Effect of process parameter on mechanical properties of friction stir welded tailored blanks from aluminium alloy 6181-T4

Tailor welded blanks ( TWBs) are produced by joining at least two sheets of dissimilar gauge and/or properties to achieve a lighter blank of desired stiffness and strength. In this way, the properties of the blank may be tailored to meet the design requirements of a panel. As in steel structures, cost and weight can be saved when using the TWB concept for aluminium. However, use of aluminium is a concern in the automotive industry because of well documented weldability and reproducibility problems, since relatively minor changes in welding parameters may affect the quality of the weld. Friction stir welding offers an attractive alternative to conventional fusion welding methods because of the excellent properties ( particularly ductility), reproducibility, robustness and surface finish obtained. However, the working envelope for friction stir welded tailored blanks has yet to be fully explored. In the present study TWBs of the alloy 6181-T4 in a thickness combination 1 to 2 mm have been produced. The influence of welding parameters and welding tools on the weld quality and mechanical properties has been determined. Satisfactory surface finish with no detrimental effects to the mechanical properties has been observed. Weld efficiencies 90% have been consistently achieved.