The concentration dependence of the interdiffusion coefficient was determined, by means of electron probe microanalysis, at temperatures which were above and below the Cu3Au ordering transition. It was found that, at temperatures above the ordering transition, minima appeared in the concentration dependence when close to Cu3Au. At temperatures which were slightly below the ordering transition, the concentration dependences were monotonic. At more than 20K below the transition, maxima appeared in the concentration dependence, and increased in magnitude with decreasing temperature. These results were explained in terms of a concentration dependence of the thermodynamic factor. The temperature and concentration dependences of the latter were calculated within the framework of the tetrahedron approximation of the cluster variation method, and the agreement with experimental data was found to be good.

B.Straumal, E.Rabkin, W.Gust, B.Predel: Acta Metallurgica et Materialia, 1995, 43[5], 1817-23