The Defining Role of Local Shear on the Development of As-Rolled Microstructure and Crystallographic Texture in Steel

This study involved laboratory unidirectional (UDR) and reverse (RR) cold rolling of steel, and corresponding direct (and indirect) observations of surface (and sub-surface) microstructures. Though both processes had identical strain mode of plane strain compression (PSC), the as-rolled surface grains showed clear differences in imposed mesoscopic shear strains. Further, the surface microstructure and its orientation sensitivity differed remarkably between the two processes. RR had more dislocation density, grain misorientations and non-crystallographic microbands, but exhibited insignificant differences between different crystallographic orientations. These effects appeared significant in low carbon interstitial free (IF) steel, but noticeably less so for high strength low alloy (HSLA) grade. The crystallographic textures of both the processes were identical in the mid-thickness section. However, the surface textures differed noticeably irrespective of the steel grade. These were captured quantitatively with a crystal plasticity model, and by introducing parametrically positive (UDR) and negative (RR) local shear strains for the respective surfaces. In summary, this study established, quantitatively, the defining role of local shear strain on the developments of as-rolled microstructure and crystallographic texture of steel.