MICRO-INDENTATION FRACTURE-BEHAVIOR OF AL2O3-24 VOL-PERCENT-ZRO2(Y2O3) COMPOSITES STUDIED BY TRANSMISSION ELECTRON-MICROSCOPY

The micro-indentation fracture behavior of pressureless-sintered Al2O3 -24 vol%ZrO2 composites containing different Y2O3 contents are studied by transmission electron microscopy (TEM) in Vickers indented specime ns at room temperature. The hardnesses of those composites decrease wi th increasing Y2O3, whereas the crack lengths increase. in Al2O3-ZrO2( 0%Y2O3), most of the cracks propagate along Al2O3/ZrO2 interfaces and Al2O3 grain boundaries, while a few grains of monoclinic ZrO2(m-ZrO2) fracture transgranularly. The fractured grains appear to be heavily de formed and to result in a marked reduction in the driving force of ind entation cracks. In the Al2O3-ZrO2(3%Y2O3), the main fracture mode is a mixed type with inter- and transgranular, and tetragonal-monoclinic (t-m) phase transformation in t-ZrO2 grains partially occur by the ind entation. In the Al2O3-ZrO2(8%Y2O3), the fracture is mainly transgranu lar, but serious plastic deformation is not observed in the transgranu larly fractured cubic ZrO2(c-ZrO2) grains.