic orientations of cubic yttria-stabilized zirconia and to provide a detailed atomic-scale investigation of dislocation dynamics, including the effects of Y 3+ ions on dislocation behavior.