Effects of grain boundary volume fraction on the threshold dose of irradiation-induced SiC amorphization at 30 °C

SiC fiber-reinforced matrix composites (SiCf/SiC) have limited applications because of the irradiation-induced shrinkage of SiC fibers; the fiber shrinkage mechanism is still not fully understood. In this study, we tried to clarify the effect of annealing temperature on the proportion of fiber shrinkage and swelling. SiCf/SiC was irradiated at 30 °C to 100 dpa, and the deterioration of mechanical properties was evaluated after irradiation. The compressive displacement of > 60% of the fibers before failure increased to more than 1.5 times that of the as-received specimen. Significant swelling was observed, indicating that the proportion of swelling was higher than that of shrinkage after irradiation. This can be attributed to the amorphization of SiC, and its amorphization threshold dose increased with decreasing grain boundary volume fraction. The findings of this study provide insights into the mechanism of irradiation-induced fiber amorphization and can be useful in developing improved SiCf/SiC.