Effects of B4C particle size on the microstructures and mechanical properties of hot-pressed B4C-TiB2 composites

Full dense B4C-30 vol% TiB2 composites were prepared by hot pressing at 2000 degrees C under 35 MPa from four different starting B4C powders with their medium particle sizes ranging from 0.5 to 35.8 mu m. The effects of B4C particle size on the microstructures and mechanical properties of composites were investigated. The results indicated that both B4C and TiB2 grains grew during sintering process, and each kind of grains had a pinning effect on the grain growth of the other. With coarse B4C powders as raw materials, TiB2 grains in obtained B4C-TiB2 composites tended to grow with the [001] zone axis parallel to the applied pressure direction, which possibly reinforced the composites. When the particle size of the starting B4C powder was 7.09 mu m, the obtained B4C-TiB2 composite exhibited the optimized mechanical properties including a flexural strength of 754 MPa, a Vicker hardness of 30.01 GPa and a fracture toughness of 5.23 MPa m(1/2), respectively, due to the most homogenous and finest microstructures.