Microstructure and corrosion resistance analysis of aluminum/steel "arc+ friction stir" hybrid additive manufacturing

In order to realize the manufacturing of aluminum-steel composite structures, this study proposed a new method of "arc + friction stir" hybrid additive manufacturing. First, BC-MIG welding is applied to deposit a thin transition layer of aluminum alloy on the surface of galvanized Q235 steel, and after which the transition layer and the the 6061 aluminum alloy is produced by friction stir additive manufacturing. During the arc deposition of the transition layer, the galvanized layer and the bypass arc have promoted the wetting and spreading of droplets on the steel surface, thus help to form a flat surface.The subsequent friction stir additive manufacturing process eliminated porosity and cracks in the transition layer and brought about a well-formed and defect-free aluminum-steel composite structure.The effects of different wire compositions (Al-Si and Al-Mg) on the microstructure and corrosion resistance of Al-steel composite structures were investigated.The results showed that the wire composition, instead of affecting the weld formation, will affect the thickness of the Fe-Al intermetallic compounds layer at the interface. Besides, the corrosion resistance of Al-steel structures filled with Al-Si wire is better than that with Al-Mg wire, as galvanic corroion will occur among the intermetallic compounds at the interface, while the substrate is tend to be corroded first, so that the corrosion resistance of the Al-steel composite structure is decreased.