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MM: Fachverband Metall- und Materialphysik
MM 19: Transport
MM 19.3: Talk
Tuesday, March 15, 2011, 14:30–14:45, IFW D
Grain Boundary Diffusion in Ultra Fine Grained Copper Produced by High Pressure Torsion — •Matthias Wegner1, Jörn Leuthold1, Martin Peterlechner1, Daria Setman2, Michael Zehetbauer2, Sergiy Divinski1, and Gerhard Wilde1 — 1Institut für Materialphysik, Universität Münster, D-48149 Münster, Germany — 2Physics of Nanostructured Materials, University of Vienna, A-1090 Wien, Austria
Short-circuit diffusion paths in Ultra Fine Grained copper produced by High Pressure Torsion (HPT) are investigated by the radiotracer method. *Ultra fast* diffusion in addition to conventional grain boundary diffusion is observed. This feature might be related to the existence of so called Non Equilibrium Grain Boundaries (NEGBs) acting as ultra fast diffusion paths. According to the existing models of grain refinement by severe plastic deformation (as e.g. HPT), the abundance of lattice dislocations created during the severe straining serves to modify the grain boundary structure of high angle grain boundaries such that NEGBs with enhanced excess free energy densities are created. The kinetics and structural properties of NEGBs are thoroughly investigated. Furthermore, a network of percolating porosity introduced during the HPT process is observed. This unexpected feature is investigated utilizing the radiotracer technique. A strong dependence of the effective diffusivity and the volume fraction of the porosity on the applied quasi-hydrostatic pressure during HPT is elucidated.