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Flaw-driven Failure in Nanostructures

Gu, X. Wendy and Wu, Zhaoxuan and Zhang, Yong-Wei and Srolovitz, David J. and Greer, Julia R. (2013) Flaw-driven Failure in Nanostructures. California Institute of Technology , Pasadena, CA. (Submitted)

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Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices that have components or microstructural elements at the nanometer length scale. No consensus exists on the effect of flaws on fracture in bulk nanostructured materials or in nanostructures. Proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with virtually no experimental support. We explore fracture mechanisms in nanomaterials via nanomechanical experiments on nanostructures with pre-fabricated surface flaws in combination with molecular dynamics simulations. Nanocrystalline Pt cylinders with diameters of ~120 nm with intentionally introduced surface notches were created using a template-assisted electroplating method and tested in uniaxial tension in in-situ SEM. Experiments demonstrate that 8 out of 12 samples failed at the notches and that tensile failure strengths were ~1.8 GPa regardless of whether failure occurred at or away from the flaw. These findings suggest that failure location was sensitive to the presence of flaws, while strength was flaw-insensitive. Molecular dynamics simulations support these observations and show that incipient plastic deformation commences via nucleation and motion of dislocations in concert with grain boundary sliding. We postulate that such local plasticity reduces stress concentration ahead of the flaw to levels comparable with the strengths of intrinsic microstructural features like grain boundary triple junctions, a phenomenon unique to nano-scale solids that contain an internal microstructural energy landscape. This mechanism causes failure to occur at the weakest link, be it an internal inhomogeneity or a surface feature with a high local stress.

Item Type:Report or Paper (Discussion Paper)
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URLURL TypeDescription Paper
Greer, Julia R.0000-0002-9675-1508
Additional Information:X.W.G. is grateful for financial support from the National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a. JRG acknowledges the financial support of the National Science Foundation (DMR-1204864). X.W.G. and J.R.G. thank the Kavli Nanoscience Institute at Caltech for the availability of critical cleanroom facilities. We thank V. Deshpande and D. Jang for helpful discussion, and D. Jang and C. Garland for TEM assistance. The authors gratefully acknowledge the financial support from the Agency for Science, Technology and Research (A*STAR), Singapore and the use of computing resources at the A*STAR Computational Resource Centre, Singapore.
Group:Kavli Nanoscience Institute
Funding AgencyGrant Number
National Defense Science and Engineering Graduate (NDSEG) Fellowship32 CFR 168a
Agency for Science, Technology and Research (A*STAR)UNSPECIFIED
Subject Keywords:size effect, nanocrystalline, mechanical properties, fracture, molecular dynamics
Record Number:CaltechAUTHORS:20130729-080552163
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39614
Deposited By: Tony Diaz
Deposited On:29 Jul 2013 21:48
Last Modified:03 Oct 2019 05:09

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