GRAIN-BRIDGING MECHANISMS IN MONOLITHIC ALUMINA AND SPINEL

The postfracture tensile (PFT) test procedure is implemented to study wake zone stresses in monolithic alumina, which contribute toward the cumulative component of toughening. This novel procedure allows for th e direct evaluation of the critical wake zone stress and stress distri bution as a function of crack face separation. These PFT results for t he current alumina yield a maximum wake zone stress which compares fav orably with the theoretical and experimental citations in the literatu re. We present the controlling relationship between the grain size dis tribution and fracture mode, and the PFT curve character as a means wh ich may lead to microstructural design. Finally, the grain interlockin g mechanism is quantitatively shown to be more effective in this noncu bic material than in cubic magnesium aluminate spinel microstructures.