Thermal Migration of Iron Implanted in Aluminium at High Doses

摘要

The anneal behaviour of the Fe-Al metastable system produced by implantation of Fe exp + ions at 30 keV has been reported. The implant concentrations between 18-42 at percent have been chosen, in order to exceed the normal solid solubility of Fe in Al by about three orders of magnitude. Isothermal annealing has been done under vacuum (55 x 10 exp -6 Torr) at 400deg C and 570 deg C. The iron depth profiles have been determined, by Rutherford backscattering of 2 MeV He exp + ions. It has been found that 1) as annealing proceeds, all specimens show rapid enhanced diffusion initially (upto about 30 m), followed by a much slower diffusion as iron ions migrate inwards (2) at implant concentrations 23 at percent, double peaks appear in iron depth profiles, followed by rapid migration of diffused iron towards surface and (3) at still higher anneal times, the out-diffused iron moves inward again. This kind of out-diffusion behaviour in a metallic system has not been reported earlier in the literature. Also, the presence of Fe sub 4 Al sub 13 has been identified as terminal phase, using x-ray diffraction techniques. (Atomindex citation 10:442524)