Deformation substructure in beryllium after prism slip

The development of cell structure during room-temperature tensile deformation of beyllium oriented for prism slip was studied by a combination of a new x-ray diffraction technique (synergy method) and transmission electron microscopy. It was convenient to divide the development of the cell structure into three stages. In stage one, dislocations moving on the prism plane pulled out small segments of dislocations lying on the basal plane to form long dipoles and numerous pinched-off loops. During the second stage, dense dislocation clusters developed which became interconnected by dislocation tangles. The final stage consisted of the formation of well-developed cell walls with regular hexagonal networks of dislocations. The striking feature of all the stress-strain curves was the low work-hardening rate extending up to ε=15% strain. The low work-hardening rate was ascribed to nucleation and propagation of new slip bands into hitherto undeformed volumes of the crystal.