机械应力、化学势和覆盖度对铁素体钢晶界氢致脱聚过程中氢溶解度的影响：第一性原理研究
Effects of mechanical stress, chemical potential, and coverage on hydrogen solubility during hydrogen-enhanced decohesion of ferritic steel grain boundaries: A first-principles study
AI总结：
本文通过第一性原理计算研究铁素体钢两类对称倾转晶界中应力、化学势和覆盖度对氢溶解度及氢致脱聚的影响，发现应力可促使氢向更强晶界重新分布，并分析了C、V、Cr、Mn合金元素的作用，为抗氢脆微观结构设计提供依据。
摘要：
氢致脱聚（HEDE）是氢脆的众多机制之一，氢脆现象严重影响铁及铁合金等结构材料。晶界（GBs）在该机制中起关键作用，它们可以提供捕获位点或充当氢扩散通道。H与晶界及其他晶体缺陷的相互作用，以及由此决定的H在微观结构中的溶解度和分布，取决于浓度、化学势和局部应力。因此，为了定量评估HEDE，需要将广义溶解能与作为氢覆盖度函数的结合强度相结合。本文中，我们采用密度泛函理论计算，以体心立方Fe中的Σ5(310)[001]和Σ3(112)[1$\ar{1}$0]对称倾转晶界为例，研究H对开放结构和密排结构晶界脱聚的影响。提出了一种识别晶界面偏析位点的方法。结果表明，在较高局部浓度下，H导致晶界面的结合强度显著降低，且在Σ5晶界处比在Σ3晶界处显著得多。有趣的是，在有限应力下，Σ3晶界变得更有利于H溶解，这与零应力情况下Σ5晶界更具吸引力的情形相反。这表明，在某些条件下，微观结构中的应力可以导致H重新分布到更强的晶界，这为设计抗氢微观结构开辟了途径。为完善我们的研究，我们考察了铁素体钢中典型合金元素C、V、Cr和Mn对H溶解度和晶界强度的影响。
英文摘要：
Hydrogen-enhanced decohesion (HEDE) is one of the many mechanisms of hydrogen embrittlement, a phenomenon that severely impacts structural materials such as iron and iron alloys. Grain boundaries (GBs) play a critical role in this mechanism, where they can provide trapping sites or act as hydrogen diffusion pathways. The interaction of H with GBs and other crystallographic defects, and thus the solubility and distribution of H in the microstructure, depends on the concentration, chemical potential, and local stress. Therefore, for a quantitative assessment of HEDE, a generalized solution energy in conjunction with the cohesive strength as a function of hydrogen coverage is needed. In this paper, we carry out density functional theory calculations to investigate the influence of H on the decohesion of the $Σ$5(310)[001] and $Σ$3(112)[1$\bar{1}$0] symmetrical tilt GBs in bcc Fe, as examples for open and close-packed GB structures. A method to identify the segregation sites at the GB plane is proposed. The results indicate that at higher local concentrations, H leads to a significant reduction of the cohesive strength of the GB planes, significantly more pronounced at the $Σ$5 than at the $Σ$3 GB. Interestingly, at finite stress, the $Σ$3 GB becomes more favorable for H solution, as opposed to the case of zero stress, where the $Σ$5 GB is more attractive. This suggests that, under certain conditions, stresses in the microstructure can lead to a redistribution of H to the stronger grain boundary, which opens a path to designing H-resistant microstructures. To round up our study, we investigate the effects of typical alloying elements in ferritic steel, C, V, Cr, and Mn, on the solubility of H and the strength of the GBs.
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