Atomistic insights into nanoindentation-induced deformation of a-Al2O3 single crystals

The plastic deformability of brittle ceramics, e.g., Al2O3, at a small scale can expand their potential structural applications. In this work, we propose to investigate the nanomechanics and plasticity of a-Al2O3 using molecular dynamics (MD) simulations at room temperature. First, nanoindentation MD simulations are performed with single crystalline a-Al2O3. Four crystallographic orientations are investigated, m [1100], a [2110], R [1012] and c [0001], including a detailed analysis of Al2O3 dislocation-based mechanisms. The results show that the O atoms undergo a phase transformation, changing from the hexagonal close-packed structure to face-centered cubic and body-centered cubic structures. Second, during nanoindentation, we focus on pop-in events and the transformation point from elastic to inelastic response during loading forces. The results are discussed in the context of recent transmission electron microscope experiments, possibly opening new doors towards ceramic bulk material processes.