Abstract
A three point bending specimen was made from sintered Al2O3/SiC composite ceramics and commercial Al2O3 material, upon which a semi‐elliptical surface crack of 100 μm in diameter (aspect ratio = 0.9) was introduced. The following materials: Al2O3/SiC composite ceramics (1300 °C temperature, one hour crack‐healing time) and monolithic Al2O3 (1000 °C or 1450 °C temperature, one hour crack‐healing time) were used to heal the crack samples. Two main conclusions were obtained as follows: 1. Bending strength of cracked Al2O3 and crack‐healed Al2O3/SiC are 180 MPa and about 850 MPa, respectively. Static fatigue limit of cracked Al2O3 and crack‐healed Al2O3/SiC are 160 MPa and 600 MPa, respectively. In addition, the cyclic fatigue limit of crack‐healed Al2O3/SiC is 700 MPa. From these test results, it can be concluded that Al2O3/SiC has excellent crack‐healing ability. Crack healing is an attractive technology for the structural integrity of Al2O3/SiC. 2. Monolithic Al2O3 is able to recover the strength of a cracked sample by heat treatment. The recovery was performed by sintering process or by removal of tensile residual stress before cracking. Furthermore, when temperature is above 1400 °C, the sintering mechanism is a dominant process. However, when temperature is below 1300 °C, the annealing mechanism is a dominant process.
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