Influence of material characteristics on plastomechanics of the FSW process for T-joints

The potential of friction stir welding (FSW) has thoroughly been investigated by several authors, however their focus has primarily been on butt joints. T-joints are of paramount interest for transportation industries especially due to their capacity to straighten panels. Welding of T-joints is very challenging due to thin walls, poor location of the rib–web interface and the requirements for corner-fillets. This paper investigates FSW of T-joints of two popular aluminum alloys, i.e. 2024-T4 and 6082-T6, and the role played by the material characteristics on joining. First, an experimental study is carried out with specially designed fixture to determine the effect of process conditions. Then, the joints are metallurgically and mechanically evaluated. Finally using a numerical model of the process previously developed by the authors, the thermal and plastic flow fields for the two alloys are calculated and compared. It is found that the material dependent thermal and plastic fields affect the state of TMAZ, HAZ and nugget-region in the joint and that the low-strength high-work hardening alloy 6082 provides a much better joint integrity than the higher-strength low-hardening 2024 primarily due to the greater penetration of the plastic zone in the former.