Formation of ultrafine-grained microstructure in HSLA steel profiles by linear flow splitting
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Linear flow splitting is a new cold forming process for the production of branched sheet metal structures in integral style. It induces extremely high deformation degrees without formation of cracks in the split sheets due to hydrostatic compressive stresses. Investigations on a HSLA steel (ZStE 500) show the formation and fragmentation of a dislocation cell structure in the severely deformed regions of the steel sheet. This results in ultrafine-grained microstructures and improved mechanical properties, similar to SPD processes as Equal Channel Angular Pressing (ECAP) or High Pressure Torsion (HPT). EBSD measurements reveal a gradient in grain size with an increase in direction perpendicular to the surface, whereas micro hardness decreases in the same direction. Based on these results, basic principles of linear flow splitting and its expected potential are discussed.
KeywordsFlange HSLA Steel Equal Channel Angular Pressing Process Zone High Pressure Torsion
The investigations presented in this article are supported by the German Research Foundation (DFG). The authors thank the DFG for funding the subproject C1 of the Collaborative Research Center 666 “Integral sheet metal design with higher order bifurcations—Development, Production, Evaluation”.
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