Properties of UFG HSLA Steel Profiles Produced by Linear Flow Splitting

Bruder, Enrico; Bohn, Tilman; Müller, Clemens

doi:10.4028/www.scientific.net/msf.584-586.661

Cited by 15 publications

(8 citation statements)

References 9 publications

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“…Neither the flange angle α nor the flange thickness sf or the sheet thickness s0 seem to have a strong effect on the resulting distribution of mechanical properties. For all LFS parameters and materials investigated in this work or previously [13,[20][21][22][23], the gradients are very similar exhibiting a steep decrease in hardness with increasing distance to the split surface to a depth of 300 to 500 µm and a flatter decrease or even constant hardness down to the lower side of the flange. This gradient correlates with a decrease in HAGB fraction and aspect ratio as well as an increase in grain size.…”

Section: Characteristic Properties In Lfs and Lbs Profilessupporting

confidence: 51%

Integral sheet metal design via severe plastic deformation – state of the art and future challenges

Bruder

Kaune

Müller

2014

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. The innovative forming processes Linear Flow Splitting (LFS) and Linear Bend Splitting (LBS) were developed to facilitate the continuous production of branched profiles with tailored sheet thickness by inducing severe plastic strain. In contrast to most SPD processes the stress state in LFS and LBS is very complex and plastic deformation is confined to limited volumes which results in steep strain gradients and consequently ultrafine grained (UFG) gradient microstructures. Even though the processes have been commercialized, the increased lightweight potential that originates from the local grain refinement remains mostly idle since it is neither fully understood nor easily assessable yet. The present work shows the state of the art for the LFS and LBS processes and compares the microstructures and distribution of mechanical properties for different steels processed with different LFS parameters. The data is used to identify characteristic manufacturing induced properties that are insensitive to processing parameters. Based on the experimental results a material flow model for the processing zone is proposed which is discussed with respect to the current understanding of plasticity at severe strains.Keywords: Surface Severe Plastic Deformation, Work Hardening, Linear Flow Splitting, Linear Bend Splitting, Gradient Microstructures IntroductionThe use of Severe Plastic Deformation (SPD) as top down approach to refine microstructures of metals and alloys to the submicron range has been investigated extensively during the last decades [1][2][3]. Aside from the scientific interest in fundamental research on plasticity phenomena at large strains, there is also a strong technological interest in these processes which is driven by the exceptional mechanical properties that are associated with the presence of ultrafine grained (UFG) microstructures [1]. Even though high strength materials are needed for a wide range of commercial applications where lightweight design is mandatory, the commercial success of SPD processes is rather limited so far [4]. The main reason for this are most likely the high processing costs of the predominantly discontinuous SPD processes but there is also a strong competition from materials based on modern alloy design and thermo-mechanical processing [5]. However, the Linear Flow Splitting (LFS) and Linear Bend Splitting (LBS) processes that are reviewed in the present paper demonstrate that UFG microstructures by SPD and commercial success in mass markets are no antagonisms. The LFS and LBS processes also referred to as split profiling and split bending have an exceptional position in the field of SPD. In contrast to conventional SPD processes their primary objective is not the generation of UFG microstructures while retaining the initial shape of the workpiece but the production of branched profiles from plain sheet metal [6][7][8]. However, since LFS and LBS induce severe strains under high hydrostatic compressive stresses they generate UFG microstructures by the same mechanisms [9]...

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Section: Characteristic Properties In Lfs and Lbs Profilessupporting

confidence: 51%

Integral sheet metal design via severe plastic deformation – state of the art and future challenges

Bruder

Kaune

Müller

2014

IOP Conf. Ser.: Mater. Sci. Eng.

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“…Nevertheless it imposes severe strains and produces an ultrafine grained (UFG) microstructure in a surface layer [5]. The process zone is less defined than in the previously mentioned SPD processes and exhibits steep strain gradients [6], leading to strong microstructure and yield strength gradients in the flange thickness direction [7]. Earlier investigations using electron backscattering diffraction (EBSD) have shown that the crystallographic texture also varies along with the other gradients [8].…”

Section: Introductionmentioning

confidence: 97%

Quantification of local and global elastic anisotropy in ultrafine grained gradient microstructures, produced by linear flow splitting

Niehuesbernd

Müller

Pantleon

et al. 2013

Materials Science and Engineering: A

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“…The heterogeneous material flow in the process zone leads to the development of characteristic microstructure and yield strength gradients in thickness direction of the produced flanges, Fig. right . At the split surface, i.e.…”

Section: Introductionmentioning

confidence: 99%

Improving the formability of linear flow split profiles by laser annealing

Niehuesbernd

Monnerjahn

Bruder

et al. 2016

Materialwissenschaft Werkst

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The effect of laser annealing on the mechanical properties of severely deformed low alloy steel is discussed. Two different sets of annealing parameters were used to achieve improvements in formability. The resulting microstructures, tensile properties and hardness distributions are reviewed. Annealing at temperatures around 700 °C with very high heating and cooling rates leads to recrystallization at the surface and moderate grain growth in subsequent layers. The improvement in ductility is proven to be sufficient to prevent cracking during bending operations.

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Properties of UFG HSLA Steel Profiles Produced by Linear Flow Splitting

Cited by 15 publications

References 9 publications

Integral sheet metal design via severe plastic deformation – state of the art and future challenges

Integral sheet metal design via severe plastic deformation – state of the art and future challenges

Quantification of local and global elastic anisotropy in ultrafine grained gradient microstructures, produced by linear flow splitting

Improving the formability of linear flow split profiles by laser annealing

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