Monte Carlo simulations, EDX-TEM and other techniques were used to reveal the relationship between diffusion composition paths and ordered structures in Cu3Au/Pd diffusion couples which were annealed at 573K. A Cu3Au layer which included Pd, a CuAu layer which included Pd, a CuPd layer and a Pd layer which included Cu existed in that order between Cu3Au and Pd. The Au concentration increased via up-hill diffusion from the Cu3Au layer to the CuAu layer, whereas Au hardly diffused from CuAu into the CuPd layer. The diffusion composition path deviated from the Cu3Au-Pd line, in the Cu-Au-Pd Gibbs triangle, and followed an S-shaped curve through the CuAu and CuPd existence regions. The atomic configurations in the L10-type phase were highly ordered and were consistent with the equilibrium state. In Monte Carlo simulations, diffusion couples were produced virtually. The diffusion composition paths, Fourier power spectra and Warren-Cowley parameters were thereby estimated. Strong ordering interactions of the Cu-Au pair and Cu-Pd pair in the first-nearest neighbor, and the high activation barrier to the migration of Au, reproduced the experimental results.

Ordered Phase Formation and Diffusion Composition Path in Cu3Au/Pd Couple. T.Morimura, M.Hasaka, A.Nagata: Journal of Alloys and Compounds, 2002, 347[1-2], 141-8