The tracer diffusion coefficient of 181W in α-Fe was determined at 833 to 1173K using a serial sputter-microsectioning method. The temperature dependence of the diffusion coefficient over the whole temperature range of α-Fe across the Curie temperature (1043K), could be expressed by:

D (m2/s) = 1.5 x 10-2 exp[-287(1+0.086s2)(kJ/mol)/RT]

where s was the ratio of the spontaneous magnetization at TK to that at 0K. The factor of 0.086 in the above equation was smaller than the 0.156 for self-diffusion, showing that the influence of the magnetic transformation on the diffusion of W in α-Fe was smaller than that on the self-diffusion. The activation energy 287kJ/mol for W diffusion in paramagnetic Fe was much higher than to 250.6kJ/mol for self-diffusion.

S.Takemoto, H.Nitta, Y.Iijima, Y.Yamazaki: Philosophical Magazine, 2007, 87[11], 1619-29