Year: 1994
Type: article
Abstract: The paper summarizes studies of SiC whisker-reinforced alumina composites their properties and the influence of composition and microstructure. Both steady-state toughness and R-curve response increase with whisker content and diameter. Room temperature flexure strength of aluminas with different grain sizes also increases with whisker content. Resistance to slow crack growth under both monotonic and cyclic loading is improved by whisker reinforcement compared to alumina and other ceramics. The thermal conductivity and electrical resistivity exhibit a substantial increase and decrease, respectively, with whisker loadings above 10 vol %. Thermal expansion coefficients decrease in a systematic fashion with increase in whisker content. However, the expansion coefficients are greater parallel to hot pressing axis compared to perpendicular direction owing to internal stresses and preferred orientation of whiskers. The changes in mechanical and thermal properties due to SiC whisker additions result in substantial improvement in thermal shock resistance for samples of various sizes. At elevated temperatures, tests in air show that improvements in strength and resistance to strength degradation are associated with SiC whisker reinforcement. The limiting factors in elevated temperature mechanical response of the composite at 1200C and above are related to surface oxidation-reaction processes and creep. On the other hand, the creep resistance of the composite is far greater than alumina with a similar fine grain size at temperatures {le} 1200C. Furthermore by increasing the grain size of the alumina matrix, creep resistance of the composite can be increased. In essence, SiC whisker reinforced alumina composites provide an example of a system whose properties can be tailored through control of microstructure and composition.
Language: English
Subfield: Ceramics and Composites
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W61700284