In situ-toughened silicon carbide-titanium carbide composites

Abstract

A process based on liquid-phase sintering and subsequent annealing for grain growth is presented to obtain lit situ-toughened SiC-30 wt% TiC composites, Its microstructures consist of uniformly distributed elongated alpha-SiC grains, matrixlike TiC grains, and yttrium aluminum garnet (YAG) as a grain boundary phase, The composites mere fabricated from beta-SiC and TiC powders with the liquid forming additives of Al2O3 and Y2O3 by hot pressing. During the subsequent heat treatment, the beta --> alpha or phase transformation of SiC led to the in situ growth of elongated alpha-SiC grains, The fracture toughness of the SiC-30 wt% TiC composites after 6-h annealing mas 6.9 MPa . m(1/2), approximately 60% higher than that of as-hot-pressed composites (4.4 MPa . m(1/2)). Bridging and crack deflection by the elongated alpha-SiC grains appear to account for the increased toughness of this new class of composites.