It is well known that aluminum alloys have inherent and versatility properties such as resistance to corrosion, good formability, a good strength to weight ratio, low density and electrical and thermal conductivity. These properties make it a high-demand material compared to the steel alloys in industrial application, particularly in the automotive, shipbuilding, packaging, construction and architecture fields, etc. With the growth of demand for aluminum alloys in a wide variety of applications, the welding and manufacturing process of aluminum alloys requires special knowledge and experiences. The welding of aluminum alloys by fusion welding techniques produces some defects such as pores, loss of some elements, hot cracking, stress corrosion cracking, and mismatch between the filler alloy and the workpiece material in dissimilar welding, causing the loss of strength of the weld joint [1
]. To overcome these problems, the solid-state welding techniques are the best alternatives for the welding of aluminum alloys.
Aluminum-magnesium alloys are non-heat-treatable alloys which provide good mechanical properties, corrosion resistance, and good workability and weldability. These excellent properties make it an attractive material in a wide range of construction and structural applications in the automotive and shipbuilding industries. Aluminum alloy EN AW5083 is one of the aluminum-magnesium alloys and it has high mechanical strength and fusion weldability [2
]. The aluminum-magnesium-silicon alloys are heat-treatable alloys and have a medium strength with excellent corrosion resistance. These alloys are being used in automotive parts, especially in body sheets to decrease their weight. EN AW6082 alloy is one of the aluminum-magnesium-silicon alloys and it has very good weldability, but its strength is lowered in the weld zone [3
]. Many studies have focused on the friction stir welding (FSW) process of aluminum alloys and it is well known that some of aluminum alloys cannot be welded by the fusion welding process. Therefore, in order to achieve more information about the FSW process, critical factors such as the tool design, rotational speed and welding speed have been subjected to investigation. There are many studies related to the FSW of EN AW5083 and EN AW6082, but the dissimilar FS welding of these alloys is limited. Also, in most of the studies, the tool pin shape is a straight, cylindrical threaded profile. There are some studies in the literature on dissimilar FS welding of EN AW6082 and EN AW5083. Peel et al. [4
] performed studies to determine the effect of the tool rotational and welding speed on the microstructure of welding zones and weld properties of dissimilar FSW EN AW5083–EN AW6082 joints. Donatus et al. [5
] focused on identifying corrosion-susceptible regions of dissimilar friction stir welds of EN AW5083-O and EN AW6082-T6. Donatus et al. [6
] performed dissimilar FSW studies on EN AW5083-O and EN AW6082-T6 to investigate the material flow in the friction stir welds. Steuwer et al. [7
] investigated the effect of the welding parameters on the residual stress profiles on the same welds. Apart from these studies, Leitão et al. [8
] conducted two-stage experimental studies in order to determine the effect of FSW parameters on each material and the weldability of dissimilar alloys at high temperature. Sun et al. [9
] studied the dissimilar friction stir welding of ultrafine-grained 1050 and 6061-T6 aluminum alloys to understand joint characterization. Aval et al. [10
] investigated the thermo-mechanical behavior and microstructural events of dissimilar FSW of AA6061-T6 and AA5086-O.
The present study is focused on the effect of tool geometry and the ratio of the tool rotational speed to the welding speed (υ ratio) on the mechanical and macrostructural properties of dissimilar FSW of EN AW6082-T6 and EN AW5083-H111 alloys.