关键词: C-SiC-B4C, Cfg, 热压, 力学性能, 分层诱导韧化

Abstract: C-SiC-B4C composites were prepared with such raw materials as flake graphite Cfg, SiC, B4C and TiO2 by a sintering process, i.e., under 25 MPa hot-pressing at 1750-1900°C × 30 min. The result showed that the bulk density, flexural strength and fracture toughness of all the composites increase obviously with increasing sintering temperature. With the pressure and temperature kept unchanged, the flexural strength decreases and fracture toughness increases with the increasing flake graphite content. And the composite has the best comprehensive mechanical properties where the flexural strength is 142.5 MPa and fracture toughness 4.8 MPa·m^1/2 when the mass fractions are Cfg20%, SiC 61.7%, B4C 12.3% and Tift 6% at 1900°C × 30 min. The primary crystalling phase of the composite is lamellar flake graphite of which the interlayer particles are of SiC and B4C and the TiB2 formed in situ. It was found that the toughening mechanism of the composites is mainly that the thermal stress due to the heat expansion mismatching between Cfg and ceramic phase, which results in the toughening effect induced by the lamination of weak crystal boundary.