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Abstract: Short-carbon-fiber-reinforced SiC composites were prepared by precursor pyrolysis–hot pressing with MgO–Al2O3–Y2O3 as sintering additives. The effects of the amount of sintering additives on microstructure and mechanical properties of the composites were investigated. The results showed that the composites could be densified at a relatively low temperature of 1800°C via the liquid-phase sintering mechanism and the composite density and mechanical properties improved with the amount of additives. The amorphous interphase in the composites with more additive content, not only avoided the direct contact of the fibers with matrix, but also improved the fiber–matrix bonding. It proved that the fiber–matrix interphase characteristics played a key role in controlling mechanical properties of the composites. [Copyright &y& Elsevier]

Abstract: Self-toughening α-SiAlON/6H-SiC composites containing both α-SiAlON and α-SiC elongated grains in the microstructures were previously fabricated by spark plasma sintering (SPS). In this study, the α-SiAlON/6H-SiC composites were heat treated at 1850°C for 3h. The effects of the heat treatment on the phase compositions, microstructures, and mechanical properties were investigated. The results showed M′ phases formed from crystallization of the intergranular glassy films. No polytype transformation for the SiC phase was observed. Both α-SiAlON and α-SiC grains grow anisotropic in the heat treatment, rather than converted into the brittle equiaxed morphologies. The flexural strength and fracture toughness of the post heat-treated composites were further increased and the 40wt% SiC composition reached 907MPa and 8.5MPam1/2, respectively. [Copyright &y& Elsevier]