The long-range forces between dislocation loops and dislocations

The long-range elastic interactions between dislocations and loops, both prismatic and shear, have been calculated for an isotropic medium. From the energy of interaction the magnitude and direction of the forces acting in the slip directions of both the dislocation and the loop have been derived and compared with the force required to move the loop by slip. It has been shown that in a typical pure metal loops in certain orientations lying within a distance x 2 of a moving dislocation with a parallel Burgers vector can be swept along by the dislocation without intersecting it, the value of x 2 depending on the (critical shear stress to move the loop)−1/2. In copper if the macroscopic shear stress is used, then x 2 ∼ 1000 Å for 200 Å loops. Loops in other orientations should be sucked into the dislocation over a similar distance. Electron microscope pictures have been obtained of the ‘sweeping-up’ effect during the annealing of neutron irradiated copper.