Yield stress reversibility and the operation of Frank-Read sources in L1{sub 2} alloys in the anomalous regime for (111) slip

Conference · Tue Aug 01 04:00:00 EDT 1995

OSTI ID:78303

Ezz, S S; Hirsch, P B ^[1]

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1. Univ. of Oxford (United Kingdom). Dept. of Materials

The yield stress {tau}{sub y} at small strains ({approx} 0.01%) is strain rate independent, and has the same anomalous temperature dependence as that of the 0.2% strain. {tau}{sub y} is considered to be the stress at which Frank-Read sources operate in a virgin crystal. For successful operation, {tau}{sub y} must exceed the stress {tau}{sub s}, 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.

• OSTI ID: 78303
• Report Number(s): CONF-941144--; ISBN 1-55899-265-0
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DISLOCATIONS
EDGE DISLOCATIONS
FLOW STRESS
INTERMETALLIC COMPOUNDS
SCREW DISLOCATIONS
STRAINS
STRESSES