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Atomic mechanism and prediction of hydrogen embrittlement in iron


Hydrogen embrittlement in metals has posed a serious obstacle to designing strong and reliable structural materials for many decades, and predictive physical mechanisms still do not exist. Here, a new H embrittlement mechanism operating at the atomic scale in α-iron is demonstrated. Direct molecular dynamics simulations reveal a ductile-to-brittle transition caused by the suppression of dislocation emission at the crack tip due to aggregation of H, which then permits brittle-cleavage failure followed by slow crack growth. The atomistic embrittlement mechanism is then connected to material states and loading conditions through a kinetic model for H delivery to the crack-tip region. Parameter-free predictions of embrittlement thresholds in Fe-based steels over a range of H concentrations, mechanical loading rates and H diffusion rates are found to be in excellent agreement with experiments. This work provides a mechanistic, predictive framework for interpreting experiments, designing structural components and guiding the design of embrittlement-resistant materials.

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Figure 1: Atomic configurations of the near-crack-tip region, shown as views along the crack line, for orientation I at various levels of H and applied load.
Figure 2: Atomic configurations of the near-crack-tip region, shown as views along the crack line, for orientation II at various levels of H and load.
Figure 3: The amount of H in the system normalized along the crack line direction, NH/Lz, versus the stress intensity KI at which either dislocation emission or brittle cleavage occurs, as found in simulations for orientations I and II.


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The authors acknowledge partial support of this work by the US Office of Naval Research (grant # N00014-05-1-0504), by the General Motors/Brown Collaborative Research Lab on Computational Materials and by the NSERC Discovery grant (grant # RGPIN 418469-2012).

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The project was planned and supervised by W.A.C. The simulations were performed and the data were collected by J.S. The results were analysed and discussed by J.S. and W.A.C. The manuscript was prepared by J.S. and W.A.C.

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Correspondence to W. A. Curtin.

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The authors declare no competing financial interests.

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Song, J., Curtin, W. Atomic mechanism and prediction of hydrogen embrittlement in iron. Nature Mater 12, 145–151 (2013).

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