Influence of Hydrogen on Local Mechanical Properties of Pure Fe with Different Dislocation Densities Investigated by Electrochemical Nanoindentation

Tomatsu, Kota; Omura, Tomohiko; Nishiyama, Yoshitaka; Todaka, Yoshikazu

doi:10.2355/isijinternational.isijint-2016-189

Cited by 5 publications

(3 citation statements)

References 20 publications

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“…12,13) In other research on hydrogen-induced softening and hardening phenomena, Lee et al reported that the hardness of steel softened or hardened depend on indenter tip blunting. 14) Tomatsu et al 15) applied electrochemical nanoindentation tests on various pure heat-treated irons and reported that softening occurs at lower indentation speed in materials with high dislocation density, and also reported that hydrogen trapped in the vicinity of dislocations suppresses work hardening and softening occurs due to increased dislocation mobility. Zhao et al 16) conducted nanoindentation tests on steels and reported that the nanohardness transitions from hardening to softening depend on the hydrogen-charging method (hardening occurs upon electrochemical charging and softening upon gas charging).…”

Section: Effect Of Hydrogen Concentration On Nanoindentation Softenin...mentioning

confidence: 99%

“…For Fe-3wt.%Si, one set of 10 tests was conducted on samples exposed for 0, 24, 48, 72, 96, and 168 h. Each of these sets of experiments taking a few hours, and thermal drift increasing as the test time increased. 15) In this study, the windshield covering the experimental setup was covered with Styrofoam to minimize temperature fluctuations during the experiments. Furthermore, the influence of external micro-vibrations was reduced by installing the apparatus on an active table-top vibration isolator.…”

Section: Nanoindentation Testing and Evaluationmentioning

confidence: 99%

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Effect of Hydrogen Concentration on Nanoindentation Softening and Hardening in Iron: Ferrite Phase of S25C and Single-crystal Fe-3wt.%Si

Taketomi,

Taniguchi,

Yamamoto

et al. 2024

ISIJ Int.

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Plastic deformation is key to understanding hydrogen embrittlement in steels. Although macroscopic to microscopic observations and analyses have reported softening and hardening behavior in the presence of hydrogen, the mechanisms causing these effects and the overall mechanisms remain unclear. Therefore, this study applies nanoindentation tests to the ferrite phase of bcc-structured polycrystalline carbon steel S25C and single-crystalline iron with 3 wt.% silicon (Fe-3wt.%Si). The change in indentation work is evaluated by varying the exposure time in air between the uncharged and hydrogen-charged materials, focusing on the hydrogen concentration. The change in work per unit indentation volume caused by hydrogen (hydrogen-induced work) is investigated, revealing that the specimens harden immediately upon hydrogen charging, and then gradually soften with increasing exposure time before returning to their original state. This variation is attributed to the change in hydrogen concentration. The softening and hardening behavior with and without hydrogen, as confirmed by nanoindentation tests, is suggested to quantitatively affect the macroscopic mechanical response, which is determined by the mobility of screw dislocations in these materials.

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Section: Effect Of Hydrogen Concentration On Nanoindentation Softenin...mentioning

confidence: 99%

Section: Nanoindentation Testing and Evaluationmentioning

confidence: 99%

Effect of Hydrogen Concentration on Nanoindentation Softening and Hardening in Iron: Ferrite Phase of S25C and Single-crystal Fe-3wt.%Si

Taketomi,

Taniguchi,

Yamamoto

et al. 2024

ISIJ Int.

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show abstract

“…14,15) The authors also developed EC-NI with a wide dynamic range of load duration time, and investigated hydrogendislocation interactions for both face-and body-centered cubic metals. 16,17) The device configuration of EC-NI is comparatively simple. Moreover, a bare surface without a compound layer can be obtained during the hydrogen charging if the electrolyte is properly selected.…”

Section: Introductionmentioning

confidence: 99%

<i>In-situ</i> Microbending Tests of Ni–Cr Alloy during Cathodic Hydrogen Charging by Electrochemical Nanoindentation

et al. 2017

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To investigate hydrogen embrittlement susceptibility of an individual grain boundary, microcantilevers were fabricated on Ni-Cr bialloy surfaces by focused ion beam, and microbending tests were conducted during hydrogen charging by electrochemical nanoindentation. For microcantilevers fabricated across a twin boundary and inside a grain, no crack was formed by the bending both in air and during hydrogen charging. On the other hand, for microcantilevers fabricated across a random grain boundary, a crack was formed by the bending during hydrogen charging, whereas no crack was formed in air. Thus, it was identified that, for Ni-Cr bialloy, random grain boundaries are more susceptible to hydrogen than twin boundaries and crystalline planes. To validate these experimental results, slow strain-rate tensile tests were also performed, and subcracks of the fractured specimens were analyzed by electron beam back-scattering diffraction. In accordance with the microbending test results, subcracks were predominantly formed along random grain boundaries, but never along twin boundaries and inside grains. Higher hydrogen susceptibility of the random grain boundaries with lower cohesive energy (i.e., work for separation), smooth fracture surfaces without dimples or tear ridges, and no correlation between strain accumulation and subcrack formation indicate that hydrogen embrittlement of Ni-Cr bialloy is caused by decohesion mechanism, where hydrogen atoms lower cohesive energy at grain boundaries.

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Atomistic Investigation of the Influence of Hydrogen on Mechanical Response during Nanoindentation in Pure Iron

Lou

Cheng

Wang

et al. 2023

Acta Metall. Sin. (Engl. Lett.)

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Influence of Hydrogen on Local Mechanical Properties of Pure Fe with Different Dislocation Densities Investigated by Electrochemical Nanoindentation

Cited by 5 publications

References 20 publications

Effect of Hydrogen Concentration on Nanoindentation Softening and Hardening in Iron: Ferrite Phase of S25C and Single-crystal Fe-3wt.%Si

Effect of Hydrogen Concentration on Nanoindentation Softening and Hardening in Iron: Ferrite Phase of S25C and Single-crystal Fe-3wt.%Si

<i>In-situ</i> Microbending Tests of Ni–Cr Alloy during Cathodic Hydrogen Charging by Electrochemical Nanoindentation

Atomistic Investigation of the Influence of Hydrogen on Mechanical Response during Nanoindentation in Pure Iron

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