Tracer diffusion coefficient of 181W in α-Fe was determined in the temperature range between 833 and 1173K using a serial sputter-microsectioning method. The temperature dependence of the diffusion coefficient, D, 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 the paramagnetic Fe was much higher than 250.6kJ/mol for the self-diffusion. Atomic size effect was predominant in the activation energies for diffusion of transition elements in the paramagnetic α-Fe.

Diffusion of Tungsten in α-Iron. S.Takemoto, H.Nitta, Y.Iijima, Y.Yamazaki: Philosophical Magazine, 2007, 87[11], 1619-29