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Atomistic Studies of Dislocation Glide in γ-TiAl

Published online by Cambridge University Press:  11 February 2011

R. Porizek ,
S. Znam ,
D. Nguyen-Manh ,
V. Vitek  and
D. G. Pettifor
R. Porizek
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, 19104–6272, U.S.A
S. Znam
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, 19104–6272, U.S.A
D. Nguyen-Manh
Affiliation:
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
V. Vitek
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, 19104–6272, U.S.A
D. G. Pettifor
Affiliation:
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
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Abstract

Computer simulation of the core structure and glide of ordinary 1/2<110] dislocations and <101] superdislocations in L10 TiAl has been performed using the recently constructed BondOrder Potentials. This description of atomic interactions includes explicitly, within the tight-binding approximation, the most important aspects of the directional bonding, namely d-d, p-p and d-p bonds. The ordinary dislocation in the screw orientation was found to have a non-planar core and, therefore, high Peierls stress. The superdislocation was found to possess in the screw orientation either a planar (glissile) or a non-planar (sessile) core structure. However, the glissile core transforms into the sessile one for certain orientations of the applied stress. This implies a strong asymmetry of the yield stress and the break down of the Schmid law when the plastic flow is mediated by superdislocations. At the same time, this may explain the orientation dependence of the dislocation substructure observed in the single-phase γ-TiAl by electron microscopy.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 753: Symposium BB – Defect Properties and Related Phenomena in Intermetallic Alloys , 2002 , BB4.3
Copyright
Copyright © Materials Research Society 2003

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References

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