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Creep Deformation of Ta Modified Gamma Prime Single Crystals

Published online by Cambridge University Press:  28 February 2011

D.L. Anton
Affiliation:
United Technologies Research Center, East Hartford, CT 06108
D.D. Pearson
Affiliation:
United Technologies Research Center, East Hartford, CT 06108
D.B. Snow
Affiliation:
United Technologies Research Center, East Hartford, CT 06108
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Abstract

The role of substitutional element alloying of single phase γ' has become of primary interest to alloy designers who would like to exploit its low density and excellent oxidation resistance. Current γ' alloys have not shown sufficient strength to be useful in a creep limited environment. In order to maximize the potential of single phase γ' alloys and to more fully understand the creep strengthening mechanisms in two phase Ni-base superalloys, it has become necessary to clarify the role of Al-substitution elements. Ta is a potent strengthening element in γ' as well as imparting beneficial surface stability to superalloys; its effect on the creep properties of Ni3Al is the subject of this paper. The 1300°C isotherm of the Ni-Al-Ta system was determined in order to establish the γ' single phase field. Comrpositions were fabricated having chemistries which systematically varied both the Al:Ta ratio at Ni=75% and Ni:(AI+Ta) ratio at Ta=6%. Creep tests were conducted on <001> oriented single crystals at 760, 871 and 982°C. Electron microscopy was used to characterize the nature of slip deformation, confirm phase purity and to determine the existence of tetragonal distortions in these crystals. In this manner the strengthening due to Ta was examined in the absence of grain boundary effects. These γ' mono—crystals did not display classical creep response. Incubation creep was observed in all of the specimens tested. Surprisingly, the maximum incubation time was found to occur in the high ratio Ni:(Al+Ta) compounds, where less than 0.5% creep strain was obtained after 200 hours at stress. After incubation, either tertiary creep leading to failure, or apparently classic primary, secondary and tertiary creep ensued. In addition extremely long elongations, to 85%, were measured.

Type
Research Article
Copyright
Copyright © Materials Research Society 1987

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References

REFERENCES

1. Giamei, A.F., Pearson, D.D. and Anton, D.L., High Temperature Ordered Intermetallic Ally, Koch, C.C., Liu, C.T. and Stoloff, N.S. eds., Materials Research Society, Pittsburgh, PA, 1985, p 293308.Google Scholar
2. Liu, C.T. and White, C.L., ibid, p 365380.Google Scholar
3. Inoue, A., Tomioka, H. and Masumoto, T., J. Mat. Sci. Letters, 1, 377380, (1982).CrossRefGoogle Scholar
4. Churwick, R., “Strengthening Mechanisms in Nickel-Base Superalloys”, Ph.D. Dissertation, University of Minnesota, 1972.Google Scholar
5. Kear, B.H. and Pope, D.D., 1984 ASM Conference on Refractory Aloying ASM, Metals Park, Ohio, 1984, p 135151.Google Scholar
6. High-Temperature Ordered Intermetallic Alloys, Koch, C., Liu, C. and Stoloff, N. eds., Materials Research Society, Pittsburgh, PA, 1985.Google Scholar
7. Schneibel, J.H., Petersen, G.F. and Liu, C.T., J. Mater. Res., 1, 6872, (1986).Google Scholar
8. Thornton, P. H., Davies, R. G., and Johnston, T. L., Metall. Trans., 1, 207218, (1970).Google Scholar
9. Porter, A. J., Shaw, M. P., Ecob, P. C. and Ralph, B., Phil. Mag. A, 44, 11351148, (1981).Google Scholar
10. Fraser, H. L., in Microbeam Analysis = 1982, Heinrich, K. F. J., ed., San Francisco Press, San Francisco, 1982, p. 54.Google Scholar
11. Kaufman, M. J., Pearson, D. D. and Fraser, H. L., Phil. MAg. A 54, 7992, (1986).CrossRefGoogle Scholar
12. Rawlings, R.D. and Staton-Bevan, A.E., J. Mat. Sci., 10, 505514, (1975).Google Scholar
13. Willemin, P., Dugue, O., Durand-Charre, M. and Davidson, J.H., Mat. Sci. and Tech., 2, 344348, (1986).CrossRefGoogle Scholar
14. Johnston, W.G., J. Appl. Phys., 33, 27162730, (1962).Google Scholar