Void shrinkage and disappearance in stainless steel during electron irradiation

It has been observed that stainless steel foils irradiated in the Harwell High Voltage Electron Microscope in the temperature range 600-7000C thin by erosion of the lower surface after a threshold exposure. The thinning rate is very dependent on temperature, increasing from approximately zero at 5000C to a peak of about 0.1 nm per second at 6500C and decreasing to zero again by 7500C. The thinning effect, which can be non-uniform, is attributed to the surface diffusion of atoms from regions of high diffusion rate to regions of lower activity. The localisation of the effect to the lower foil surface is ascribed to cleaning of this surface by electron sputtering. Electron sputtering alone does not account for the experimental observations. The observed shrinkage and dissappearance of voids close to the lower surface is tentatively attributed to the preferential condensation of interstitial atoms at voids, as compared with the foil surface. (Auth.)