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Interpreting the ductility of nanocrystalline metals1

Published online by Cambridge University Press:  29 May 2013

John A. Sharon ,
Henry A. Padilla II  and
Brad L. Boyce
John A. Sharon
Affiliation:
Materials Science and Engineering Center, Sandia National Laboratories, Albuquerque, New Mexico, 87123
Henry A. Padilla II
Affiliation:
Materials Science and Engineering Center, Sandia National Laboratories, Albuquerque, New Mexico, 87123
Brad L. Boyce*
Affiliation:
Materials Science and Engineering Center, Sandia National Laboratories, Albuquerque, New Mexico, 87123
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

Nanocrystalline (NC) metals are known for having excellent strength but perceived to have poor ductility. Miniature tensile tests on NC Ni–Fe measured ultimate strengths of 2 GPa and elongations, by digital image correlation, of up to 10%. Detailed examination of the fracture surface revealed dimpled rupture and cross-section reduction up to 75%, suggesting an intrinsic ability for small grained Ni–Fe to accommodate plasticity. A survey of published studies on NC metals reveals that this behavior is quite common; despite low macroscopic elongation, NC metals often achieve extensive deformation suggesting good intrinsic ductility. Unfortunately, the common sheet-like configuration of NC tensile specimens muddies a simple evaluation of ductility based on elongation, since thin and wide geometries promote localized necking that expedites catastrophic failure. This paper presents a compact review of ductility concepts and literature to interpret the experimental ductility measurements of an electrodeposited nickel alloy.

Keywords

nanostructureductilityfracture
Type
Invited Feature Paper
Information
Journal of Materials Research , Volume 28 , Issue 12 , 28 June 2013 , pp. 1539 - 1552
Copyright
Copyright © Materials Research Society 2013 

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Footnotes

1

This work of authorship was prepared as an account of work sponsored by an agency of the United States Government. Accordingly, the United States Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so for United States Government purposes. Neither Sandia Corporation, the United States Government, nor any agency thereof, nor any of their employees make any warranty, express or imply, or assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represent that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by Sandia Corporation, the United States Government, or any agency thereof. The views and opinions expressed herein do not necessarily state or reflect those of Sandia Corporation, the United States Government or any agency thereof.

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