B4C ceramics toughened by TiB2–graphite-agglomerated inclusions

In this study, B 4 C–TiB 2 –graphite ceramic composites were prepared via reactive hot-pressing sintering using B 4 C and TiC as the raw materials. The reaction process, microstructure, and mechanical properties were investigated. The solid-phase reaction is a diffusion-controlled process, wherein the B atoms diffuse into TiC and react to form TiB. Thereafter, TiB 2 is generated with the entry of subsequent B atoms. A core–shell structure is formed, wherein TiB 2 particles are wrapped by layered graphite. The products TiB 2 and graphite inhibit the growth of B 4 C matrix grains, which are instrumental in fine grain strengthening. In addition, the novel TiB 2 –graphite-agglomerated structure significantly improves the fracture toughness of the ceramic composites through crack deflection, bridging, and branching toughening mechanisms. Therefore, the comprehensive properties of B 4 C–TiB 2 –graphite ceramic composites are better than those of pure B 4 C ceramics. Specifically, the fracture toughness is approximately 6.77 MPa m 1/2 , which is considerably higher than that of pure B 4 C ceramics (2.47 MPa m 1/2 ).