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Abstract:The fabrication of dissimilar joints for electrical applications raises challenges for conventional joining technologies. Within solid-state processes, friction stir welding (FSW) provides numerous advantages to realize different joint configurations. However, depending on the intermixing of the materials, defects like hooking and significant intermetallic compound formation around copper fragments are observed and lead to a decrease in joint properties. Therefore, stationary shoulder FSW was applied to produce 2 mm EN AW1050/CW024A lap joints with minimized intermixing at the interface. Compared to conventional FSW, the range of the friction-based heat input can be increased without risking excessive plastification under the tool shoulder. The influence of the pin length on the interfacial structure as well as the mechanical properties were investigated. A pin length of 2.2 mm and hence a plunging of approximately 0.2 mm into the lower copper sheet was found to obtain the highest failure load. A further increase caused the formation of hooking defects, which led to void formation at the interface and failure within the area of the thinned aluminium sheet. The results were also transferred to lap joints with a tin and silver interlayer of 10 µm and also showed good results in terms of bond strength and contact area.

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The following paper describes a feasibility study of butt joining friction stir welding between aluminum alloy AA6016 and magnesium alloys AZ91 and AM50. Because of the variety of inimitable properties according to lightweight design and constructions, the interest in aluminum and magnesium alloys is increasing in many fields of industry. Due to the low solubility of aluminum in magnesium and inverse, these alloys tend to the formation of intermetallic phases during the joining process. This leads to an increasing micro hardness within the seam, which should be avoided. By the use of joining methods with low process temperatures, the formation of intermetallic phases is reduced. According to this circumstance, friction stir welding is an excellent alternative to fusion welding techniques used to join this alloys. The main welding process variables were exposed in the studies of similar butt joints of Al/Al and Mg/Mg. These were examined in connection to their transferability to the dissimilar joints and tailored blanks. Furthermore, the influence of different tool geometry on seam quality was investigated. The effect of process variables (mainly welding speed and revolution speed) were correlated to the results of tensile strength test. The welded samples were assayed in the presence of intermetallic phases.

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Within the last decade, Friction Stir Welding (FSW) has increasingly been gaining relevance for joining nonferrous metals, especially aluminum alloys. Possible applications range from the aerospace and automotive sector up to manufacturing electrical components. Compared to conventional fusion welding processes, FSW offers numerous advantages, as it for example does not require shielding gas or filler material. However, FSW is still not applied or taken into account during the product development process in proportion to its potential. This is mainly caused by the lack of data in order to evaluate the process economically and differentiate it to other processes like arc and laser welding, also regarding technological factors. Therefore, this investigation focusses on the possibilities and limits when joining wrought and cast aluminum alloys, like EN AW-6082 T6, EN AW-7075 T651 and AlSi11Mg0,3, respectively, by FSW compared to MIG. The weld quality of the samples is characterized by tensile testing, hardness measurements and microstructure analysis. Furthermore, an approach to reduce the process forces by using FSW tools with reduced diameters and respectively adjusted process parameters is presented.

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