TiB₂-TiC eutectic composite ceramics prepared by combustion synthesis under high gravity

TiB₂-TiC eutectic composite ceramics were prepared by combustion synthesis under high gravity. XRD ,SEM and EDS results show that TiB₂-TiC composites are mainly composed of the eutectic microst ructures of TiC matrix, in which a large number of the fine TiB₂ platelet grains are dispersed uniformly ; meanwhile, at the boundaries of the eutectic microst ructures there discontinuously disperse the ε-carbides with the enrichment of Tiatoms, and a few of isolated , irregular α-Al₂O₃ grains and Al₂O₃-ZrO₂ colonies are also observed. Because high-temperature chemical reaction results in the full-liquid products, and the introduction of high gravity induces the Stocks flow in the melts, leading to the formation of layered melt s consisting of liquid Ti-Cr-C-B and liquid oxides, it is considered that TiB₂-TiC composites grow through eutectic t ransformation far away f rom the equilibrium state.The results of properties indicate that with increasing mass fraction of B₄C + Ti + C in combustion systems , the relative density and f racture toughness of TiB₂-TiC composites are all among 97 %～99 % and 6. 5 ～7. 1 MPa·m^1/2 , respectively, and the Vickers hardness and flexural strength are increased gradually to the maximum values of 28. 6 GPa and 615 MPa, respectively.