Effects of excess point defects flow and interface orientation on grain boundary migration under irradiation

Fe-Cr-Ni, Ni-Al and Ni-Si alloys, and 316L stainless steels as reference were electron-irradiated using a high voltage electron microscope (1MV), and in-situ observations of structural evolution and micro-chemical analysis were carried out. From the compositional analysis it was found that nickel was enriched and chromium depleted near grain boundary in Fe-Cr-Ni alloys including 316L stainless steels, and that simultaneously grain boundary migration was caused during irradiation, even if no grain boundary migration occurred in the un-irradiated area at the same irradiation temperature. The occurrence of boundary migration strongly depended upon orientation relationship between boundary interfaces. It is suggested that grain boundary migration under irradiation remarkably occurs in the alloys in which solute enrichment is taken place at the grain boundary as a result of the flow of radiation-introduced point defects into grain boundary and that their magnitude depend upon net flow of point defect, especially that of under-sized interstitial atoms.