ABSTRACT
Dislocation arrangements at the early stage of deformation were observed in single crystals of pure copper and Cu-0.5at% Al alloy by x-ray topography. In the alloy as well as in pure copper, multiplied dislocations are mostly of screw in character, which suggests that screw dislocations are less mobile than edge dislocations. A new model which explains the immobility of screw dislocations is proposed. Screw dislocations are supposed to take a special configuration (twist configuration), in which segments of a screw dislocation change their slip planes alternatingly along the lengthwise direction. This model is suitable for the explanation of the ease of cross slip as well.
