Transmission electron microscopic observations were made of the dislocation sub-structures which developed in high-purity single crystals that were deformed at 4.2K. Results which were based upon weak-beam transmission electron microscopy showed that the dislocation sub-structure contained a very high density of narrow dislocation dipoles of vacancy type. These dipoles became progressively refined in scale as deformation continued. In situ annealing experiments, carried out in the transmission electron microscope, permitted the stability of these structures against annealing at room, and high, temperatures to be studied. The observations suggested that fine dislocation dipoles could be annealed out by processes such as pipe diffusion, and that these defects represented the recoverable component of electrical resistivity. Comparison studies of Cu-5at%Ni crystals indicated that the recoverable component of resistivity in this alloy was smaller due to the effect of Ni upon pipe diffusion. In addition, transmission electron microscopy indicated the complexity of the processes which occurred at the twin/parent interfaces that were produced in Cu that was deformed at 4.2K. These interfaces played an important role in debris storage, and in processes which occurred after large plastic strains at 4.2K.

Deformation of Copper Single Crystals to Large Strains at 4.2K – II. Transmission Electron Microscopy Observations of Defect Structure. M.Niewczas, Z.S.Basinski, J.D.Embury: Philosophical Magazine A, 2001, 81[5], 1143-59