Ultrasonic spot welding of aluminium to steel for automotive applications—microstructure and optimisation

Abstract

Energy efficient methods for joining aluminium to steel have potential for major applications in the automobile industry. Results are reported where 1 mm gauge 6111 aluminium and DC04 steel automotive sheet have been successfully joined using the novel process of high power ultrasonic spot welding. The microstructure and performance of the joints were examined, as a function of the welding conditions. A maximum failure load of 2·8 kN was obtained in lap shear tests, compared with 2·9 kN for comparable AI-AI joints. The failure mode changed from interfacial debonding to nugget pullout and back to interfacial failure as the weld energy increased. A thin <2 μm reaction layer of FeAI3 and Fe2Al5 formed at the interface with increasing weld energy. The factors determining the joint characteristics, interface reaction, and the microstructure evolution in the welds are discussed.

Interfacial Characterization of Dissimilar Joints Between Al/Mg/Al-Trilayered Clad Sheet to High-Strength Low-Alloy Steel

“…It is seen that the interface microstructure in both joining conditions appeared similar. In contrast to the results reported, [29][30][31][32] no visible intermetallic compound (IMC) layer at the interface was observed. To confirm this, an EDS line scan across the interface in both joining conditions was performed, and the obtained results are shown in Fig.…”

“…These observations are believed to be associated with the low welding energy and very short welding time (0.1-0.4 s), in comparison with those applied by others (0.1-3 s). 29,30 Certainly, Al has a fairly high solubility in Fe and it can form disordered solid solution in Fe up to $11 wt.% of alloying as seen from Fe-Al binary phase diagram. 34,35 Beyond this critical amount of Al, some brittle IMCs such as D0 3 -based Fe 3 Al and B2-based FeAl would emerge.…”

Mechanical analysis of ultrasonic welding considering knurl pattern of sonotrode tip

“…Under the combined effect of normal stress and vibratory shear stress caused by ultrasonic vibration of sonotrode, large areas of materials come into plastic deformation phase [21]. Experimental results [22][23][24][25][26] showed that localized frictional heating and plastic deformation at the contact area are critical factors for the initial formation of ultrasonic weld joints. A great deal of plastic deformation and material flow occurs across the faying interfaces of workpieces.…”

Optimised design of electrode morphology for novel dissimilar resistance spot welding of aluminium alloy and galvanised high strength steel

“…Several solid state welding methods such as explosive welding [11,12], ultrasonic welding [13], magnetic pulse welding [14], friction welding [15] and friction stir welding [16][17][18] are adopted to weld aluminium alloy and steel. The brittle intermetallic compounds are desired to be diminished by using these solid state welding methods.…”

“… 13. shows numerical simulated distribution of current density in the welded joint and electrodes during resistance spot welding of…”