In situ crack-healing behavior of Al2O3/SiC composite ceramics undercyclic-fatigue strength

Alumina/silicon carbide (Al2O3/SiC) composite ceramics were sintered and subjected to three-point bending. A semicircular surface crack 50–320 µm in diameter was made on each sample. Crack-healing behavior was systematically studied, as a function of cyclic-fatigue strength, crack-healing temperature, healing time, and crack size, and the bending strength of the crack-healed sample from room temperature to 1500 °C were investigated. Four main conclusions were drawn from the present study. (1) Crack-healed Al2O3/SiC sample exhibited very high cyclic-fatigue limit of 700 MPa. (2) Al2O3/SiC composite ceramics have the ability to heal after cracking, from 1000–1400 °C. (3) The composite material can completely heal a 300 µm diameter semi-elliptical crack (aspect ratio 0.8–0.9). (4) The heat-resistance limit for monotonic loading of the crack-healed sample goes up to 1300 °C, and ~ 68% of the samples fracture, outside the crack-healed zone in the testing-temperature range 600–1300 °C. From these test results, it can be concluded that Al2O3/SiC has an excellent crack-healing ability and that crack healing is a desirable technology for the structural integrity of Al2O3/SiC.