MICROSTRUCTURE AND FRACTURE-BEHAVIOR OF AN AL2O3-ZRO2-SICW CERAMIC COMPOSITE

The microstructure, mechanical properties, fracture behavior and tough ening mechanisms of the Al2O3-25 vol% ZrO2(2 mol% Y2O3)-25 vol% SiCw ( AZS) ceramic composite were investigated by means of XRD, SEM, TEM, EP MA techniques and three-point bending and Vicker's hardness tests. It is shown that the material shows an excellent combination of strength and toughness. The Al2O3 matrix is simultaneously strengthened and tou ghened by both ZrO2 particles and SiC whiskers. The flexural strength and indentation toughness of the AZS at room temperature are 676 MPa a nd 10.8 MPa m1/2, respectively. The load-displacement curve of three-p oint bending of the AZS is sawtoothed in shape which is the result of repeated initiation and stopping of crack propagation by whiskers. Fin ally, a model of the toughening mechanisms of both ZrO2 particles and SiCw is discussed.