Effect of carbon content on mechanical properties of SiC/B₄C prepared by reaction sintering

SiC/B₄C composite was obtained by reaction sintering with Si infiltration, and the effects of carbon content on mechanical properties and the microstructure were investigated. The results showed that the mechanical properties of the SiC/B₄C composite improved firstly and then worsened with increasing carbon content. The optimum comprehensive properties of the composite were obtained by addition of 10vol% carbon. The hardness, bending strength, and fracture toughness of the composite were 19.63 GPa, 358 MPa and 3.96 MPa·m^1/2, respectively. In addition, at carbon levels below 10vol%, the microstructure became more uniform as the carbon content increased. However, at carbon levels above 10vol%, the addition of carbon led to a fracture mode transformation, from combination of intergranular and transgranular to transgranular, which contributed to a change in the mechanical properties of the SiC/B₄C composite.