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Effect of prestrain on hydrogen diffusion and trapping in structural steel
Park, Cheolho,Kang, Namhyun,Kim, Myunghyun,Liu, Stephen Elsevier 2019 Materials letters Vol.235 No.-
<P><B>Abstract</B></P> <P>Hydrogen permeation tests were electrochemically performed to measure hydrogen diffusion and trapping in EH 36 steel. Permeation transients were measured through charging and decaying cycles, for specimens prestrained to varying degrees (0–20%). With increasing prestrain, the effective hydrogen diffusivity (<I>D<SUB>eff</SUB> </I>) decreased, while the total/reversible hydrogen content (<I>C<SUB>o</SUB> </I> and <I>C<SUB>r</SUB>, respectively</I>) increased. The immobile dislocation of the 20%-prestrained specimens decreased <I>D<SUB>eff</SUB> </I> by approximately ten times and increased <I>C<SUB>o</SUB> </I> and <I>C<SUB>r</SUB> </I> by approximately three times. The amount of irreversibly trapped hydrogen (<I>C<SUB>irr</SUB> </I>) remained approximately the same, regardless of the prestrain. The dislocations delay the motion of hydrogen and contain more reversible hydrogen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrogen permeation tests successfully measured the hydrogen diffusivity and concentration. </LI> <LI> As the prestrain increased from 0 to 20%, the effective hydrogen diffusivity decreased. </LI> <LI> Total and reversible hydrogen concentrations increased with the prestrain. </LI> <LI> Irreversible hydrogen showed mostly the same value regardless of prestrain. </LI> <LI> The dislocations delay the motion of hydrogen and contain more reversible hydrogen. </LI> </UL> </P>
Cheolho Park,Namhyun Kang,Stephen Liu,Juseung Lee,Eunjoon Chun,Sun‑Joon Yoo 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.3
Hydrogen can provide pure and clean energy; however, to use it as an energy source, facilities such as hydrogen carriersand recharging stations need to be constructed. Structural steels are affected by hydrogen embrittlement (HE), and theirsusceptibility to this needs to be investigated prior to their use in construction. Most structural steels are normally fabricatedusing thermomechanical controlled processing, which produces a large dislocation density to increase strength. This studyinvestigated the prestrain effect on HE susceptibility of EH 36 steels using thermal desorption spectroscopy (TDS) andin situ slow-strain-rate testing. Hydrogen was electrochemically charged into specimens, and the reversible hydrogen contentand that relating to trap sites were measured using TDS. With an increase in prestrain, there was increase in the diffusiblehydrogen content; furthermore, with hydrogen charging, there was a drastic reduction in total elongation with an increasein prestrain. In addition, there was an increase in HE susceptibility with an increase in prestrain compared to when an aircondition was employed. Specifically, there was an abrupt increase in HE sensitivity at a prestrain value between 10 and15%; strain hardening was more dominant below a prestrain value of 10%; and HE was more dominant above a prestrainvalue of 15% for EH 36 steels.