Dislocation pinning in neutron-irradiated O.F.H.C. and 99·999% copper

Abstract

Internal friction experiments have been carried out on neutron-irradiated copper of two purities: O.F.H.C. copper of 99·95% nominal purity and 99·999% copper. The specimens were annealed isochronally from room temperature to 200°c, and two pinning stages were observed, centred around 70°c and 150°c. The 70°c stage is stronger in the 99·95% copper than in the purer copper, and the pinning in this stage is found to be governed by an activation energy of 1·03±0·07 ev. It is thought that this pinning is due to the migration to the dislocations of vacancies released from traps. The logarithmic decrement has been found to have a t ^2/3 dependence, and it is calculated that the vacancies make 10³ jumps before reaching a dislocation.