The preparation and properties of SiCw/B4C composites infiltrated with molten silicon

Silicon carbide whisker (SiCw) toughened B4C composites have been prepared by pressureless infiltration of B4C–SiCw–C preforms with molten silicon under vacuum at 1500 °C. The effect of SiCw addition on bulk density, hardness, bending strength, fracture toughness and microstructure of SiCw/B4C composites is discussed. It is revealed that the addition of SiCw improves the fracture toughness of B4C ceramic, but reduces its bending strength at the same time. The maximum fracture toughness for SiCw/B4C composite with 24 wt% SiCw addition is 4.88 MPa m1/2, which is about 9% higher than that of the one without SiCw, but at the same time, the bending strength reduces to the minimum value 243 MPa, reduced by 25%. XRD analysis shows that the phase composition of reaction bonded SiCw/B4C composites is B4C, SiC, Si, and B12 (C, Si, B)3, with no residual C. And the main toughening mechanism of SiCw is whisker pulling up.