Abstract
The effects of internal hydrogen on the deformation microstructures of 304L austenitic stainless steel have been characterized using electron backscattered diffraction (EBSD), transmission Kikuchi diffraction (TKD), high-resolution scanning transmission electron microscopy (HRSTEM), and nanoprobe diffraction. Samples, both thermally precharged with hydrogen and without thermal precharging, were subjected to tensile deformation of 5 and 20 pct true strain followed by multiple microscopic interrogations. Internal hydrogen produced widespread stacking faults within the as-forged initially unstrained material. While planar deformation bands developed with tensile strain in both the hydrogen-precharged and non-precharged material, the character of these bands changed with the presence of internal hydrogen. As shown by nanobeam diffraction and HRSTEM observations, in the absence of internal hydrogen, the bands were predominantly composed of twins, whereas for samples deformed in the presence of internal hydrogen, ε-martensite became more pronounced and the density of deformation bands increased. For the 20 pct strain condition, α′-martensite was observed at the intersection of ε-martensite bands in hydrogen-precharged samples, whereas in non-precharged samples α′-martensite was only observed along grain boundaries. We hypothesize that the increased prevalence of α′-martensite is a secondary effect of increased ε-martensite and deformation band density due to internal hydrogen and is not a signature of internal hydrogen itself.
Highlights
PLANAR deformation bands are often observed in the microstructures of deformed austenitic stainless steels.[1,2,3,4,5,6] It is important to understand the formation and arrangements of these microstructural features as the heterogeneous localization of deformation can negatively impact critical mechanical properties including ductility, fatigue resistance, and fracture toughness.[5,6,7] Deformation bands are often dominated by planar dislocation slip, but in some systems, deformation structures can be tied to shear-coupled crystallographic transformations
The initial microstructures consist of dense arrangements of dislocations that have organized into extensive cell blocks spanning multiple microns across the grains
We have characterized the influence of internal hydrogen on the development of planar deformation bands and associated deformation microstructures in forged 304L austenitic stainless steel strained in uniaxial tension
Summary
PLANAR deformation bands are often observed in the microstructures of deformed austenitic stainless steels.[1,2,3,4,5,6] It is important to understand the formation and arrangements of these microstructural features as the heterogeneous localization of deformation can negatively impact critical mechanical properties including ductility, fatigue resistance, and fracture toughness.[5,6,7] Deformation bands are often dominated by planar dislocation slip, but in some systems, deformation structures can be tied to shear-coupled crystallographic transformations. Perhaps the most fundamental of these transformations is deformation twinning.[8,9] Additional transformations are observed in austenitic stainless steels, such as the shear-induced transformation to hexagonal closed packed (HCP).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
