Diffusion in Metals, Intermetallics, Silicides, Quasicrystals and Metallic Glasses
Effect of alloying on iron diffusion in Fe3Al intermetallic compounds
Diffusion of iron and several foreign elements in Fe3Al alloys was already extensively studied in
the reasearch group of Prof. Mehrer. Special alloying of iron aluminides is used to develop them for
advanced technological applications. The knowledge of the diffusion characteristics and the point defect
behaviour are of great importance for the research and design of industrial materials. We have investigated the
effect of temperature and alloying on Fe diffusion in Fe3Al-based alloys using the
radiotracer technique and Fe-59 radioisotope. The Fe-26Al-(2&4)Ti and Fe-26Al-0.3Nb alloys were
examined. A minor influence of the addition of Ti and Nb on the bulk mobility of iron and the total concentration
of vacancies is deduced from the radiotracer diffusion study. However, the alloying causes a strong returdation
effect on Fe grain boundary diffusion, which is related to a pronounced grain boundary segregation of Ti and
especially Nb atoms. These measurements were combined with the investigation of the
mechanical spectroscopy (internal friction) and the positron annihilation spectroscopy. The results were also
applied to interpret anelastic relaxation effects caused by C atoms and vacancies in
Fe3Al-based alloys with and without strong carbide forming elements (Ti and Nb). The change in
the content of interstitially dissolved C was shown to be the main reason for the observed changes of the peaks
in the internal friction spectra. The effect of heat treatments on thermal vacancy concentration was carefully
evaluated by the positron annihilation spectroscopy.
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