Experimental investigation on the weldability and forming behavior of aluminum alloy tailor-welded blanks

Aluminum alloy tailor-welded blanks (TWBs) have developed rapidly due to increasing interest and market pressure from the automotive industry to further reduce the weight and cost of automotive components [1]. In this study, a 5754-0 aluminum alloy with a thickness of 1mm was laser-welded by a 2kW Nd:YAG laser to produce a total of approximately 120 samples of TWBs with a similar thickness combination of 1mm/1mm. From the knowledge of the weld surfaces, weld profiles and tensile properties of the specimens of TWBs, the optimal welding parameters were identified and used to produce TWBs of varying widths and welding orientations for the Swift forming test. Thus, it was possible to measure and analyse the forming behavior, including the failure mode and the forming limit diagram (FLD), of the TWBs. In this study, satisfactory TWBs were produced by applying a pulsed laser beam with an average power of 1100W and a welding speed of 35mm/s. Despite some failures of the specimens at the welds during the tensile test, it was found that all of the TWBs provided almost the same yield strength (YS) and ultimate tensile strength (UTS) as those of their parent metal, while the TWBs with transverse welds retained over 94% of their original ductility. Irrespective of the major loading direction during the forming test, the failures appeared somewhere away from the welds and heat-affected zones (HAZs) on the TWBs, with transverse welds such that the TWBs provided the same formability as the original 5754-0 sheets. For TWBs with longitudinal welds, the failures were found to have initiated at the weld propagating perpendicularly to the major loading direction. This resulted in a lower level of FLD.