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

Abstract

Interstitial free sheet steels show transient work hardening behavior, i.e. the Bauschinger effect and cross hardening after changes in 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, as well as 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 crystallographic texture on the dislocation structure

In-plane biaxial compression and tension testing of thin sheet materials

“….on the c-fiber. Strengthening at the same orientations were also reported for a low carbon steel grade during uniaxial tension and plane-strain tension (Clausmeyer et al, 2013). These changes in texture are also likely related to the higher r-values after this final manufacturing step.…”

Comparison of two models for anisotropic hardening and yield surface evolution in bcc sheet steels

“…This conclusion was substantiated by later crystal plasticity modeling (e.g., Peeters et al, 2002). Related to this are more recent EBSD investigations on DC06 (Boers et al, 2010;Clausmeyer et al, 2012), which imply that the rolling-induced texture in this steel does not change considerably for strains lower than 35% in simple tension. This may be the case in other ferritic steels (e.g., LH800: Clausmeyer et al, 2012;Noman et al, 2010) as well.…”

“…Related to this are more recent EBSD investigations on DC06 (Boers et al, 2010;Clausmeyer et al, 2012), which imply that the rolling-induced texture in this steel does not change considerably for strains lower than 35% in simple tension. This may be the case in other ferritic steels (e.g., LH800: Clausmeyer et al, 2012;Noman et al, 2010) as well. These results imply that it is sufficient to account for the effect of the initial (e.g., rolling) texture on the anisotropic hardening and flow behavior in the material model.…”

“…In these investigations, the material was subjected to monotonic shear, reverse shear, as well as orthogonal tension-shear, loading. Clausmeyer et al (2012); van Riel and van den Boogaard (2007); Wang et al (2008) have documented these effects in the IF sheet steel DC06 with the help of monotonic tension, reverse shear, and orthogonal tension-shear, tests, all under plane-strain conditions. In particular, cross hardening occurs during discontinuous (e.g., tension-shear: Bouvier et al, 2005Bouvier et al, , 2006aBouvier et al, , 2003 and continuous (e.g., tension-shear: Noman et al, 2010;van Riel and van den Boogaard, 2007;Wang et al, 2008) orthogonal tension-shear tests.…”

“…These include for example dense dislocation wall structures. The morphology and orientation of such walls depends for example on grain orientation, the type of loading, and the loading direction in relation to the grain orientation (e.g., Clausmeyer et al, 2012;Nesterova et al, 2001a,b;Thuillier and Rauch, 1994). A change in loading direction or type activates new glide systems for which existing walls act initially as obstacles, resulting in cross hardening.…”