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A connection between the effects of solute hydrogen (H) on macroscopic flow stress and microscopic dislocation mobility has been a subject for understanding the plastic flow behavior of H-charged austenitic steels and other face-centered cubic (FCC) alloys. In this study, we try to solve this problem by examining the room temperature creep of a Fe-24Cr-19Ni-based Type310S austenitic stainless steel uniformly charged with 9000 at. ppm solute H in a pressurized gaseous H2 environment. Stress-dip test to decompose the flow stress into effective (thermal) and internal (athermal) stresses, as well as a brief analysis of dislocation structure development in deformed uncharged and H-charged samples by electron channeling contrast imaging and hardness measurement, were supplementally employed. It is emphasized that solute H atoms consistently act as short-range obstacles hindering the movement of dislocations and thereby causes significant solid solution-hardening. Nevertheless, two opposite H-effects to accelerate and retard the creep rate were macroscopically identified depending on whether the stress level applied to H-charged specimens is above or below the flow stress under non-charged condition. These newly found, seemingly contradicting phenomena were interpreted based on the stress-dependent change of the rate-controlling mechanisms predominating thermally activated dislocation motion. Primary rate-controlling obstacles are H atoms themselves when creep acceleration manifests at high stress, while H atoms, other alloying elements, and forest dislocations cooperatively work to retard creep under low stress. The potential model of dislocation motion under the presence of these multiple obstacle types is finally proposed.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Austenitic steel, Plasticity, Hydrogen, Themal activation

刊行年月日: 2024-12-16

出版者: Elsevier BV

掲載誌:

• Acta Materialia (ISSN: 13596454) vol. 285 120659

研究助成金:

• National Institute for Materials Science
• Kyushu University
• Japan Society for the Promotion of Science JP21K14045
• Japan Society for the Promotion of Science 24K17180

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1016/j.actamat.2024.120659

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更新時刻: 2025-01-09 16:31:01 +0900

MDRでの公開時刻: 2025-01-20 12:30:59 +0900