Heterogeneous precipitation methods were used to produce 5 vol% SiC-Al2O3 nanocomposite powder, from aqueous suspension of Nano-SiC (70 nm), aqueous solution of aluminium chloride and ammonia. The SiC-Al2O3 nanocomposites were superfast densified by spark plasma sintering (SPS) process with heating to a sintering temperature range from 1350 to 1550 degrees C, at a heating rate of 600 degrees C/min, without holding time, and then fast cooling to 600 degrees C within 2 similar to 3 minutes; and high density nanocomposites were obtained. The experimental results show that bending strength of 5 vol% SiC-Al2O3 nanocomposites sintered at 1450 degrees C is as high as 1000 MPa, while vickers hardness about 19 GPa. Fracture toughness of the sample sintered at 1500 degrees C is about 4 MPa.m(1/2), a little bit higher than that of Al2O3 ceramics. Microstructure studies show that nano-SiC particles are mainly located in Al2O3 grains and the fracture mode of the nanocomposites is mainly transgranular fracture. Due to the expansion coefficient, mismatch and most of SiC particles located in Al2O3 gains, the tensile stress, which weakens matrix grains and originates the transgranular fracture, will appear when the samples cool down from the sintering temperature.
