Diffusion in the bulk and in a symmetric tilt grain boundary of the Fe[sbnd]Cr system

Abstract

Classical and quantum calculations were performed in characterizing the interstitials transport parameters in the bulk of a diluted FeCr alloy and, in the Σ5 symmetric tilt grain boundary (GB) structure. For the bulk, in the same line of ideas as the multi-frequency model, we obtain the relevant transport parameters, namely: i) the involved jump frequencies in the associated multi-frequency model, ii) the full set of phenomenological Onsager coefficients, iii) the interstitial wind parameter, as well as, iv) the tracer self- and solute diffusion coefficients. Our calculations include the effects of entropy and ferromagnetic transition in the activation energy. We compare present calculations with available experimental data. As is expected, we have found in the bulk that Fe and Cr diffuse mainly via a vacancy mechanism, while diffusion by interstitials is several orders of magnitudes slower. For the GB, our calculations are in accordance with experimental data and show that diffusion is almost two orders of magnitude higher than in the bulk. Also, contrary to the bulk Cr diffuses slower than Fe in the GB. Present results show that both, interstitial and vacancy mechanisms, are important in studying diffusion in the GB.