High-temperature properties and microstructure evolution of C/C-ZrC-SiC composites fabricated by reactive melt infiltration

C/C-ZrC-SiC composites prepared by reactive melt infiltration at 1700 degrees C contained residual Zr2Si, which affected the mechanical properties at high temperature. Thus, the C/C-ZrC-SiC composites were heat treated from 1400 degrees C to 2000 degrees C for 1 hour, which exhibited the optimum flexural properties of 287 MPa and 19.2 GPa after annealing at 1600 degrees C. After heat treatment at 2000 degrees C, the Zr2Si phase completely disappeared and Si filled in the cracks in the ZrC matrix and at the PyC-ZrC interface in the form of SiC, indicating that the high-temperature treatment promoted the diffusion and reaction of Zr and Si to consume Zr2Si. The flexural strength of composites was higher at 1800 degrees C and 2000 degrees C than at room temperature, which was 313 MPa and 307 MPa, respectively. This indicated that high-temperature treatment could mitigate the thermal stress mismatches in the ZrC matrix, ZrC-SiC-C interphase, and Cf-C matrix to enhance the mechanical properties.