An investigation was made of the depinning transition which occurred in dislocation assemblies. In particular, consideration was given to the cases of regularly spaced pile-ups and low-angle grain boundaries interacting with a disordered stress landscape provided by solute atoms or by other immobile dislocations present in non-active slip systems. Using linear elasticity, the stress originated by small deformations of these assemblies, and the corresponding energy-cost in 2 and 3 dimensions, were computed. Contrary to the case of isolated dislocation lines, which were usually approximated as being elastic strings with an effective line tension, the deformation of a dislocation assembly could not be described by local elastic interactions with a constant tension or stiffness. A non-local elastic kernel resulted as a consequence of the long-range interactions between dislocations. In the light of this result, statistical de-pinning theories of dislocation assemblies were revised, and the theoretical results were compared with numerical simulations and experimental data.

Depinning Transition of Dislocation Assemblies – Pile-Ups and Low-Angle Grain Boundaries. P.Moretti, M.C.Miguel, M.Zaiser, S.Zapperi: Physical Review B, 2004, 69[21], 214103 (11pp)