DISLOCATION RELAXATION IN HIGH-PURITY IRON AT MEGAHERTZ FREQUENCIES

The internal-friction spectrum of high-purity polycrystalline and sing le-crystal iron is studied at 5, 10 and 30 MHz, over the temperature r ange 50-250 K. The results lead to the following conclusions: the temp erature of the peak is essentially independent of the orientation; the temperature of the peak decreases with deformation and then starts to increase slightly with further deformation; the peak height increases with increasing deformation. Measurements on polycrystalline iron sub jected to successive doses of neutron and gamma irradiation showed a r eduction in the relaxation strength by increasing the irradiation dose s.