Isotope effect and self-diffusion in face-centred cubic cobalt

Self-diffusion in cobalt is investigated from 896 to 1745 K by means of the standard radio-tracer method using lathe sectioning in the paramagnetic and sputter sectioning in the ferromagnetic region. The diffusion coefficients vary between about 10−17 cm2 s−1 and 10−9 cm2 s−1; their temperature dependence can be described by DT = 0.55 exp (−2.99 eV/kT) cm2 s−1. In contrast to iron no influence of the magnetic order−disorder transition on the diffusivity is observed within the experimental accuracy. The isotope effect for self-diffusion is measured at seven temperatures in the range 1451 to 1745 K. Its magnitude and its decrease with increasing temperature indicate that diffusion occurs mainly via monovacancies with an increasing but small contribution of divacancies with increasing temperature.