The internal friction spectra of high-purity polycrystalline and monocrystalline material was studied at 5, 10 or 30MHz, and temperatures ranging from 50 to 250K. The results indicated that the  peak of Fe was of the same type as the Bordoni peak in face-centered cubic metals, that the temperature of the peak was essentially independent of the orientation, that the temperature of the peak decreased with deformation and then began to increase slightly with further deformation, and that the peak height increased with increasing deformation. Measurements of polycrystalline material which was subjected to successive doses of neutron and gamma irradiation revealed a reduction in the relaxation strength with increasing radiation dose. This was attributed to the effect of high-energy electrons which resulted from Compton-effect processes within specimens that were irradiated with gamma particles. These were more likely to reach the dislocation loops and pin them. This then explained the linear drops in peak height which occurred as the irradiation dose was increased.

M.M.Zein: Journal of Physics - Condensed Matter, 1994, 6[42], 8745-57