Abstract
This study focuses on the self-crack-healing process of Al_2O_3/30 vol.% SiC composites. Specimens with cracks were subjected to thermal treatment at 1000℃ and 1200℃, their strengths were measured by a three-point bending test, and nano/micro structural analysis of crack-healed zone was performed using scanning electron microscope (SEM) and focused ion beam (FIB) which are arranged orthogonally. A 100μm semi-elliptical surface crack healed completely at 1200℃ for over 5 hours in the air. The fracture origins of the complete crack-healing specimens were outside the crack-healed zone. On the other hand, the fracture origins of the specimen which did not accomplish complete crack-healing transit from the tip of crack-healed zone to the vicinity of a Vickers indentation as the strength of specimens become higher. As the result of analysis to the crack-healed zone nearing the indentation using FIB-SEM, it is found that main self-crack-healing process is the filling of the cracks by the oxidation formed from SiC reaction site and these oxidation formed bridge structure between interior surfaces of crack. Thus we revealed self-crack-healing mechanisms through the multi-scale structural analysis and established how to investigate the structure of crack-healed-zone.
