Interdiffusion of Al-13.6Si and the Fe-Cr-Al alloy was studied by means of electron microprobe analysis, scanning electron microscopy, optical microscopy and X-ray analysis. The formation of intermetallic phases during interdiffusion was observed only for Al contents above 30at%. The effects of deviations, from the Boltzmann-Matano and thin-film geometry, upon the resulting diffusivities were assessed numerically. The results were of general interest for diffusion measurements which involved samples of a certain geometry. The tracer diffusivities of Al and Si in Crofer 18 were found to be quite similar and were close to that of Fe. They were somewhat smaller than those for diffusion in pure Fe. The intrinsic diffusion coefficient of Al exhibited a small increase, with increasing Al concentrations up to 20at%. This was due mainly to a corresponding increase in the thermodynamic factor. Interdiffusion at high Al concentrations was much faster and was therefore not rate-limiting.

Aluminium and Silicon Diffusion in Fe-Cr-Al Alloys. A.Heesemann, E.Schmidtke, F.Faupel, A.Kolb-Telieps, J.Klower: Scripta Materialia, 1999, 40[5], 517-22