B4C-TiB2 composite with modified microstructure and enhanced properties from optimal size coupling of raw powders

B4C-15 vol% TiB2 composites were fabricated by in situ reactive spark plasma sintering with B4C, TiC, and amorphous B powders as the raw materials. The size coupling of initial B4C and TiC particles was optimized based on the reaction mechanism to derive B4C-TiB2 composites with enhanced microstructure and properties. During the reactive sintering, fine B4C-TiB2 particles were firstly formed by an in situ reaction between TiC and B. Then, large B4C particles tended to grow at the cost of small B4C particles. The in situ TiB2 grains gradually grew up and interconnect, distributing around the large B4C grains to form an intergranular TiB2 network. The results showed that the B4C-15 vol% TiB2 composite prepared from 3.12 mu m B4C powder and 0.80 mu m TiC powder had the optimal comprehensive properties, with a relative density of 99.50%, a Vickers hardness of 31.84 GPa, a flexural strength of 780 MPa, a fracture toughness of 5.77 MPa center dot m(1/2), as well as an electrical resistivity of 3.01 x 10(-2) omega center dot cm.