Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 29: Topical Session Bulk Nanostrucured Materials VI - Mechanical Properties I

MM 29.3: Talk

Wednesday, March 28, 2012, 11:00–11:15, H 0107

Grain boundary mediated plasticity in nanocrystalline metals and their alloys: On the interplay of mesoscopic sliding, coupled motion and segregating solutes — •Jonathan Schäfer and Karsten Albe — TU Darmstadt, Darmstadt, Germany

As the grain size is decreased into the lower nanometer (nm) range, the contribution of grain boundary (GB) mediated processes to low temperature plastic deformation increases. Hahn and Padmanabhan postulated that in nanocrystalline materials neighboring GBs can align themselves, allowing for GB sliding on a mesoscopic scale. Depending on the misorientation of the boundary, it was shown by Cahn et al., that GB motion can couple to shear deformation and move perpendicular to the shearing direction (out of the shear plane). This leads to a competition between mesoscopic GB sliding and coupled GB motion. For studying this competition and the effect of segregating solutes, we utilize molecular dynamics simulations, where nc Cu and CuNb serve as model systems. By testing a suitable microstructure under tensile and compressive load, we find that depending on the type of the GB, coupled motion out of the sliding plane is observed. This inevitably hinders any potential alignment and therefore prohibits mesoscopic GB sliding. For the case of samples with segregating solutes in the GB we show that it is a delicate function of composition, whether a given GB is pinned in place allowing for mesoscopic sliding or can leave the slide plane by coupled GB motion.