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Indentation response of nanoporous gold from atomistic simulations

Published online by Cambridge University Press:  10 April 2018

Diana Farkas*
Affiliation:
Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA
Joshua Stuckner
Affiliation:
Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA
Rachel Umbel
Affiliation:
Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA
Bryan Kuhr
Affiliation:
Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA
Michael J. Demkowicz
Affiliation:
Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843, USA
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

We present classical potential molecular dynamics simulations of nanoporous gold (np-Au) impacted by a spherical indenter. The atomic structure was generated using a phase field model as a template. In agreement with previous experiments, we observe densification in the region under the indenter. The hardness values obtained from our simulations exhibit a transition from an initially perfect-plastic plateau to hardening behavior in the later stages of indentation. This transition occurs when the relative density beneath the indenter exceeds ∼0.9. Hardness values obtained from the nanoindentation simulations reach 0.6 GPa, due to the densification of the material under the indenter. Elevated dislocation densities are observed in the densified region. The mechanism of pore collapse in the densified layer under the indenter is seen to switch from uniaxial to triaxial, consistent with a change in deformation mechanism from one based on shearing of individual ligaments in np-Au to one involving dislocation-mediated plasticity around voids in a Au single crystal undergoing uniaxial compression.

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Article
Copyright
Copyright © Materials Research Society 2018 

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References

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