The Experts below are selected from a list of 25065 Experts worldwide ranked by ideXlab platform
Yuhei Ogawa - One of the best experts on this subject based on the ideXlab platform.
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the role of intergranular fracture on hydrogen assisted fatigue crack propagation in Pure Iron at a low stress intensity range
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: Yuhei Ogawa, Domas Birenis, Øystein Prytz, Osamu Takakuwa, Junichiro Yamabe, Hisao Matsunaga, Annett ThogersenAbstract:Abstract Hydrogen-assisted fatigue crack growth (HAFCG) in Pure Iron at a relatively low stress intensity range exhibits brittle-like intergranular (IG) fracture, while the macroscopic crack acceleration is not significant. The present study focuses on the mechanism of IG fracture in terms of the microscopic deformation structures near the crack propagation paths. We found that the IG fracture is attributed to hydrogen-enhanced dislocation structure evolution and subsequent microvoid formation along the grain boundaries. The impact of such IG cracking on the macroscopic fatigue crack growth (FCG) acceleration is evaluated according to the dependency of IG fracture tendency on the hydrogen gas pressure during testing. It is demonstrated for the first time that increased hydrogen pressure results in a larger fraction of IG fracture and correspondingly faster FCG. On the other hand, the gaseous hydrogen envIronment also has a positive role in decelerating the FCG rate relative to air due to the absence of oxygen and water vapor. The macroscopic crack propagation rate in hydrogen gas is eventually determined by the competition between the said positive and negative influences.
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multi scale observation of hydrogen induced localized plastic deformation in fatigue crack propagation in a Pure Iron
Scripta Materialia, 2017Co-Authors: Yuhei Ogawa, Domas Birenis, Øystein Prytz, Osamu Takakuwa, Annett Thogersen, Hisao Matsunaga, Junichiro YamabeAbstract:Abstract In order to study the influence of hydrogen on plastic deformation behavior in the vicinity of the fatigue crack-tip in a Pure Iron, a multi-scale observation technique was employed, comprising electron channeling contrast imaging (ECCI), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The analyses successfully demonstrated that hydrogen greatly reduces the dislocation structure evolution around the fracture path and localizes the plastic flow in the crack-tip region. Such clear evidence can reinforce the existing model in which this type of localized plasticity contributes to crack-growth acceleration in metals in hydrogen atmosphere, which has not yet been experimentally elucidated.
Junichiro Yamabe - One of the best experts on this subject based on the ideXlab platform.
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the role of intergranular fracture on hydrogen assisted fatigue crack propagation in Pure Iron at a low stress intensity range
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: Yuhei Ogawa, Domas Birenis, Øystein Prytz, Osamu Takakuwa, Junichiro Yamabe, Hisao Matsunaga, Annett ThogersenAbstract:Abstract Hydrogen-assisted fatigue crack growth (HAFCG) in Pure Iron at a relatively low stress intensity range exhibits brittle-like intergranular (IG) fracture, while the macroscopic crack acceleration is not significant. The present study focuses on the mechanism of IG fracture in terms of the microscopic deformation structures near the crack propagation paths. We found that the IG fracture is attributed to hydrogen-enhanced dislocation structure evolution and subsequent microvoid formation along the grain boundaries. The impact of such IG cracking on the macroscopic fatigue crack growth (FCG) acceleration is evaluated according to the dependency of IG fracture tendency on the hydrogen gas pressure during testing. It is demonstrated for the first time that increased hydrogen pressure results in a larger fraction of IG fracture and correspondingly faster FCG. On the other hand, the gaseous hydrogen envIronment also has a positive role in decelerating the FCG rate relative to air due to the absence of oxygen and water vapor. The macroscopic crack propagation rate in hydrogen gas is eventually determined by the competition between the said positive and negative influences.
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multi scale observation of hydrogen induced localized plastic deformation in fatigue crack propagation in a Pure Iron
Scripta Materialia, 2017Co-Authors: Yuhei Ogawa, Domas Birenis, Øystein Prytz, Osamu Takakuwa, Annett Thogersen, Hisao Matsunaga, Junichiro YamabeAbstract:Abstract In order to study the influence of hydrogen on plastic deformation behavior in the vicinity of the fatigue crack-tip in a Pure Iron, a multi-scale observation technique was employed, comprising electron channeling contrast imaging (ECCI), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The analyses successfully demonstrated that hydrogen greatly reduces the dislocation structure evolution around the fracture path and localizes the plastic flow in the crack-tip region. Such clear evidence can reinforce the existing model in which this type of localized plasticity contributes to crack-growth acceleration in metals in hydrogen atmosphere, which has not yet been experimentally elucidated.
Guang Chen - One of the best experts on this subject based on the ideXlab platform.
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Dynamics and mechanism of columnar grain growth of Pure Iron under directional annealing
Acta Materialia, 2007Co-Authors: Zhongwu Zhang, Guang ChenAbstract:The dynamics and mechanism of columnar grain growth of Pure Iron with small equiaxed grains were experimentally investigated under directional annealing. The results prove the existence of both a lower- and an upper limit of the withdrawing velocity for columnar grain growth. Importantly, there is an optimum withdrawing velocity at which the largest aspect ratio of columnar grains can be obtained. A kinetic approach is suggested to describe the growth of the columnar grains. The aspect ratio of the columnar grains can be successfully predicted by this approach. The mechanism of the columnar grain growth essentially can be described as selective growth or competitive migration of the grain boundaries. As a result of selective growth, the boundaries between the columnar grains abound in low-energy boundaries. Small island-like grains inside the columnars grain can be left over due to the low mobility of their small-angle boundaries or twin boundaries.
