Effects of electron and ion irradiation on the dislocation structure of [001] twist boundaries in FeS alloys

Abstract

Previous work has demonstrated that the dislocation structures of small and large angle [100] twist boundaries in FeS alloys are changed as S is implanted. It was not clear from that work, however, to what extent the radiation damage accompanying the implantation played a role in the change of boundary structure. In the present work the influence of irradiation on the dislocation structures of small angle and large angle (near Σ = 5) twist boundaries in the FeS system was studied using 80 keV S + ions, 80 keV Ar + ions, 1.5 and 0.8 MeV Ne + ions and 800 keV electrons. Electron irradiation produced no change in structure of the boundary in the irradiated region. However, a neighboring region showed a change of structure which is due possibly to diffusion of S related to the high concentration of point defects produced by the electron irradiation (radiation-induced segregation). Ne + ion irradiation also had no effect on the dislocation structure of the boundaries. With a similar mass as S, Ar + ions create a defect structure very similar to that of implanted S +. Ar + ion implantation caused no change in the structure of the large angle boundary, but did transform small areas of the small angle grain boundary. This is substantially different behavior from that caused by S + ion implantation. These results lead to the conclusion that the observed change of structure as a result of implantation of S in the vicinity of [001] twist boundaries in FeS alloys is due primarily to the presence of the S, and that the point defects which are a product of the irradiation may affect only the kinetics of the structural transformation.