DIFFUSION OF CHROMIUM IN ALPHA-IRON

Tracer diffusion coefficient of 51Cr in α-iron has been determined by a serial radio-frequency sputter-microsection-ing method in the temperature range 885 to 1174 K. In α-iron of the paramagnetic state from the Curie temperature to the α-γ transformation temperature the diffusion coefficient of chromium shows a linear Arrhenius relationship with negligible influence of the short range magnetic spin ordering. Below the Curie temperature, temperature dependence of the diffusion coefficient deviates from the linear Arrhenius relationship owing to the magnetic spin ordering. Taking into account the influence of the magnetic transformation, the temperature dependence of the diffusion coefficient, D, in the whole temperature range of α-iron across the Curie temperature can be expressed by m2 s-1, where s is the ratio of the spontaneous magnetization at TK to that at 0 K. The factor (0.133) in the above equation is smaller than 0.156 in the case of the self-diffusion in α-iron, indicating that the influence of the magnetic transformation on the diffusion of chromium in α-iron is smaller than that on the self-diffusion, as expected from the negative magnetic moment of chromium atom in the lattice of ferromagnetic iron. © 1990, The Japan Institute of Metals. All rights reserved.