Development of FSW to manufacture tailor welded blanks for lightweight transport applications

Abstract

Vehicle light-weighting has been identified as the most effective way of addressing the reduction of energy consumption and CO2 emissions in the transportation industry. With recent advances in manufacturing technologies, the production of tailor welded blanks (TWBs) from lightweight metal alloy such as aluminium has become a viable and low cost solution. The present research work was conducted in the framework of the ongoing project “LightBlank – make it lighter, with less”, at The Welding Institute (TWI) aiming at the development of the friction stir welding (FSW) process for the production of TWBs in aluminium AA 6082-T6 with dissimilar thickness for the automotive, rail and aerospace industries. Two thickness combinations were addressed: 3 to 5 mm and 2 to 2.5 mm. At first stage, multiple weld beads with different welding parameter combinations were produced in order to determine the process window for each dissimilar joint. Using metallographic analysis techniques and mechanical testing, the influence of the parameter combinations on the welded joints was characterized which allowed to determine the parameter combination that produced the weld beads with the best quality while maximizing the welding speed. On the 3 to 5 mm thickness combination, extra tests were conducted to determine the influence in the quality of the weld of a horizontal offset in the alignment of the tool with the joint line and the thicker plate in the advancing side, i.e, a change in the plate positioning in relation to the welding direction. The results have shown that for each thickness combination, there is a process parameter window which allows the production welds with a suitable quality while retaining between 65 to 80 % of the base material mechanical properties.