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MM: Fachverband Metall- und Materialphysik

MM 3: Transport - Atoms and Ions I

MM 3.5: Vortrag

Montag, 16. März 2020, 11:15–11:30, IFW A

Mutual dependence of oxygen and vacancy diffusion in dilute iron alloys and the influence of substitutional atoms — •Xiaoshuang Wang, Jürgen Faßbender, and Matthias Posselt — Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany

By combination of density functional theory (DFT) and an efficient method based on Atomistic Kinetic Monte Carlo (AKMC) the mutual influence of oxygen (O) and vacancy (v) diffusion in α-Fe and the effects of substitutional atoms (Ti, Y) are studied. Both oxygen and vacancy are mobile while the substitutional atoms are assumed to be immobile. Using DFT, binding energies between oxygen and vacancy at different neighbour distances and migration barriers for oxygen in the environment of a vacancy and for vacancy in the environment of an oxygen atom are determined. The most attractive state for oxygen and vacancy was found at the 1st neighbour distance. The O-v pair at the 6th neighbour distance is unstable and therefore it is impossible to reach via oxygen/vacancy jump. The newly-found simultaneous jumps of both O and v compensate the lack of state 6. By using the data obtained by DFT as inputs, the diffusion coefficient of oxygen and of vacancy are determined for given concentration of vacancy and oxygen atoms by an AKMC-based efficient method. Additionally, oxygen and vacancy diffusion were calculated in the first stage of thermal processing of ODS steel where O, Y, and Ti is purposely introduced.