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 the direct evaluation of the critical wake zone stress and stress distribution as a function of crack face separation. These PFT results for the current alumina yield a maximum wake zone stress which compares favorably with the theoretical and experimental citations in the literature. We present the controlling relationship between the grain size distribution and fracture mode, and the PFT curve character as a means which may lead to microstructural design. Finally, the grain interlocking mechanism is quantitatively shown to be more effective in this noncubic material than in cubic magnesium aluminate spinel microstructures.