Effect of Difference in Crack-healing Ability on Fatigue Behavior of Alumina/Silicon Carbide Composites

Crack healing has great effect on monotonic strength of ceramics. Also the crack-healing effect on fatigue behavior is an interesting issue. Three kinds of Al ₂ O ₃ /30 vol.% SiC composites that have differences in crack-healing ability and fracture toughness were hot pressed. Static fatigue behaviors of these crack-healed specimens were investigated. From the experimental results, the static fatigue limits of three kinds of Al ₂ O ₃ /30 vol.% SiC composites were 800, 700, and 1000 MPa, respectively. Furthermore, the fractures seldom initiated from the healed crack. Therefore, it was found that using the crack-healing forbade stress corrosion cracking from the original surface cracks, thereby leading to large increment in fatigue strength. The results, however, demonstrated that fatigue cracks were generated by applying high tensile stress. The general mechanism of fatigue cracks was discussed by using surface morphology.