In situ TEM study of microplasticity and Bauschinger effect in nanocrystalline metals

Author(s)

Jagannathan Rajagopalan, Christian Rentenberger, Hans-Peter Karnthaler, Gerhard Dehm, Taher Saif

Abstract

In situ transmission electron microscopy straining experiments with concurrent macroscopic stress–strain measurements were performed

to study the effect of microstructural heterogeneity on the deformation behavior of nanocrystalline metal films. In microstructurally

heterogeneous gold films (mean grain size dm = 70 nm) comprising randomly oriented grains, dislocation activity is confined to

relatively larger grains, with smaller grains deforming elastically, even at applied strains approaching 1.2%. This extended microplasticity

leads to build-up of internal stresses, inducing a large Bauschinger effect during unloading. Microstructurally heterogeneous aluminum

films (dm = 140 nm) also show similar behavior. In contrast, microstructurally homogeneous aluminum films comprising mainly two

grain families, both favorably oriented for dislocation glide, show limited microplastic deformation and minimal Bauschinger effect

despite having a comparable mean grain size (dm = 120 nm). A simple model is proposed to describe these observations. Overall, our

results emphasize the need to consider both microstructural size and heterogeneity in modeling the mechanical behavior of nanocrystalline

metals.

Organisation(s)

Physics of Nanostructured Materials

External organisation(s)

University of Illinois at Urbana-Champaign, Montanuniversität Leoben

Journal

Acta Materialia

Volume

Pages

4772-4782

No. of pages

ISSN

1359-6454

DOI

https://doi.org/10.1016/j.actamat.2010.05.013

Publication date

2010

Peer reviewed

Yes

Austrian Fields of Science 2012

210006 Nanotechnology, 103018 Materials physics

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