THE DISLOCATION MICROSTRUCTURE OF CYCLICALLY DEFORMED NICKEL SINGLE-CRYSTALS AT DIFFERENT TEMPERATURES

Using transmission electron microscopy a systematic study of the dislo cation microstructure after cyclic deformation of nickel single crysta ls 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 w ere 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 m ean dipole height as well as the dipole annihilation distance and the critical dipole height were found to increase with increasing temperat ure while tile dislocation density decreased. The dipole heights turne d out to be independent of the position of tile dipoles in the disloca tion substructure. The results are discussed with regard to the develo pment of microstructure-based models of cyclic deformation and fatigue dislocation patterning.