Evaluation and Modeling of Anisotropic Stress Effect on Hydrogen Diffusion in Bcc Iron

  • NAGASE Shuki
    Department of Mechanical Engineering and Science, Graduate School of Engineering, Kyoto University
  • MATSUMOTO Ryosuke
    Nagamori Institute of Actuators, Kyoto University of Advanced Science

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  • bcc 鉄における水素拡散挙動の非等方応力依存性評価とモデル化
  • bccテツ ニ オケル スイソ カクサン キョドウ ノ ヒ トウ カタ オウリョク イソンセイ ヒョウカ ト モデルカ

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Abstract

<p>The diffusion behavior of interstitial hydrogen in steel should be clarified to reveal the mechanism of hydrogen embrittlement. In this study, we performed molecular dynamics (MD) simulations to elucidate the relationship between various stress conditions and the diffusion coefficients of interstitial hydrogen in body-centered-cubic (bcc) iron. The results revealed that the diffusion coefficients are independent of isotropic stress and exhibit strong anisotropic stress de-pendence under uniaxial stress along the 〈100〉 direction. The deformation of the atomic structure around the octahedral interstitial site (O site) resulting from stress was examined to elucidate the origin of the anisotropy of the stress depen-dence. Moreover, a model that predicts the activation enthalpy was derived by quantitatively evaluating the deformation around the O site. The activation enthalpy predicted by the model was consistent with the results of MD simulations when the deformation around the O site was not significant.</p>

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