Irradiation creep due to dislocation climb and glide

Abstract

Gittus has proposed a model of irradiation creep which depends on the sequential climb and glide of dislocations. In this mechanism the climb of the dislocations occurs due to the preferential absorption of irradiation produced interstitials, the vacancies condensing in excess at voids. The creep strain arises from the subsequent slip of the dislocations under the influence of the applied stress. In this note the Gittus mechanism is formulated in a way which enables vacancy losses to other neutral sinks, such as grain boundaries, to be included in a rate theory calculation. It is shown that, in the absence of voids, grain boundaries alone cannot account for the measured creep rate. However, the total creep rate resulting from the stress-induced preferential absorption of point defects by dislocations (SIPA) and the Gittus climb-glide process is in agreement with the principal features of the experimental observations.