This research concerns a dissimilar metal joining of steel and aluminium (Al) alloys by means of zinc (Zn) insertion. The authors propose a joining concept for achieving strong bonded joints between Zn-coated steel and Al alloys. A eutectic reaction between Zn in the Zn coating and uniform Al-Fe intermetallic compound (IMC) layer at the joint interface, leading to a strong bonded joint. The ultimate aim of this research was to apply this joining concept in the resistance spot welding process for manufacturing vehicle bodies. As a practical issue characteristic to joints of dissimilar metals, anticorrosion measures against electrochemical corrosion must be undertaken. If there is moisture near a joint interface of dissimilar metals, electrochemical erosion will progress. Therefore, a sealing function that could prevent moisture intrusion is required. By applying the above-mentioned welding process to a set of metals with thermosetting resin spread in between, we realized seal spot welding, which not only prevented moisture intrusion but also retained high tensile strength. In this research, first, a cyclic corrosion test was performed on the seal spot-welded joint of galvanized (GI) steel, a steel grade widely distributed in Japan, and Al alloy was bonded by seal spot welding, and the following topics are discussed. Complete removal of sealant from the joint interface is the key to realizing the high tensile stress joint, because remaining sealant will lead to reduction in tensile strength. Therefore, heat generation at the interface was monitored by measuring electrical current and potential difference between the two electrodes, and a precise temperature control was performed. Moreover, the bonding process was clarified by stepwise analysis of the joint interface using optical microscopy, and a guideline for producing strong joints was proposed. And finally, a TEM observation also confirmed that the interface structure of the seal spot-welded joint was the same as joints without the resin; a thin and uniform Al-Fe IMC layer was formed and a strong metallurgical bonding was achieved.
This research describes a dissimilar metals joining of steel and aluminum (Al) alloy by means of zinc (Zn) insertion. The authors proposed a joining concept for achieving strong bonded joints between Zn coated steel and Al alloy. A eutectic reaction between Zn in the Zn coating and Al in Al alloy is used to remove the dense, strong oxide film on Al alloy surface at low temperature, thereby resulting in the formation of a thin, uniform Al-Fe intermetallic compound (IMC) layer at the joint interface, leading to a strong bonded joint. The ultimate aim of this research is to apply this joining concept in the resistance spot welding process for manufacturing vehicle bodies. This paper discusses the effectiveness of this joining concept by bonding galvanized (GI) steel sheet with Al alloy sheet, and galvannealed (GA) steel sheet with Al alloy sheet, by resistance spot welding.A precise observation of the combination of GI steel sheet and Al alloy sheet joint interface confirmed that a thin, uniform Al-Fe IMC layer can be formed with this process as a result of enveloping the oxide layer on the Al alloy surface in the eutectic melt and effectively evacuating it from around the periphery of the joint area. An excellent joint property was achieved by the realization of such a metallurgical bonding. As for the combination of GA steel sheet and Al alloy sheet, oxide film on Al alloy surface was removed by liquid phase formed by diffusion between Al and Fe-Zn alloyed coating layer; the formation of Al-Fe IMC layer was confirmed by observation of the joint interface. The Al-Fe IMC layer was thick and non-uniform, compared with GI steel and Al alloy. The difference is believed to be based on the difference in bonding process caused by different coating types.The region with Al-Fe IMC layer thickness of less than 2μm was defined as the effective bonded length. A clear correlation between the effective bonded length and the tensile strength was seen. An improvement of tensile strength was attempted by optimization of electrode shapes and welding conditions, considering differences in bonding processes of each metal combination, and a guideline for realizing high tensile strength was clarified.From above considerations, dissimilar metals joining between steel and Al alloy by the resistance spot welding was realized.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.