Issue 17, 2016

Quantifying and observing viscoplasticity at the nanoscale: highly localized deformation mechanisms in ultrathin nanocrystalline gold films

Abstract

This study unveils the stress relaxation transient deformation mechanisms in 100 nm-thick, nanocrystalline Au films thanks to a robust quantitative in situ TEM MEMS nanomechanical testing approach to quantify stress relaxation and to perform in situ observations of time-dependent deformation in ultrathin nanocrystalline films. The relaxation is characterized by a decrease in plastic strain rate of more than one order of magnitude over the first ∼30 minutes (from 10−4 to less than 10−5 s−1). For longer relaxation experiments, the plastic strain rate decreases down to 10−7 s−1 after several hours. The power-law exponent n, relating plastic strain rate and stress, continuously decreases from initial large values (n from 6 to 14 at t = 0) down to low values (n ∼ 1–2) after several hours. In situ TEM observations reveal that the relaxation behavior is initially accommodated by highly localized, sustained, intergranular and transgranular dislocation motion. Over time, the dislocation sources become less operative or exhausted, leading to a transition to grain-boundary-diffusion based mechanisms. The results also highlight a promising technique for nanoscale characterization of time-dependent deformation.

Graphical abstract: Quantifying and observing viscoplasticity at the nanoscale: highly localized deformation mechanisms in ultrathin nanocrystalline gold films

Supplementary files

Article information

Article type
Paper
Submitted
26 Jan 2016
Accepted
07 Apr 2016
First published
08 Apr 2016

Nanoscale, 2016,8, 9234-9244

Quantifying and observing viscoplasticity at the nanoscale: highly localized deformation mechanisms in ultrathin nanocrystalline gold films

E. Hosseinian, M. Legros and O. N. Pierron, Nanoscale, 2016, 8, 9234 DOI: 10.1039/C6NR00710D

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