Identification of two aluminum alloys and springback behaviors in cold bending

Abstract

Aluminum alloys have drawn more and more attention in automobile and electronics industry. However, springback is a big challenge in cold forming of aluminum alloy sheets. In order to identify two aluminum alloys and their heat treatment condition, chemical composition detections, microstructure observation by OM (Optical Microscope), SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscope) were carried out. With additional hardness tests, the results indicate that the two aluminum alloys should be 6xxx aluminum alloy. They went through solution heat treatment after hot rolling and then underwent different time of natural aging. For the purpose of investigating springback behaviors of the two aluminum alloys sheets in cold forming, strain hardening exponents (n), strength coefficient (K) and plastic strain ratios (r) in three directions were calculated by tensile tests. Then cold bending experiments and finite element (FE) simulations with the implementation of the calculated n and r were carried out. The tensile results show that the formability of the two aluminum alloy sheets in cold forming is poor for the small values of n and anisotropy was found based on the r values. The cold bending results indicate that the springback decreased with the increasing bending angle and thicker sheets had smaller springback. Besides, the simulation and experiments agreed well with each other, indicating that the springback prediction using the calculated values of n and r were suitable. It will provide significant guide in in springback prediction of aluminum alloys in cold forming and help to design the tools.