Composite ceramics of B4C containing up to 30vol% SiC whisker were fabricated by hot pressing at 2000°-2200°C under 30MPa for 30min. The mechanical properties (bending strength, fracture toughness, hardness, elastic modules) of the hot pressed bodies were measured. Fully dense B4C-SiC whisker composite ceramics were obtained at the whisker contents up to 30vol% at a sintering temperature above 2100°C. These composites had maximum strength at the whisker content of 10 or 20vol% depending upon the hot pressing temperature. The composite containing 10vol% SiC whisker, fired at 2100°C, had the highest strength (about 830MPa), which was 40% larger than that of monolithic B4C. Slight increase of fracture toughness were obtained in the composites because there was no pull-out of whiskers and no crack deflection in the fracture process. The strength and fracture toughness of the composites containing whiskers with a small diameter were lower than those of the composites with a large diameter, since the whiskers with a small diameter could not maintain their original morphology after sintering. The hardness and elastic modulus were 30GPa and 430GPa, respectively, independent of whisker addition.
