Effect of post weld heat treatment on the springback of dissimilar aluminium and steel tailor welded blanks fabricated using friction stir welding

Springback is a common geometrical defect that occurs in the sheet metal forming process and depends on material properties. Different methods have been used to compensate or minimise the springback effect to date. One of the methods is post-weld heat treatment. However, not all materials are heat treatable. In this study, post-weld heat treatment effect on the springback of dissimilar materials AA6061 and SAE1020 fabricated by friction stir welding was investigated using free bending. Different artificial ageing times during the heat treatment process were explored to identify the optimum duration to minimise springback via experiment and finite element analysis. Punch stroke and punch offset tests were conducted to evaluate the effect of multiple parameter values on springback. It was found that an artificial ageing time of 6 hours results in the lowest springback. Springback is inversely proportional to punch stroke as higher punch strokes produce lower springback. For punch offset, the springback increases as the punch is offset towards AA6061 and decreases when offset towards SAE 1020. Interestingly, samples that went through post-weld heat treatment recorded lower springback on both sides even for non-treatable material. The experimental results show a similar pattern and acceptable tolerance compared to the simulation results.