Fracture Strength–Fracture Resistance Response and Damage Resistance of Sintered Al2O3–ZrO2 (12 mol% CeO2) Composites

The fracture strengths of sintered Al[sub 2]O[sub 3] containing 20 and 40 vol% ZrO[sub 2](12 mol% CeO[sub 2])--zirconia-toughened alumina (ZTA)--composites along with the fracture resistance can be increased (e.g., to [approximately]900 MPa and >12 MPa[center dot]m[sup 1/2], respectively), by increasing the mean grain size of the t-ZrO[sub 2] (and the Al[sub 2]O[sub 3]) from [approximately]0.5 [mu]m to [approximately]3 [mu]m. At these lower t-ZrO[sub 2] contents, the fracture strength-fracture resistance curves show a continuous rise as opposed to the strength maxima observed in polycrystalline t-ZrO[sub 2] (12 mol% CeO[sub 2]), CeTZP, and ZrO[sub 2] (12 mol% CeO[sub 2]) ceramics containing [<=] 20 vol% Al[sub 2]O[sub 3]. The toughened composites also exhibit excellent damage resistance with fracture strengths of 500 MPa retained with surfaces containing [approximately]150-N Vickers indentations which produce cracks off [approximately]160-[mu]m radius. Greater damage resistance correlates with an increase in the apparent R-curve response of these composites.