Diffusion of Silicon in Ferrite

Abstract

WE have recently carried out some measurements on the diffusion of silicon at low concentrations in ferrite at one temperature near to the melting point. Specimens (cylinders of in. diameter) were made of pure iron butt-welded to a 3-4 per cent silicon iron alloy. These were heated for differing times at the temperature 1,435 ± 5°C., cooled and sectioned along a plane perpendicular to the weld interface. The diffusion of silicon into the iron across the interface was measured by traversing the section with a spectrograph spark. By correcting for the finite size of the sparked zone and standardizing the spectrograph with samples of known silicon content, curves of silicon concentration versus distance were plotted. The diffusion coefficient of silicon was obtained by applying Fick's law and the result (mean of five determinations) was Dγ Combining double low line 1.1 × 10-7 cm.2/sec. The grain-sizes of the specimens were large enough to assume that at the temperature used the contribution of grain-boundary diffusion was small, and it is thought that overall error in D should not be greater than ± 20 per cent. © 1953 Nature Publishing Group.