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MM: Fachverband Metall- und Materialphysik

MM 18: Mechanical Properties I

MM 18.4: Vortrag

Dienstag, 15. März 2011, 14:45–15:00, IFW B

Properties of non-equilibrium grain boundaries in UFG nickel produced by severe plastic deformation — •Gerrit Reglitz, Sergiy Divinski, Harald Rösner, and Gerhard Wilde — Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany

Ultra-fine grained (UFG) materials produced by severe plastic deformation (SPD) have become an important target of research due to their improved properties and the promise they hold with respect to novel applications. It has been suggested by several authors that so-called non-equilibrium grain boundaries in SPD processed materials are largely responsible for their properties. These non-equilibrium grain boundaries contain a high density of extrinsic (excess) dislocations and an increased excess free volume. The existence and the properties of non-equilibrium grain boundaries can be studied in great detail by grain boundary diffusion measurements, because such non-equilibrium grain boundaries should represent ultra-fast diffusion paths in comparison to conventional, relaxed high-angle grain boundaries in coarse grained materials.

Grain boundary self-diffusion in UFG Ni prepared by Equal Channel Angular Pressing (ECAP) has been measured by applying the 63Ni radioisotope in combination with the parallel sectioning technique. The results indicate the existence of ultra-fast diffusion paths. The influence of the ECAP processing parameters will be presented. The origin of the ultra-fast diffusion pathways and their possible relation to non-equilibrium grain boundaries will be discussed.