Dresden 2020 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 33: Topical Session: Interface-dominated phenomena - Hydrogen at Interfaces

MM 33.1: Talk

Wednesday, March 18, 2020, 10:15–10:30, IFW A

Effect of grain boundaries on self-diffusion and hydrogen diffusion in bcc iron — •Daria Smirnova, Sergei Starikov, Matous Mrovec, and Ralf Drautz — Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universität Bochum, Bochum, Germany

Grain boundaries (GBs) are known to affect diffusion processes in most materials. In this work, we employed atomistic simulations to investigate how both self-diffusion and hydrogen diffusion processes are altered in the vicinity of various GBs in body-centered cubic (bcc) iron. The investigations were performed using accurate ab initio calculations based on density functional theory and large-scale molecular dynamics simulations with various interatomic potentials. We found that for symmetric tilt GBs the self-diffusion is mostly driven by interstitial atoms while in general GBs Fe atoms diffuse predominantly via an exchange mechanism that does not involve a particular defect and is similar to liquid diffusion. In most investigated cases, the self-diffusion along GBs is significantly enhanced compared to that in bulk. In contrast, the motion of H atoms along GBs is at ambient temperatures several orders of magnitude slower than the H bulk diffusion. This outcome is related to larger migration barriers in the distorted crystal structure of GBs, compared to a very low H migration barrier in bulk bcc Fe. We present temperature variations of diffusion coefficients for different GBs and compare the simulation predictions with available experimental data.