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MM: Fachverband Metall- und Materialphysik
MM 4: Materials for the Storage and Conversion of Energy
MM 4.9: Vortrag
Montag, 17. März 2025, 12:15–12:30, H22
The impact of Mn and Al on the trapping and diffusion of hydrogen in γ-Fe: An atomistic insight — •Bikram Kumar Das1, Poulami Chakraborty1, Mauricio Rincón Bonilla1, and Elena Akhmatskaya1,2 — 1Basque Center for Applied Mathematics, Bilbao, Spain — 2Ikerbasque - Basque Foundation for Science, Spain
We propose a first principles-based framework to systematically unlock the physical underpinnings of local distribution of the solute atoms on hydrogen trapping and diffusion in Mn/Al-alloyed γ-Fe. In our scheme, all thermodynamically stable substitutional solute sites were identified (<= 5.4 wt% Mn; <= 4 wt% Al) up to the third nearest neighbour (NN) shell of a single H atom. The impact of Mn/Al on H-binding was quantitatively evaluated, indicating a surprisingly strong correlation with the local Al distribution regardless Mn content, and indirect stabilization by Al when present in the 2nd NN shell. Nonetheless, Al strongly repels H bonding. The contradictory role of Al was explained in terms of bonding/anti-bonding orbitals occupancy in H-M interactions (M = Al, Mn, Fe). The barriers to H hopping between adjacent local environments and the corresponding jump frequencies were subsequently calculated, providing insights into the limits imposed by the presence of Al and Mn on H mobility in Mn/Al-alloyed γ-Fe. Most notably, presence of Al in the 2nd NN shell of H severely reduces the H jump frequency, leading to irreversible trapping at high Al contents. Such behaviour may critically contribute to mitigate H-induced delayed fracture in Al-rich austenite steel.
Keywords: Hydrogen trapping; Hydrogen diffusion; Hydrogen embrittlement; Steel; DFT