A theory of the Snoek-Köster relaxation (cold-work peak) in metals

The paper attributes the Snoek-Köster relaxation in b.c.c. metals to the formation of kink pairs in screw dislocations in the presence of a high local concentration of foreign interstitial atoms (C, N, or O). It is shown that the activation enthalpy of the process is the sum of the kink-pair formation enthalpy of the pure metal and the migration enthalpy of the foreign atoms involved. In those cases where reliable data are available, this relationship is quite well satisfied. The theory is further supported by the recent observation that the relaxation strength of the Snoek-Köster effect in niobium is substantially greater after 77 K deformation than after room-temperature deformation, which indicates that the dislocations participating are indeed screw dislocations.