Diffusion in intermetallic phases of the system Al-Fe

Self-diffusion of Fe and solute diffusion of In and Zn was studied as a function of temperature in three alloys of the Fe-Al system with the nominal compositions Fe₃Al, Fe₂Al and FeAl employing the radiotracer technique. Most of the measurements were performed in the B2-structure regions of the phase diagram, some in the A2-region, and few in the D0₃-structure region. Diffusion of In and Zn is slightly faster than Fe diffusion in all three alloys. For Fe₃Al the ordering transitions between A2 and B2 and between B2 and D0₃ lead to slightly higher activation enthalpies in the phases with the higher degree of order. Within the B2 phase-field increasing Al content also leads to slight increases of activation enthalpies. This increase is correlated with an increase in long-range order. Possible diffusion mechanisms are briefly discussed in the light of experimental information on the defect structure in Fe-Al and in context with ab-initio calculations of defect properties.

Interdiffusion studies were performed in the Fe-Al system using diffusion couples. Concentration depth profiles were measured by electron microprobe analysis. Interdiffusion coefficients deduced thereof show linear Arrhenius behaviour over the investigated temperature range. From the interdiffusion coefficients Al diffusion coefficients were deduced via Darken-Manning's equation using Fe tracer diffusion coefficients and theoretical results for the thermodynamic factor. Al diffusion is in the same range as Fe diffusion.

Drittmittelgeber:

Deutsche Forschungsgemeinschaft, German-Israeli Foundation for Scientific Research and Development

Beteiligte Wissenschaftler:

Prof. Dr. S. Dorfman (Technion Haifa, Israel), Dr. M. Eggersmann (bis März 1999), Dr. K. Freitag (Universität Bonn), Prof. Dr. D. Fuks (Ben Gurion University, Beer Sheva, Israel), Dipl.-Phys. R. Galler, Prof. Dr. G. Inden (MPI für Eisenforschung, Düsseldorf), Dipl.-Phys. Chr. Khoukaz (bis Mai 2000), Prof. Dr. V. Liubich (Ben Gurion University, Beer Sheva, Israel), Dipl.-Phys. H. Mehrer (Leiter), Dipl.-Phys. M. Salamon

Veröffentlichungen:

Liubich, V., S. Dorfman, D. Fuks, H. Mehrer: Thermodynamic factor evaluated from diffuse X-ray scattering, Materials Transactions, JIM, 40, 132 - 136 (1999)

Eggersmann, M., H. Mehrer: Diffusion in Fe-Al intermetallics, Metal Physics and Advanced Technologies 22, 21 - 25 (1999)

Mehrer, H., M. Eggersmann, M. Salamon, Chr. Khoukaz, R. Galler, S. Dorfman, D. Fuks: Long range order and diffusion in iron-aluminides, The Japan Institute of Metals, Proceedings Vol. 12 (JIMIC-3), M. Koiwa, K, Otskuda, T. Miyazaki (Eds.), The Japan Institute of Metals, 1999, pp. 477

Eggersmann, M., H. Mehrer: Diffusion in intermetallic phases of the Fe-Al system, Phil. Mag. A 80, 1219 - 1244 (2000)

Eggersmann, M., H. Mehrer: Tracer diffusion in iron-aluminides, Mat. Sci. Forum, in print

Salamon, M., S. Dorfman, D. Fuks, G. Inden, H. Mehrer: Interdiffusion and Diffusion of Al in Iron-Aluminides, Mat. Sci. Forum, in print