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Planar Growth Faults in Nb3Al

Published online by Cambridge University Press:  01 January 1992

L.S. Smith
Affiliation:
IRC in Materials for High Performance Applications, and School of Metallurgy and Materials, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
T-T. Cheng
Affiliation:
IRC in Materials for High Performance Applications, and School of Metallurgy and Materials, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
M. Aindow
Affiliation:
IRC in Materials for High Performance Applications, and School of Metallurgy and Materials, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
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Abstract

A transmission electron microscopy study of planar growth faults in the A15 intermetallic phase Nb3Al is presented. These faults are not observed in plasma melted material but a high density of these features is observed in arc-melted material which is cooled more slowly. The faults are found most frequently on planes {100}, often changing from one plane to another along their length. It has not been possible to obtain a full diffraction contrast analysis from the faults but HREM images indicate that they are intrinsic with a displacement vector R=l/4<120>. Since this vector does not lie in the plane, they cannot form by glide processes alone and therefore probably arise when vacancies coalesce into sheets on {100}. Since this value of R is consistent with the removal of an Al-rich plane {004}, it is argued that the formation of these faults may help to stabilise the Al5 phase to Nb-rich compositions.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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References

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