The Hydrogen Cold Work Peak in BCC Iron: Revisited, with First Principles Calculations and Implications for Hydrogen Embrittlement

We examine experimental and theoretical results on the cold-work (Snoek-Köster) peak in bcc Fe due to H using density functional theory (DFT). We reaffirm that Seeger’s interpretation of the H cold-work peak (Hcwp), involving motion of H with kinks on non-screw dislocations associated with the intrinsic-dislocation α peak, has experimental backing. Use of the solute-dragging theory of Schoeck suggests a H-mixed dislocation binding energy of 0.3 eV. The theory of Hirth, that the Hcwp involves H-screw dislocation interaction manifested as the temperature-reduced intrinsic-dislocation γ peak by the presence of H, has merit in that our DFT calculations disclose a similar magnitude, 0.2 eV, of H-screw dislocation binding. This result offers support for models of H-enhanced localized plasticity of H embrittlement. We also explore possible roles of H-vacancy binding, shown by DFT to be characterized by a binding energy of 0.6 eV, in H trapping and H embrittlement and lesser effects of H-solute binding involving small binding energies of ~ 0.1 eV.

本研究借助密度泛函理论（DFT），针对体心立方铁（bcc Fe）中由氢引发的冷加工（斯涅克-克斯特，Snoek-Köster）峰相关的实验与理论研究成果展开分析。我们再次确认，泽格尔针对氢冷加工峰（Hcwp）提出的解释具备实验支撑：该理论认为氢冷加工峰与氢在与本征位错α峰相关的非螺型位错上的扭折运动相关。运用舍克提出的溶质拖拽理论，可推算得到氢混合位错结合能为0.3电子伏特（eV）。赫思提出的理论认为，氢冷加工峰涉及氢-螺型位错相互作用，该相互作用因氢的存在表现为温度降低的本征位错γ峰；我们的DFT计算结果显示氢-螺型位错结合能大小约为0.2 eV，这为该理论提供了合理性依据。该结果可为氢脆的氢增强局部塑性模型提供理论支撑。此外，本研究还探讨了氢-空位结合在氢捕陷与氢脆过程中的潜在作用：DFT计算表明该结合能为0.6 eV；同时分析了结合能约为0.1 eV的氢-溶质结合所产生的较弱影响。