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Crystal structure of intermetallic phase in Fe–20Cr–4Al–0.5Y alloy by convergent beam electron diffraction

Published online by Cambridge University Press:  31 January 2011

Raghavan Ayer ,
J. C. Scanlon ,
T. A. Ramanarayanan ,
R. R. Mueller ,
R. Petkovic-Luton  and
J. W. Steeds
Raghavan Ayer
Affiliation:
Exxon Research & Engineering Company, Annandale, New Jersey 08801
J. C. Scanlon
Affiliation:
Exxon Research & Engineering Company, Annandale, New Jersey 08801
T. A. Ramanarayanan
Affiliation:
Exxon Research & Engineering Company, Annandale, New Jersey 08801
R. R. Mueller
Affiliation:
Exxon Research & Engineering Company, Annandale, New Jersey 08801
R. Petkovic-Luton
Affiliation:
Exxon Research & Engineering Company, Annandale, New Jersey 08801
J. W. Steeds
Affiliation:
University of Bristol. Bristol. United Kingdom
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Abstract

The crystal structure and chemical composition of the intermetallic phase in a Fe-20%Cr-4%Al-0.5%Y (wt. %) alloy were investigated by electron microscopy. Convergent beam diffraction studies revealed that the intermetallic phase forms in three different crystal structures that could coexist in a single grain of the phase. The dominant crystal structure was shown to be hexagonal (a = 0.85, c = 0.84 nm) with a space group most likely to be P63/mmc. Within the hexagonal phase, regions of a rhombohedral crystal structure (a = 0.85, c = 1.26 nm) were observed that had grown in without an apparent phase boundary separating the two crystal structures. The third crystal structure was determined to be monoclinic (a = 0.97, b = 0.85, c = 1.07 nm, and beta = 97.3°) and formed by twinning on the {10$\overline 1$1} planes of the hexagonal phase. The chemical compositions of regions with different crystal structures were comparable and the stoichiometry of the intermetallic phase corresponds to (Fe,Cr)17 (Al,Y)2. The relationship of the observed crystal structures to those previously reported is discussed.

Type
Articles
Information
Journal of Materials Research , Volume 2 , Issue 1 , February 1987 , pp. 16 - 27
Copyright
Copyright © Materials Research Society 1987

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References

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