Surface stress distribution due to an array of 60° dislocations on an oblique glide plane

Abstract

When single crystals of Cu-7.5 at.% Al alloys with the [331] {1̄10} {1̄1̄6} orientation are deformed in tension, narrow slip bands are introduced in which only one or the other of the two equivalent {1̄1̄1} 〈101〉 and {1̄1̄1} 〈011〉 glide systems is activated. Along the gauge length, bands due to the activation of the two glide systems appear in equal numbers. To facilitate the interpretation of these results a model for the relaxation process has been set up and analyzed. The stress distributions at and near the surface due to a single 60° dislocation and to a group of uniformly spaced 60° dislocations on an oblique (1̄1̄1) glide plane have been calculated. The results lead to an interpretation of the experimental observations and suggest that a stress difference of 0.038–0.083 kg mm−2 in a resultant resolved shear stress of 1.34–1.54 kg mm−2 is sufficient to cause preferential activation of one of the two equivalent glide systems. They provide a clear and equivocal demonstration of the role of internal stresses in dislocation generation processes in single crystals of α-phase Cu–Al alloys with this orientation.