Atomistic insights into nanoindentation-induced deformation of α-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 α-Al₂O₃ using molecular dynamics (MD) simulations at room temperature. First, nanoindentation MD simulations are performed with single crystalline α-Al₂O₃. Four crystallographic orientations are investigated, m 11̄00, a 21̄1̄0, R 1̄012 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.