Constitutive equation and FEM analysis of incremental cryo-rolling of UFG AA 1050 and AA 5052

Abstract In this study, ultrafine grained aluminum sheets AA1050 and AA5052 are incrementally cryo-rolled after precooling in liquid nitrogen. Cryogenic deformation is considered as an effective approach to postpone saturation of the grain refinement by conventional severe plastic deformation. However, for a quantitative understanding of the resulted microstructure and mechanical properties, accurate values of the deformation parameters (strain, strain rate and temperature) are needed. The aim of this study is, therefore, to find values of the applied cryo-rolling parameters. As the experimental measurements of parameters such as temperature are infeasible in the thin specimens, a FEM simulation is developed and used, instead. Flow stress data at various conditions is obtained by plane strain compression and tension tests. A proper constitutive equation which is found to match well with the experiments is used to couple with the FEM model. Thermal contacts and other physical parameters are also carefully determined to achieve a reliable FEM simulation. Deformation parameters at various incremental rolling passes are obtained by this approach. Capability of the model is also verified by cryo-rolling of thick specimens at different thickness reductions. As the deformation parameters of the present experiments are defined in this study, accurate analyses of the resulted microstructures and mechanical properties can be performed.