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

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 {alpha}-SiC grains, matrixlike TiC grains, and yttrium aluminum garnet (YAG) as a grain boundary phase. The composites were fabricated from {beta}-SiC and TiC powders with the liquid forming additives of Al{sub 2}O{sub 3} and Y{sub 2}O{sub 3} by hot pressing. During the subsequent heat treatment, the {beta} {yields} {alpha} 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 was 6.9 MPa{center_dot}m{sup 1/2}, approximately 60% higher than that of as-hot-pressed composites (4.4 MPa{center_dot}m{sup 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.

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