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The Structure and Properties of Boundaries in Bicrystals of Boron-Doped Ni3(Al,l at% Ta)

Published online by Cambridge University Press:  26 February 2011

M. J. Mills ,
S. H. Goods  and
S. M. Foiles
M. J. Mills
Affiliation:
Sandia National Laboratories, Livermore, CA 94551–0969.
S. H. Goods
Affiliation:
Sandia National Laboratories, Livermore, CA 94551–0969.
S. M. Foiles
Affiliation:
Sandia National Laboratories, Livermore, CA 94551–0969.
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Abstract

The effect of boron on the structure and macroscopic properties of an isolated grain boundary in bicrystals of a non-stoichiometric Ni3Al alloy (76 at% Ni, 23 at% Al, 1 at%Ta) has been studied. The room temperature tensile ductility and fracture mode of the bicrystals varies dramatically with the rate of cooling after elevated temperature heat treatment. In the absence of significant segregation of boron to the boundary, the bicrystals fail via brittle interfacial fracture with little or no ductility. When the segregation of boron to the boundary is maximized, the bicrystals are highly ductile. High resolution transmission electron microscopy reveals that this ductile state is achieved without the formation of a detectable region of compositional disorder at the boundary. Atomistic calculations using a Monte Carlo scheme predict that only partial disordering of the planes immediately adjacent to the boundary should occur for Ni-rich alloys both with and without boron. These results suggest that the presence of boron causes an increase in the cohesive energy of the boundaries rather than a change in the local compositional ordering.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 213: Symposium Q – High-Temperature Ordered Intermetallic Alloys IV , 1990 , 423
Copyright
Copyright © Materials Research Society 2006

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References

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