Cracking Process Related to Hydrogen Behavior in a Duplex Stainless Steel

Effect of Strain Rates on Mechanical Properties of a Duplex Stainless-Steel Sheet Charged in Hydrogen Plasma

“…The overall appearance of the fracture surface of the present plasma-charged specimen is also markedly different (roughly homogeneous) from that of the previous electrolytically charged specimen that was characterized with step cracks and delaminations, both caused by the exclusive embrittlement in ferrite phase grains. 24) These differences imply somewhat common deg-radation effect of the charged hydrogen atoms on the two phases in the plasma-charged specimen. This is consistent with the fact that the severest degradation has appeared in the plasma-charged specimen at the two magnitude slower strain rate than the electrolytically charged specimen, 21) as the diffusivity of hydrogen in the austenite phase is much slower than in the ferrite phase.…”

“…Although it was impossible to elucidate these trapping sites and lattice defects, it is deduced that these trapping sites and lattice defects are attributable to the slower strain rate for the severest degradation and the more homogeneous aspect of the fracture surface of the plasma-charged specimen in the present study than in the electrolytically charged specimen in the previous study. 24) Regarding the amount of hydrogen, we failed to assess it by integrating the spectra shown in Fig. 7(a).…”

“…In aluminum, it has been reported that larger amount of hydrogen can be charged using plasma hydrogen charging method than using electrolytical hydrogen charging. 22) In this study, the experimental procedures will be approximately the same as in the authors study carried out before 21,[23][24][25] but charging method will be changed to plasma hydrogen charging. It will be expected that the amount of charged hydrogen will be increased by changing the method, leading to the more marked tendency of HE, which then will help us reveal the mechanism of HE, since it is generally accepted that the higher the concentration of hydrogen, the larger the effects of hydrogen.…”

“…The material used in this study is the JIS SUS329J4L sheet with 1 mm thickness, annealed at 1 050°C for 1 min and then water-cooled, which is exactly the same as used in our previous papers. 21,[23][24][25] According to the latest phase map data taken by electron back scattering diffraction, 25) phase fraction (austenite to ferrite) was 0.536 to 0.444 by ignoring the fraction of undefined area. Tensile test pieces with gage length of 12 mm and width of 5 mm were cut from the 1 mm-thick sheet, so that the tensile direction is parallel to the rolling direction.…”