(SiC,TiB_2)/B_4C复合材料的微观结构及性能

MICROSTRUCTURES AND PROPERTIES OF (SiC,TiB_2)/B_4C COMPOSITES

以B4C与Si3N4和少量SiC,TiC为原料,Al2O3和Y2O3为烧结助剂,烧结温度为1800～1880℃,压力为30MPa的热压条件下制备(SiC,TiB2)/B4C复合材料。用透射电子显微镜、扫描电子显微镜和能谱分析进行显微结构分析。结果表明:在烧结过程中反应生成了SiC,TiB2和少量的BN。复合材料的主晶相之间有长棒状架构弥散相和束状弥散相,在部分B4C晶粒内部出现了内晶结构。结合对复合材料性能的分析表明:新形成相、均匀细晶和棒状结构对提高材料的性能具有重要作用。通过对材料断口形貌和裂纹扩展模式分析认为,复合材料的断裂机制主要为裂纹偏转。

The （SiC, TiB2）/B4C composites were fabricated with the original powders B4C, Si3N4, small quantities of SiC, TiC, and the sintering additive Al2O3 and Y2O3 under hot pressing of 1 800-1 880℃ and 30 MPa. The microstructures of the composites were analyzed by transmission electron microscope, scanning electron microscope and the energy spectrum method. The results show that the SiC, TiB2, and a small amount of BN are formed during the sintering and reacting procedures. A clubbed frame dispersion phase and a bunchy dispersion phase are among the main crystal boundaries. There are some inner crystal structures in the B4C grain. Combined with the analyses of the composite＇ properties, these results show that the new formed phase, uniform and fine grains, and clubbed structure play an important role in improving the composites＇ properties. The analyses of the fractography and the crack growth mode indicate that the composites＇ fracture mechanism is mainly crack deflection.