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In situ study of thermally activated flow and dynamic restoration of ultrafine-grained pure Cu at 373 K

Published online by Cambridge University Press:  18 September 2017

Wolfgang Blum*
Affiliation:
Institut für Werkstoffwissenschaften, University of Erlangen-Nürnberg, Erlangen D-91058, Germany
Petr Král
Affiliation:
Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno CZ-61662, Czech Republic
Jiri Dvořák
Affiliation:
Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno CZ-61662, Czech Republic
Martin Petrenec
Affiliation:
Tescan Orsay Holding a.s., Brno CZ-62300, Czech Republic
Philip Eisenlohr
Affiliation:
Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan 48824, USA
Vaclav Sklenička
Affiliation:
Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno CZ-61662, Czech Republic
*
a) Address all correspondence to this author. e-mail: wolfgang.blum@fau.de
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Abstract

Pure Cu was made ultrafine-grained by equal channel angular pressing on route BC at ambient temperatures and deformed in situ in a scanning electron microscope at the elevated temperature of 373 K and at a constant total strain rate of 10−4 s−1. Deformation was repetitively stopped to take micrographs of the grain structure on the same area of observation, revealing limited activity of discontinuous dynamic recrystallization. During the stops of deformation, the flow stress was relaxing. The relaxation of stress as function of time was used to determine the rate of inelastic deformation as a function of stress, from which the activation volume ${V^ * }$ of the thermally activated flow was derived. It is found that the normalized values of ${V^ * }$ were lying in the same order generally found for coarse-grained pure materials. This seems to be in conflict with the literature. However, the conflict is resolved by noting that the literature results refer to quasistationary deformation with the concurrent dynamic recovery in contrast to the present results obtained at a virtually constant microstructure. The interpretation of the two kinds of activation volumes for thermally activated flow is discussed.

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Articles
Copyright
Copyright © Materials Research Society 2017 

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Footnotes

Contributing Editor: Mathias Göken

Dedicated to Prof. Hael Mughrabi on the occasion of his 80th birthday.

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In situ study of thermally activated flow and dynamic restoration of ultrafine-grained pure Cu at 373 K
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