Abstract: The butt welding-brazing joining of 5A06 aluminum alloy to the galvanized steel sheet with filler powder is successfully conducted by a new welding method named the arc-assisted laser welding-brazing. The weld bead appearance and the interfacial microstructure of butt joint are analyzed, and the tensile strength of the joint is measured. The results indicate that a high quality welding-brazing joining can be achieved using the appropriate welding parameters. With this new technology, the assisted arc greatly makes the melting of aluminum increased, and effectively enhances the wetability of liquid metal on the back of steel. In addition, the interfacial reaction is improved at the bottom of the joint. A non-uniform intermetallic compounds(IMC) is formed by the galvanized steel reacting with the melted metal at the interfacial layer, and this reaction layer thickness is not constant along the seam-steel joint since it varies from 3 to 12 μm. The thickness of IMC increases with the increasing of welding current. Energy dispersive spectrometer(EDS) and X-ray diffraction(XRD) show that the one is Fe2Al5, tongue-like, close to steel substrate. The other is Fe4Al13, floccule-like, close to the seam. When the welding current increases from 10 A to 20 A, the tensile strength of the brazed-fusion welded joint firstly increases and then decreases. Its maximum tensile strength is up to 163 MPa. The fracture begins at the bottom of the joint and the lower part of the welded seam-steel interfacial layer, which is the weak bonding zone of the joint. Comparing with the single laser welding-brazing method, the reactive wetting and spreading behavior of molten aluminum on steel are improved with the assisted arc, thus the superior joint strength can be obtained in the condition.

Key words: aluminum alloy and steel, arc-assisted, intermetallic compounds, mechanical property, welding-brazing