Sapphire matrix composites reinforced with single crystal YAG phases

Abstract

An investigation of fabrication technology on eutectic composites consisting of Al2O3 phases and YAG (Y3Al5O12) phases was carried out by applying the unidirectional solidification process. Unidirectionally solidified eutectic composites consisting of 〈1 1 0〉 sapphire phases and 〈4 2 0〉 single crystal YAG phases could be fabricated successfully by lowering a Mo crucible at a speed of 5 mm h-1 under a pressure of 10-5 mmHg of argon. These eutectic composites have excellent high-temperature properties up to 1973 K. For example, the flexural strength is 360-500 MPa independent of testing temperature from room temperature to 1973 K. Oxidation resistance at 1973 K in an air atmosphere is superior to SiC and Si3N4 and the microstructure of these eutectic composites is stable even after heat treatment at 1773 K for 50 h in an air atmosphere. © 1996 Chapman & Hall.