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

B4C ceramics doped with different Si contents were fabricated by the spark plasma sintering technique. Pure B4C 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 B4C 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 center dot m1/2. The improvement in hardness and strength was attributed to grain refinement. Crack deflection due to the thermal expansion mismatch between the B4C and SiC was found to be the main toughening mechanism.