Effect of shear-inducing γ-fiber on ridging of ferritic stainless steels

This study employs polycrystal-based grain scale numerical simulations, utilizing crystal plasticity finite element (CP-FE) method and simplified roping model (SRM), to investigate the effect of texture components on ridging (micro-scale surface corrugation) in cold-rolled ferritic stainless steel (FSS) sheets. The ridging occurrence mechanism is analyzed in uniaxial tensioned samples not multiaxial for comparing the affection of the shear strain with that of the r-value (Lankford's coefficient). To enhance simulation accuracy, the 3D texture is measured via serial cross-sectional segmentation to generate five-layer texture data based on the electron backscatter diffraction (EBSD). Since the CP-FE model validates that severe shear strain-induced texture components are the major cause of ridging, this study is specifically attentive to the mechanistic relationship between the ridging and the γ-fiber texture of shear dominant deformation. The SRM constructs shear strain maps in an extended Euler space, neglecting crystal symmetry for computational efficiency. The shear strain map efficiently recognizes the crystal orientations associated with the regions under severe shear strain and high volume fraction of γ-fiber. Experiment and simulation results both reveal that the elements with severe shear strains exhibit {111}<341> texture components, representing one of the γ-fiber orientations with a high volume fraction. Additionally, a simplified mathematical model derived by analyzing the {111}<341> texture components from the EBSD and considering the signs of the shear strains aligns well with the predicted ridging profiles.