DIFFUSION OF COBALT IN IRON-COBALT ALLOYS

Self-diffusion of Co**6**0 in the bcc (alpha) and fcc (gamma) phases of iron-cobalt alloys has been measured between 630degreeC and 1310**degreeC by the residual activity technique. Interesting changes in the diffusivity result from the alphaminusgamma phase change, the magnetic transition in the alpha and gamma phase, and the order-disorder transformation in the alpha phase. In both the phases, the activation energy for diffusion in the ferromagnetic state is larger than in the paramagnetic state. The diffusivity decreases discontinuously due to the alpha-gamma transformation, and the order-disorder transformation causes a nonlinear relationship between log D and 1/T in the alpha phase.