Effect of Holding Time on the Microstructure and Mechanical Properties of B4C-Based Composite Materials

In this study, B 4 C–TiB 2 composite materials were successfully fabricated via in situ reaction using a high-pressure and high-temperature sintering with 90 wt % B 4 C and 10 wt % TiO 2 as raw materials. The influence of holding time (2–10 min) at a constant pressure of 5 GPa and temperature of 1500°C on the densification behavior, phase composition, microstructure evolution, and mechanical properties was investigated. The results reveal that the holding time significantly affects both the densification kinetics and the formation of the TiB 2 reinforcing phase. Optimal mechanical performance was achieved when the holding time was 8 min, yielding a relative density of 99.6%, Vickers hardness of 35.3 GPa, flexural strength of 675 MPa, and fracture toughness of 6.8 MPa m 1/2 . The enhanced mechanical properties are primarily attributed to the complete in-situ formation of TiB 2 particles, which effectively improve fracture toughness through mechanisms such as crack deflection and bridging. This work provides critical insights into optimizing the sintering process for high-performance B 4 C-based composites, offering a scientific basis for their development and application in extreme environments.