The deviation from a perfect low-energy dislocation structure was considered for boundaries in deformed polycrystals. In the case of polycrystals with approximately equiaxed grains, it was argued that the existence of grain boundaries introduced a population of geometrically necessary dislocations around the boundaries. Because of the associated long-range stresses, this population did not represent a perfect low-energy dislocation structure. However, the deviation was moderate. In polycrystals with flat grains, and in polycrystals with grains that were sub-divided into flat bands, the geometrically necessary dislocations could remain in the grain or band boundaries but still represented a certain moderate deviation from low-energy dislocation structures. A distinction was drawn between 2 contributions which geometrically necessary dislocations made to hardening. One was a conservative hardening that was associated with long-range stresses, and the other was a frictional hardening which was associated with the dislocation density.

T.Leffers: Physica Status Solidi A, 1995, 149[1], 69-84