Bonding mechanism and interface characterisation during dissimilar friction stir welding of an aluminium/polymer bi-material joint

Abstract

In the present study, detailed microstructural characterisation of a friction-stir-welded joint between AA5059 alloy and high-density polyethylene was carried out using field-emission scanning and high-resolution-transmission electron microscopy analysis. The structural features indicate large numbers of macro-, micro-and nano-mechanical interlocks between the Al-fragments and melted/re-solidified polymer matrix at the stir zone of the joint, with a 30-nm thick semi-crystalline aluminium structure layer elevated in levels of O, and traces of C at the interface. An ultrafinegrained structure with an average cell size of <100 nm was formed for the embedded Al-alloy fragments in the polymer matrix, as a result of low-temperature severe plastic deformation during friction-stir welding process. The interfacial chemical reactions assisted by generation of nanoscale pores inside the metal surface at the interface and secondary Van der Waals bonding are suggested as the main joining mechanisms, leading to significant improvements in the mechanical properties.

Improving appearance and mechanical strength of aluminum-polypropylene/talc composite friction stir joint using a novel tool design

“…Covalent bonds or Van der Waals attraction can be formed between this oxide layer and carbon and hydrogen from the polymer chains in the SZ which may enhance adhesion between them. Other researchers have also reported formation of Al 2 O 3 at the aluminum/polymer interface and formation of hydrogen bonds between oxygen from the oxide layer and hydrogen from the polymer chains [23,33]. Additionally, Meng et al [36] reported that a porous oxide layer created intentionally on the aluminum surface before joining (for example using chemical or electrochemical treatments) was more effective in formation of secondary bonds.…”

“…FSJ, based on the friction stir welding concept, is claimed to include the advantages of both mechanical and chemical joining mechanisms for the metal-polymer joints. Compared to the other joining methods, FSJ also needs less surface preparation and provides shorter joining time, as well as low energy consumption and high economic advantages [20][21][22][23].…”

Assessment of dissimilar joining between metal and polymer hybrid structure with different joining processes

“…Rotating tool helps in the formation of Al chips in the weld stir zone by movement of tool along the bonding line. 49 Aluminum fragments found in the stir zone shown in Figure 1 shows the schematic diagram of FSW and Bonding mechanism of dissimilar metal to polymer. Where the size of Al fragments minimized by increasing the tool rotational speed or by decreasing the tool traverse speed.…”

Comparative assessment on weldability of Al 6061 to polycarbonate for dissimilar sheets placement in friction stir lap welding using sensor signals

“…Here, the joint is formed by mechanical interlocking in the weld stirred zone due to severe plastic deformation at the weld interface even at low frictional heat input conditions. 10 The weld hardness increases with welding speed in dissimilar friction stir butt welding of AA6061 and poly-methyl methacrylate in which the interlocking has also found a significant role. 11 Thus, the feasibility of FSW in dissimilar Al 7075 alloy to polycarbonate butt welding has also been studied.…”