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

Abstract

C/C-ZrC-SiC composites prepared by reactive melt infiltration at 1700℃ contained residual Zr₂Si, which affected the mechanical properties at high temperature. Thus, the C/C-ZrC-SiC composites were heat treated from 1400 °C to 2000 °C for 1 hour, which exhibited the optimum flexural properties of 287 MPa and 19.2 GPa after annealing at 1600 °C. After heat treatment at 2000℃, 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°C and 2000°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 C_f-C matrix to enhance the mechanical properties.