Effect of Heat Treatment on Fracture Toughness of Alumina‐Diamond Composites Sintered at High Pressures

Alumina composites containing dispersed diamond particles were fabricated under very high pressure at a temperature where diamond is stable. Subsequent heat treatment in vacuum improves the toughness of the 5 vol% composite but not that of the 10 vol% composite. The heat treatment time was varied for both composites, and the influence of graphitization and morphology of the second-phase particles on toughness were studied.