Synergistic effects of heavy ion and helium irradiation on microstructural and dimensional change in β-SiC

The influences of helium on microstructural development and dimensional stability in high purity beta-SiC after Si2+-ion irradiation with and without He+-ion injection at high temperature were studied. The microstructural observations of beta-SiC irradiated up to 10dpa in irradiation temperature,. of 1073, 1273. and 1673 K were performed by transmission electron microscopy, respectively. 'Black spot' defects and dislocation loops were observed densely in all irradiated beta-SiC. Small cavities were formed at grain interior of beta-SiC above 1273 K. Helium increased the number density of cavities, but helium dose not effect on the cavity size. Swelling in beta-SiC irradiated up to 3 dpa at 1273 K was measured by precision-surface profilometry. The influences of damage rate (dpa/s) and helium on the swelling were-studied, The swelling values were saturated above 1 dpa after single-ion and dual-ion irradiation under higher dpa/s condition (1.0 x 10(-5) dpa; s). In lower dpa/s case (5.0 x 10(-5) dpa/s). the swelling was also saturated after single-ion irradiation but the saturated swelling value was approximately half of the higher dpa/s case. On the contrary, the swelling value of beta-SiC irradiated with dual-ion under the lower dpa/s condition increased at 3dpa without saturation. Small cavities observed in this specimen. which were formed on {111} family planes, may cause the enhanced swelling all 3 dpa.