Hostname: page-component-77c89778f8-7drxs Total loading time: 0 Render date: 2024-07-20T17:45:20.876Z Has data issue: false hasContentIssue false
  • English
  • Français

A microstructural study of a Ni2AlTi–Ni(Al, Ti)–Ni3(Al, Ti) three-phase alloy

Published online by Cambridge University Press:  31 January 2011

R. Yang ,
J.A. Leake  and
R.W. Cahn
R. Yang
Affiliation:
University of Cambridge, Department of Materials Science and Metallurgy, Pembroke Street, Cambridge CB2 3QZ, England
J.A. Leake
Affiliation:
University of Cambridge, Department of Materials Science and Metallurgy, Pembroke Street, Cambridge CB2 3QZ, England
R.W. Cahn*
Affiliation:
University of Cambridge, Department of Materials Science and Metallurgy, Pembroke Street, Cambridge CB2 3QZ, England
*
a)Address correspondence to this author.
Get access

Abstract

Early studies showed that the two-phase ordered alloy of semi-coherent β–Ni2AlTi (L21) and β–Ni(Al, Ti) (B2) exhibits excellent elevated-temperature creep strength, and the precipitation of the “rod-like” γ'–Ni3(Al, Ti) (L12) from either the β or the β' phase improves the room-temperature ductility of the phases concerned. In the present investigation an attempt is being made to combine the above microstructural features in β'–β–γ' three-phase alloys and for this purpose the composition Ni63Al22Ti15, near the β'–γ' edge of the three-phase region in the recently estimated Ni–Al–Ti isotherm at 900 °C, has been selected for detailed study. The expected precipitation of both the β and the γ' phases occurs in the dendritically solidified β' phase after a 1100 °C/3 h homogenization and a 900 °C/115 h anneal, although the original interdendritic γ' phase remains. The morphology of the two types of precipitates and their orientation relationships with the β' parent phase have been examined using transmission electron microscopy and diffraction, and the experimentally obtained data compared with those predicted by Khachaturyan's elastic strain energy theory. The β precipitates are nearly cuboidal in shape and are bounded by interface dislocations of aβ〈100〉 edge type. For the β precipitates, both morphology and orientation relation agree with those predicted by the theory. The γ' precipitates were found to obey the Nishiyama–Wassermann orientation relationship with the parent phase. These precipitates are about 0.5 μm thick and elongated along their 〈211〉 directions, and in all cases consist of two twin-related variants, giving a sword-like morphology. The {11} twin planes, parallel to the {10} of the parent phase, have been identified as the habits of the precipitation. The theory, however, predicts a habit of {0.732, 0, 0.681}γ' type and a Baker–Nutting orientation relationship. This discrepancy has been attributed to the inapplicability of some assumptions made in the theory: equal elastic moduli between parent and product phases and a tetragonal transformation strain based on Bain's model of the bcc → fcc transformation. The presence of diffuse streaks in the diffraction patterns of the parent phase, which can be correlated with the 〈110〉〈10〉 shear waves, suggests high elastic anisotropy and lends credit to Zener's model. Crystallographic consideration shows that this model is feasible for the L21 → L12 transformation and explains the observed morphological features of the γ' precipitates. Some earlier studies are also discussed.

Type
Articles
Information
Journal of Materials Research , Volume 6 , Issue 2 , February 1991 , pp. 343 - 354
Copyright
Copyright © Materials Research Society 1991

