Diffusion in the intermetallic phase Fe3Si studied by Tracer and Mossbauer techniques

Diffusion in the DO3 phase of the Fe-Si system (Fe concentrations from 75 to 82 at. %) has been studied in a joint venture between researchers from the Universitat Munster, who examined tracer diffusion of the radioisotopes Fe-59 and Ge-71 (serving as a substitute for Si) and from the Universitat Wien, who used quasielastic Mossbauer spectroscopy (QMS) of Fe-57. The tracer investigations were performed over a wide temperature range using a precision grinding device for serial sectioning. The study of three different alloy compositions revealed that Fe diffusion is very fast in the nearly stoichiometric compound and decreases significantly with increasing Fe content. Diffusion of Ge (and Si) is by several order of magnitude slower than Fe diffusion. The pressure dependence of Fe diffusion in Fe76Si24 at 934 K yielded an activation volume of 1.27 mean atomic volumes. QMS experiments show that Fe diffuses via nearest neighbour jumps in the stoichiometric compound. For the off-stoichiometric compounds antistructure sites play a role.