Preparation of TiB2-B4C composites by high pressure sintering

Sintered composites in the TiB2-xB(4)C (x = 0.3-1.0) system were prepared by high pressure sintering of the TiB2-xB(4)C powders which were synthesized by a solid state reaction between TiCxN1-x and amorphous boron. The effects of sintering parameters (pressure, temperature and soaking time) on microstructures and mechanical properties of sintered composites were investigated; the effects of the crystallinity, dispersibility and composition of the starting composite powder were also investigated. TiB2-xB(4)C composite compact with a high density was obtained under the optimum sintering conditions of 5 GPa, 1800 degrees C and 15 min. The microhardness Hv increased from 3000 to 3600 kg mm(-2) and fracture toughness K-Ic decreased from 5 to 3 MN m(-3/2) with B4C content. The sintered compacts having higher contents of B4C (x = 0.7-1.0) were composed of fine-grained and well-crystallized TiB2 particles dispersed in a low crystalline B4C matrix which resulted in higher toughness due to the grain boundary fracture between TiB2 and B4C particles.