It was noted that the plastic instability which was associated with the formation of narrow flow channels resulted from dislocation pinning and unpinning by defect clusters. The dynamics of dislocation interactions with radiation-induced defect clusters were investigated here; especially with regard to sessile self-interstitial atom clusters in dislocation decorations and to stacking-fault tetrahedra in the matrix. It was shown that the critical stress required to free trapped dislocations from pinning atmospheres could be a factor of 2 smaller than the values deduced on the basis of rigid dislocation interactions. The unpinning mechanism was a result of the growth of morphological instabilities on the dislocation line. Dislocation sources were activated in spatial regions having a low stacking-fault tetrahedra density; where their destruction by glide dislocations led to the subsequent growth of localized plasticity in dislocation channels. It was shown that the removal of stacking-fault tetrahedra was associated with simultaneous dislocation glide and climb. Jogs having atomic dimensions formed when a fraction of the stacking-fault tetrahedra vacancies was absorbed by pipe diffusion. The width of a flow channel was explained in terms of 2 length-scales: one was the size of an individual stacking-fault tetrahedron, and the other was of the order of the dislocation-source to boundary distance. The latter was of the order of μm. Whereas dislocation segments climbed by a few atomic planes upon each stacking-fault tetrahedron destruction event, the dislocation-source to boundary distance governed the total number of such events. The numerically estimated channel-widths (70 to 150nm), and the magnitude of radiation hardening in Cu, were consistent with experimental observations.

On Dislocation Interaction with Radiation-Induced Defect Clusters and Plastic Flow Localization in FCC Metals. N.M.Ghoniem, S.H.Tong, B.N.Singh, L.Z.Sun: Philosophical Magazine A, 2001, 81[11], 2743-64