Dimensional change and micro-mechanical degradation of SiCf/SiC composite after ion irradiation

Cansas3303 SiC_f/SiC composites with pyrolytic carbon (PyC) interphase were irradiated by 5 MeV Xe ions under 500 °C and 750 °C. The microstructure, dimension and micro-mechanical properties of composite constituents before and after irradiation were systematically investigated. The in-situ mechanical properties of all constituents were obtained through micro-mechanical tests (micro-pillar compression, micro-cantilever bending and fiber push-in). After irradiation, the proportion of carbon packets in Cansas3303 fibers decreased while the average grain size increased with rising irradiation temperature, which caused shrinkage and strength degradation of fibers. SiC matrix swelled due to defect accumulation. The anisotropic displacement and migration behavior of carbon atoms along different axes resulted in the expansion of locally-ordered regions in PyC, thereby causing shrinkage along fiber axis. The interfacial debonding energy increased, reducing its capability of crack deflection. This work can provide accurate and effective data for the design and performance prediction of SiC_f/SiC composites for nuclear applications.