Fracture behaviour of alumina-YAG particulate composites

Particulate composites of the Al2O3–YAG system were produced by precipitation of the yttrium oxide precursor in the aluminium oxide suspension. The solid state reaction took place during thermal treatment of the resulting powder and led to the creation of the YAG phase. This method allowed fine and homogenously distributed YAG inclusions within the alumina matrix to be obtained. The performed investigations involved determining of the critical stress intensity factor (KIC), Vickers hardness and bending strength of the materials. The composites showed higher hardness (HV) than α-Al2O3. The presence of YAG inclusion in the amount higher than 7.5 vol.% improved also fracture toughness when compared to polycrystalline alumina. In the case of the material with the best mechanical properties measurements of subcritical cracking were conducted and the threshold value of KIC (KI0) was determined.