Influence of process parameters on grain refinement in AA1050 aluminum during cold rolling

The microstructure evolution during cold rolling of commercial purity AA1050 aluminum is investigated through numerical simulations. A finite strain elasto-viscoplastic constitutive model is employed, where the dislocation density and average grain size are taken as variables characterizing the deformed microstructure. Grain size evolution due to dynamic recrystallization is considered and the microstructure quantities are allowed to influence the macroscopic material behavior in terms of the flow stress and deformation-rate dependence. The effects of such process parameters as rolling friction, thickness reduction in each rolling pass and amount of rolling asymmetry are discussed. The results indicate that grain refinement due to dynamic recrystallization is most significantly affected by the amount of thickness reduction in each pass and the level of rolling friction and to a lesser extent by the asymmetry of the rolling process. An increasing degree of asymmetry will, however, reduce the variations in grain size through the sheet thickness and leave the material more homogeneously recrystallized.