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This paper presents a quantitative model of the formation of slip avalanches (strain bursts) which are observed during cyclic deformation of single-glide orientated crystals. By means of a dislocation-dynamical approach, the scaling relations found by experiment are related to the physical parameters characterising the microstructural evolution. The strain-burst phenomenon, discovered and subjected to detailed experimental studies by Neumann, is observed during stress-amplitude controlled cyclic deformation of single-glide-orientated face-centred cubic or hexagonal monocrystals. If the applied stress amplitude is slowly increased in the course of such a test, the crystal may respond by large oscillations of the cyclic strain amplitude. This manifests itself as a regular sequence of sharp peaks (strain bursts) during each of which the strain amplitude rises by a factor of 2 to 100, depending on the experimental conditions. Two prerequisities for the appearance of this phenomenon have been identified: (i) deformation has to occur in single glide, that is, strain bursts are neither observed in polycrystals nor in monocrystals where several glide systems are active. They can also be suppressed in single-glide-orientated crystals by prestraining into stage II of the work hardening curve; (ii) the phenomenon is restricted to sufficiently low deformation temperatures and/or high cycle frequencies. This gives evidence that thermal activation of dislocation motion must be suppressed to some extent, that is, a nonvanishing thermal flow stress contribution is required.

Additional information

Authors: ZAISER M, Max-Planck-Institut für Metallforschung, Institut für Physik, Stuttgart (DE);HÄHNER P, JRC Ispra (IT)
Bibliographic Reference: Article: Scripta Metallurgica et Materialia, Vol. 31 (1994) pp. 1587-1592
Record Number: 199510552 / Last updated on: 1995-04-21
Original language: en
Available languages: en
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