ELECTRON-MICROSCOPY OF CRACK PARTICLE INTERACTIONS IN AL2O3/SIC NANOCOMPOSITES/

Crack/particle interactions in alumina/silicon carbide nanocomposites have been investigated by scanning electron microscopy and transmissio n electron microscopy, with cracks induced by Vickers microindentation . Intergranular cracks are frequently deflected into grains by SiC par ticles on grain boundaries inclined to the average direction of crack propagation, This mechanism is proposed to explain the change in the f racture mode from intergranular fracture for monolithic alumina to pre dominantly transgranular fracture for the nanocomposites. Neither stre ss-induced microcracking around SiC particles nor significant crack de flection by intragranular particles was found to occur in the nanocomp osites. It is argued that an addition of nanoparticles may not be a pr omising approach for increasing the toughness of alumina.