The so-called reversible γ relaxation observed in Nb, and the β relaxation of plastically deformed body-centered cubic metals, were both shown to be caused by the stress-assisted thermally activated generation of kink pairs on {110} slip planes in screw dislocations with a Burgers vector of a/2<111>. The classical irreversible γ relaxation was due to an analogous process occurring on {112} planes. The differing slip planes resulted from differing core configurations of the screw dislocations. Internal friction experiments performed on O-doped Nb, and a comparison of the flow stress of modest-purity Nb with that of high-purity body-centered cubic metals, demonstrated that the transition between the low-temperature {110} configuration and the high-temperature {112} configuration could be shifted to higher temperatures by the incorporation of foreign interstitial atoms into the cores of the screw dislocation. This process could also account for the suppression of anomalous slip by interstitial impurities.

Dislocation Relaxation Processes in BCC Metals - β versus γ Relaxation. A.Seeger: Philosophical Magazine, 2004, 84[2], 79-86