Enhanced Long-Term Reliability of Seal DeltaSpot Welded Dissimilar Joint between 6061 Aluminum Alloy and Galvannealed Steel via Excimer Laser Irradiation

Abstract

Structural-adhesive-assisted DeltaSpot welding was used to improve the weldability and mechanical properties of dissimilar joints between 6061 aluminum alloy and galvannealed HSLA steel. Evaluation of the spot-weld-bonded surfaces from lap shear tests after long-term exposure to chloride and a humid atmosphere (5% NaCl, 35 °C) indicated that the long-term mechanical reliability of the dissimilar weld in a corrosive environment depends strongly on the adhesive–Al6061 alloy bond strength. Corrosive electrolyte infiltrated the epoxy-based adhesive/Al alloy interface, disrupting the chemical interactions and decreasing the adhesion via anodic undercutting of the Al alloy. Due to localized electrochemical galvanic reactions, the surrounding nugget matrix suffered accelerated anodic dissolution, resulting in an Al6061-T6 alloy plate with degraded adhesive strength and mechanical properties. KrF excimer laser irradiation of the Al alloy before adhesive bonding removed the weakly bonded native oxidic overlayers and altered the substrate topography. This afforded a low electrolyte permeability and prevented adhesive delamination, thereby enhancing the long-term stability of the chemical interactions between the adhesive and Al alloy substrate. The results demonstrate the application of excimer laser irradiation as a simple and environmentally friendly processing technology for robust adhesion and reliable bonding between 6061 aluminum alloy and galvannealed steel.

Effect of intermetallic compound on the corrosion behaviour of resistance spot welding joints between 5182 aluminium alloy and galvanized DP780 dual-phase steel

“…Structural adhesives dramatically reduced galvanic corrosion between aluminium alloy and steel substrates [7,10,11]. Joo et al [12] further indicated that the long-term mechanical reliability of the aluminium/steel RSW joints in a corrosive environment is strongly dependent on the bond strength. Including the metal substrates and the Zn coatings, the interfacial intermetallic compound (IMC) layer are essential for bonding between aluminium and steel substrate in RSW joint [2,7,10].…”

Archives of Metallurgy and Materials

“…hot-dip Zn-galvanized steel sheets are widely used in various industrial applications, such as building construction and automotive panels, because of their high corrosion resistance owing to the sacrificial protection of Zn, which possesses relatively low corrosion potential as compared to Fe [1,2]. many studies have been conducted for further improving their corrosion resistance by alloying mg and al with Zn to meet industrial demands and reduce the Zn-resource consumption [3][4][5][6].…”