High voltage electron microscope studies of void nucleation in nickel

Abstract

SUMMARYThe influence of dislocation behaviour on void formation in the high voltage electron microscope (HVEM) has been predicted theoretically and confirmed by experiment. The probability of void nucleation has been computed as a function of the radial distance from a dislocation line in a finite cylinder of material. The observation of strings of voids associated with dislocation lines supports the predictions of the model. Void formation in the HVEM is closely related to the detailed microstructural changes that occur immediately upon electron irradiation, and a good correlation is obtained between the initial interstitial loop density and subsequent swelling by electrons. A minimum foil thickness is necessary for void growth in the HVEM, otherwise the surfaces dominate and the dislocation density always remains low.