Kinetics of surface segregation in alloys
The kinetics of surface segregation in ordering alloys are studied with the help of a multilayer model in slabs of different thicknesses. The time evolution of the concentrations of atomic layers perpendicular to the (100) planes of an AB-type BCC ordering alloy (CoFe) are calculated. As a result of...
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Published in | Surface science Vol. 290; no. 3; pp. 345 - 361 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Lausanne
Elsevier B.V
20.06.1993
Amsterdam Elsevier Science New York, NY |
Subjects | |
Online Access | Get full text |
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Summary: | The kinetics of surface segregation in ordering alloys are studied with the help of a multilayer model in slabs of different thicknesses. The time evolution of the concentrations of atomic layers perpendicular to the (100) planes of an AB-type BCC ordering alloy (CoFe) are calculated. As a result of the competition between the surface segregation of A atoms and ordering in the bulk, a metastable configuration with two anti-phase boundaries (APB) inside the slab, with odd numbers of layers, was obtained if we started from an ordered initial state with B atoms on the free surfaces (B-termination). The effect of the temperature was also investigated for a slab with 41 layers and from the calculation of the free energies of the metastable and stable states it was shown that the metastable state can exist below
T
1 = 0.95
T
c
, where
T
c
is the critical temperature of the order-disorder transition in bulk. It was obtained that
T
1 decreases with decreasing thickness of the slab, while the difference of free energies of the metastable and stable states slightly increases. The effect of the slab thickness is a typical size effect: the time necessary to reach the steady state decreases with decreasing number of layers. |
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ISSN: | 0039-6028 1879-2758 |
DOI: | 10.1016/0039-6028(93)90718-Y |