Monte Carlo simulation and other techniques were used to reveal the relationship between diffusion composition path and ordered structures in Cu3Au/Pd diffusion couples annealed at 573K. A Cu3Au layer including Pd, a CuAu layer including Pd, a CuPd layer and a Pd layer including Cu existed in sequence between Cu3Au and Pd. The Au concentration increased, via up-hill diffusion, from the Cu3Au layer to the CuAu layer whereas Au scarcely diffused from the CuAu into the CuPd layer. The diffusion composition path deviated from the Cu3Au-Pd line in the Cu-Au-Pd Gibbs triangle and exhibited 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 the Monte Carlo simulations, diffusion couples were virtually produced. The diffusion composition paths, Fourier power spectra and Warren-Cowley parameters were estimated. Strong ordering interactions of the Cu-Au pair and Cu-Pd pair in the first-nearest neighbor range, and a high activation barrier for 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