Effect of sintering pressure on microstructure and mechanical properties of (TiB₂–SiC)/B₄C composite ceramics

In this study, spark plasma sintering technology was used for fabricating B₄C composite ceramics that contained 30 wt% (TiB₂ + SiC) by altering the sintering pressures (0 MPa, 50 MPa, and 80 MPa) at a comparatively low temperature of 1650 °C. This study showed how sintering pressure affected the densification behavior, microstructures, and mechanical characteristics of composite ceramics. Elevating the sintering pressure led to the inhibition of grain growth during the sintering process, ultimately resulting in the refinement of grains within the composite ceramics. At the same time, the quantity of internal pores in the composite ceramics was reduced, and the relative densities increased, so the flexural strength and hardness of the composite ceramics could be effectively improved. The quantity of microcracks and large aspect ratio second phase particles decreased with an increase in sintering pressure, which adversely affected the fracture resistance characteristics of the composite ceramics. In addition, the growth of B₄C grains was hindered by TiB₂ and SiC generated by in-situ reactions, thus improving the mechanical characteristics of the composite ceramics. Comprehensive analysis showed that the composite ceramics had the best comprehensive mechanical properties when the sintering pressure was 80 MPa, displaying a relative density of 98.65%, a Vickers hardness of 30.71 GPa, a flexural strength of 531.19 MPa, and a fracture toughness of 5.78 MPa m^1/2.