Experimental evaluation of toughening mechanisms in alumina-zirconia composites

The contributions of transformation toughening and microcrack toughening in an 85Al(2)O(3). 15ZrO(2) (vol%) composite were quantitatively evaluated. T hree types of hot-pressed samples with similar size (similar to 0.5 mu m) a nd size distribution of ZrO2 grains, but with different contents (vol%) of monoclinic- (m-) ZrO2 (0 (AZS), 45 (AZT), and 67 (AZM)) were prepared using Y2O3 and MoO2 dopants. Therefore, the possible effect of ZrO2 grain size o n each toughening mechanism was eliminated. When the measured fracture toug hnesses of m-ZrO2 volume fractions before and after fracture were compared, the transformation-toughening constant was estimated as 3.0 MPa.m(1/2) and the microcrack-toughening constant 0.2 MPa.m(1/2) for a 100% monoclinic tr ansformation of ZrO2 grains. This result indicates that transformation toug hening was the dominant toughening mechanism in the studied composite.