Conclusions
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1.
Formation of σ-phase in high-temperature alloy KhN65VMTYu is governed to a considerable degree by its chemical composition.
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2.
Calculation of the chemical composition by the Phacomp method makes it possible to predict quite accurately the probability of σ-phase formation from the number of electron vacancies (Nv). For alloy KhN65VMTYu without iron and with 1–2% Fe, formation of σ-phase occurs with Nv≥2.30 and 2.20 respectively.
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3.
The σ-phase in alloy KhN65VMTYu has an acicular structure. No differences in σ-phase morphology were detected in cast, extruded, and forged metal.
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4.
There is most intense sigmatization in cast metal having a high degree of inhomogeneity. As structural homogeneity increases for the metal (cast → extruded → forget) the intensity of σ-phase formation decreases.
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Literature cited
L. R. Woodyatt and C. T. Sims, and H. J. Beattie, Trans AIME,236, 519–534 (1966).
C. T. Sims and W. C. Hagel (eds.), The Superalloys, Wiley (1972).
V. S. Kovalenko, Metallographic Reagents (Handbook) [in Russian], 3rd ed., Metallurgiya, Moscow (1981).
Additional information
Elektrostal' Factory. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 38–40, April, 1987.
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Bulavina, L.S., Mel'kumov, I.N. Formation of sigma-phase in alloy KhN65VMTYu. Met Sci Heat Treat 29, 291–293 (1987). https://doi.org/10.1007/BF00769428
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DOI: https://doi.org/10.1007/BF00769428