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1771469 
Journal Article 
Combination of in situ straining and ACOM TEM: A novel method for analysis of plastic deformation of nanocrystalline metals 
Kobler, A; Kashiwar, A; Hahn, H; Kuebel, C 
2013 
1 
Ultramicroscopy
ISSN: 0304-3991 
128 
68-81 
23524380 
WOS:000317917100007 
Nanocrystalline metals are expected to exhibit different
deformation mechanisms when compared to their coarse grained counterparts because the dislocation
storage capacity decreases and the grain boundary mediated processes become more pronounced with
decreasing grain size. As a new approach to directly image and quantify the plastic deformation
processes in nanocrystalline thin films, a combination of automated crystal orientation mapping
in microprobe STEM mode with in situ straining inside a TEM was developed. ACOM-TEM closes the
gap between EBSD and BF/DFTEM by providing full orientation maps with nanometer resolution. The
novel combination with in situ straining provided for the first time the possibility to directly
image and quantify the structural changes of all crystallites in the ensemble of a thin film at
the nanometer scale during mechanical deformation. It was used to characterize the metallographic
changes during tensile deformation of a nanocrystalline Au thin film prepared by magnetron
sputtering. The investigation of the grain size, grain orientation and twinning on a global
(grain average over a micron sized area) and local (assembly of selected grains) scale allowed
for the development of an in depth picture of the deformation processes. Grain boundary motion
and local grain rotation were two of the processes acting to dissipate the applied stress.
Additionally, twinning/detwinning occurred simultaneously during straining. These processes,
which occurred locally already in the micro-plastic regime, led to global grain growth starting
at the transition to the macro-plastic deformation regime. (C) 2013 Elsevier B.V. All rights
reserved. 
In situ straining; Nanocrystalline metals; STEM; ACOM-TEM; Quantitative crystallographic analysis; Deformation mechanism