Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-23T12:19:24.390Z Has data issue: false hasContentIssue false
  • English
  • Français

Electronic, elastic, and fracture properties of trialuminide alloys: Al3Sc and Al3Ti

Published online by Cambridge University Press:  31 January 2011

C. L. Fu
C. L. Fu
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge., Tennessee 37831–6114
Get access

Abstract

The electronic mechanism behind the brittle fracture of trialuminide alloys is investigated using the full-potential linearized augmented plane-wave (FLAPW) total-energy method within the local density functional approach. To this end, the bulk phase stability, the elastic constants, the anti-phase boundary (APB) energy, the superlattice intrinsic stacking fault (SISF) energy, and the cleavage energy on different crystallographic planes have been determined. A small energy difference (=0.10 eV/unit formula) is found between the DO22 and L12 structures of Al3Ti. In general, the trialuminide alloys have large elastic modulus, small Poisson's ratio, and small shear modulus to bulk modulus ratio. An extremely high APB energy (=670 mJ/m2) on the (111) plane is found for Al3Sc, indicating that the separation between ½(110) partials of a (110)(111) superdislocation is small. Since the total superdislocation has to be nucleated essentially at the same time, a high critical stress factor for dislocation emission at the crack tip is suggested. The high APB energy on the (111) plane is attributed to the directional bonding of Sc(d-electron)-Al(p-electron). The same type of directional bonds is also found for Al3Ti. In addition, moderately high values of SISF energy (=265 mJ/m2) on the (111) plane and APB energy (=450 mJ/m2) on the (100) plane are found for Al3Sc. The brittle fracture of trialuminide alloys is attributed to the higher stacking fault energies and a lower cleavage strength compared to those of a ductile alloy (e.g., Ni3Al). While the (110) surface has the highest surface energy, the cleavage strength (=19 GPa) of Al3Sc is found to be essentially independent of the crystallographic planes. The directional Sc—Al bond becomes even stronger on the (110) surface, which may explain the preferred (110) type cleavage observed by experiment.

Type
Articles
Information
Journal of Materials Research , Volume 5 , Issue 5 , May 1990 , pp. 971 - 979
Copyright
Copyright © Materials Research Society 1990

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

1Yamaguchi, M., Umakoshi, Y., and Yamane, T., Phil. Mag. A 55, 301 (1987).CrossRefGoogle Scholar
2Umakoshi, Y., Yamaguchi, M., Yamane, T., and T. Hirano, Phil. Mag. A 58, 651 (1988).CrossRefGoogle Scholar
3George, E. P., Porter, W. D., Henson, H. M., Oliver, W. C., and Oliver, B. F., J. of Mater. Res. 4 (1), 78 (1989).CrossRefGoogle Scholar
4Turner, C. D., Powers, W. O, and Wert, J. A., Acta Metall. (to be published).Google Scholar
5Huang, S.C., Hall, E.L., and Gigliotti, M.F. X., J. Mater. Res. 3 (1), 1 (1988).CrossRefGoogle Scholar
6Tarnacki, J. and Kim, Y.W., Scripta Metall. 22, 329 (1988).CrossRefGoogle Scholar
7Schneibel, J. H., Becher, P.F., and Horton, J. A., J. Mater. Res. 3 (6), 1272 (1988).CrossRefGoogle Scholar
8Carlsson, A. E. and Meschter, P. J., J. Mater. Res. 4 (5), 1060 (1989).CrossRefGoogle Scholar
9Hong, T., Watson-Yang, T. J., Oguchi, T., and A. J. Freeman (to be published).Google Scholar
10Nicholson, D. M., Stocks, G. M., Temmerman, W. M., Sterne, P., and Pettifor, D. G., in High-Temperature Ordered Intermetallic Alloys III (MRS, 1989), p. 17.Google Scholar
11Rice, James R. and Thomson, Robb, Phil. Mag. 29, 73 (1974).CrossRefGoogle Scholar
12Jokl, M.L., Vitek, V., and McMahon, C.J., Jr., Acta Metall. 28, 1479 (1980).CrossRefGoogle Scholar
13Ohr, S. M., Mater. Sci. and Eng. 72, 1 (1985); and the references therein.CrossRefGoogle Scholar
14Hohenberg, P. and Kohn, W., Phys. Rev. B 136, 864 (1964).CrossRefGoogle Scholar
15Kohn, W. and Sham, L. J., Phys. Rev. A 140, 1133 (1965).CrossRefGoogle Scholar
16Wimmer, E., Krakauer, H., Weinert, M., and Freeman, A. J., Phys. Rev. B 24, 864 (1981); and the references therein.Google Scholar
17Fu, C. L., Weinert, M., and Freeman, A. J. (to be published).Google Scholar
18Fu, C. L. and Yoo, M. H., Phil. Mag. Lett. 58, 199 (1988).Google Scholar
19Fu, C. L. and Yoo, M. H., in High-Temperature Ordered Intermetallic Alloys III (MRS, 1989), p. 81.Google Scholar
20Fu, C. L., Freeman, A. J., Wimmer, E., and Weinert, M., Phys. Rev. Lett. 54, 2261 (1985).CrossRefGoogle Scholar
21Villars, P. and Calvert, L. D., Pearson's Handbook of Crystallographic Data for Intermetallic Phases (American Society for Metals, Metals Park, OH, 1985).Google Scholar
22Hultgren, R., Desai, P. D., Hawkins, D.T., Gleiser, M., and Kelley, K. K., Selected Values of the Thermodynamic Properties of Binary Alloys (American Society for Metals, Metals Park, OH, 1973).Google Scholar
23Simpson, W. A. (unpublished work).Google Scholar
24Pugh, S. F., Phil. Mag. 45, 823 (1954).Google Scholar
25Schneibel, J. H. (to be published).Google Scholar
26George, E. P., Schneibel, J. H., and Horton, J. A. (to be published).Google Scholar
27Vasudevan, Vijay K., Wheeler, Robert, and Fraser, Hamish L., in High Temperature Ordered Intermetallic Alloys III (Proc. Mater. Res. Soc. Symp.), edited by Liu, C.T., Taub, A.I., Stoloff, N.S., and Koch, C. C. (Materials Research Society, Pittsburgh, PA, 1989), Vol. 133, p. 705.Google Scholar
28Chen, S.P., Voter, A.F., and Srolovitz, D. J., J. de Phys. C 5, 157 (1988). J. Mater. Res., Vol. 5, No. 5, May 1990 979Google Scholar