Verbesserung des Meß-und Auswerteverfahrens zur Bestimmung der gemeinsamen und partiellen Diffusionskoeffizienten am Beispiel von Kupfer-Gold-Legierungen/An Improved Method for Measuring and Analysing Chemical and Intrinsic Diffusion Coefficients Applied to Copper-Gold Alloys

A method is described which enables the determination of the chemical diffusion coefficients D̃ in a binary system as well as the intrinsic diffusion coefficients of both components with sufficient accuracy. The difference in concentration between the diffusion couples should not exceed 5 at%. Numerous diffusion profiles at different annealing times are taken by electron microprobe analysis from each specimen before calculating D̃ according to a method proposed by Sauer and Freise Combining the results for different pairs of specimens with overlapping concentration range mean values of D̃ are obtained in the total concentration range unter consideration. An analytical expression for D̃ is given, which is used to determine the diffusion profile for a special diffusion couple according to the method of Wagner4 . By this one obtains the total diffusion profile including the flat ends which cannot be accurately determinated by electron microprobe analysis. The determination of the intrinsic diffusion coefficients according to van Loo5 is based on these calculated profiles with additional knowledge of the position of the welding interface. This method has been applied to diffusion measurements in Cu-Au alloys. The following relation for D̃ has been found in the concentration range between 0 and 32 at% Au at 911 °C D̃(N)Cu Au911 °C =3,71·10-10 + 5.04·10-9 N+1.76·10-10 N2 + 1.01 -10-11 N3 [cm2 sec-1 ]. N = mole fraction of Au.