Determination of Fracture Toughness in Fine-Grained Alumina with Glassy Phase by Controlled Indentation-Induced Cracks at Room and High Temperature

The fracture toughness, Kc, of a fine-grained alumina with grain boundary glassy phase was measured by an indentation technique at room temperature, 600 and 800°C. Both as-indented and annealed specimens were studied.Indentation flaw evolution upon bending was analysed by ,a crack staining technique. This allows to evaluate the crack shape factor and the indentation residual stress factor as function of the crack extension. Constant fracture toughness values around 3.0 - 3.4 MPa?m, independent on temperature, were measured.