Abstract: 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℃, at a
heating rate of 600℃/min, without holding time, and then fast cooling to 600℃ within 2～3 minutes; and high density nanocomposites
were obtained. The expermental results show that bending stregth of 5 vol% SiC-Al₂O₃ nanocomposites sintered at 1450℃ is as high as 1000 MPa,
while vickers hardness about 19 GPa. Fracture toughness of the sample sintered at 1500 ℃ 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.

Key words: SiC nanocomposites, superfast densification, spark plasma sintering