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B2 and B32 ordering transformations of equiatomic bcc alloys with ballistic and thermal atom movements

Published online by Cambridge University Press:  03 March 2011

L.B. Hong ,
L. Anthony  and
B. Fultz
L.B. Hong
Affiliation:
Division of Engineering and Applied Science, California Institute of Technology, 138-78, Pasadena, California 91125
L. Anthony
Affiliation:
Division of Engineering and Applied Science, California Institute of Technology, 138-78, Pasadena, California 91125
B. Fultz
Affiliation:
Division of Engineering and Applied Science, California Institute of Technology, 138-78, Pasadena, California 91125
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Abstract

We used Monte Carlo simulations to study the kinetics and steady states of B2 and B32 ordering in an equiatomic binary bcc alloy having both thermal and ballistic atom movements. Atom movements occurred by a vacancy mechanism, where first-neighbor atoms exchanged sites with the vacancy. In the thermodynamic case, where this jump probability was set by a Boltzmann factor alone, we found the formation of large amounts of transient B2 (B32) during disorder → B32 (B2) order transformations. The transient order developed in distinct regions, but vanished completely when equilibrium was attained. Ballistic jumps were included as random interchanges of the vacancy with one of its neighboring atoms. Even with small fractions of ballistic jumps, there were large changes in the transient states and steady states of order in the alloy. A kinetic explanation is proposed, in which the presence of ballistic jumps contributed a greater amount of internal energy to the B2 phase than to the B32 phase when there was a strong asymmetry in the second-nearest neighbor pair potentials (VAA2 ↗ VBB2). A two-phase coexistence in the steady state was explained by fluctuations in the local density of ballistic jumps.

Type
Articles
Information
Journal of Materials Research , Volume 10 , Issue 1 , January 1995 , pp. 126 - 132
Copyright
Copyright © Materials Research Society 1995

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References

REFERENCES

1Sato, H., Gschwend, K., and Kikuchi, R., J. Phys. (Paris) C7, 357 (1977).Google Scholar
2Gschwend, K., Sato, H., and Kikuchi, R., J. Chem. Phys. 69, 5006 (1978).CrossRefGoogle Scholar
3Mohri, T., Acta Metall. Mater. 38, 2455 (1990).CrossRefGoogle Scholar
4Mohri, T., Sugawara, Y., Watanabe, K., and Sanchez, J. M., Mater. Trans. JIM 33, 558 (1992).CrossRefGoogle Scholar
5Fultz, B., Acta Metall. 37, 823 (1989).CrossRefGoogle Scholar
6Anthony, L. and Fultz, B., J. Mater. Res. 4, 1132 (1989).CrossRefGoogle Scholar
7Fultz, B., J. Mater. Res. 5, 1419 (1990).CrossRefGoogle Scholar
8Fultz, B., J. Mater. Res. 7, 946 (1992).CrossRefGoogle Scholar
9Martin, G., Phys. Rev. B 30, 1424 (1984).CrossRefGoogle Scholar
10Bellon, P. and Martin, G., Phys. Rev. B 38, 2570 (1988).CrossRefGoogle Scholar
11Bellon, P. and Martin, G., Phys. Rev. B 39, 2403 (1989).CrossRefGoogle Scholar
12Martin, G., Phys. Rev. B 41, 2279 (1990).CrossRefGoogle Scholar
13Haider, F., Bellon, P., and Martin, G., Phys. Rev. B 42, 8274 (1990).CrossRefGoogle Scholar
14Salomons, E., Bellon, P., Soisson, F., and Martin, G., Phys. Rev. B 45, 4582 (1992).CrossRefGoogle Scholar
15Martin, G. and Bellon, P., MRS Bull. (December 1991).Google Scholar
16Bellon, P., Phys. Rev. B 45, 7517 (1992).CrossRefGoogle Scholar
17Bellon, P., Soisson, F., and Martin, G., in Diffusion in Ordered Alloys, edited by Fultz, B., Cahn, R. W., and Gupta, D. (TMS, Chicago, 1992).Google Scholar
18Haider, F., in Ordering and Disordering in Alloys, edited by Yavari, A. R. (Elsevier, Amsterdam, 1992).Google Scholar
19Richards, M. J. and Cahn, J. W., Acta Metall. 19, 1263 (1971).CrossRefGoogle Scholar
20Allen, S. M. and Cahn, J. W., Acta Metall. 20, 423 (1972).CrossRefGoogle Scholar
21Anthony, L. and Fultz, B., J. Mater. Res. 9, 348 (1994).CrossRefGoogle Scholar
22Anthony, L., Ph.D. thesis, California Institute of Technology (1993).Google Scholar
23Fultz, B., J. Chem. Phys. 87, 1604 (1987).CrossRefGoogle Scholar
24Ouyang, H. and Fultz, B., J. Appl. Phys. 66, 4752 (1989).CrossRefGoogle Scholar
25Warren, B. E., X-Ray Diffraction (Addison-Wesley, Reading, MA, 1969), Chap. 12.Google Scholar
26Ducastelle, F., Order and Phase Stability in Alloys (North-Holland, Amsterdam, 1991), Sec. 5.1.2.Google Scholar
27Fultz, B., J. Chem. Phys. 88, 3227 (1988).CrossRefGoogle Scholar