Fabrication, characterization and mechanical properties of SiC-whisker-reinforced Y-TZP composites

The microstructure and mechanical properties of hot-pressed yttria-stablized tetragonal zirconia polycrystals (Y-TZP) reinforced with up to 30 vol % SiC whiskers were investigated. The homogeneously dispersed and fully dense SiC whisker/Y-TZP composites were fabricated by wet-mixing the constitutents and uniaxially hot-pressing the resulting powder. The grain size of the matrix depended on the whisker volume fraction and the hot-pressing temperature. The significant increase of fracture toughness of about MPa m^1/2 at 10 Vol % SiC and a small increase in strength were achieved by uniformly dispersing the whiskers in the Y-TZP matrix. Fracture surfaces revealed evidence of toughening by the mechanisms of crack deflection, pullout, and crack bridging by the whiskers and also a phase transformation of ZrO₂. The observed increase in the fracture toughness of Y-TZP due to the addition of SiC whiskers was correlated with existing models of toughening mechanisms. Good agreement was achieved between the theoretical predictions and the experimental toughness values, obtained from the Y-TZP/SiC_w composites.