Temperature Gradient in Multi-Diffusion Couples for Experimental Determination of Thermodynamic Response from Systems with Numerous Components

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Diffusion couples are used since several decades to determine thermodynamic data and thereby to construct phase diagrams. By using multi-diffusion couples 4 segments plus enclosure material can be analyzed. This allows to analyze up to 9 binary and 6 tertiary systems. The new approach in this proposal is to incorporates a temperature gradient. Thereby we obtain different isothermal sections in different heights of the sample. This leads to a very effective determination of diffusion processes in general and to diffusion controlled phase changes in systems with several components over a wide compositional and temperature range.Target material at the beginning are chromium based alloys with Cr-Si-X-Y composition. Several interesting options exist for the additional elements X and Y. The element Ni, so far used as enclosure material drops out because of its low melting temperature. Therefore, a new enclosure material has to be determined. The next step will be to adjust an already existnt cold-wall vacuum furnace for heat treating the diffusion multiples in a temperature gradient. Finally, the diffusion multiple will be cut in different heights (corresponding to different annealing temperatures) and analyzed. This allows a very efficient way to determine isothermal cuts of phase diagrams and diffusion mechanisms in systems with several components.