X-Ray Topographic Study of Tensile Deformation in Nearly Perfect Copper Crystals

Abstract

Copper crystals of a cross section 0.5×0.1 cm and of an initial dislocation density N 50–5000 cm/cm3 were deformed in tension, and Borrmann x-ray topographs were taken after successive stress increments. All dislocations were observed and Burgers vectors determined. Stereo pairs were made. The grown-in dislocations were moved very little by the applied stresses. For crystals of lower initial N most of the dislocation generation could be related to localized stresses in the grip regions, while in the crystals with higher initial N the generation probably was related to grown-in dislocations. Slip bands were formed; neither the source nor the generation mechanism of dislocations in these bands was determined. Screw dislocations were left by edge segments running across the crystal. These screw dislocations cross slipped frequently at stresses of a few grams/mm2, and this process tended to fill the volume of crystal between the bands with dislocations. By counting all new dislocations the shear strain was computed and ``stress-strain'' curves were obtained.