Fabrication and mechanical behavior of 2D-C_f/Ta_xHf_1−xC–SiC composites by a low-temperature and highly-efficient route

C_f/Ta_xHf_1−xC–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles. However, how to synthesize Ta_xHf_1-xC powders and efficiently fabricate C_f/Ta_xHf_1-xC–SiC composites still faces some challenges. Furthermore, mechanical properties and thermophysical properties of Ta_xHf_1−xC vary with the composition, but not monotonically. In-depth analysis of mechanical behaviors of the C_f/Ta_xHf_1−xC–SiC composites is extremely important for their development and applications. In this study, the Ta_xHf_1−xC powders (x = 0.2, 0.5, 0.8) were successfully synthesized via solid solution of TaC and HfC at a relatively low temperature of 1800 ℃, with a small amount of Si as an additive. Subsequently, the efficient fabrication of 2D-C_f/Ta_xHf_1–xC–SiC composites was achieved by slurry impregnation and lamination (SIL) combined with precursor infiltration and pyrolysis (PIP). In addition, the mechanical behavior of the composites was investigated systematically. It is demonstrated that the composites present remarkable non-brittle fractures, including a large number of fiber pull out and interphase debonding. Also, the fracture failure involves a complex process of microcrack generation and propagation, matrix cracking, and layer fracture. Moreover, the interfacial bonding between the fibers and the matrix is enhanced as the Ta∶Hf ratio decreases from 4∶1 to 1∶4. As a result, C_f/Ta_0.2Hf_0.8C–SiC composites exhibit exceptional flexural strength of 437±19 MPa, improved by 46% compared with C_f/Ta_0.8Hf_0.2C–SiC (299±19 MPa). This study provides a new perception of design and fabrication of ultra-high-temperature ceramic (UHTC) matrix composites with high performance.