Microscopic mechanisms of shear strain-induced ridging of asymmetric-rolled ferritic stainless steel foils

In this study, the microscopic mechanism of shear strain-induced ridging in ferritic stainless steel (FSS) foils processed by asymmetric rolling (ASR) is revealed by a combination of cross-scale numerical simulation and experimental work. The present study demonstrates that the differential speed ratio (DSR) exerts a non-linear effect on the ridging behavior of materials by modulating the grain orientation evolution and dislocation density distribution. In the case of DSR=1.5, a substantial differentiation in the ridging height occurs between the fast and slow sides (10.262 μm on the fast side and 8.365 μm on the slow side, with a difference of 18.5%). Micro-mechanism analysis reveals that the {111} <112> orientation, characterized by a high Schmid factor, activates multiple slip systems and accommodates deformation more readily, while the {111} <110> orientation, with a lower Schmid factor, exhibits limited slip activity and higher deformation resistance. The balance between these hard and soft γ-fiber subcomponents therefore directly affects strain compatibility during subsequent tensile deformation. Meanwhile, the GND gradient formed by ASR significantly affects recrystallization behavior during annealing. Preferential nucleation in high dislocation density zones leads to grain refinement and grain-size heterogeneity. As a result, the ridging resistance is governed by the combined effects of γ-fiber subcomponent balance and microstructural heterogeneity through a strain mismatch mechanism.