Abstract
Al_2O_3monolithic, Al_2O_3/SiC composite ceramics was sintered by hot pressing. Semi-elliptical surface crack of 100 μm in diameter was made on the specimen. Four kinds of specimens (as-received, heal treated, pre-cracked and heal treated cracked), crack healing behavior and high temperature strength were tested systematically. The main conclusions were obtained as follows : (a) Al_2O_3monolithic, Al_2O_3/SiC composite ceramic has ability to heal crack. (b) Pre-cracked Al_2O_3monolithic and Al_2O_3/SiC composite ceramic to be healed completely at 1450℃ for 1hr and 1300℃ for 1hr, in air each other. (c) Crack healed part of Al_2O_3monolithic has approximately the same strength of smooth specimen up to 1000℃ and Al_2O_3/SiC composite ceramic has approximately the same strength of smooth specimen of Al_2O_3monolithic up to 1300℃ and most specimens of Al_2O_3monolithic, Al_2O_3/SiC composite ceramic failed outside the pre-cracked zone.
