The Dislocation Microstructure of Cyclically Deformed Nickel Single Crystals at Different Temperatures

Using transmission electron microscopy a systematic study of the dislocation microstructure after cyclic deformation of nickel single crystals was undertaken in order to describe quantitatively the influence of deformation temperature on microstructural parameters. The frequency distributions of the heights and lengths of edge dislocation dipoles were measured in the walls and channels of persistent slip bands and in the matrix bundles after deformation at 77, 293, 600 and 750 K. The mean dipole height as well as the dipole annihilation distance and the critical dipole height were found to increase with increasing temperature while the dislocation density decreased. The dipole heights turned out to be independent of the position of the dipoles in the dislocation substructure. The results are discussed with regard to the development of microstructure-based models of cyclic deformation and fatigue dislocation patterning.