Microstructure and fracture toughness of in-situ-toughened SiC composites

Silicon carbide composites with toughened microstructure were prepared by two-step process based on liquid-phase sintering for densification and subsequent annealing for grain growth. The resulting composites consist of uniformly distributed elongated alpha-SiC grains, matrix-like TiC grains, and an amorphous grain boundary phase. The in-situ toughening is a result of the beta-to-alpha phase transformation of SiC or the controlled grain growth of SiC during annealing. Crack deflection by the elongated alpha-SiC grains appears to account for the increased toughness of this new class of composites.