Lattice Diffusion and Grain Boundary Diffusion of Cobalt in γ-Iron

The lattice diffusion and the grain boundary diffusion of cobalt in γ-iron were measured in the temperature range from 1140 to 1340°C by using the radioactive tracer Co60 and by a lathe-sectioning method. The grain growth in polycrystalline specimens of γ-iron was also investigated and a rapid grain growth treatment was taken during diffusion annealing. The data were analysed by the theory for grain boundary diffusion based on the instantaneous source model, previously developed by the present author. The lattice diffusion coefficient D was found asD=1.25exp(−72,900⁄RT)cm2sec−1,while the grain boundary diffusion coefficient D′ asD′=0.5exp(−33,000⁄RT)cm2sec−1.