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Bicrystals with Strain Gradient Effects

Published online by Cambridge University Press:  10 February 2011

John Y. Shu ,
Norman A. Fleck  and
Wayne E. King
John Y. Shu
Affiliation:
Chemistry and Materials Science Department, Lawrence Livermore National Laboratory, Livermore, CA 94550
Norman A. Fleck
Affiliation:
Cambridge University Engineering Department, Trumpington Street, Cambridge, CB2 1PZ, U.K.
Wayne E. King
Affiliation:
Chemistry and Materials Science Department, Lawrence Livermore National Laboratory, Livermore, CA 94550
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Abstract

The boundary between two perfectly bonded single crystals plays a very important role in determining the deformation of the bicrystal. This work addresses the role of the grain boundary by considering the elevated hardening of a slip system due to a slip gradient. The slip gradients are associated with geometrically necessary dislocations and their effects become pronounced when a representative length scale of the deformation field is comparable to the dominant microstructural length scale of a material. A new rate-dependent crystal plasticity theory is presented and has been implemented within the finite element method framework. A planar bicrystal under uniform in-plane loading is studied using the new crystal theory. The strain is found to be continuous but non-uniform within a boundary layer around the interface. The lattice rotation is also non-uniform within the boundary layer. The width of the layer is determined by the misorientation of the grains, the hardening behavior of slip systems, and most importantly by the characteristic material length scales. The overall yield strength of the bicrystal is also obtained. A significant grain-size dependence of the yield strength, the Hall-Petch effect, is predicted.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 458: Symposium W – Interfacial Engineering for Optimized Properties , 1996 , 295
Copyright
Copyright © Materials Research Society 1997

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References

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