Grain boundary diffusion of 59Fe in high-purity copper

International audienceGrain boundary diffusion of iron in high purity polycrystalline copper is measured using the radiotracer technique and applying the 59Fe isotope. At lower temperatures, K, the measurements are performed under Harrison's C-type kinetic regime and the grain boundary diffusion coefficient of Fe in Cu. Unconventional penetration profiles are measured for Fe grain boundary diffusion in Cu at higher temperatures ( 949 K) under the intended B-type kinetic regime, in fact formal C-type profiles are systematically observed instead. Molecular dynamics simulation with the literature Finnis-Sinclair type interatomic potentials [Ackland et al., Phil. Mag. A, 1997] discovered an unexpected response of Cu grain boundaries on a partial Fe coverage at temperatures above 900 K. A model of Fe penetration in polycrystalline Cu in such conditions is proposed, which explains the untypical shape of the penetration profiles. The combination of the B- and C-type grain boundary diffusion measurements predict a strong segregation of Fe in Cu with a low segregation enthalpy