TOUGHENING MECHANISM FOR CERAMICS BY A DUCTILE METALLIC PHASE

The basic objective of this study is to establish the material design concepts for the coexistence of good high-temperature mechanical prope rties and super heat resistance in the systems of ceramic/metal and ce ramic/ceramic functionally gradient materials (FGMs). Flexural and fra cture toughness tests were conducted on gas-pressure combustion-sinter ed Cr3C2 ceramic and its composites with Ni and TiC (Cr3C2/Ni, Cr3C2/T iC) in a vacuum environment up to 1 200 degrees C using a newly develo ped materials testing system. Fracture characteristics were investigat ed on the basis of fracture mechanics and fractography. The toughness of Cr3C2 can be improved by the addition of metallic particles. It is found that the principal mechanism of toughness improvement in these c omposites (ductile-phase reinforced ceramic matrix composites) is attr ibutable to crack-tip plastic blunting by a ductile metallic phase.