热压烧结C-SiC-B_4C复合材料组织与性能(Ⅰ)

以Cfg,SiC,B4C,TiO2为原料,热压工艺为1750~1 900℃×30 min,25 MPa,制备了C-SiC-B4C复合材料,并研究了材料的组织与性能.结果表明随热压温度升高,复合材料的体积密度、抗折强度、断裂韧性均升高;相同热压温度下随Cfg含量增加,其抗折强度降低、断裂韧性升高.在1 900℃热压,原料质量配比(质量分数,%)为Cfg20,SiC 61.7,B4C 12.3和TiO26时,复合材料的综合力学性能最佳,抗折强度为142.5MPa,断裂韧性为4.8 MPa.m21.复合材料的主晶相为层状结构的Cfg,在Cfg层间为SiC,B4C和原位生成的TiB2颗粒.复合材料的增...

Microstructure and properties of C-SiC-B4C composites prepared by hot pressing sintering (I)

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.