Experimental characterization of microstructure development during loading path changes in bcc sheet steels

Enthalten in
Journal of Materials Science 
Volume
48
Issue
2
Start Page
674
End Page
689
Citation
Journal of Materials Science 48 (2): 674-689 (2013)
Publisher DOI
10.1007/s10853-012-6780-9
Scopus ID
2-s2.0-84871614002
Publisher
Springer Nature
Interstitial free sheet steels show transient work hardening behavior, i.e., the Bauschinger effect and cross hardening, after changes in the loading path. This behavior affects sheet forming processes and the properties of the final part. The transient work hardening behavior is attributed to changes in the dislocation structure. In this work, the morphology of the dislocation microstructure is investigated for uniaxial and plane strain tension, monotonic and forward to reverse shear, and plane strain tension to shear. Characteristic features such as the thickness of cell walls and the shape of cells are used to distinguish microstructural patterns corresponding to different loading paths. The influence of the crystallographic texture on the dislocation structure is analyzed. Digital image processing is used to create a "library" of schematic representations of the dislocation microstructure. The dislocation microstructures corresponding to uniaxial tension, plane strain tension, monotonic shear, forward to reverse shear, and plane strain tension to shear can be distinguished from each other based on the thickness of cell walls and the shape of cells. A statistical analysis of the wall thickness distribution shows that the wall thickness decreases with increasing deformation and that there are differences between simple shear and uniaxial tension. A change in loading path leads to changes in the dislocation structure. The knowledge of the specific features of the dislocation structure corresponding to a loading path may be used for two purposes: (i) the analysis of the homogeneity of deformation in a test sample and (ii) the analysis of a formed part. © 2012 Springer Science+Business Media, LLC.
DDC Class
530: Physik
Projekt(e)
PAK 250 “Identifikation und Modellierung der Werkstoffcharakteristik f ̈ur die Finite-Element-Anal-yse von Blechumformprozessen" 
Funding Organisations
Deutsche Forschungsgemeinschaft (DFG) 
More Funding Information
Financial support for this work provided by the German Science Foundation (DFG) under contract PAK 250 (TP3, TP4, TP5) is greatly acknowledged.