Insights into the local mechanical response and microplastic deformation mechanisms of AlON ceramics

This study investigates the local mechanical behavior of aluminum oxynitride (AlON) ceramics through nanoindentation and microstructural analysis. The intragranular region exhibits a higher hardness than the grain boundaries (29.0 GPa vs. 26.4 GPa at 5 mN), a difference that diminishes with increasing load. A distinct indentation size effect is observed, which is less pronounced near the grain boundaries (Meyer index, n = 1.58) than within the grains (n = 1.50). Microstructural characterization reveals the influence of grain boundaries on dislocation nucleation and slips band evolution. Notably, high-density dislocations, slip bands, and deformation twins are identified beneath the indentation tip, demonstrating that the localized plastic deformation is accommodated by both dislocation slip and twinning. These findings clarify the local mechanical response and unveil the underlying micro-deformation mechanisms of AlON ceramics, providing valuable insights for their microstructural design and reliability optimization in advanced structural applications.