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Dislocation Core Structure and the Normal Yield Behavior of L12 Ordered Alloys

Published online by Cambridge University Press:  21 February 2011

G. Tichy ,
V. Vitek  and
D. P. Pope
G. Tichy
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104
V. Vitek
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104
D. P. Pope
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104
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Abstract

A rapid increase of the yield stress with increasing temperature, often observed in L12 ordered alloys, is commonly called the “anomalous flow behavior”. This phenomenon is believed to result from the thermally activated transformation of the core of 1/2<110> screw dislocations from a glissile form to a sessile form at high temperatures. It is shown here that another class of L12 alloys exists in which these two forms of the screw dislocation core are not available. These are the alloys in which the APB on {111} planes is not stable and the atomistic studies of screw dislocations in such alloys show that their cores are always sessile. The yield stress of these alloys then increases with decreasing temperature and no increase at high temperatures occurs. Such behavior has been observed, for example, in Pt3Al. This “normal” behavior is analogous to that of b.c.c. metals and a theory of the temperature dependence of the yield stress has been developed along the same lines as in the case of b.c.c. metals. Comparison of this theory with measurements on Pt3Al single crystals shows a good agreement.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 39: Symposium G – High-Temperature Ordered Intermetallic Alloys I , 1984 , 213
Copyright
Copyright © Materials Research Society 1985

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References

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