Edge dislocation-circular inclusion interactions at elevated temperatures

Abstract

While previous analyses of dislocation-inclusion interactions during the creep of dispersion strengthened systems have generally concluded that the dislocation climbs over the inclusion, detailed consideration of the associated elastic and diffusive problems, analyzed here, indicate that climb by-pass of the inclusion is not possible. In order to keep the elastic problem tractable, we consider a straight edge dislocation interacting with a cylindrical inclusion of infinite extent. Additionally, since we are concerned with interactions at elevated temperatures, we allow the matrix-inclusion interface to slip. We find that along approximately 1 2 of the glide planes intersecting the inclusion, the dislocation is attracted toward the inclusion. Dislocations originally lying on those glide planes, where the dislocation-inclusion interaction is repulsive, respond by either climbing on to a glide plane where the interaction is attractive or by diffusionally relaxing the repulsion. Therefore, a dislocation that is gliding on my plane that intersects the inclusion will end its trajectory at the inclusion-matrix interface. When the dislocation-inclusion separation is of order a dislocation core diameter, the dislocation core relaxes into the inclusion-matrix interface, thereby pinning the dislocation. Unpinning the dislocation requires a stress of order the Orowan stress, which is believed to give rise to the observed threshold stress for creep in dispersion strengthened systems.