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Atomic-scale Study of a Transition Phase Precipitate and Its Interfacial Chemistry in an Fe−15 at.% Mo−5 at.% V Alloy

Published online by Cambridge University Press:  02 February 2002

Dieter Isheim*
Affiliation:
Department of Materials Science and Engineering, Northwestern University, 2225 N. Campus Drive, Evanston, IL 60208-3108
Olof C. Hellman
Affiliation:
Department of Materials Science and Engineering, Northwestern University, 2225 N. Campus Drive, Evanston, IL 60208-3108
David N. Seidman
Affiliation:
Department of Materials Science and Engineering, Northwestern University, 2225 N. Campus Drive, Evanston, IL 60208-3108
Frédéric Danoix
Affiliation:
Groupe de Physique des Matériaux, UMR CNRS 6634, Faculté des Sciences de Rouen, F-76821, Mont Saint Aignan Cedex, France
Alain Bostel
Affiliation:
Groupe de Physique des Matériaux, UMR CNRS 6634, Faculté des Sciences de Rouen, F-76821, Mont Saint Aignan Cedex, France
Didier Blavette
Affiliation:
Groupe de Physique des Matériaux, UMR CNRS 6634, Faculté des Sciences de Rouen, F-76821, Mont Saint Aignan Cedex, France
*
*Corresponding author
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Abstract

A Mo-rich precipitate in an Fe-rich matrix and the heterophase interface bounding the precipitate have been examined on an atomic scale by three-dimensional atom-probe (3DAP) microscopy and transmission electron microscopy (TEM). The Mo-rich precipitate was generated by isothermal solid-state decomposition at 500°C of an Fe-15 at.% Mo-5 at.% V alloy. After this heat treatment, TEM reveals a characteristic modulated strain contrast structure. The precipitate has a composition of Mo-13.0 at.% Fe-4.9 at.% V as measured by 3DAP microscopy. The alloy decomposes at a nearly constant 5 at.% V, constituting a metastable tie-line between Fe-rich and Mo-rich bcc solid solutions. The formation of the equilibrium intermetallic phases is kinetically impeded. A local vanadium enrichment of 21 at.% is detected at the interface of the precipitate in a matrix region about 0.27 nm or 1–2 atomic layers in thickness. The corresponding value of the Gibbsian interfacial excess of vanadium is 3.3 ± 1.3 nm−2.

Type
Research Article
Copyright
Copyright © Microscopy Society of America 2001

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