FRACTURE BEHAVIOUR OF A DIRECTIONALLY SOLIDIFIED Al2O3/YAG EUTECTIC

The mechanical behaviour of an eutectic ceramic Al2O3/YAG processed by directional solidification in a Bridgman furnace was analysed. Fracture toughness and Young's modulus were measured through three point bend tests from room temperature up to 1650 C. These tests were performed under stroke control using two different cross-head speeds to analyse the influence of strain rate on the fracture behaviour. The material was brittle up to 1400 C and plastic deformation was found at higher temperature. Plastic deformation was reduced, or even disappeared, when the strain rate was increased. The investigation was completed with an analysis of the deformation and fracture micromechanisms in the crack tip. 23 refs.