Dresden 2006 – wissenschaftliches Programm

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MM: Metall- und Materialphysik

MM 7: Symposium Severe Plastic Deformation II

MM 7.1: Fachvortrag

Montag, 27. März 2006, 14:45–15:15, IFW A

Determination of long-range internal stresses in cyclically deformed Ni with submicro-crystalline grain structure — •Ellen Hieckmann¹, Lutz Hollang², and Werner Skrotzki² — ¹Institut für Angewandte Physik, Technische Universität Dresden, 01062 Dresden, Germany — ²Institut für Strukturphysik, Technische Universität Dresden, 01062 Dresden, Germany

It is well accepted that, in fcc metals with a submicro- to nano-cyrstalline grain structure, the typical dimensions of deformation induced dislocation arrangements are determined by the size of grains/subgrains. In this context, the long-range internal stresses considered here are assumed to be the mean stresses in grains/subgrains and in dislocation structure elements, respectively. These stresses can arise from granular constraints caused by the sample production processes and from heterogeneous plastic deformation from grain to grain during the subsequent cycling. The latter should lead to a change of the long-range internal stresses during one loading cycle. A concept is proposed to determine these stresses from their contribution to the broadening of Bragg-diffraction profiles. The basic idea is to analyse the changes of the profile shape within a mechanically stabilized loading cycle in comparison with the diffraction profile in the as-produced state of the specimen. Results of high resolution X-ray diffraction measurements are presented for Ni samples, where the submicro-crystalline grain structure is produced by equal-channel angular pressing or by electrodeposition.