Misorientation standard deviation as a microstructural factor governing surface roughening in polycrystalline sheets analyzed with crystal plasticity modeling

Free-surface roughening is a critical instability that degrades the surface quality of polycrystalline sheet metals during plastic deformation. While empirical studies have reported a nearly linear relation between surface roughness and strain, the crystallographic factors governing the magnitude of roughening remain insufficiently understood. In this study, a crystal plasticity finite element method (CPFEM) framework was developed to investigate how orientation spread and central orientation influence roughening evolution. A thin-sheet model subdivided into 1200 grains by Voronoi tessellation was constructed, and systematic simulations were performed for five canonical rolling texture components: Cube, Goss, Brass, Copper, and S. The arithmetic mean roughness increased linearly with strain for all cases, and the slope of this relation, defined as the roughening coefficient c , was strongly dependent on both orientation spread and central orientation. A clear hierarchy was identified, with sensitivity following S > Copper ≈ Brass > Cube ≈ Goss. Mechanistic analysis showed that this hierarchy originates from differences in orientation rotation and the symmetry of active slip systems, which together determine intragranular strain heterogeneity. Comparisons with uniaxial tensile tests on A2024-O and C1220-O sheets confirmed that differences in roughening coefficients between the two alloys arise from distinct central orientations, validating the predictive capacity of the CPFEM model. These results establish orientation spread and central orientation as coupled microstructural descriptors of roughening, providing a predictive framework for the design of polycrystalline sheet metals with improved surface quality. • CPFEM reveals orientation spread governs surface roughening evolution • Central orientation produces a clear hierarchy of roughening sensitivity • Mechanisms linked to orientation rotation and slip symmetry • Predictions validated against tensile tests on A2024-O and C1220-O