**2. Experimental Methods**

In this study, sheets of aluminum alloy EN AW-6014 T4 were joined with sheets of galvanized mild steel DC04 by means of the single-sided cold metal transfer [47,48] process. The metal sheets were clamped gap-free in horizontal butt-joint position, as schematically illustrated in Figure 1. The dimensions were 250 mm × 150 mm × 0.80 mm for the steel sheet, and 250 mm × 150 mm × 1.15 mm for the aluminum alloy sheet.

**Figure 1.** Schematic illustrations of the welding configuration (dimensions in mm): (**a**) front view of the weld butt [46], (**b**) top view showing the positions and the numbering of six thermocouples.

The welding equipment included a Fronius CMT Advanced 4000 power source and a Fronius CMT Braze + torch (Pettenbach, Austria), mounted to the arm of a KUKA KR 30-2 robot (Augsburg, Germany). A filler wire of non-commercial aluminum alloy Al-0.3Mg-0.5Sc-0.4Zr was used. Both feeding of the filler wire and supply of the shielding gas were achieved through the welding torch. The main process parameters applied in the welding experiments are summarized in Table 2, and the nominal compositions (wt %) of the materials are listed in Table 3.




**Table 3.** Nominal compositions (wt %) of the materials used in the experiments [46].
