Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 40: Topical Session Bulk Nanostrucured Materials IX - Functional Properties II
MM 40.5: Vortrag
Mittwoch, 28. März 2012, 17:30–17:45, H 0106
Short-Circuit Diffusion in Ultrafine-Grained Copper Processed by High Pressure Torsion — •Matthias Wegner1, Jörn Leuthold1, Martin Peterlechner1, Daria Setman2, Michael Zehetbauer2, Sergiy Divinski1, and Gerhard Wilde1 — 1Institut für Materialphysik, WWU Münster, Wilhelm-Klemm-Straße 10, D-48149 Münster, Germany — 2Physics of Nanostructured Materials, Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Wien, Austria
Short-circuit diffusion paths in ultrafine-grained copper processed by High Pressure Torsion are investigated by the radiotracer method. *Ultra fast* diffusion rates in addition to *conventional* rates of grain boundary (GB) diffusion are observed. The *ultra fast* diffusion is related to a so-called *non-equilibrium* state of GBs. According to existing models of grain refinement by severe plastic deformation, the abundance of lattice dislocations created during the severe straining serves to modify the structure of high angle GBs towards a non-equilibrium state with an enhanced excess free energy density. The kinetic and structural properties of these *non-equilibrium* GBs are thoroughly investigated and compared with previous results obtained on Cu and Cu alloys deformed by Equal Channel Angular Pressing. Furthermore, a network of percolating porosity is observed. This unexpected feature resembles previously discovered porosity in ECAP processed Cu. A strong dependence of the volume fraction of the porosity on the processing parameters is elucidated. The anisotropy of the percolating porosity is examined with respect to the shear direction.