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

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.

DFG Programme Research Grants