Investigation of Mechanical and Microstructural Properties of Welded Specimens of AA6061-T6 Alloy with Friction Stir Welding and Parallel-Friction Stir Welding Methods

Abstract

The present study investigates the effect of two parameters of process type and tool offset on tensile, microhardness, and microstructure properties of AA6061-T6 aluminum alloy joints. Three methods of Friction Stir Welding (FSW), Advancing Parallel-Friction Stir Welding (AP-FSW), and Retreating Parallel-Friction Stir Welding (RP-FSW) were used. In addition, four modes of 0.5, 1, 1.5, and 2 mm of tool offset were used in two welding passes in AP-FSW and RP-FSW processes. Based on the results, it was found that the mechanical properties of welded specimens with AP-FSW and RP-FSW techniques experience significant increments compared to FSW specimens. The best mechanical and microstructural properties were observed in the samples welded by RP-FSW, AP-FSW, and FSW methods, respectively. Welded specimens with the RP-FSW technique had better mechanical properties than other specimens due to the concentration of material flow in the weld nugget and proper microstructure refinement. In both AP-FSW and RP-FSW processes, by increasing the tool offset to 1.5 mm, joint efficiency increased significantly. The highest weld strength was found for welded specimens by RP-FSW and AP-FSW processes with a 1.5 mm tool offset. The peak sample of the RP-FSW process (1.5 mm offset) had the closest mechanical properties to the base metal, in which the Yield Stress (YS), ultimate tensile strength (UTS), and elongation percentage (E%) were 76.4%, 86.5%, and 70% of base metal, respectively. In the welding area, RP-FSW specimens had smaller average grain size and higher hardness values than AP-FSW specimens.

Effects of Underwater Friction Stir Welding Heat Generation on Residual Stress of AA6068-T6 Aluminum Alloy

“…Thus, this process is placed in solid-state joining techniques. The rotational FSW tool produces frictional heat and soft surrounding materials [ 4 ]. The FSW tool traverses along the weld line and stirs the softened materials for mixing and joining.…”

Investigation of the Effects of Tool Positioning Factors on Peak Temperature in Dissimilar Friction Stir Welding of AA6061-T6 and AA7075-T6 Aluminum Alloys

“…These factors directly impact heat generation, temperature distribution, and plastic flow patterns [21,22]. Changing process parameters generally leads to a significant change in total generated heat and material flow [23]. These changes result in variation in the mechanical and microstructural properties of the final joint.…”

“…Using a tilt angle leads to significant changes in forged material volume and plastic flow pumped in weld regions [26]. The plunge depth parameter indicates the value of shoulder penetration in workpieces during the FSW run [23,27]. Plunging the shoulder into workpieces creates severe friction and plastic flow in the upper zone, leading to extensive changes in heat generation, heat distribution, stir zone shape, and positioning different welding zones in the welded cross-section [28].…”

Effect of Tool Positioning Factors on the Strength of Dissimilar Friction Stir Welded Joints of AA7075-T6 and AA6061-T6

“…Rotation, penetration, and linear traveling of a non-consumable tool causes material joining [ 3 ]. Generated heat by friction between tool and workpiece and materials plastic flow are the main factors of materials joining [ 4 ]. Many factors affect mechanical and metallurgical properties of FSW joints, which can be categorized in two main groups: tool geometry and process parameters [ 5 ].…”