High Strain Rate Tensile Testing of Silver Nanowires: Rate-Dependent Brittle-to-Ductile Transition

Rajaprakash Ramachandramoorthy, Wei Gao, Rodrigo Bernal, Horacio Dante Espinosa*

*Corresponding author for this work

Research output: Contribution to journalArticle

39 Scopus citations

Abstract

The characterization of nanomaterials under high strain rates is critical to understand their suitability for dynamic applications such as nanoresonators and nanoswitches. It is also of great theoretical importance to explore nanomechanics with dynamic and rate effects. Here, we report in situ scanning electron microscope (SEM) tensile testing of bicrystalline silver nanowires at strain rates up to 2/s, which is 2 orders of magnitude higher than previously reported in the literature. The experiments are enabled by a microelectromechanical system (MEMS) with fast response time. It was identified that the nanowire plastic deformation has a small activation volume (<10b 3 ), suggesting dislocation nucleation as the rate controlling mechanism. Also, a remarkable brittle-to-ductile failure mode transition was observed at a threshold strain rate of 0.2/s. Transmission electron microscopy (TEM) revealed that along the nanowire, dislocation density and spatial distribution of plastic regions increase with increasing strain rate. Furthermore, molecular dynamic (MD) simulations show that deformation mechanisms such as grain boundary migration and dislocation interactions are responsible for such ductility. Finally, the MD and experimental results were interpreted using dislocation nucleation theory. The predicted yield stress values are in agreement with the experimental results for strain rates above 0.2/s when ductility is pronounced. At low strain rates, random imperfections on the nanowire surface trigger localized plasticity, leading to a brittle-like failure.

Original languageEnglish (US)
Pages (from-to)255-263
Number of pages9
JournalNano Letters
Volume16
Issue number1
DOIs
StatePublished - Jan 13 2016

Keywords

  • bicrystalline
  • dynamic testing
  • flexible electronics
  • nanoscale plasticity
  • nanostructure
  • nanoswitches
  • nanowire
  • rate effects
  • tension test

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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