Fabrication and mechanical properties of 3-D Cf/C-SiC-TiC composites prepared by RMI

Abstract

In this paper, the three-dimensional needled carbon fiber reinforced C-SiC-TiC ceramic composites (Cf/C-SiC-TiC) were successfully fabricated by chemical vapor infiltration (CVI) and Ti, Si mixed powders (Si content is the eutectic point of the Ti-Si alloy, 9.2 w.t.%) reactive melt infiltration (RMI) process. The open porosity and bulk density were about 4.71% and 2.14 g/cm3. The formation and distribution of the composites were investigated by XRD and EDS maps, and no residual Ti or Si phases were found. TiC and a layered SiC ceramics were formed in carbon fiber reinforced pyrolytic carbon (Cf/C) preforms due to the in situ reaction between pyrolytic carbon and Ti, Si powders. Their mechanical properties were improved compared with Cf/C-SiC composites. The flexural strength, flexural modulus and failure strains of the prepared composites were 218.44 ± 16.23 MPa, 68.17 ± 8.69 GPa and 2.22 ± 0.12%, respectively. In addition, the Cf/C-SiC-TiC composites showed a pseudoplastic fracture behavior because of debonding and pullout of fibers as well as propagation and deflection of cracks. Furthermore, the enhanced mechanism of the composites was proposed.