Interactions of Dissolved Atoms and Carbon Diffusion in Fe-Cr and Fe-AI Alloys

摘要

Peculiarities of carbon diffusion in Fe-Cr and Fe-AI alloys were studied as a function of interatomic C-Fe, C-Cr and C-A1 interactions. Parameters of carbon mobility in solid solution were evaluated using temperature-dependent internal friction measurements (the Snoek relaxation). It was shown that the effect of Cr concentration on C diffusion in an α-Fe based solid solution is considerably stronger than that of Fe concentration in a Cr-based solid solution; the ordering of Al atoms enhances C diffusion in the Fe-Al solid solution. These effects were accounted for by 'C-substitution atom' interaction. The employed atom-interaction model is based on the long-range strain-induced ('elastic') interaction supplemented by a short-range 'chemical' interaction. The model assumes that the interactions of dissolved atoms affect both the distribution (short-range order) and energies of carbon atoms and consequently the activation energy of their diffusion. It was shown that the difference in influence of the substitutional atoms on C diffusion in α-Fe and in Cr results from: (1) the stronger C-Cr elastic attraction in α-Fe than the C-Fe attraction in Cr, and (2) from the difference in their 'chemical' interactions, that is, C-Cr attraction in α-Fe and C-Fe repulsion in Cr. The change in carbon diffusion mobility due to Al DO_3-ordering is brought about by the change in C atoms distribution in the solid solution and its 'effective' energy of interaction with Al atoms.