FABRICATION, CHARACTERIZATION AND MECHANICAL-PROPERTIES OF SIC-WHISKER-REINFORCED Y-TZP COMPOSITES

The microstructure and mechanical properties of hot-pressed yttria-sta blized tetragonal zirconia polycrystals (Y-TZP) reinforced with up to 30 vol % SiC whiskers were investigated. The homogeneously dispersed a nd fully dense SIC whisker/Y-TZP composites were fabricated by wet-mix ing 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 fractur e toughness of about MPa m(1/2) at 10 Vol % SIC and a small increase i n 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 whi skers and also a phase transformation of ZrO2. The observed increase i n the fracture toughness of Y-TZP due to the addition of SiC whiskers was correlated with existing models of toughening mechanisms. Good agr eement was achieved between the theoretical predictions and the experi mental toughness values, obtained from the Y-TZP/SICw composites.