Study of hydrogen embrittlement behavior by using pure Fe containing high-density lattice defects

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Grain refinement is important to create high strength metals, since both strength and toughness can be improved by grain refining. During the past decade, fabrication of bulk nano- / submicron- structured metals by severe plastic deformation (SPD), such as high-pressure torsion (HPT) straining, has evolved. Such SPD-processed metals often show extraordinary high strength and ductility. However, increase in tensile strength over 1.2 GPa in steels generally lead to hydrogen embrittlement (HE).In this study, HE behavior was investigated by means of tensile test with wide-range strain rate of 10 -3 ~ 10 +3 s-1 in the nano-structured pure Fe produced by HPT-straining, since this investigation focused on the interaction of lattice defects and hydrogen in the sample during tensile test. In addition, we made the correlation between the influence of hydrogen on the void formation / crack propagation and the fracture / dynamic response by means of fractography.