THE INFLUENCE OF AN ORDERING TRANSITION ON THE INTERDIFFUSION IN AU-CU ALLOYS

The concentration dependencies of the interdiffusion coefficient, ($) over tilde D(c), have been determined with the aid of electron probe m icroanalysis at 11 temperatures above and below the temperature T-ord of the Al-Ll(2) (Cu3Au) ordering transition. At temperatures T > T-ord there are minima on these dependencies near the Cu3Au composition. Sl ightly below T-ord the ($) over tilde D(c) dependencies are monotonous . At T < (T-ord - 20 K) maxima appear on ($) over tilde D(c) which gro w with decreasing temperature. Such a behaviour is explained by the co ncentration dependence of the thermodynamic factor Phi. Dependencies P hi (c, T) have been calculated within the framework of the tetrahedron approximation of the cluster variation method. The calculated depende ncies are in good agreement with the experimental data.