It was recalled that the usual picture of the Snoek-Köster relaxation in body-centered cubic metals was based upon the Schoeck and Seeger models. The former treated the dragging of a cloud of interstitial foreign atoms by a dislocation in terms of the string model. The latter was based upon the concept of kink-pair formation on dislocations. It was noted that new insight into Snoek-Köster could be obtained if a coupling model was used to interpret the mechanical loss spectra which were introduced by the motion of dislocations that dragged a Cottrell cloud of interstitial foreign atoms. This phenomenological model provided a very general scenario for 2 distinct regions of the relaxation process: exponential and stretched exponential. The model implied that the relaxation function could cross over continuously from a Debye function to a stretched-exponential function. A one-sided Fourier transform of the derivative of the normalized relaxation function yielded the same loss-peak asymmetry as that observed for the C Snoek-Köster peak of deformed ultra-high purity α-Fe. The present work summarized experimental observations of Snoek-Köster relaxation with regard to the effects of the degree of plastic deformation and the deformation temperature and well as the thermal stability and broadening of the peaks. It was concluded that the concept of cooperative migration of interstitial foreign atoms in the Cottrell cloud clarified the primary and secondary features of Snoek-Köster peaks.

Snoek-Köster Relaxation - New Insights New Paradigms. L.B.Magalas: Journal de Physique IV, 1996, 6[8], 163-72