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MM: Fachverband Metall- und Materialphysik
MM 10: Topical Session: Hydrogen in Materials: from Storage to Embrittlement I
MM 10.3: Talk
Monday, March 18, 2024, 16:30–16:45, C 130
Effect of mechanical stress, chemical potential, and coverage on hydrogen solubility during decohesion of ferritic steel grain boundaries — Abril Azocar Guzman1 and •Rebecca Janisch2 — 1IAS-9, Forschungszentrum Jülich, 52425 Jülich, DE — 2ICAMS, Ruhr-Universität Bochum, 44801 Bochum, DE
Hydrogen embrittlement (HE) mechanisms in structural materials such as iron and iron alloys present a complex scenario, in which the interaction of H with different crystal defects and the solubility of H in the system depends on the concentration, chemical potential and applied mechanical stress. Therefore, understanding these processes at the atomic level is fundamental for developing methods that can mitigate the detrimental effects of H. Grain boundaries (GBs) play a critical role in hydrogen enhanced decohesion mechanism, where H weakens the interatomic bonds causing intergranular fracture. In this work, we carry out DFT calculations to investigate the decohesion of the Σ5(310)[001] and Σ3(112)[110] symmetrical tilt GBs in bcc Fe. To address the aforementioned open questions regarding the solubility of H, both thermodynamic limits of the separation of segregated interfaces are analysed. The results indicate that at higher local concentrations, H leads to a significant reduction of the cohesive strength of the GB planes, more pronounced at the Σ5 GB due to a more open local atomic environment. However, at higher applied mechanical stress and chemical potential, the solubility becomes higher at the Σ3 GB. To proceed from Fe to ferritic steel, also the effects of the alloying elements C, V, Cr and Mn at the GB are studied.
Keywords: Hydrogen embrittlement; Density functional theory; Grain boundary segregation; Mechanical properties of interfaces