Friction stir welding, FSW, of harder metal alloys is difficult to perform, like here dissimilar welding of titanium alloy to stainless steel in butt joint configuration. One major limitation is tool wear which can be reduced by preheating with a laser beam. A mathematical model to calculate the tool forces during FSW was developed further. The calculations show that the laser beam reduces forces at the pin and shoulder of the FSW-tool, accompanied by reduced heat generation through the tool. Within its operating limits, the process has low sensitivity on the lateral position of the leading laser beam. The model supports the understanding and optimisation of the complex interaction zone of forces and heat around the FSW-tool.

Welding of thick section butt joints experiences limitations for different techniques. One option is to fill a narrow gap layer by layer with laser melted wire, a laser metal deposition technique where the complexity of a keyhole is avoided. The presented results show that wire addition can enable relatively thick layers. In particular, when electrically preheating the wire the process becomes more energy-efficient and favorable wetting conditions might be achieved. Since the wire was preheated by an electric current conducted through the wire to the workpiece, high speed imaging has shown that the wire tip can occasionally ignite small electric arcs. The wire deposited in the narrow gap also shows a fluctuating but self-stabilizing movement of the tip. Imperfections that have to be avoided are hot cracks, cavities, lack of fusion, and an irregular final weld surface topology. The technique shows high potential.

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.