Paper Title:
Atomic Migration as a Mechanism of Superstructure Formation in Intermetallic Compounds
  Abstract

“Order-order” relaxations driven by atomic migration in superstructures proceed in nonsteady- state of a system, which relaxes to the equilibrium atomic configuration. Hence, the corresponding studies are complementary to standard steady-state diffusion investigations. Two time scales operating in “order-order” relaxations in L12-ordered (Ni3Al) and L10-ordered (FePd, FePt) binary intermetallics were experimentally observed. On the other hand, in B2-ordered NiAl – known of a giant vacancy concentration, “order-order” relaxations appeared surprisingly slow. Definite relationships between the activation energies for diffusion ( ) D A E and “order-order” relaxations ( ) O O A E − were revealed: ( ) D A E < ( ) O O A E − in L12-type superstructure; ( ) D A E ³ ( ) O O A E − in L10- and in B2-type superstructures. Corresponding simulation studies elucidated the specific atomistic mechanism of the processes. It has been shown that different time scales active in “order-order” relaxations in L12 and L10-ordered systems follow from specific atomic-jump correlations, which result from non-steady-state conditions and particular superlattice geometries: the availability of easy diffusion channels. A model of “order-order” kinetics in NiAl as controlled by a triple-defect mechanism is proposed.

  Info
Periodical
Defect and Diffusion Forum (Volumes 237-240)
Edited by
M. Danielewski, R. Filipek, R. Kozubski, W. Kucza, P. Zieba, Z. Zurek
Pages
609-620
DOI
10.4028/www.scientific.net/DDF.237-240.609
Citation
R. Kozubski, M. Kozłowski, S. Czekaj, V. Pierron-Bohnes, W. Pfeiler, "Atomic Migration as a Mechanism of Superstructure Formation in Intermetallic Compounds", Defect and Diffusion Forum, Vols. 237-240, pp. 609-620, 2005
Online since
April 2005
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$32.00
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