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Crystals 2018, 8(3), 128; https://doi.org/10.3390/cryst8030128

Thickness-Dependent Strain Rate Sensitivity of Nanolayers via the Nanoindentation Technique

1
State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2
School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA
*
Authors to whom correspondence should be addressed.
Received: 14 January 2018 / Revised: 19 February 2018 / Accepted: 21 February 2018 / Published: 9 March 2018
(This article belongs to the Special Issue Crystal Indentation Hardness)
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Abstract

The strain rate sensitivity (SRS) and dislocation activation volume are two inter-related material properties for understanding thermally-activated plastic deformation, such as creep. For face-centered-cubic metals, SRS normally increases with decreasing grain size, whereas the opposite holds for body-center-cubic metals. However, these findings are applicable to metals with average grain sizes greater than tens of nanometers. Recent studies on mechanical behaviors presented distinct deformation mechanisms in multilayers with individual layer thickness of 20 nanometers or less. It is necessary to estimate the SRS and plastic deformation mechanisms in this regime. Here, we review a new nanoindentation test method that renders reliable hardness measurement insensitive to thermal drift, and its application on SRS of Cu/amorphous-CuNb nanolayers. The new technique is applied to Cu films and returns expected SRS values when compared to conventional tensile test results. The SRS of Cu/amorphous-CuNb nanolayers demonstrates two distinct deformation mechanisms depending on layer thickness: dislocation pileup-dominated and interface-mediated deformation mechanisms. View Full-Text
Keywords: thin film; nanoindentation; strain rate sensitivity; deformation mechanisms thin film; nanoindentation; strain rate sensitivity; deformation mechanisms
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Song, J.; Liu, Y.; Fan, Z.; Zhang, X. Thickness-Dependent Strain Rate Sensitivity of Nanolayers via the Nanoindentation Technique. Crystals 2018, 8, 128.

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