Phase transformation, microstructure and mechanical properties of Si3N4/SiC composite

The influence of SiC fine particle dispersion on phase transformation, microstructure and mechanical properties of Si3N4 ceramics has been investigated. While the SiC dispersion simply decreased the densification, it caused complex effects on the phase transformation behavior; the transformation was enhanced at low temperatures but suppressed at high temperatures. Since the phase transformation is a nucleation-grain growth process of β-Si3N4, SiC particles plausibly enhance formation of a great number of β-Si3N4 nuclei due to the high Si3N4–SiC interfacial energy, but inhibit their further phase transformation and grain growth. The mean size and the aspect ratio of the obtained β-Si3N4 grains decreased as a result of the SiC dispersion, thus bringing about increased flexural strength and decreased fracture toughness.