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.

我们采用密度泛函理论（DFT），研究了氢（H）诱导体心立方铁（bcc Fe）中冷加工（斯努克-克斯特尔，Snoek-Köster）峰的实验与理论成果。我们再次证实，泽格尔（Seeger）对氢冷加工峰（Hcwp）的解释具备实验支撑——该理论认为氢会与非螺型位错上的位错扭折一同运动，且这一过程与本征位错α峰相关。借助舍克（Schoeck）提出的溶质拖拽理论，我们推算出氢混合位错结合能为0.3 eV。赫思（Hirth）提出的理论认为，氢冷加工峰（Hcwp）源于氢-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-螺型位错结合能的量级与之相近，约为0.2 eV，这为该理论提供了依据。这一结果为氢脆相关的氢增强局部塑性模型提供了支撑。我们还探讨了氢-空位结合在氢俘获与氢脆过程中可能发挥的作用——DFT计算表明该结合的结合能为0.6 eV；同时分析了氢-溶质结合的较弱影响，此类结合的结合能仅约为0.1 eV。