Effect of Thermal Cycling on Microstructure and Mechanical Properties of Cf/SiC-Al Composites

Thermal cycling inevitably affects the microstructure and mechanical properties of composites due to the differences in thermal expansion coefficients (CTEs) of each component. Herein, the evolution of the microstructure and in-plane compressive properties of C-f/SiC-Al composites after different thermal cycles at different temperature differences are investigated. Moreover, the magnitude and state of residual thermal stress in each component of the composites after thermal cycling are further analyzed by X-ray diffraction and nanoindentation methods. The results show that with the increase of the temperature difference and the number of thermal cycles, the residual stress in each component gradually accumulates, accompanied by interface debonding and microcracks in the fiber/matrix interface area, which can release part of the residual stress. The evolution of the residual stress and the interface microstructure has a significant effect on the in-plane compressive strength of the composites. The release of residual stress and the generation of some microcracks are beneficial to the compressive strength, but too many microcracks can reduce the strength.