Microstructures and mechanical properties of B4C-SiC and B4C-SiC-TiB2 ceramic composites fabricated by hot pressing

Boron carbide (B4C) ceramic composites with excellent mechanical properties were fabricated by hot-pressing using B4C, silicon carbide (SiC), titanium boride (TiB2), and magnesium aluminum silicate (MAS) as raw materials. The influences of SiC and TiB2 content on the microstructural evolution and mechanical properties of the composites were systematically investigated. The mechanism by which MAS promotes the sintering process of composites was also investigated. MAS exists in composites in the form of amorphous phase. It can effectively remove the oxide layer from the surface of ceramic particles during the high temperature sintering process. The typical values of relative density, hardness, bending strength, and fracture toughness of B4C-SiC-TiB2 composites are 99.6%, 32.61 GPa, 434 MPa, and 6.20 MPa m(1/2), respectively. Based on the microstructure observations and finite element modeling, the operative toughening mechanism is mainly attributed to the crack deflection along the grain boundary, which results from the residual stress field generated by the thermal expansion mismatch between B4C and TiB2 phase.