Liquid interlayer formation during friction stir spot welding of aluminum/copper
The fabrication of dissimilar aluminum/copper joints for electrical application raises the challenges for conventional joining technologies. Within the solid-state processes, friction stir welding (FSW) provides numerous advantages to realize different joint configurations, especially by minimizing the heat input and hence the formation of brittle intermetallic phases. However, the joints also have to provide a high contact interface with firm bonding in order to provide a minimal contact resistance. Therefore, joints of 1 mm ENCW004A and EN AW1050A with a controlled melt layer formation were produced by friction stir spot welding (FSSW). By using a pinless tool and the positioning of copper as the upper joining partner, local melt formation at the interface with a eutectic composition was promoted without significant intermixing, resulting in wetting of the aluminum and a contact area increase. The rotational speed was varied between 1800–2400 rpm, in which range samples with up to 300-μm-thick melt layers were produced. The wetting effect at the interface shows a positive influence on the shear strength with ductile failure behavior even at high layer thickness. The microstructural composition at the interface showed a eutectic composition for small layer thickness and an inhomogeneous composition with hypo- and hypereutectic solidification structures for higher thickness values. However, the formation of intermetallic compounds other than CuAl2 was mostly inhibited by the short process times and high cooling rate.
KeywordsFriction stir welding Solidification Electric contacts Lap joints Dissimilar materials
The IGF Project No. 19.036 B of the research association “Schweißen und verwandte Verfahren e.V.” of the DVS, Aachener Straße 172, 40223 Düsseldorf, was, on the basis of a resolution of the German Bundestag, promoted by the Federal Ministry for Economic Affairs and Energy via AiF within the framework of the program for the promotion of joint industrial research and development (IGF). The authors thank all the participants for the support.
The authors thank all the participants for the funding.
- 7.Schürer R, Weigl M, Döhner J, Bergmann JP (2015) Robotergestütztes Rührreibschweißen als flexibleLösung in der modernen Fertigung. DVS Congress, NürnbergGoogle Scholar
- 9.Mubiayi MP, Akinlabi ET (2015) Friction stir spot welding between copper and aluminium: microstructural evolution. Proceedings of the International MultiConference of Engineers and Computer Scientists, Vol 2Google Scholar
- 10.Heideman R, Johnson C, Kou S (2010) Metallurgical analysis of Al/Cu friction stir spot welding, Scienceand Technology of Welding and Joining, Vol. 15, Issue 7Google Scholar
- 12.Gündüz M, Cadirli E Directional solidification of aluminium–copper alloys. Mater Sci Eng 327:167–185Google Scholar
- 14.Han Y, Ben L, Yao J, Feng S, Wu C (2015)Investigation on the interface of Cu/Al couples during isothermal heating, Int J Miner Metall Mater, Volume 22Google Scholar
- 15.Yang YK, Dong H, Kou S (2008) Liquation tendency and liquid-film formation in friction stir spot welding. Weld J 87:202–211Google Scholar
- 17.Sun SH, Li J, Zhao YW, Zhao HL, Xu R, Liu RP (2008) Study on eutectic transformation in Al-Cu alloys under 5 GPa pressure condition. Phys Test Chem Anal Part A 44:465–466Google Scholar