Improving the Fracture Toughness of Boron Carbide via Minor Additions of SiC and TiB2 Through Hot-Press Sintering

Boron carbide (B₄C) is an essential material in various high-performance applications due to its light weight and hardness. In this work, B₄C-based composites were fabricated via a powder route consisting of powder mixing, precursor preparation, and hot-pressing under vacuum. The composites' mechanical properties and microstructure were analyzed to investigate the effect of adding minor second-phase particles. In addition to homogenizing the grain size, the addition of SiC (≤10 wt%) to B₄C increased its strength and improved its fracture toughness, with values reaching 551 MPa and 3.22 MPa m^1/2, respectively. Meanwhile, the addition of TiB₂ (≤10 wt%) significantly improved the strength and fracture toughness only, with values reaching 548 MPa and 3.92 MPa m^1/2, respectively, with only a minimal decrease in hardness. Microstructural analysis revealed that the second-phase particles were uniformly distributed and reduced the average grain size, contributing to the increase in strength. Additionally, the TiB₂ particles impeded crack propagation and induced crack deflection at the interface, indicating the formation of an intergranular fracture mode. On the contrary, the addition of SiC primarily resulted in transgranular fracture behavior, though it still improved the toughness of the B₄C. These results suggest that small amounts of SiC and TiB₂ can effectively enhance the mechanical properties of B₄C ceramics while maintaining the lightweight characteristics critical for military and aerospace applications.