SEGREGATION OF CASCADE INDUCED INTERSTITIAL LOOPS AT DISLOCATIONS - POSSIBLE EFFECT ON INITIATION OF PLASTIC-DEFORMATION

In metals and alloys subjected to cascade damage dislocations are freq uently found to be decorated with a high density of small clusters of self-interstitial atoms (SIAs) in the form of dislocation loops. In th e present paper it is shown that this effect may be attributed to tile glide and trapping of SIA loops, produced directly in cascades (rathe r than to the enhanced agglomeration of single SIAs), is the strain fi eld of the: dislocations. Tnt conditions for the accumulation of gliss ile SIA loops near dislocations as well as thr dose and temperature de pendencies of this phenomenon are discussed. II is suggested that the decoration of dislocations with loops may play a key role in radiation hardening subjected to cascade damage. It is shown, for example, that the increase in the upper yield stress followed by a yield drop and p lastic instability in metals and alloys subjected to cascade damage ca nnot be rationalized in terms of conventional dispel-sed barrier harde ning (DBH) but may he understood in terms of cascade induced source ha rdening (CISH) in which the dislocations are considered to be locked b y the loops decorating them. Estimates for the stress necessary to pul l a dislocation away from its loop 'cloud' are used to discuss the dos e and temperature dependence of plastic flow initiation. (C) 1997 Else vier Science B.V.