Fracture behavior of monazite-coated alumina fiber-reinforced alumina-matrix composites at elevated temperature

High-temperature strength, fracture behavior and microstructure were observed for monazite-coated alumina fiber-reinforced alumina matrix composites hot-pressed at 1200-1300degreesC. The composites with 27-41vol% alumina fiber showed no significant change in strength at 25-1100degreesC. However, the strength of the composites decreased markedly at a test temperature higher than 1100degreesC. The composites hot-pressed at a temperature lower than 1250degreesC fractured in a pseudoductile manner in the test temperature range from 25degreesC to 1100degreesC. Young's modulus of the elastic region decreased with increasing test temperature. These composites showed larger deformation at a test temperature above 1100degreesC. On the other hand, the composites hot-pressed at more than 1250degreesC fractured in a brittle manner at 25degreesC-1200degreesC of test temperature. The fracture energy of the composite increased with increasing test temperature and decreased with sintering temperature.