Beryllium Research and Development Program. Volume 4. A Study of the Brittle Behavior of Beryllium by Means of Transmission Electron Microscopy
Technical documentary rept. 1 Jul 1960-31 Mar 1963
NUCLEAR METALS INC CONCORD MA
Pagination or Media Count:
Glide dislocations in beryllium specimens were studied by direct observation with an electron microscope. Glide dislocations in beryllium are strongly hindered in their movements and are often pinned by lattice imperfections and larger precipitate particles, especially in beryllium of commercial purity. Dislocation tangles have been observed in deformed Pechiney flake beryllium and in crystals of commercial purity the presence of round as well as elongated prismatic dislocation loops is in evidence. Dislocations of different slip systems may react to form incipient networks. In specimens where dislocation pinning is less pronounced, dislocations have a tendency to align themselves along crystallographic directions. In high purity tensile specimens, dislocation bundles of high density are found to lie in the the basal plane in a 1100 direction perpendicular to the principal glide direction. Many of these dislocations are dipoles. It is found that most dislocation reactions are confined to relatively thin glide packets parallel to the basal plane. Rarely have dislocation motions been observed under the stress created by a high-intensity electron beam in the microscope. A high Peierls-Nabarro force ass s well as high stacking fault energy in beryllium is concluded. An inference is drawn with regard to the brittleness problem of beryllium.
- Metallurgy and Metallography