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Abstract: 5052 aluminum alloy sheets and galvanized mild steel sheets were joined in lap configuration by alternate-current double pulse gas metal arc welding with pure Al, Al–5Si, Al–12Si and Al–4.5Mg (wt%) filler wires. The effect of alloying elements on the microstructure of intermetallic compounds (IMC) layers formed between weld seam and steel, and tensile strength of the resultant joints were investigated. The thickness of IMC layer in all samples varied along the cross-section of the joint, the intermediate part of the IMC layer was thicker than the head and root parts. The diffusion of Si into Fe2Al5 sub-layer could restrain the growth of Fe2Al5 sub-layer and IMC layer, and joint's mechanical property improved with the increasing Si content in Fe2Al5 phase. Due to the high hot crack sensitivity of Al–4.5Mg alloy, cracks generated at the root of joint made with Al–4.5Mg filler, resulting in poor mechanical property. [Copyright &y& Elsevier]

Abstract: 5052 Al alloy sheets and galvanized mild steel sheets were joined by gas metal arc welding with three different current modes, including direct-current pulse gas metal arc welding (DPG), alternate-current pulse gas metal arc welding (APG) and alternate-current double pulse gas metal arc welding (ADG). The effect of current mode on size, distribution and volume fraction of pores generated in Fe–Al dissimilar materials lap joint was quantitatively studied. EDS result showed that pores in Fe–Al joint were mainly caused by trapped zinc metal vapor from galvanized steel. Volume fraction of pores in joints made by APG and ADG processes was larger than that in joint resulted from DPG process. Moreover, pores in joints made by APG and ADG processes had smaller diameter, and tended to distribute in the middle of the weld seam. On the contrary, pores with large diameter were inclined to distribute close to upper weld surface of the joint resulted from DPG process. These results are attributed to the difference of arc stirring force and linear heat input in these three processes caused by different current modes. [Copyright &y& Elsevier]