Abstract
The relationship between flow stress and dislocation density in stage II has been investigated as a function of dislocation structure, using Cu-3 at. % Al single crystals with the tensile axes near (100), (111) and (110). The (100) crystal shows a typical dislocation cell structure. On the other hand, not only the (110) but also the (111) crystal shows a planar dislocation structure. The difference between the applied shear stresses on a pair of Shockley partials of the extended primary dislocation plays an important role in the formation of the planar dislocation structure in the (111) crystal. In each type of crystal, the flow stress is proportional to the square root of the mean dislocation density. The proportionality constant in the (100) crystal is larger than those in the other types of crystals. Furthermore, the stress level is always higher in the (100) crystal than in the others at the same dislocation density. Those facts imply that the dislocation cell structure is more effective in work hardening than the planar dislocation structure.