The effect of grain size and deformation temperature on the stabilized dislocation structure was studied in individual grains of fine- and coarse-grained Ni polycrystals after cyclic deformation at room temperature and at 77K. It was found that, regardless of the grain size and deformation temperature, the dislocation patterns in the individual grains were governed mainly by the axial orientation of the grains. A typical feature of the structure of coarse-grained material fatigued at room temperature was fragmentation of the grain dislocation configuration into sectors with different mesoscopic structure parameters. In fine-grained material cycled at room temperature, and in coarse-grained material cycled at 77K, no sub-division of the grain structure could be detected. Low-temperature deformation of coarse-grained Ni led to the formation of a so-called 2-phase structure that was different to the extended wall structure observed in single-slip oriented Ni monocrystals cyclically deformed at 77K.

Effect of Grain Size and Deformation Temperature on the Dislocation Structure in Cyclically Deformed Polycrystalline Nickel. C.Buque, J.Bretschneider, A.Schwab, C.Holste: Materials Science and Engineering A, 2001, 319-321, 631-6