In situ study of defect accumulation in zirconium under heavy ion irradiation

In this study, we report direct observations on heavy ion (Kr2+) irradiation induced changes in microstructures of pure Zr at different temperatures using intermediate voltage electron microscopy. Thin TEM foils were irradiated with 1 MeV Kr2+ ions. Materials have been irradiated to different damage levels ranging from 0.008 dpa to 1 dpa at different temperatures ranging from 300 degrees C to 500 degrees C. We particularly concentrate on yield of small defects directly occurring from cascade collapse at very low doses, and their evolution as the dose increases. In situ observation of growth and evolution of these small defects into complex defect structures at high dose has been carried out. Irradiation of materials at different temperatures provided an opportunity to investigate the temperature dependence of defect accumulation in Zr during irradiation. The differences in defect structures, defect densities, and therefore dynamic growth have been discussed in detail as a function of irradiation parameters (dose, temperature). Interaction of irradiation induced defects with existing microstructure and other defects is discussed. (c) 2012 Elsevier B.V. All rights reserved.