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Thermal and thermomechanical effects on defect evolution in an Al–Li superplastic alloy

Published online by Cambridge University Press:  26 July 2012

K. A. Padmanabhan
Affiliation:
Department of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt, Germany
A. G. Balogh
Affiliation:
Department of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt, Germany
W. Puff
Affiliation:
Institute of Technical Physics, Technical University Graz, A-8010 Graz, Austria
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Extract

A commercial Al–Li alloy, in which the superplastic microstructure is developed by “strain-assisted continuous recrystallization” in early stages of flow, was studied using positron annihilation lifetime spectroscopy. Results revealed that exposing the material to a temperature of 525 °C (optimal temperature of superplastic deformation for this alloy) led to agglomeration of single vacancies into vacancy clusters of size of approximately four vacancies. Evidence for superplastic strain-induced cavitation was not found at 450 °C up to an elongation of 432% and at 525 °C up to 341%, the initial strain rate of deformation in both cases being 1.0 ×10−3 s−1. These results have practical significance.

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Articles
Copyright
Copyright © Materials Research Society 1999

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