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Deformation at the nanometer and micrometer length scales: Effects of strain gradients and dislocation starvation

Nix, William D. and Greer, Julia R. and Feng, Gang and Lilleodden, Erica T. (2007) Deformation at the nanometer and micrometer length scales: Effects of strain gradients and dislocation starvation. Thin Solid Films, 515 (6). pp. 3152-3157. ISSN 0040-6090. doi:10.1016/j.tsf.2006.01.030.

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Nanomechanical devices are certain to play an important role in future technologies. Already sensors and actuators based on MEMS technologies are common and new devices based on NEMS are just around the corner. These developments are part of a decade-long trend to build useful engineering devices and structures on a smaller and smaller scale. The creation of structures and devices calls for an understanding of the mechanical properties of materials at these small length scales. Here we examine some of the effects that arise when crystalline materials are mechanically deformed in small volumes. We show that indentation size effects at the micrometer scale can be understood in terms of the hardening associated with strain gradients and geometrically necessary dislocations, while indentation size effects at the nanometer scale involve the concepts of dislocation starvation and the nucleation of dislocations. We also describe uniaxial compression experiments on micrometer size pillars of single crystal gold and find surprisingly strong size effects, even though no significant strain gradients are present and the crystals are not initially dislocation free. We argue that these size effects are caused by dislocation starvation hardening, with dislocations leaving the crystal more quickly than they multiply and leading to the requirement of continual dislocation nucleation during the course of deformation. A new length scale for plasticity, the distance a dislocation travels before it creates another, arises naturally in this treatment. Hardening of crystals smaller than this characteristic size is expected to be dominated by dislocation starvation while crystals much larger than this size should exhibit conventional dislocation plasticity.

Item Type:Article
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URLURL TypeDescription DOIArticle
Greer, Julia R.0000-0002-9675-1508
Additional Information:© 2006 Elsevier B.V. Available online 13 February 2006. The authors wish to thank Dr. Michael Uchic of the AFRL Materials Laboratory for his interest in and support of this work. The authors also gratefully acknowledge financial support of this project through grants provided by an NSF-NIRT grant (CMS-0103257) and the Department of Energy (DE-FG03-89ER45387).
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-89ER45387
Subject Keywords:Indentation size effects; Dislocation nucleation; Gold micropillars; Dislocation starvation
Issue or Number:6
Record Number:CaltechAUTHORS:20130710-153043195
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Official Citation:William D. Nix, Julia R. Greer, Gang Feng, Erica T. Lilleodden, Deformation at the nanometer and micrometer length scales: Effects of strain gradients and dislocation starvation, Thin Solid Films, Volume 515, Issue 6, 12 February 2007, Pages 3152-3157, ISSN 0040-6090,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39297
Deposited By: Tony Diaz
Deposited On:11 Jul 2013 17:43
Last Modified:09 Nov 2021 23:43

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