Abstract
The joints fabricated by two sided friction stir welding has shown higher ultimate tensile strength as compared to the joints fabricated by single pass and this trend is common for all the tool profiles.The joining of AA 2024-T351 aluminum plates with dimensions 200 mm ´ 200 mm ´ 5 mm (Length ´ width ´ thickness) was carried out by double pass friction stir welding (FSW) technique. Three friction stir welding tools with different pin height (1, 1.5 and 2) mm were used with different stirring rotation speeds and travel speed, (560, 710 and 900) RPM and (16, 20 and 25) mm/min respectively.The welded specimens were analyzed and evaluated using microstructure, macrostructure, tensile and hardness tests. The results indicated that the yield strength and tensile strength increases as the distance between the two passes (double pass) decrease, the rotational speed of 900 RPM and 560 RPM with travel speed of 16 mm/min and 25 mm/min, respectively is considered to be the most efficient and the width of the gap of the joint line decrease as the distance between the two welding pass decreases.
Highlights
Heat treatable 2xxx series aluminum alloys with high strength levels and favorable strength to weight ratios are one of the best candidate materials for meeting the challenges of structural applications in the aerospace industry
The joints fabricated by two sided friction stir welding has shown higher ultimate tensile strength as compared to the joints fabricated by single pass and this trend is common for all the tool profiles
The results indicated that the yield strength and tensile strength increases as the distance between the two passes decrease, the rotational speed of 900 RPM and 560 RPM with travel speed of 16 mm/min and 25 mm/min, respectively is considered to be the most efficient and the width of the gap of the joint line decrease as the distance between the two welding pass decreases
Summary
Heat treatable 2xxx series aluminum alloys with high strength levels and favorable strength to weight ratios are one of the best candidate materials for meeting the challenges of structural applications in the aerospace industry. The stirring of one material into the other is associated with a solid-state flow, i.e. with a very high deformation, and involves recrystallization of a portion of the joint (weld nugget) These extremely fine recrystallized grains are known to slide one over the other, leading to a super-plastic flow that accommodates the FSW process. The best results were obtained for a double-sided joint made with a pin length equal to 65% of the sheet thickness, which showed an increase of 41% in the ultimate tensile strength compared with the single-sided joint. In this study the mechanical and microstructural characteristics of two sided (double side) friction stir welding of AA 2024-T351 aluminum alloy were analyzed with respect to different friction stir welding tools pin height, stirring rotation speeds and travel speed to evaluate the best gap distance between the two sided of friction stir welding which give good welded joint
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