热压C－SiC－B4C－TiB2复合材料的组织与力学性能

C-SiC-B4C-TiB2 composites were prepared with raw materials such as flake graphite C(subscript fg), SiC, B4C and TiO2 by in situ synthesis and hot pressed. The effects of C(subscript fg) content, sintering temperatures on the microscope structure and mechanical properties of composites were studied. The results show that TiB2 particles form by the reaction of TiO2 and B4C in the composite in the sintering process. The density and flexure strength increase with increasing sintering temperature, while decrease with increasing C(subscript fg) content. The fracture toughness increases with increasing sintering temperature and C(subscript fg) content. The density, flexure strength and fracture toughness of the composite is 2.81 g/cm^3, 236.7 MPa, 5.3 MPa‧m^1/2 with 20%C(subscript fg)(mass fraction) at 2 000 ℃ and 25 MPa, as well as 2.42 g/cm^3, 103.6 MPa, 8.1 MPa‧m^1/2 with 65% C(subscript fg) at 2 000 ℃ and 25 MPa. The pyknosis degree increases and the ceramic crystal grains of the composites grow up with increasing sintering temperature, C(subscript fg) layers structure of the composites become clearly with increasing C(subscript fg) content. It is found that the toughning mechanism of the composites is mainly that the lamination between C(subscript fg) and ceramic phase, which results in the toughening effect induced by the lamination of weak crystal boundary, and the thermal stress due to the heat expansion mismatching between ceramic phase and the second phase TiB2 leads to the heat stress micro crack deflection in the composites.