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Determination of Site-Occupancies in Aluminide Intermetallics by Alchemi

Published online by Cambridge University Press:  22 February 2011

I. M. Anderson ,
A. J. Duncan  and
J. Bentley
I. M. Anderson
Affiliation:
Oak Ridge National Laboratory, Metals and Ceramics Division, P.O. Box 2008, MS-6376, Oak Ridge, TN 37831-6376
A. J. Duncan
Affiliation:
University of Florida, Department of Materials Science and Engineering, Gainesville, FL 32611
J. Bentley
Affiliation:
Oak Ridge National Laboratory, Metals and Ceramics Division, P.O. Box 2008, MS-6376, Oak Ridge, TN 37831-6376
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Abstract

The site-distributions of Fe in four B2-ordered NiAl-based alloys with Fe concentrations of 10%, 2%, and 0.5% have been determined by ALCHEMI (atom-location by channeling-enhanced microanalysis). Site-distributions have been extracted with standard errors between ∼1.5% (10% Fe concentration) and ∼6% (0.5% Fe concentration). The results show that Fe has no strong site-preference in NiAl and tends to reside on the site of the stoichiometrically deficient host element.

An improved ALCHEMI analysis procedure is outlined. The analysis explicidy addresses the phenomenon of ionization delocalization, which previously complicated the determination of site-distributions in aluminide intermetallics, leading to inaccurate and oftentimes nonphysical results. The improved ALCHEMI analysis also addresses the presence of anti-site defects. The data acquisition conditions have been optimized to minimize the sources of statistical and systematic error. This optimized procedure should be suitable for all analyses of B2-ordered alloys. Several analyses at different channeling orientations show that the extracted site-occupancies are robust as long as the data are acquired at orientations that are remote from any major pole of the crystal.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 364: Symposium L – High-Temperature Ordered Intermetallic Alloys–VI , 1994 , 443
Copyright
Copyright © Materials Research Society 1995

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