Effect of Preheating and Water Cooling on the Performance of Friction-Stir-Welded Aviation-Grade Aluminum Alloy Joints
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JMEPEG https://doi.org/10.1007/s11665-019-04183-z
Effect of Preheating and Water Cooling on the Performance of Friction-Stir-Welded Aviation-Grade Aluminum Alloy Joints Shubham Verma, Meenu Gupta, and Joy Prakash Misra (Submitted September 12, 2018; in revised form February 13, 2019) This paper examined the effect of preheating and water cooling on the thermal, mechanical, metallurgical, and texture properties of friction-stir-welded AA6082. Joints are fabricated under different preheating (FSW-P) and water cooling (FSW-C) conditions. The experimental outcomes indicate that the preheating and water cooling enhance the mechanical properties of the joint. The maximum tensile strength of 295 MPa is obtained for FSW-P1. It is also observed that preheating has more impact on microhardness. Microstructural analysis using optical microscope and electron backscatter diffraction analysis indicated that FSW produced fine equiaxed grains in the nugget zone due to dynamic recrystallization. Texture analysis shows that finer grain grains are obtained under preheating and water cooling conditions. The minimum grain size of 5.3 lm is obtained under FSW-P1. X-ray diffraction analysis shows that Mg2Si phase in nugget zone that is an indication of dissolution and formation of strengthening precipitates. Fracture analysis indicates that preheating also improves the ductility of the joint. Keywords
aluminum alloys, energy beam scattered diffraction analysis, friction stir welding, preheating, water cooling
1. Introduction Aviation industries are moving toward aluminum alloys specially 6xxx series (AA6061, AA6063, AA6082) for highperformance structural applications owing to its properties, namely highly formability, excellent corrosion resistance, and high strength-to-weight ratio. Recently, AA6061 and AA6063 are replaced by AA6082, as it possesses comparatively higher strength owing to presence of manganese that controls the grain structure. However, joining of this alloy by fusion welding techniques is found difficult owing to its low melting point. In addition, defects like porosity, distortion, oxidation, shrinkage, etc., are observed during fusion welding (Ref 1). Contrarily since last decade, FSW, a solid-state joining technique, is emerged as one of the best techniques to join low melting point alloys, namely aluminum alloys and copper alloys. It is free of filler and shielding gases, and hence, it is treated as green technology (Ref 2, 3). In FSW, a continuously rotated cylindrical shouldered non-consumable tool with a pin is used to join two faying surfaces. The relative motion (mechanical stirring) between workpiece and pin generates frictional heat to produce plasticized region at the adjacent faces. This plasticized region solidifies, and joining occurs. It is reported that application of FSW in spacecraft manufacturing increases joint Shubham Verma, Meenu Gupta, and Joy Prakash Misra, Department of Mechanical Engineering, National Institute of Technology Kurukshetra, Kurukshetra, India. Contact e-mails: shubham_6140005@nitkk
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