Determination of Site-Occupancies in Aluminide Intermetallics by Alchemi

I. M. Anderson, A. J. Duncan, J. Bentley
1994 Materials Research Society Symposium Proceedings  
The site-distributions of Fe in four BZordered 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 sitepreference in NiAl and tends to reside on the site of the stoichiometrically deficient host element. An improved ALCHEMI analysis
more » ... cedure is outlined. The analysis explicitly addresses the phenomenon of ionization delocalization, which previously complicated the determination of sitedistributions 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 BIZ-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.
doi:10.1557/proc-364-443 fatcat:6babshzidzhydkt4twjmohqh7m