This paper focuses on the improvement of hybrid Cu/Al weld performance via a combination of self-reacting brazing mechanism (for stable metallurgical transformation) and process modification approach (for the elimination of tool profile-induced stress-raiser). The modified friction stir clinching-brazing (MFSC-B) and friction stir spot welding-brazing (FSSW-B) of dissimilar AA5083-H321 aluminum and commercially pure Cu alloys are investigated with the use of a thin Zn intermediate layer. The load-bearing capacity, fracture behavior, and microstructure of the respective joints are investigated and compared. The results show that plausible intermetallic phases of Al–Cu (Al2Cu and Al4Cu9) and Cu–Zn are present at the stir zones of all the joints while the brazed zone of the MFSC-B joint is predominated by uniform lamellar eutectic structure due to higher heat input, localized two-fold Zn melting, and frictional-stirring activated eutectic transformation. The increase in the load-bearing area (brazed + stir zones) of the MFSC-B joint improved the fracture resistance of the joint by 59% as the average tensile-shear loads of about 7.0 and 4.4 kN were obtained in the MFSC-B and FSSW-B joints respectively. The use of MFSC-B is thus recommended as a reasonable alternative for improving the weld performance of dissimilar reactive metals.

Microscopic appraisal and mechanical behavior of hybrid Cu/Al joints fabricated via friction stir spot welding-brazing and modified friction stir clinching-brazing

Hybrid joining (HJ) is the combination of two or more joining techniques to produce joints with enhanced properties in comparison to those obtained from their parent techniques. Their adoption is widespread (metal to metal joint, composite to composite and composite to metal) and is present in a vast range of applications including all industrial sectors, from automotive to aerospace, including naval, construction, mechanical and utilities. The objective of this literature review is to summarize the existing research on hybrid joining processes incorporating structural adhesives highlighting their field of application and to present the recent development in this field. To achieve this goal, the first part presents an introduction on the main class of adhesives, subdivided by their chemical nature (epoxy, polyurethane, acrylic and cyanoacrylate, anaerobic and high-temperature adhesives) The second part describes the most commonly used Hybrid Joining (HJ) techniques (mechanical fastening and adhesive bonding, welding processes and adhesive bonding) The third part of the review is about the application of adhesives in dependence of performance, advantage and disadvantage in the hybrid joining processes. Finally, conclusions and an outlook on critical challenges, future perspectives and research activities are summarized. It was concluded that the use of hybrid joining technology could be considered as a potential solution in various industries, in order to reduce the mass as well as the manufacturing cost.

P.Q. Wang

Papers

Microstructure and mechanical properties of Mg-to-Al dissimilar welded joints with an Ag interlayer using ultrasonic spot welding