Observations of Dislocations in Copper using Borrmann Transmission Topographs

Abstract

Using the Borrmann diffracted beams for Ag Kα radiation, x-ray topographs have been made of copper crystal plates 1 × 1 × Z cm, Z ≦ 0.1, with (111) faces. Dislocation lines were generally recorded as lines of less intensity on the x-ray plate. Both annealed and neutron irradiated crystals were investigated. In the latter the dislocations were pinned and were not moved by the small stresses accidently imposed while making the topographs; and dislocation arrangements in the bulk crystal were determined. The Burgers vectors were deduced from {111} topographs, employing the condition that for no contrast g· b = 0. For edge dislocations, the additional condition g × n = 0 was necessary for no contrast, and it was demonstrated that this type of contrast was more pronounced for dislocations grouped in a slip trace. It was found that dislocations could be seen all the way through crystals for Z = 0.06 cm. A semiquantitative correlation has been established between etch pits formed at dislocation sites on the (111) surfaces and the dislocations revealed by the x-ray topography. It has been possible to obtain complete sets of topographs on only a few annealed crystals; for these, an analysis of the dislocations produced by accidental microstrains has been possible.