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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Control of texture and formability in ferritic stainless steels

Boulton, Catherine Dorothy January 1986 (has links)
The effects of processing variables on the microstructures, textures and press-formability of commercial 17 Cr, 0.05C (430) steel and low-interstitial Ti-stabilised 12 Cr (409) and 17 Cr (430 Ti) steels have been studied. The annealing textures have beencorrelated with tensile strain ratio measurements and from this correlation it has been possible to select combinations of cold rolling reduction and annealing treatments for texture control to improve deep drawability. Electron microscope examination has been used to identify possible nucleation mechanisms for the observed recrystallisation textures. Cold rolling texture development and tensile strain ratios have been discussed from theoretical considerations of slip in bcc metals. Pronounced differences in microstructural features between high interstitial 4-30 and low-interstitial Ti-stabilised steels are reflected in differences in texture development at all stages. Hot band condition is an important variable, affecting texture development during subsequent cold rolling and annealing. All three steels develop similar cold rolling textures, consisting mainly of ~{100} , ~{111} and ~{112} components. The ~{112} orientation is more prominent in 430 Ti steel than in 430 steel, and it is suggested that this difference may be due to irregular flow in high interstitial 430 steel. Other differences in cold rolling textures are attributed to texture inheritance from the hot band. Recrystallisation textures in 430 steel are mainly ~{114} , with ~{223} present after high reductions, and r-values are generally low. Recrystallisation textures in 409 and 430 Ti steels are mainly ~{110} after low cold rolling reductions, ~{554} after moderate or high reductions and -{223} after very high reductions. In most cases, ~{100} is only a minor component. Batch annealing of the hot rolled strip followed by cold rolling to 90% RA and rapid final annealing promotes maximum ~{554} intensity with low ~{100} intensity, and a correspondingly high r-value. The ~{223} and ~{114} orientations, attributed to grain boundary nucleation, have not been reported previously in 17 Cr ferritic stainless steels, although they have been reported occasionally in other low-carbon ferritic steels.
2

Comparative investigation of micromechanisms of plastic deformation by in-situ tensile tests of highly textured 316L steel

Kumarasinghe, Subhani January 2022 (has links)
Additive manufacturing (AM) is identified as one of the best techniques in manufacturing components addressing most of the current challenges including material scarcity, design complexity, material compatibility, etc. Stainless steel 316L is one of the promising material candidates in AM due to its extraordinary properties that are useful in a wide variety of industries. Tailoring desired properties locally is heavily investigated in metal AM. This project focuses on investigating the plastic behavior of additively manufactured SS 316L parts printed using laser powder bed fusion (LPBF) specifically to have a strong crystal orientation towards the direction of loading. Parts were printed to have (100), (110), and fiber texture perpendicular to the tensile axis by changing the laser scanning direction. In-situ tensile tests were carried out in a Scanning Electron Microscope (SEM) acquiring electron backscatter diffraction (EBSD) data from the specimen at several strain levels. Schmid Factor (SF) maps, Kernel Average Misorientation (KAM) maps, and Grain orientation spread (GOS) maps were generated using EBSD data. Micromechanisms in plastic deformation of these highly textured AM parts were analyzed based on the crystal orientation and the microstructure. When the influence of crystallographic texture on the micromechanisms of plastic deformation was observed, it was confirmed that a significant difference is present in tensile properties directed with the crystal orientation. During plastic deformation, the crystals were heavily rotated to accommodate slip formations. The slips that are generated at the grains with fiber texture are restricted by the grain boundaries and therefore, showed a higher yield strength. The (100) texture was less prone to plastic deformation. The grains with (110) crystal orientation proved a higher ductility with a perfect slip starting at the grains with higher SFs and showed {111} <110> slip systems.

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