Evolution of microstructure and mechanical properties of SiCf/SiC composites induced by He ions irradiation at various temperatures

In this study, 500 keV He ions were used to irradiate SiCf/SiC composites at various irradiation temperatures. The effects of irradiation on the microstructure and mechanical properties were examined by TEM, XRD, Raman spectroscopy and nanoindentation. TEM results show that He bubbles were only formed inside the SiC matrix after irradiation, the sizes of which were influenced by the irradiation temperature. Besides, the pre-existing carbon packets in the SiC fiber were gradually decomposed. The (111) peak in XRD patterns of SiC matrix gradually shifted to lower angle after irradiation at 350 °C, and then moved to higher angle with the increase of irradiation temperature. It is revealed from Raman spectra that the intensities of both Si–C bonds in the SiC matrix and C–C bonds in the SiC fiber decreased obviously after irradiation. Nanoindentation tests indicated that the irradiation hardening occurred in both the SiC matrixes and the fibers.