Formation of secondary defects in copper by 14 MeV neutron irradiation and their effects on microstructure evolution

Abstract

Pure copper specimens were irradiated at 25, 200 and 400°C by 14 MeV neutrons using RTNS-II to the dose of 3.6 × 10 22 n/m 2 and their damage structure was examined by means of transmission electron microscopy. At 25 and 200°C, stacking fault tetrahedra (SFT), partially dissociated Frank loops, aggregates of vacancies, and interstitial loops are nucleated by cascade collapse. They have a tendency to be formed as a group up to about 10. Because SFT are very stable under irradiation, excess interstitials corresponding to the vacancies retained in SFT are accumulated in the matrix and form their clusters. Interstitial loops nucleated near a dislocation grow preferentially by absorbing the interstitials migrating towards the dislocation. Voids were observed at 400°C. They play a very important role in void swelling at high dose.