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γ/γ′: The Key to Superalloy Behavior

Published online by Cambridge University Press:  21 February 2011

A. F. Giamei
Affiliation:
United Technologies Research Center, Silver Lane, E. Hartford, CT 06108
D. D. Pearson
Affiliation:
United Technologies Research Center, Silver Lane, E. Hartford, CT 06108
D. L. Anton
Affiliation:
United Technologies Research Center, Silver Lane, E. Hartford, CT 06108
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Abstract

Gamma prime (Ni3Al), with its unusual temperature dependence of yield strength, is the strengthening phase in Ni-base superalloys. Many facets of γ/γ′ coherent precipitation strengthening have been well studied: coarsening kinetics, volume fraction vs. strength, yield strength vs. temperature, dislocation dynamics, etc.

This contribution deals with several important aspects of two phase behavior in coherent systems (for high temperature application) which are either relatively new or have received inadequate attention. The most desirable γ/γ′ misfit, in sense and magnitude, is dependent on the temperature of application. It must be recognized that the sense and size of misfit are not only a function of alloying, but temperature as well. Sufficient data are presented for various alloying additions to γ and γ′ to allow one to roughly compute the misfit at room temperature or 1000C. The evolution and significance of the ′′ morphology are discussed. Stability of particle size and shape are related to misfit, temperature and stress. It is demonstrated that for high temperature creep resistance, a fine rafted structure is the most desirable. Finally, some data are presented which demonstrate the dependence of γ′ strength on stoichiometry as well-as temperature.

A portion of this work was sponsored by AFOSR, with A. Rosenstein as contract monitor.

Type
Research Article
Copyright
Copyright © Materials Research Society 1985

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References

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