Effect of welding parameters on mechanical properties of friction stir welded T-lap dissimilar metal joints between 7075 and 5083 aluminum alloys

Abstract

Dissimilar T-lap joint between aluminum alloy 7075-T651 and 5083-H116 was fabricated by friction stir welding. Special focus was paid to the defect formation and mechanical properties which were significantly affected by the welding parameters. The results showed that four typical types of defects were detected in the T-lap joint; tunnel, kissing bond, hook, and bonding line defects. The tunnel and bonding line defects could be avoidable by decreasing the welding rate. At low welding rate, however, the hook defect was formed and reduced the skin effective thickness. The kissing bond defect was too hard to be eliminated by using one welding pass only by changing the welding parameters. Among these defects, the hook defect played the important role in the mechanical properties of T-lap joint. It is a special finding that there was the optimum welding rate by which the maximum joint efficiency was attained. These findings were summarized into the table and map which can optimize the joint properties.

Effects of tool offset and reversed metal flow on mechanical properties of dissimilar friction stir welded T-lap joints between AA7075 and AA5083

“…It can be seen that two types of bondings were achieved along the welding interface; i.e. an interface associating with kissing bond defects (as denoted by KBs) with oxide layer, and bonding interface with little oxide layer, as reported by Hao et al (2019). It is worthy to note that the welding interface produced by the single-pass FSW was associated with pronounced KBs at the RS1 (Fig.…”

“…This might lead to the mixture of material at the AS1 was more severe than that at the RS1, as reported by Feistauer et al (2018), Donatus et al (2015), and Buffa et al (2008). In addition, the KBs at the RS1 must be achieved by horizontal material flow that moved from the RS1 to the AS1, as reported by Hao et al (2019). In other words, a mere single-pass FSW is not enough to minimize the KBs in the T-lap joint.…”

“…The tool shoulder was penetrated into the surface of skin plate with the depth of 0.2 mm during the welding process. Through this work, the welding speed and rotational speed were chosen by 100 mm/min and 400 rpm, respectively, based on the previous work (Hao et al, 2019).…”

“…However, the strength of the joint was not satisfactory. The effects of some FSW parameters on the T-joint characteristics have been investigated to improve the joint efficiency from the viewpoints of the metal flow (Fratini et al, 2009), welding speed (Cui et al, 2012;Hao et al, 2019), and tool geometry (Jesus et al, 2018). In spite of these, the T-lap joint efficiency has still been unsatisfactory, especially in stringer loading test.…”

Effect of surface oxide layers in solid-state welding of aluminium alloys – review

“…Residual oxide has a higher influence on the weld properties during FSSW than FSW. FSSW is mostly used for obtaining lap joints and recently there is an emerging trend to use the pin-less tool [97][98][99][100]. When a conventional tool (with a pin) is used to weld spot lap joints, a weld zone is only a small ring area surrounding the keyhole which arose after tool retraction.…”