First-principles study on hydrogen diffusion behavior in γ-Fe
The problem of hydrogen embrittlement in stainless steel has always been a hot topic for researchers.However,until now,the mechanism of interaction between alloying elements and vacancy and H atom in steel re-mains unclear.The diffusion activation energies,diffusion coefficients and diffusion transition states of y-Fe(Fe8H,Fe7Cr/MoH,Fe7H)of H atom in different systems are studied by using first-principles method.The diffusion difficulty of γ-Fe atoms in different systems are compared,and the interactions are explained from the electronic structure level.The results show that the existence of vacancy changes the diffusion path of H atom inγ-Fe.In the cell with vacancy,H atom stably exists in the near tetrahedral gap near the vacancy and diffuses along the tetrahedral gap near the vacancy or the octahedral to tetrahedral gap path.The effect of vacancy on H atom in γ-Fe is local.On the one hand,it is a trap to capture H atom.On the other hand,the diffusion activa-tion energy of H atom is reduced and the diffusion of H atom is promoted.However,the doping of Cr/Mo can re-duce the binding of vacancy to H atom and inhibit the diffusion of H atom.
First principlesHydrogen diffusionγ-FeDiffusion activation energyElectronic structures
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