Hexagonal boron nitride (h-BN) can reinforce boron carbide (B₄C) ceramics, but homogeneous dispersion of h-BN is difficult to achieve using conventional methods. Herein, B₄C/h-BN composites were manufactured via the transformation of cubic (c-) BN during spark plasma sintering at 1800 °C. The effects of the c-BN content on the microstructure, densification, and mechanical properties of B₄C/h-BN composites were evaluated. In situ synthesized h-BN platelets were homogeneously dispersed in the B₄C matrix and the growth of B₄C grains was effectively suppressed. Moreover, the c-BN to h-BN phase transformation improved the sinterability of B₄C. The sample with 5 vol.% c-BN exhibited excellent integrated mechanical properties (hardness of 30.5 GPa, bending strength of 470 MPa, and fracture toughness of 3.84 MPa⋅ m^1/2). Higher c-BN contents did not significantly affect the bending strength and fracture toughness but clearly decreased the hardness. The main toughening mechanisms were crack deflection, crack bridging, and pulling out of h-BN.

六方氮化硼（h -BN）可以增强碳化硼（B ₄ C）陶瓷，但是使用常规方法很难实现h -BN的均匀分散。在此，通过在1800℃下的火花等离子体烧结过程中立方（c-）BN的转变来制造B ₄ C / h -BN复合材料。评估了c -BN含量对B ₄ C / h -BN复合材料的微观结构，致密化和力学性能的影响。原位合成的h -BN血小板均匀分散在B _4中C基体和B ₄ C晶粒的生长得到有效抑制。此外，Ç -BN到ħ -BN相变改善B的烧结₄ C的样品与5体积％Ç -BN表现出30.5吉帕优良综合机械性能（硬度，弯曲470兆帕的强度，和断裂韧性3.84MPa·m ^1/2的压力。较高的c -BN含量并未显着影响弯曲强度和断裂韧性，但明显降低了硬度。主要的增韧机制是裂纹挠曲，裂纹桥接和从h -BN中拉出。