1：Experimental Design and Method Selection:

Dual beam laser welding-brazing method was used without filler metal. An orthogonal test was performed to determine optimal parameters, with the derived laser beam introduced to achieve higher temperature on the steel surface. The laser beam was inclined at 7° to prevent reflection, with +10 mm defocus and welding speed of 0.7 m/min.

2：7 m/min. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Materials were 1.2 mm thick DP590 galvanized steel and 1.0 mm thick AA7075 aluminum alloy in lap configuration with 10 mm overlap. Samples were cleaned with acetone and mechanically abraded to remove oxides.

3：2 mm thick DP590 galvanized steel and 0 mm thick AA7075 aluminum alloy in lap configuration with 10 mm overlap. Samples were cleaned with acetone and mechanically abraded to remove oxides. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: IPG fiber laser (Model: YLS-10000), six-axis Motoman industrial robot, High-YAG laser head, argon shielding gas, electrical discharge machining, optical microscope (OM), scanning electron microscope (SEM) with EDS, Zwick T1-FR020TN-A50 mechanical testing system.

4：Experimental Procedures and Operational Workflow:

Laser power varied from 0.8 to 1.6 kW. Cross-sections prepared via EDM, grinding, polishing, and etching with Keller's agent. Microstructure analyzed by OM and SEM/EDS. Tensile tests performed at 0.2 mm/min stroke rate.

5：8 to 6 kW. Cross-sections prepared via EDM, grinding, polishing, and etching with Keller's agent. Microstructure analyzed by OM and SEM/EDS. Tensile tests performed at 2 mm/min stroke rate. Data Analysis Methods:

5. Data Analysis Methods: Wetting angle and distance measured from cross-sections. IMC thickness calculated as area divided by length. Tensile strength evaluated by peak load divided by aluminum sheet area, with three specimens per condition.