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1Strutt, P. R., Polvani, R. S., and Ingram, J. C., Metall. Trans. A 7A, 23 (1976).CrossRefGoogle Scholar
2Polvani, R. S., Tzeng, W-S., and Strutt, P. R., Metall. Trans. A 7A, 33 (1976).CrossRefGoogle Scholar
3Whittenberger, J. D., Viswanadham, R. K., Mannan, S. K., and Kumar, K. S., J. Mater. Res. 4, 1164 (1989).CrossRefGoogle Scholar
4Cahn, R. W., Metals Mater. & Processes 1, 1 (1989).Google Scholar
5Khadkikar, P. S., Vedula, K., and Shabel, B. S., in High-Temperature Ordered Intermetallic Alloys, II, edited by Stoloff, N. S., Koch, C. C., Liu, C. T., and Izumi, O. (Mater. Res. Soc. Symp. Proc. 81, Pittsburgh, PA, 1987), p. 157.Google Scholar
6Russell, K. C. and Edington, J. W., Metal. Sci. J. 6, 20 (1972).CrossRefGoogle Scholar
7Moskovic, R., J. Mater. Sci. 13, 1901 (1978).CrossRefGoogle Scholar
8Schuon, S. R., lecture presented at Symposium on Intermetallics, TMS-AIME, Phoenix, AZ, January 1988.Google Scholar
9Bollmann, W., Phys. Status Solidi (a) 21, 543 (1974).CrossRefGoogle Scholar
10Ecob, R. C. and Ralph, B., Acta Metall. 29, 1037 (1981).CrossRefGoogle Scholar
11Rigsbee, J. M. and Aaronson, H. I., Acta Metall. 27, 351 (1979).CrossRefGoogle Scholar
12Smith, D. A., Knowles, K. M., Aaronson, H. I., and Clark, W. A. T., in Solid-Solid Phase Transformation, Proc. Int. Conf., edited by Aaronson, H. I., Laughlin, D. E., Sekerka, R. E., and Wayman, C. M. (Pittsburgh, PA, 1981), p. 587.Google Scholar
13Wen, S. H., Kostlan, E., Hong, M., Khachaturyan, A. G., and Morris, J. W., Jr., Acta Metall. 29, 1247 (1981).CrossRefGoogle Scholar
14Khachaturyan, A. G., Theory of Structural Transformation in Solids (John Wiley & Sons, New York, 1983), Chaps. 7–12.Google Scholar
15Wayman, C. M., in High-Temperature Ordered Intermetallic Alloys, edited by Koch, C. C., Liu, C. T., and Stoloff, N. S. (Mater. Res. Soc. Symp. Proc. 39, Pittsburgh, PA, 1985), p. 76.Google Scholar
16Delaey, L., Perkins, A. J., and Massalski, T. B., J. Mater. Sci. 7, 1197 (1972).CrossRefGoogle Scholar
17Kelly, M. J. and Stobbs, W. M., Scripta Metall. 13, 919 (1979).CrossRefGoogle Scholar
18Zener, C., Phys. Rev. 71, 846 (1947).CrossRefGoogle Scholar
19Zener, C., Elasticity and Anelasticity of Metals (Univ. of Chicago Press, Chicago, IL, 1948), Chap. 4.Google Scholar
20Nash, P., Vejins, V., and Liang, W. W., Bull. Alloy Phase Diag. 3, 369 (1982).CrossRefGoogle Scholar
21Nash, P. and Liang, W. W., Metall. Trans. A 16A, 319 (1985).CrossRefGoogle Scholar
22Saunders, N., private communication (1989); to be published.Google Scholar
23Enami, K., Hasunuma, J., Nagasawa, A., and Nenno, S., Scripta Metall. 10, 879 (1976).CrossRefGoogle Scholar
24Lasalmonie, A., Scripta Metall. 11, 527 (1977).CrossRefGoogle Scholar
25Reynaud, F., Scripta Metall. 11, 765 (1977).CrossRefGoogle Scholar
26Enami, K., Nagasawa, A., and Nenno, S., Scripta Metall. 12, 223 (1978).CrossRefGoogle Scholar
27Portier, R., Gratias, D., and Stobbs, W. M., in Proc. ICOMAT 79 (MIT Press, Cambridge, MA, 1979), p. 541.Google Scholar
28Robertson, I. M. and Wayman, C. M., Philos. Mag. A 48, 421, 443, 629 (1983).CrossRefGoogle Scholar
29Tanner, L. E., Schryvers, D., and Shapiro, S. M., Mater. Sci. Eng. A127, 205 (1990).CrossRefGoogle Scholar
30Robertson, I. M. and Wayman, C. M., Metallography 17, 43 (1984).CrossRefGoogle Scholar
31Chakravorty, S. and Wayman, C. M., Metall. Trans. A 7A, 555, 569 (1976).CrossRefGoogle Scholar
32Nishiyama, Z., Sci. Rep. Tohoku Univ. 23, 647 (1934).Google Scholar
33Wassermann, G., Arch. Eisenhiittenwes. 16, 647 (1933).Google Scholar
34Boettinger, W. J., Bendersky, L. A., Biancaniello, F. S., and Cahn, J. W., Mater. Sci. Eng. 98, 273 (1988).CrossRefGoogle Scholar
35Bendersky, L. A., Voorhees, P. W., Boettinger, W. J., and Johnson, W. C., Scripta Metall. 22, 1029 (1988).CrossRefGoogle Scholar
36Field, R. D., Darolia, R., and Lahrman, D. F., Scripta Metall. 23, 1469 (1989).CrossRefGoogle Scholar
37Wasilewski, R. J., Trans. TMS-AIME 236, 455 (1966).Google Scholar
38Ardell, A. and Nicholson, R. B., Acta Metall. 14, 1295 (1966).CrossRefGoogle Scholar
39Yoo, M. H., in High-Temperature Ordered Intermetallic Alloys, II, edited by Stoloff, N. S., Koch, C. C., Liu, C. T., and Izumi, O. (Mater. Res. Soc. Symp. Proc. 81, Pittsburgh, PA, 1987), p. 207.Google Scholar
40Villars, P. and Calvert, L. D., Pearson's Handbook of Crystallo-graphic Data for Intermetallic Phases (ASM, Metals Park, OH, 1985), Vol. 2, pp. 1038, 1043.Google Scholar
41Rusovic, N. and Warlimont, H., Phys. Status Solidi 44, 609 (1977).CrossRefGoogle Scholar
42Georgopoulos, P. and Cohen, J. B., Scripta Metall. 11, 147 (1977).CrossRefGoogle Scholar
43Krachler, R., Ipser, H., and Komarek, K. L., J. Phys. Chem. Solids 50, 1127 (1989).CrossRefGoogle Scholar