Hostname: page-component-78c5997874-t5tsf Total loading time: 0 Render date: 2024-11-19T21:58:33.335Z Has data issue: false hasContentIssue false
  • English
  • Français

Structural Unit Models for High Angle Symmetrical Tilt Boundaries in Ordered Compounds with the Ll2 Structure

Published online by Cambridge University Press:  21 February 2011

D. Farkas
D. Farkas*
Affiliation:
Department of Materials Engineering, VPI & SU, Blacksburg, VA 24061.
Get access

Abstract

Hard sphere models were used to determine densest configurations in symmetrical [100] and [110] tilt boundaries in compounds with the Ll2 structure. The minimum allowed interatomic distances used in these models were estimated from interatomic potentials and the structures of the intermetallic phases in the binary system. The structural unit model is used to analyze the possible ground states for ordering.

Two different cases were analyzed corresponding to compounds with “soft” potentials (i.e. Cu3 Au) and “hard” potentials (i.e. Ni3Al). For the Cu3Au type the grain boundary structures obtained were similar to those reported by other investigators for pure fcc metals. Several boundaries were found to be a “two phase” structure, differing in composition and ordering state. This leads to a certain degree of clustering in the boundaries. The contribution of clustering to the grain boundary energy is calculated in a point approximation based on the first coordination shell.

For compounds of the Ni3Al type the structures that are densest were found to be generally diffetent from the low energy configurations of boundaries in, pure fcc metals and Cu3 Au. These configurations preserve order, but are much less dense. The possibility of grain boundary “phases” that are not present in other fcc materials may constitute an explanation for the extreme GB weakness observed in Ni3Al and other Ll2 compounds with high ordering energy.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 39: Symposium G – High-Temperature Ordered Intermetallic Alloys I , 1984 , 133
Copyright
Copyright © Materials Research Society 1985

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

REFERENCES

1. Wolf, D., Acta Met. 32, 245 (1984).Google Scholar
2. Wolf, D., Acta Met. 5, 735 (1984)Google Scholar
3. Frost, H. J. and Spaepen, F., J. Phys. (Paris), C6, 74 (1982).Google Scholar
4. Shao, J. and Machlin, E. S., J. Phys. Chem. Solids, 44, 289 (1983).Google Scholar
5. Smith, D. A., Vitek, V. and Pond, R. C., Acta Met. 25, 475 (1977).CrossRefGoogle Scholar
6. Vitek, V., Sutton, A. P., Smith, D. A. and Pond, R. C., in “Grain Boundary Structure and Kinetics”, ASM Conference, 115 (1980).Google Scholar
7. Ellner, M., Kattner, U. and Predel, B., Journal of the Less – Common Metals, 87, 305 (1982)CrossRefGoogle Scholar
8. Enderby, J. E. and Howells, W. S., in “Interatomic Potentials and the Simulation of Lattice Defects”, Gehlen, P. C., Beeler, J. R. Jr. and Jaffe, R. I., 217 (1971).Google Scholar
9. Sutton, A. P. and Vitek, V., Phil. Trans. R. Lond. A., 309, 1 (1983)Google Scholar
10. Hashimoto, M., Ishida, Y., Yamamoto, R. and Doyama, M., Acta Met. 29, 617 (1981).Google Scholar
11. Hillert, M., in “Lectures on the Theories of Phase Transformations”, Hubert Aaronson, 1 (1975).Google Scholar
12. Takasugi, T. and Izumi, O., Acta Met. 31, 187 (1983).Google Scholar