In S/Yu‐Toughened Silicon Carbide‐Titanium Carbide Composites

Abstract

A process based on liquid‐phase sintering and subsequent annealing for grain growth is presented to obtain in situ‐toughened SiC‐30 wt% TiC composites. Its microstructures consist of uniformly distributed elongated α‐SiC grains, matrixlike TiC grains, and yttrium aluminum garnet (YAG) as a grain boundary phase. The composites were fabricated from β‐SiC and TiC powders with the liquid forming additives of A12O3 and Y2O3 by hot pressing. During the subsequent heat treatment, the β→α phase transformation of SiC led to the in situ growth of elongated α‐SiC grains. The fracture toughness of the SiC‐30 wt% TiC composites after 6‐h annealing was 6.9 MPa‐m1/2, approximately 60% higher than that of as‐hot‐pressed composites (4.4 MPa‐m1/2). Bridging and crack deflection by the elongated α‐SiC grains appear to account for the increased toughness of this new class of composites.