Preparation and Properties of Solidified TiC-TiB_2 with Hypoeutectic, Eutectic and Hypereutectic Microstructures

摘要

By using combustion synthesis under high gravity, TiC-TiB_2 fine-grained composite ceramics with hypoeutectic, eutectic and hypereutectic microstructures were prepared through rapid solidification. XRD, FESEM and EDS results show that with increasing TiB_2 content, TiC-TiB_2 composite ceramics transform the microstructures consisting of fine TiB_2 platelets from ones composed of fine TiC spherical grains, whereas when TiB_2 content reaches 50mol%, the ceramics develop the eutectic microstructures that small aspect-ratio TiB_2 platelets were embedded in TiC matrix. Mechanical properties show that relative density, Vickers hardness and flexural strength of TiC-50mol%TiB_2 all reach the maximum values (respectively as 98.6 % ,18.4 GPa, 840 MPa) due to eutectic reaction during solidification, meanwhile TiC-50mol%TiB_2 has the maximum fracture toughness of 11.5 MPa-m~(0.5) due to the cooperative action of crack deflection, crack-bridging and pull-out toughening by fine TiB_2 platelets.