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The effect of crystallographic texture on columnar grain growth in commercial Pure Iron during directional annealing
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Zhongwu Zhang, Guang ChenAbstract:The influence of crystallographic texture on the columnar grain growth in commercial Pure Iron during directional annealing has been investigated. The crystallographic texture hinders the columnar grain growth due to the high propensity to form low angle or twin boundaries between the columnar grains and the main recrystallized textures at the front of the columnar grains when the columnar grains grow along the direction of the temperature gradient in highly textured materials.
Hisao Matsunaga - One of the best experts on this subject based on the ideXlab platform.
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the role of intergranular fracture on hydrogen assisted fatigue crack propagation in Pure Iron at a low stress intensity range
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: Yuhei Ogawa, Domas Birenis, Øystein Prytz, Osamu Takakuwa, Junichiro Yamabe, Hisao Matsunaga, Annett ThogersenAbstract:Abstract Hydrogen-assisted fatigue crack growth (HAFCG) in Pure Iron at a relatively low stress intensity range exhibits brittle-like intergranular (IG) fracture, while the macroscopic crack acceleration is not significant. The present study focuses on the mechanism of IG fracture in terms of the microscopic deformation structures near the crack propagation paths. We found that the IG fracture is attributed to hydrogen-enhanced dislocation structure evolution and subsequent microvoid formation along the grain boundaries. The impact of such IG cracking on the macroscopic fatigue crack growth (FCG) acceleration is evaluated according to the dependency of IG fracture tendency on the hydrogen gas pressure during testing. It is demonstrated for the first time that increased hydrogen pressure results in a larger fraction of IG fracture and correspondingly faster FCG. On the other hand, the gaseous hydrogen envIronment also has a positive role in decelerating the FCG rate relative to air due to the absence of oxygen and water vapor. The macroscopic crack propagation rate in hydrogen gas is eventually determined by the competition between the said positive and negative influences.
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multi scale observation of hydrogen induced localized plastic deformation in fatigue crack propagation in a Pure Iron
Scripta Materialia, 2017Co-Authors: Yuhei Ogawa, Domas Birenis, Øystein Prytz, Osamu Takakuwa, Annett Thogersen, Hisao Matsunaga, Junichiro YamabeAbstract:Abstract In order to study the influence of hydrogen on plastic deformation behavior in the vicinity of the fatigue crack-tip in a Pure Iron, a multi-scale observation technique was employed, comprising electron channeling contrast imaging (ECCI), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The analyses successfully demonstrated that hydrogen greatly reduces the dislocation structure evolution around the fracture path and localizes the plastic flow in the crack-tip region. Such clear evidence can reinforce the existing model in which this type of localized plasticity contributes to crack-growth acceleration in metals in hydrogen atmosphere, which has not yet been experimentally elucidated.
Annett Thogersen - One of the best experts on this subject based on the ideXlab platform.
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the role of intergranular fracture on hydrogen assisted fatigue crack propagation in Pure Iron at a low stress intensity range
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: Yuhei Ogawa, Domas Birenis, Øystein Prytz, Osamu Takakuwa, Junichiro Yamabe, Hisao Matsunaga, Annett ThogersenAbstract:Abstract Hydrogen-assisted fatigue crack growth (HAFCG) in Pure Iron at a relatively low stress intensity range exhibits brittle-like intergranular (IG) fracture, while the macroscopic crack acceleration is not significant. The present study focuses on the mechanism of IG fracture in terms of the microscopic deformation structures near the crack propagation paths. We found that the IG fracture is attributed to hydrogen-enhanced dislocation structure evolution and subsequent microvoid formation along the grain boundaries. The impact of such IG cracking on the macroscopic fatigue crack growth (FCG) acceleration is evaluated according to the dependency of IG fracture tendency on the hydrogen gas pressure during testing. It is demonstrated for the first time that increased hydrogen pressure results in a larger fraction of IG fracture and correspondingly faster FCG. On the other hand, the gaseous hydrogen envIronment also has a positive role in decelerating the FCG rate relative to air due to the absence of oxygen and water vapor. The macroscopic crack propagation rate in hydrogen gas is eventually determined by the competition between the said positive and negative influences.
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multi scale observation of hydrogen induced localized plastic deformation in fatigue crack propagation in a Pure Iron
Scripta Materialia, 2017Co-Authors: Yuhei Ogawa, Domas Birenis, Øystein Prytz, Osamu Takakuwa, Annett Thogersen, Hisao Matsunaga, Junichiro YamabeAbstract:Abstract In order to study the influence of hydrogen on plastic deformation behavior in the vicinity of the fatigue crack-tip in a Pure Iron, a multi-scale observation technique was employed, comprising electron channeling contrast imaging (ECCI), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The analyses successfully demonstrated that hydrogen greatly reduces the dislocation structure evolution around the fracture path and localizes the plastic flow in the crack-tip region. Such clear evidence can reinforce the existing model in which this type of localized plasticity contributes to crack-growth acceleration in metals in hydrogen atmosphere, which has not yet been experimentally elucidated.
