Microstructure and mechanical properties of three dimensional Cf/SiC-ZrC-ZrB2 composites prepared by reactive melt infiltration method

Three-dimensional Cf/SiC-ZrC-ZrB2 composites were fabricated by reactive melt infiltration of ZrSi2 alloys into porous Cf/B4C-C preforms prepared through a sol-gel process. The influence of pore structure of the Cf/B4C-C preforms on microstructure and mechanical performances of the Cf/SiC-ZrC-ZrB2 composites was studied. It was found that the microstructure and mechanical performances of the composites showed a strong dependence on the pore structure of the preforms. Residual ZrSi2 content in the composites was significantly reduced with the decreases in the porosity and pore size of the Cf/B4C-C preforms. At the same time, fiber erosion in the composites was also gradually mitigated, which led to a significant improvement in the fracture behaviors of the composite, as failure mode of the composites changed from brittle to pseudo-plastic. When the porosity of the preforms decreased from 53.7% to 31.3%, the flexural strength of the composites increased from 53 MPa to 184 MPa.