Static indentation responses of AlON transparent ceramics

In this study, instrumented indentation experiments were performed under different loads on the polished surface of aluminum oxynitride (AlON) ceramics to investigate their surface fracture behavior and indentation response under quasi-static conditions. The results showed that the AlON transparent ceramics exhibited a typical indentation size effect (ISE) at the microloading scale, unlike the nano-indentation experiments, owing to a change in the material's destruction mechanism. The loading response process of the ceramics under the indenter shape was analyzed using different material parameters. The strain gradient effects were considered, and the ISE on the materials was characterized and analyzed. Based on the experimentally derived indentation stress-strain curve, an improved analytical model is proposed to estimate the stress field around an elastoplastic indentation/contact. The proposed model demonstrates excellent agreement with finite element analysis. The results suggest that a significant geometrical similarity exists in the conical indenter loading, and the state of the stress field is strongly dependent on the indentation index εi.