Densification and Mechanical Properties of Spark Plasma Sintered B4C with Si as a Sintering Aid

B 4 C ceramics doped with different Si contents were fabricated by the spark plasma sintering technique. Pure B 4 C ceramic could be densified to 99% of the theoretical density. The sinterability could be further improved by the addition of a small amount of Si due to the formation of liquid Si during sintering. The incorporation of Si could also remarkably increase the mechanical properties of B 4 C ceramics. The Vickers hardness, flexural strength, and fracture toughness of the sample with 8 wt% Si could reach 41.8 GPa, 640 MPa, and 6.1 MPa. m 1/2 . The improvement in hardness and strength was attributed to grain refinement. Crack deflection due to the thermal expansion mismatch between the B 4 C and SiC was found to be the main toughening mechanism.