The shapes of irradiation-produced voids in nickel

Voids were produced in nickel by protons and Ni++ ions at 500°C. Methods for an accurate determination and quantitative description of the shape of voids are discussed. The voids thus produced in Ni are prominently cubo-octahedral with 100% truncation, or octahedral with partial {100} truncation, and occasionally cubic with partial {111} truncation. The present results, coupled with previous observations, thus assert a ready change in shape of the voids. Reasons for the wide shape change are explained in terms of the anisotropy of surface energy, the kinetics of growth of void surfaces, and a preferential adsorption of carbon atoms on the {100} surfaces of voids during irradiation.