The self-diffusion coefficient of 57Co in the B2-type compound, with Al concentrations of 42, 46, 50 and 52at%Al, was determined between 1250 and 1630K by using serial radio-frequency sputter-microsectioning techniques. It was found that the diffusion coefficient of Co decreased, with increasing Al concentration, from the Co-rich composition to stoichiometry (table 1). The diffusivity of Co in Al-rich Co-52at%Al alloy was almost equal to that at stoichiometry. At homologous temperatures above 0.8, the diffusivity of Co deviated upward from the Arrhenius line. This suggested that the diffusion mechanism changed, with increasing temperature, from a monovacancy to a divacancy mechanism.

Self-Diffusion of Cobalt in B2 Type Intermetallic Compound CoAl. R.Nakamura, Y.Iijima: Intermetallics, 2005, 13[2], 163-7