3Y-TZP/Al2O3 composites containing 0 to 30 vol% alumina were fabricated by sintering at 1550 οC for 2 h. The fracture toughness was measured using a range of techniques. The fracture toughness measured using the single edge V-notched beam (SEVNB) method, the controlled surface flaw and indentation strength in bending methods decreased with increasing Al2O3 content. This can be explained by the increased critical transformation stress, decreased volume fraction of transformable t- ZrO2 and increased residual tensile stress. In contrast, the value obtained by the indentation fracture (IF) method showed an increasing tendency. Accordingly, the IF method is unsuitable for evaluating the fracture toughness of 3Y-TZP/Al2O3 composites. The SEVNB method is considered one of the most reliable methods for determining the fracture toughness of ceramic materials.

Keywords: 3Y-TZP/Al2O3 composites, Fracture toughness, Single edge V-notched beam, Residual stress.