The static and dynamic properties of dislocation dipoles were investigated under conditions of isotropic and anisotropic elasticity. In elastically isotropic systems, for a dislocation character of between 35 and 40°, a dipole assumed the same stress-free equilibrium angle of 90° as the screw dipole. This could be affected by elastic anisotropy, as in Cu, where the equilibrium angle assumed by a screw dipole (about 59°) was unchanged up to a dislocation character of 22°. In contrast, the static properties of near-edge dislocation dipoles were little affected by elastic anisotropy. Certain dipole passing properties, but not the passing stress, were also modified by elastic anisotropy. For large heights, and/or in the case of undissociated dislocations, the minimum passing stress corresponded to a dipole character of about 60° and exhibited a sharp maximum in screw orientation. Reasonably moderate dislocation reorientations were expected to facilitate the passing of near-screw dislocations in fatigue channels. Within a certain range of applied stresses, the passing of dipoles comprised of unlike attractive dislocations was accompanied by the sweeping of one dislocation by the other over a limited distance. Dissociation played a prominent role in determining both static and dynamic properties for dipole heights of less than a few times the dissociation distance of an isolated dislocation.

Equilibrium and Passing Properties of Dislocation Dipoles. P.Veyssière, Y.L.Chiu: Philosophical Magazine, 2007, 87[23], 3351-72