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Yield Stress Reversibility and the Operation of Frank-Read Sources in Li2 Alloys in the Anomalous Regime For (111) Slip

Published online by Cambridge University Press:  22 February 2011

S. S. Ezz  and
P. B. Hirsch
S. S. Ezz
Affiliation:
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PFL U.K.
P. B. Hirsch
Affiliation:
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PFL U.K.
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Abstract

The yield stress τy at small strains (≈ 0.01%) is strain rate independent, and has the same anomalous temperature dependence as that of the 0.2% strain. τy is considered to be the stress at which Frank-Read sources operate in a virgin crystal. For successful operation, τy must exceed the stress τs at which screws propagate dynamically through the crystal, and the source dislocation must pass rapidly through the unstable Frank - Read configuration. This can be achieved by the bowing edge dislocation overcoming local obstacles before reaching that configuration. Loops elongated along the screw direction are expected to be formed in the microstrain region. Under certain conditions such loops are unstable on unloading, thereby generating long edge dislocations which can operate successfully as sources at low but not at high temperatures, explaining the reversibility phenomenon.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 364: Symposium L – High-Temperature Ordered Intermetallic Alloys–VI , 1994 , 35
Copyright
Copyright © Materials Research Society 1995

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