MECHANISMS FOR DECORATION OF DISLOCATIONS BY SMALL DISLOCATION LOOPS UNDER CASCADE DAMAGE CONDITIONS

In metals under cascade damage conditions, dislocations are frequently found to be decorated with a high density of small clusters of self-i nterstitial atoms (SIAs) in the form of dislocation loops, particularl y during the early stages of the microstructural evolution in well ann ealed pure metals. This effect may arise as a result of either (a) mig ration and enhanced agglomeration of single SIAs in the form of loops in the strain field of the dislocation or (b) glide and trapping of SI A loops (produced directly in the cascades) in the strain field of the dislocation, In the present paper, both of these possibilities are ex amined. It is shown that the strain field of the dislocation causes a SIA depletion in the compressive as well as in the dilatational region resulting in a reduced rather than enhanced agglomeration of SIAs. (S IA depletion may, however, induce enhanced vacancy agglomeration near dislocations.) The decoration of dislocations by SIA loops is therefor e considered to be due to the trapping of glissile loops. Conditions f or the operation of this mechanism are discussed. (C) 1997 Elsevier Sc ience B.V.