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In situ Transmission Electron Microscopy Observations of Toughening Mechanisms in Ultra-fine Grained Columnar Aluminum Thin Films

Published online by Cambridge University Press:  01 July 2005

K. Hattar
Affiliation:
Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801
J. Han
Affiliation:
Department of Mechanical and Industrial Engineering, University of Illinois, Urbana, Illinois 61801
M.T.A. Saif
Affiliation:
Department of Mechanical and Industrial Engineering, University of Illinois, Urbana, Illinois 61801
I.M. Robertson*
Affiliation:
Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801
*
a)Address all correspondence to this author. e-mail: ianr@uiuc.edu This author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs.org/publications/jmr/policy.html.
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Abstract

A unique straining device, fabricated using microlithographic techniques, has been developed to permit real-time investigation in the transmission electron microscope (TEM) of the deformation and failure mechanisms in ultrafine-grained aluminum. The tensile specimen is a freestanding thin film with a columnar microstructure that has a uniform cross-section (100 × 0.125 μm) and a gauge length of 300 μm. In situ TEM straining experiments show the fracture mode is intergranular with no accompanying general plasticity. Propagating cracks were halted at large grains, and crack blunting occurred through grain-boundary-mediated processes. The blunting process was accompanied by dislocation emission and deformation twinning in the grain responsible for arresting the crack. Voids or microcracks nucleated and grew on grain boundaries ahead of the arrested crack, and crack advance occurred through linkage of the microcracks and the primary crack.

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Articles
Copyright
Copyright © Materials Research Society 2005

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