Abstract
In response to global environment and fuel efficiency regulations aiming to reduce CO2 emissions, multi-material structures that use lightweight materials are currently being developed to realize the weight reduction of vehicles in automotive manufacturing. The dissimilar welding of aluminum alloy to steel has great importance, but it is still challenging due to their widely varying thermo-physical properties and the formation of intermetallic compounds. This study aimed to investigate the effect of process parameters on the wettability, mechanical properties, and microstructure in AC Pulse MIG welded joints of AA6061-T6 and galvanized steel sheets. A parametric study on torch aiming position and welding current with EN ratio variation was performed to optimize the process parameters. The result showed that the amount of metal deposition increased with EN ratio. When the EN ratio was higher, the wire feeding speed increased and the heat input process lowered. Moreover, the wetting length increased, ranging from 6.6 to 8.4 mm, and the wetting angle increased from 31.2 to 67.6°, respectively. As a result of the tensile shear test, the maximum tensile shear load of dissimilar welded joints produced at 70 A with a 20% EN ratio was approximately 8.8 kN. From the result of scanning electron microscopy with energy-dispersive spectrometry, FeAl3 IMC was observed at the joint interface, and the IMC layer thickness decreased with EN ratio at 70 A.
Highlights
An environmental problem, global warming, has recently been in the spotlight
Dissimilar braze welds were produced under the following welding parameters: welding current of 70 A with an EN ratio of 0%, welding voltage of 19 V, and welding speed of 500 mm/min
The result indicated that the torch aiming position, the distance from the edge of the Al alloy sheet, had a considerable effect on wettability and joint strength
Summary
An environmental problem, global warming, has recently been in the spotlight. Intermetallic compounds (IMCs) are generated at the joint interface, which is significantly brittle. Due to the formation of brittle intermetallic compounds, the weld is weakened and the strength decreases. It is necessary to reduce the generation of intermetallic compounds, and a low-heat input process is required as a solution. Yagati et al studied the dissimilar joining of an Al alloy to galvanized steel (GI), galvanized steel (GA), and uncoated steel using double pulse MIG welding. They reported that the spreadability and wettability of the filler wire were significantly improved due to the zinc (Zn) layer, when the hot-dip GI steel sheet was used to join the dissimilar materials. The lap joining of a 1 mm-thick Al alloy and stainless steel (STS)
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