The influence of dislocations on the nucleation of voids in nickel

Abstract

The influence of dislocation behaviour on void formation and growth has been studied in the High Voltage Electron Microscope (HVEM). Variation of the interstitial loop density has been used to control the concentration of biased linear sinks available for point defects, and thereby the vacancy excess required for void growth. The interstitial loops were nucleated by neutron irradiation at 50°c and a good correlation was obtained between the loop concentration and swelling by electron irradiation at 400°c. Void development was closely related to the detailed microstructural changes that occurred immediately upon electron irradiation. A minimum foil thickness is necessary for void growth in the HVEM, otherwise the surfaces dominate, and the dislocation density always remains low. Voids do not grow if the dislocation density is less than 109 lines/cm2.