Stage III recovery in cold-worked niobium

Stage III recovery in nobium, cold-worked at room temperature, is investigated by means of electrical resistivity measurements. The associated activation energy is found to be constant in the temperature range 80 to 180° C and equal to 1.20 ± 0.04 eV. Furthermore, the results indicate that the recovery process can be described as a diffusion-controlled bimolecular reaction which follows Waite kinetics. It is concluded that this recovery is caused by recombination of intrinsic points defects.
On the basis of the presently available data the possibility of this recovery being caused by migration of vacancies to trapped interstitials cannot be excluded. In view, however, of the relatively small activation energy found for this stage, and of the direct analogy with stage III recovery in the f.c.c. metals. It is tentatively proposed that stage III recovery in b.c.c. metals is due to interstitial migration to vacancies.