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MM: Fachverband Metall- und Materialphysik

MM 22: Topical Session TEM VI

MM 22.4: Talk

Wednesday, March 16, 2011, 12:15–12:30, IFW B

In situ tensile testing of Au nanowires — •Burkhard Roos¹, Bahne Kapelle¹, Gunther Richter², and Cynthia A. Volkert¹ — ¹Institut für Materialphysik, Universität Göttingen — ²Max-Planck-Institut für Metallforschung, Stuttgart

Increasing strength with decreasing size is a common phenomenon in metals, and is often explained in terms of dislocation pile-ups and interactions. However, for free standing samples with dimensions below 150 nm, dislocation storage is hard to envision and a convincing explanation for the size-dependent strength is still missing. The goal of this study is to directly observe dislocations in small volumes, using in situ TEM during deformation. Single crystal Au nanowires with diameters between 40 and 250 nm have been used for this study. In wires with diameters above 180 nm, full dislocation based deformation and dislocation storage is observed. Wires with diameters below 180 nm show a different deformation behaviour. Stacking faults appear during deformation as a result of the nucleation and motion of partial dislocations. The stacking faults form homogenously along the wire length and appear and disappear in less than 50 ms. The stacking faults do not move as the wire is further deformed, but may eventually thicken into nanotwins through the sequential activation of partial dislocations on neighbouring (111) planes. Post-deformation TEM studies show that fracture often occurs at a nanotwin. A possible explanation for the dependence of the deformation mode on wire diameter and stress will be discussed in terms of the splitting distance of partial dislocations.