Abstract
The influence of different coatings on the weldability of Al/steel was assessed in this study. Different kinds of the coatings, which included pure zinc coating, Fe-Zn coating and without coating, were considered. The thickness of the coating was also studied. Different configuration of overlap and butt joint was used, and different welding methods including cold metal transfer (CMT) welding-brazing and laser welding-brazing with filler metal were investigated. Samples were fabricated and the weld appearance, microstructure and composition analyses of the joints were examined. It was found that the Al to steel without coating could not be welded due to the formation of large amount of brittle Fe-Al intermetallic compounds (IMC). The coating helped suppress the formation of IMC and a welding-brazing joint was produced. However, pure Zn coating enhanced the wetting of molten filler onto the solid steel substrate, but Fe-Zn coating barely enhanced the molten filler to wet the steel substrate. The coating with a thickness of 10-20 μm contributed to a better performance of Al/steel joint.
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