Regensburg 2016 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 19: Mechanical Properties I

MM 19.2: Talk

Tuesday, March 8, 2016, 10:30–10:45, H52

Flaw sensitivity of nanowires — •Christian Brandl — Institute for Applied Materials, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany

With decreasing dimensions of the metals, the strength is increasing with decreasing dimensions can approach the theoretical strength limit - down to a regime, where the strength is theoretically predicted to be flaw insensitive.

Using atomic simulation, we investigate the effect of predefined flaws, i.e. notches, in intrinsic brittle Si nanowires and intrinsic ductile Au nanowires. The flaw size and wire diameter dependent strength and ductility in the molecular dynamics (MD) simulations show the existence of the flaw insensitive size regime. The defect evolution, flow stresses and the strain hardening in the MD simulations of Au nanowires is compared to experimental studies, where gold nanowires were structured by He-ion beams with sub-50 nm diameter well-defined holes. The experimental microstructure after deformation - as seen by (high-resolution) transmission electron microscopy - suggests the formation of a nano-grained substructure at the failure location, which is also consistently observed in our MD simulation.

The striking similarities between MD simulations and the experimental data are critically discussed and explained by strain hardening in a strength regime of theoretical shear strength in Au. More generally, the implications of strain rate dependence and temperature dependence of the flow stresses are discussed for nanowires in the size regime of flaw insensitivity.