Dresden 2014 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 13: Topical Session: Nanomechanics of nanostructured materials and systems III - Small scale plasticity

MM 13.5: Vortrag

Montag, 31. März 2014, 17:15–17:30, BAR 205

On The Importance Of Twinning Wedges in Nanowhisker Bending — Johannes J. Möller, Wolfram Nöhring, and •Erik Bitzek — Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)

Single crystalline metallic nanowhiskers have attracted substantial interest due to their special mechanical behavior. Similar to other nanostructured metals, like nano-pillars, thin films and nanocrystalline samples, they show a pronounced "smaller is stronger"-effect. However, not only the strength but also the deformation mechanisms can be size-dependent. Recently, twinning has been observed to be the governing deformation mechanism of <110>-oriented gold nanowhiskers under tension, whereas under compression they deform by nucleation and glide of full dislocations. Here, we address the question how nanowhiskers deform under bending loads. For this purpose we performed atomistic simulations of Au, Cu and Mo nanowhiskers using set-ups modeling three-point bending and the bending of a clamped cantilever beam. Independent on temperature, deformation rate, size and aspect ratio, the occurrence of wedge-shaped twins in the tensile region of the bent whisker was a characteristic feature in all simulations. Whereas the tendency for twinning can be explained by analyzing the generalized stacking fault energy and the resolved shear stresses on the partial dislocations, the particular wedge shape of the twins can be directly rationalized by the strain gradient within the bent whiskers.