Dynamic recrystallizations and dislocation slips in AZ31 Mg alloy under high-strain-rate large-deformation hot extrusion: a FEM-informed VPSC study

: Magnesium alloys fabricated via extrusion-bending integrated forming show significant potential for lightweight automotive structures and high-strength components, where recrystallized microstructures induced by high-temperature extrusion control continuous online bending performance. However, the intermediate evolution of recrystallization and associated dislocation slip cannot be fully characterized in situ, requiring numerical simulations. This study employs a top-down cross-scale algorithm to simulate microstructural evolution during hot extrusion. By characterizing microstructural differences induced by variations in extrusion speeds and ratios, a quantitative relationship among extrusion parameters, recrystallized microstructures, and orientation-weighted Schmid factors (related to bending load) is established. Simulation results reveal that at a large extrusion ratio, lowering speed enhances pyramidal <c+a> slip but reduces basal and prismatic slip. In turn, higher speed produces more fully recrystallized structures with soft orientations, increasing Schmid factors of basal and prismatic slip and improving deformation compatibility. The cross-scale predictions agree well with experimental data, and a combination of large extrusion ratio and high extrusion speed optimizes the deformation compatibility of basal and prismatic slip during extrusion-bending integrated forming.