By using the multiple-markers method, the intrinsic Au and Fe diffusion coefficients in Au-Fe couples were determined (figure 9). It was found that the ratio of DAu to DFe, in Au-()Fe couples at 1133K, was equal to 1.06 at the Kirkendall interface (27at%Fe), and increased gradually, with increasing Fe content, up to 1.60 near to the phase boundary (50at%Fe). This ratio, in the case of Au-()Fe couples at 1263K, was equal to 1.02, and was almost constant over the studied concentration range. The latter behavior was attributed to the fact that there was an insufficient vacancy flux from the -Fe phase and towards the Au-rich phase; because of the very low diffusivity in the -Fe phase of the Au-()Fe couple. It was concluded that this was also the main reason for the retardation of interdiffusion in Au-()Fe couples as compared with that in Au-()Fe couples.

Y.Iijima, K.Funayama, T.Kosugi, K.Fukamichi: Philosophical Magazine Letters, 1996, 74[6], 423-8