Experimental evaluation of toughening mechanisms in alumina-zirconia composites

Abstract

The contributions of transformation toughening and microcrack toughening in an 85Al(2)O(3). 15ZrO(2) (vol%) composite were quantitatively evaluated. Three types of hot-pressed samples with similar size (similar to 0.5 mu m) and 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 on each toughening mechanism was eliminated. When the measured fracture toughnesses 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 transformation of ZrO2 grains. This result indicates that transformation toughening was the dominant toughening mechanism in the studied composite.