Elevated‐Temperature‐Delayed Failure of Alumina Reinforced with 20 vol% Silicon Carbide Whiskers

Alumina composites reinforced with 20 vol% SiC whiskers were exposed to applied stresses in four- point flexure at temperatures of 1000{degrees}, 1100{degrees}, and 1200{degrees}C in air for periods of up to 14 weeks. At 1000{degrees} and 1100{degrees}C, an apparent fatigue limit was established at stresses of {approx}75% of the fast fracture strength. However, after long-term ({gt}6 weeks) tests at 1100{degrees}C, some evidence of crack generation as a result of creep cavitation was detected. At 1200{degrees}C applied stresses as low as 38% of the 1200{degrees}C fracture strength were sufficient to promote creep deformation and accompanying cavitation and crack generation and growth resulting in failures in times of {lt}250 h.

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