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Properties of the Deformation Microstructure in Al-Rich γ-TiAl Deformed by Ordinary Dislocations

Published online by Cambridge University Press:  15 February 2011

Fabienne Grjégori  and
Patrick VeyssiÈRe
Fabienne Grjégori
Affiliation:
LPMTM, Institut Galilée, Av J. B. Clément, 93430 Villetaneuse, France, fg@lpmtm.univparis13.fr
Patrick VeyssiÈRe
Affiliation:
LEM, CNRS-ONERA, BP 72, 92322 Chatillon cedex, France, patrickv@onera.fr
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Abstract

In the near vicinity of the [021] load orientation, γ-TiAl deforms via ordinary dislocations (Burgers vector b = 1/2<110]). As for deformation by <110] dislocations, the flow stress shows a peak at about 600°C. Results of an extensive microstructural investigation aimed at identifying the origin of this mechanical anomaly are presented. The analysis was conducted on single crystals oriented for single slip. It confirmed that ordinary dislocations tend to align themselves along the screw direction. This preferential line direction becomes gradually accentuated as the deformation temperature is raised up to the peak temperature. This effect is accompanied by a strong tendency towards forming cusps, but there is indication that the immobilisation along the screw direction takes place prior to dislocation pinning. In the vicinity of the peak temperature, screw dislocations gather in the form of bundles. No clear correlation is found between the temperature dependence of the flow stress and that of the density of pinning points. The relationship between these microstructural findings and the occurrence of a flow stress anomaly is discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 578: Symposia A/C – Multiscale Phenomena in Materials - Experiments in Modeling , 1999 , 187
Copyright
Copyright © Materials Research Society 2000

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References

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