Processing and Characterization of SiC-Whisker-Reinforced Alumina-Matrix Composites

Brittle monolithic alumina can be reinforced with highstrength single‐crystal SiC whiskers with the effect of increasing fracture toughness. In this study, well‐mixed and nearly fully dense SiC whisker/alumina composites were fabricated by wet‐blending the constituents and uniaxially hot‐pressing the resulting powder. The alumina‐matrix grain size depended on whisker volume fraction, whisker surface‐oxygen content, and hot‐pressing environment. Fracture toughness, measured by an indentation‐fracture method, increased from 3.0 MPa·m1/2 for the hot‐pressed unreinforced alumina to 10.7 MPa·m1/2 for the composite containing 25 vol% SiC whiskers. Fracture surfaces revealed evidence of toughening by the mechanisms of crack deflection, pullout, and crack bridging by the whiskers. The observed increase in fracture toughness of alumina due to the addition of SiC whiskers was correlated with existing models of toughening mechanisms.