Dresden 2011 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 19: Transport

MM 19.2: Talk

Tuesday, March 15, 2011, 14:15–14:30, IFW D

Fast grain boundary self-diffusion in ultrafine grained Ag produced by equal channel angular pressing — •Jochen Michael Fiebig¹, Werner Skrotzki², Sergiy V. Divinski¹, Martin Peterlechner¹, and Gerhard Wilde¹ — ¹Institut für Materialphysik, Westfälische Wilhelms Universität, 48149 Münster — ²Institut für Strukturphysik, Technische Universität Dresden

We performed a systematic study of grain boundary self-diffusion in ultrafine grained silver produced by equal channel angular pressing (ECAP) using samples deformed up to 3 passes according to route A. The resulting ultra-fine grained microstructure was studied by transmission electron microscopy and electron backscatter diffraction. The radiotracer method (^110mAg-tracer solution) in combination with parallel sectioning by microtome slicing was used to obtain the diffusion properties. The activity of each section was counted by a high-purity Ge detector. The grain boundary diffusion was measured depending on the deformation state and the resulting profiles unambiguously revealed the existence of grain boundaries with enhanced excess energy density, i.e. so-called non-equilibrium grain boundaries. Percolating porosity, as already observed for Cu and Cu-alloys produced by ECAP also exists in ECAP-Ag. Applying Borisov’s formalism the excess energy of non-equilibrium grain boundaries was determined. The energy of general high-angle grain boundaries was measured to be about 0.5 J/m². The grain boundary energy of non-equilibrium grain boundaries is about 10% to 15% higher.