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A differential cluster variation method for analysis of spiniodal decomposition in alloys
A differential cluster variation method (DCVM) is proposed for analysis of
spinoidal decomposition in alloys. In this method, lattice symmetry operations
in the presence of an infinitesimal composition gradient are utilized to deduce
the connection equations for the correlation functions and to reduce the number
of independent variables in the cluster variation analysis.
Application of the method is made to calculate the gradient energy
coefficient in the Cahn-Hilliard free energy function and the fastest growing
wavelength for spinodal decomposition in Al-Li alloys. It is shown that the
gradient coefficient of congruently ordered Al-Li alloys is much larger than
that of the disordered system. In such an alloy system, the calculated fastest
growing wavelength is approximately 10 nm, which is an order of magnitude
larger than the experimentally observed domain size. This may provide a
theoretical explanation why spinodal decomposition after a congruent ordering
is dominated by the antiphase boundaries.Comment: 15 pages, 7 figure
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