Just another WordPress site - Ruhr-Universität Bochum

Abstract

Bulk and grain boundary (GB) diffusion of atoms in Fe was investigated with use of atomistic simulation based on a new interatomic potential. The potential was designed to simulate Fe-Cr-H ternary system and, hence, allowed us to study self-diffusion and impurity diffusion processes in the framework of the united model. In addition, at the study of bulk diffusion, we combined the classical molecular dynamics modeling with spin-dynamics simulation. Such complex model revealed a strong dependence of vacancy formation energy on temperature and non-Arrhenius behaviour of the self-diffusion coefficient due to magnetic excitation at heating. Also, we found that atomic self-diffusion in symmetric tilt GBs is mostly driven by self-interstitial atoms. On the other hand, in general GBs, atoms diffuse predominantly via an exchange mechanism that does not involve a particular defect but is similar to diffusion in liquid. Most observed mechanisms lead to a significant enhancement of self-diffusion along GBs compared to diffusion in the bulk Fe. It is interesting to note that we obtain the opposite trend at study of hydrogen diffusion: for hydrogen, bulk mobility is much higher than mobility along the GBs. The results of simulations are verified by comparison with the available experimental data.