Dresden 2009 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 48: Nanostructured Materials IV
MM 48.2: Vortrag
Freitag, 27. März 2009, 10:30–10:45, IFW B
Ultra-fast diffusion pathways in severely deformed Nickel — •Gerrit Reglitz1, Yuri Estrin2, Sergiy Divinski1, and Gerhard Wilde1 — 1Institut für Materialphysik, Universität Münster, Germany — 2Monash University, Claytoon, Victoria, Australia
During recent years, so-called non-equilibrium grain boundaries with high densities of extrinsic (excess) dislocations have been suggested to exist in severely deformed materials. These defects that are supposedly characterized by a large excess energy density are brought forward in explanations of the unusual properties and property combinations of such materials. However, such grain boundaries should also present highly unusual diffusion properties, i.e. the grain boundary diffusivity of non-equilibrium grain boundaries should be much higher than the diffusivity of conventional high-angle grain boundaries.
In order to analyze the possible existence of these non-equilibrium defects, grain boundary diffusion studies on Ni after severe plastic deformation by Equal Channel Angular Pressing has been carried out by applying the 63Ni radioisotope in combination with the parallel sectioning technique. First results indicate the existence of ultra fast short-circuit diffusion parts with duffusivities of several orders of magnitude higher than the diffusivities of relaxed high-angle grain boundaries. These results together with recent results obtained on pure Cu and Cu-rich alloys deformed also by ECAP are discussed with respect of the origin of these ultra-fast diffusion pathways and their possible relation to non-equilibrium grain boundaries.