MICROSTRUCTURE AND FRACTURE-TOUGHNESS OF HOT-PRESSED SILICON-CARBIDE REINFORCED WITH SILICON-CARBIDE WHISKER

The effects of beta-SiC whisker addition on the microstructural evolution and fracture toughness (K-IC) of hot-pressed SiC were investigated. Most of the whiskers added disappeared during the densification process by transformation into the alpha-phase. the remaining whiskers acted as nuclei for grain growth, resulting in the formation of large tabular grains around the whiskers. The tabular grains around the whiskers were believed to be formed because of the extreme anisotropy of the interfacial energy between alpha- and beta-SiC. The K-IC of the material was improved significantly by the whisker addition. The increase in the K-IC was attributed to crack bridging followed by grain pullout as a result of the formation of tabular grains in a fine matrix.