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Thermal Expansions of the Beta and Gamma Phases in a Co–Ni–Fe Superalloy Determined by X-ray Diffraction

Published online by Cambridge University Press:  31 January 2011

M. S. Seehra*
Affiliation:
Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315
C. Cionca
Affiliation:
Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315
A. Manivannan
Affiliation:
Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315
*
a)Address all correspondence to this author. e-mail: mseehra@wvu.edu
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Abstract

Commercially useful multiphase alloy Inconel 783 is made up of Ni(28%), Fe(25%), and Co(35%) with smaller amounts of Cr, Al, Nb, Mo, Ti, C, and Si. In this work, relative temperature variations of the lattice constants a(T)/a0 of the gamma (face-centered-cubic) and beta (body-centered-cubic) phases of this alloy are determined from 97 to 773 K using analyses of their x-ray diffraction (XRD) patterns. Plots of a(T)/a0 for the two phases vary from 1.0 at 97 K to 1.012 at 773 K and show that (i) for T = 500 K, thermal expansion of the β phase is larger than that of the = phase; and (ii) an abrupt jump is observed near 300 K. The appearance of new lines above 700 K in XRD representing Co2CrO4 and CoCr2O4 is interpreted in terms of the oxidation of the γ phase, whereas the β phase is oxidation resistant. The anomalous change in a(T)/a0, observed near 300 K and accompanied by a similar change in the temperature variation of the initial magnetic susceptibility, is not well understood. A brief discussion on the implications of these results is presented.

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Articles
Copyright
Copyright © Materials Research Society 2000

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References

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