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Dislocation Nucleation Versus Cleavage in Ni3AI and Ni

Published online by Cambridge University Press:  26 February 2011

Yuemin Sun ,
James R. Rice  and
Lev Truskinovsky
Yuemin Sun
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138
James R. Rice
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138
Lev Truskinovsky
Affiliation:
Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis, MN 55455
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Abstract

Recent advances in the modelling of dislocation nucleation from a crack tip are used here to compare the critical energy release rate associated with emission in Ni3Al and Ni. The method for analyzing nucleation makes use of a Peierls-type stress versus displacement relation ahead of the crack tip. It has been shown recently by Rice [1] that the energy release rate for emission scales with γus, the “unstable stacking” energy associated with the sliding of atomic planes past one another. The advantage of this approach is that it allows for an extended dislocation core during nucleation, thus eliminating the need for a core cutoff radius. Preliminary calculations which take into account only the shear stress on a slip plane show that it is more difficult to emit a dislocation in Ni3Al than in Ni. Working within the framework of the competition between atomic decohesion and blunting by dislocation emission, the implications for explaining the brittleness of Ni3Al are also discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 213: Symposium Q – High-Temperature Ordered Intermetallic Alloys IV , 1990 , 243
Copyright
Copyright © Materials Research Society 1991

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References

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