Springback behaviors of extruded 6063 aluminum profile in subsequent multi-stage manufacturing processes

The process for manufacturing automotive aluminum profiles is a multi-stage process, which includes porthole die extrusion, aging treatment, bending, and electrophoretic painting. Prediction and reduction of springback are essential in quality control of bent profiles. However, existing researches related to springback issues were mainly focused on bending process stage. This study aimed to investigate the springback behaviors of extruded aluminum profile during the whole manufacturing process by numerical simulations with experimental validations. Formation mechanism and rule of springback for aluminum profile at different process stages were revealed. The optimum process route for manufacturing bent aluminum profiles was proposed. The research results reveal that compared with the transient bending region, the springback of aluminum profile during bending process induced by the finished bending region and two straight regions is relatively small. Springback angle increases with increasing bending angle and aging time. After bending tools unloading, the stresses of the two straight zones are almost completely relaxed. However, large residual tensile and compressive stresses exist in the material adjacent to the neutral layer of aluminum profile in transient and finished bending regions. Consequently, residual stress relaxation causes additional springback of bent profiles during subsequent heat treatment processes. The additional springback angle shows linear correlation with bending angle and parabola correlation with aging time. The total springback angle is minimum for process route 3 that extruded profile is firstly bent to required shape, then treated by artificial aging and finally treated by electrophoretic painting.