Study of Dislocations in Lightly Deformed Copper Crystals Using Borrmann X-Ray Topography

Copper crystals of dislocation density [Formula: see text] were deformed in compression at resolved stresses 7–22 g/mm2, then irradiated with fast neutrons, either with the stress applied to immobilize the dislocations in their "stress-applied" positions, or with the stress removed to immobilize them in their relaxed positions. The crystals were then sectioned along {111} planes by acid sawing, and these lamellae were examined by Borrmann X-ray topography. In the stress-applied condition the dislocations produced by the stress were long, often > 0.5 cm and lay predominantly in the screw orientation. Dislocation sources, though not identified, appeared to be at or near the crystal surfaces. The dislocation configurations in the "stress-relaxed" condition were markedly different from those in the stress-applied condition. "Bundles" of dislocations and dipoles were observed only in the stress-relaxed condition. It is postulated that dipoles were formed during the relaxation process.