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.