The Interaction of HVEM-Generated Point-Defects with Dissociated Dislocations

Abstract

This paper describes experiments we have performed to investigate the mechanisms of interaction of IIVEM-gcncralcd point-defects with dissociated dislocations in a scries of austcniticFc-Ni-Cr alloys and reviews earlier work in Cu-AI alloys and in Ag. In the Fc-Ni-Cr alloys interstitial climb was observed only at favourable sites such as pre-existing jogs, whilst vacancies clustered near dislocations to form stacking-fault tetrahedra. These observations arc similar to these in Ag; the complex climb mechanisms seen in Cu-AI alloys were not found. The differences bet ween materials is believed to be due to differences in the case of interstitial pipe diffusion. INTRODUCTIONThe interaction of radiation-produced point defects witli dislocations is central to the understanding of phenomena which give rise to dimensional or mechanical-property changes in nuclear reactors. As part of a more general effort to understand microslructural evolution under irradiation, studies of the mechanisms of interaction of IIVEM-gcncralcd point-defects with dissociated dislocations have been carried out in Oxford, Harwell and Argonnc over the past 11 years. Various model materials have been chosen, starling with very low slacking-faull energy (SFE) CuAl alloys with wide partial separations and progressing towards the structural steels of practical importance. These studies have demonstrated that dislocation climb in these materials may be far from straightforward. In this paper we briefly review early studies in CuAl alloys and in Ag and present some of our more recent results in Fc-Ni-Cr alloys, The observations in the different materials will be compared and contrasted and possible origins for differences and similarities between materials will be discussed.