B <sub>4</sub> C‒TiB <sub>2</sub> composite with modified microstructure and enhanced properties from optimal size coupling of raw powders
Jun Zhao, Zheyu Fang, Xing Jin, Dong Wang, Xiang Ding, Songlin Ran
Abstract
Abstract B 4 C‒15 vol% TiB 2 composites were fabricated by in situ reactive spark plasma sintering with B 4 C, TiC, and amorphous B powders as the raw materials. The size coupling of initial B 4 C and TiC particles was optimized based on the reaction mechanism to derive B 4 C‒TiB 2 composites with enhanced microstructure and properties. During the reactive sintering, fine B 4 C–TiB 2 particles were firstly formed by an in situ reaction between TiC and B. Then, large B 4 C particles tended to grow at the cost of small B 4 C particles. The in situ TiB 2 grains gradually grew up and interconnect, distributing around the large B 4 C grains to form an intergranular TiB 2 network. The results showed that the B 4 C‒15 vol% TiB 2 composite prepared from 3.12 μm B 4 C powder and 0.80 μm 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·m 1/2 , as well as an electrical resistivity of 3.01 × 10 −2 Ω·cm.