Size-induced weakening and grain boundary-assisted deformation in 60 nm grained Ni nanopillars

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Nanocrystalline metals generally exhibit high strengths and good fatigue resistance Their strengthening scales with the inverse of grain size through square root dependence down to grain sizes of similar to 20 nm, representing the well-known Hall-Petch relation Here we show that in surface-dominated structures with sub-micron dimensions, i e nanopillars, 60 nm grained Ni-W alloys exhibit lower tensile strengths with decreasing pillar diameter, form shear bands and undergo mechanical twinning Moreover, there appears to be a transition in the deformation mechanism from dislocation-driven deformation in pillars with diameters larger than 100 nm to grain-boundary mediated deformation in pillars of 100 nm and below, including grain rotation and grain-boundary migration, processes previously observed only in grain sizes below 20 nm in materials of the same composition We postulate that the presence of free surfaces activates these grain-boundary mediated deformation processes at much larger grain sizes than observed before and results in lower attained strengths (C) 2010 Acta Materialia Inc Published by Elsevier Ltd All rights reserved
Publisher
PERGAMON-ELSEVIER SCIENCE LTD
Issue Date
2011-01
Language
English
Article Type
Article
Keywords

THIN-FILMS; NANOCRYSTALLINE ALUMINUM; MECHANICAL-PROPERTIES; TENSILE DEFORMATION; BEHAVIOR; STRESS; METALS; NICKEL; STRAIN; PLASTICITY

Citation

SCRIPTA MATERIALIA, v.64, no.1, pp.77 - 80

ISSN
1359-6462
DOI
10.1016/j.scriptamat.2010.09.010
URI
http://hdl.handle.net/10203/187280
Appears in Collection
NE-Journal Papers(저널논문)
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