Fundamental investigations of hydrogen embrittlement by using electron microscopy
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- Fysisk institutt [3682]
Abstract
The scope of this thesis was to explore the applications of electron microscopy in the field of hydrogen embrittlement (HE). The fundamental understanding of HE is still lacking and requires some advanced approaches to improve it. Electron energy-loss spectroscopy (EELS) was tested as a potentially viable technique for indirect hydrogen detection at nano-scale with transmission electron microscope (TEM). Hydrogen trapped at the grain boundaries or dislocations changes electronic structure of local iron atoms in pure Fe specimens as predicted by density functional theory (DFT). Such alterations could in principle be observed by EELS experiments, however they were not successful presumably due to knock out damage by the high dose electron beam, and high background signal because of low concentration of hydrogen. In addition, dislocation structures were studied in post-mortem specimens fractured in hydrogen, air and nitrogen gases. Scanning electron microscopy and scanning TEM have shown plasticity and dislocation organization variations in different atmospheres, which implied that hydrogen alters dislocation motion.List of papers
Paper I: Yuhei Ogawa, Domas Birenis, Hisao Matsunaga, Annett Thøgersen, Øystein Prytz, Osamu Takakuwa, Junichiro Yamabe. Multi-scale observation of hydrogen-induced, localized plastic deformation in fatigue-crack propagation in a pure iron. Scripta Materialia 140 (2017) 13–17. DOI: 10.1016/j.scriptamat.2017.06.037. The article is not available in DUO due to publisher restrictions. The published version is available at: https://doi.org/10.1016/j.scriptamat.2017.06.037 |
Paper II: Domas Birenis, Yuhei Ogawa, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen. Interpretation of hydrogen-assisted fatigue crack propagation in BCCiron based on dislocation structure evolution around the crack wake. Acta Materialia 156 (2018) 245-253. DOI: 10.1016/j.actamat.2018.06.041. The article is not available in DUO due to publisher restrictions. The published version is available at: https://doi.org/10.1016/j.actamat.2018.06.041 |
Paper III: Yuhei Ogawa, Domas Birenis, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen. The role of intergranular fracture on hydrogen-assisted fatigue crack propagation in pure iron at a low stress intensity range. Materials Science&Engineering A 733 (2018) 316-328. DOI: 10.1016/j.msea.2018.07.014. The article is included in the thesis. Also available at: https://doi.org/10.1016/j.msea.2018.07.014 |
Paper IV: Domas Birenis, Yuhei Ogawa, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen. Hydrogen-assisted crack propagation in α-iron during elasto-plastic fracture toughness test. Materials Science&Engineering A, vol 756, 22 May 2019, 396-404. DOI: 10.1016/j.msea.2019.04.084. The manuscript is included in the thesis. Published version is available at: https://doi.org/10.1016/j.msea.2019.04.084 |