Effect of Additive Ti(3)SiC(2) Content on the Mechanical Properties of B(4)C–TiB(2) Composites Ceramics Sintered by Spark Plasma Sintering

B(4)C–TiB(2) composite ceramics with ultra-high fracture toughness were successfully prepared via spark plasma sintering (SPS) at 1900 °C using B(4)C and Ti(3)SiC(2) as raw materials. The results showed that compared with pure B(4)C ceramics sintered by SPS, the hardness of B(4)C–TiB(2) composite ceramics was decreased, but the flexural strength and fracture toughness were significantly improved; the fracture toughness especially was greatly improved. When the content of Ti(3)SiC(2) was 30 vol.%, the B(4)C–TiB(2) composite ceramic had the best comprehensive mechanical properties: hardness, bending strength and fracture toughness were 27.28 GPa, 405.11 MPa and 18.94 MPa·m(1/2), respectively. The fracture mode of the B(4)C–TiB(2) composite ceramics was a mixture of transgranular fracture and intergranular fracture. Two main reasons for the ultra-high fracture toughness were the existence of lamellar graphite at the grain boundary, and the formation of a three-dimensional interpenetrating network covering the whole composite.