Microstructure of B4C/TiB2 composite fabricated by reaction sintering of B4C and TiC

Abstract

TiB2-dispersed B4C ceramics was fabricated by reaction sintering of B4C and TiC powders. The microstructure of this composite was observed mainly by transmission electron microscopy. TiB2 particles dispersed uniformly in the boundaries of B4C matrix. The interfaces of B4C-B4C, TiB2-TiB2 and B4C-TiB2 connect directly without inter-granular phase, defect and impurity, and have no preferred orientation. However; `ribbon-like structure' carbon layer sometimes precipitates at B4C-B4C, TiB2-TiB2 and B4C-TiB2 interfaces, which form in parallel to (002) plane of carbon. The degradation of bending strength and the constant fracture toughness observed in the composites containing more than 20 vol%TiC in starting material are caused by the increase of carbon precipitation.