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MM: Fachverband Metall- und Materialphysik

MM 29: Invited Talk (Hauptvortrag) Divinski

MM 29.1: Hauptvortrag

Dienstag, 1. April 2014, 15:00–15:30, BAR 205

Grain boundaries in metals: phase and structure transitions studied by tracer diffusion — •Sergiy Divinski — Institut für Materialphysik, Universität Münster

Recent advances in measurement techniques have allowed extending the radiotracer experiments on grain boundary diffusion of solutes in bicrystals to substantially lower temperatures. As a result, the data on grain boundary diffusion coefficients and those of the product of the solute segregation and the grain boundary width were independently evaluated and compared with the polycrystalline data [1]. The segregation of Ag at Cu Σ 5 and Σ 17 grain boundaries is found to be significantly stronger as compared to that at general high-angle grain boundaries as they are present in annealed polycrystalline copper. The grain boundary diffusion data predict a structural transition in the Σ 5 grain boundary at a temperature of about 850 K what was recently confirmed by dedicated MD simulations [2]. Strong solute segregation could induce grain boundary phase transitions, too. An abrupt increase of the grain boundary diffusivity was observed in a two-phase (solid+liquid) region of the Cu-Bi phase diagram [3]. Such diffusion enhancement exists even in a single phase (solid solution in Cu) region manifesting the existence of a pre-wetting GB phase transition in this system. These and other findings with respect to short-circuit diffusion in bi- and tri-crystals are reviewed and critically discussed.

[1] S.V. Divinski, et al. Phys Rev B 85 (2012) 144104.

[2] T. Frolov, et al. Phys Rev Lett 110 (2013) 255502.

[3] S.V. Divinski, et al. Phys Rev B 71 (2005) 104.