The Effect of Tool Design on the Friction Stir Welding of Thick Aluminum Alloy AA6082-T651 Extruded Flats
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TECHNICAL ARTICLE
The Effect of Tool Design on the Friction Stir Welding of Thick Aluminum Alloy AA6082‑T651 Extruded Flats D. Bajaj1 · A. N. Siddiquee1 · A. K. Mukhopadhyay2 · N. Ali1 Received: 4 August 2020 / Revised: 13 October 2020 / Accepted: 29 October 2020 © ASM International 2020
Abstract Fifteen-millimeter-thick aluminum alloy AA6082-T651 extruded flats were friction-stir-welded by using three different types of tool pin profiles, i.e., (1) conical with only left-hand threads (CL), (2) conical with both left-hand and right-hand threads (CLR), and (3) conical cam-tri-flute with left-hand threads (CTFL) up to a height of 6 mm from the pin tip. The microstructures and the mechanical properties across the weld thickness were characterized. Tunneling defect was found at the weld-bottom for the CL tool pin profile and at the weld-top for the CLR pin profile. The reasons behind the formation of such defects have been analyzed and discussed. On the other hand, a defect-free joint was obtained with the CTFL pin profile. Tensile test samples were machined from top, middle, and bottom sections of the welds, and tensile strengths were measured for all the sections to determine the joint efficiencies. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were employed to identify and study the morphology of the coarse phase particles present in the base material and in different regions of the welds. These results were correlated with the microhardness contours plotted across the weld cross section. Keywords Aluminum alloy AA6082 · Thick extruded flats · Friction stir welding · Tool design · Tensile properties · Microhardness · Scanning electron microscopy
Introduction Friction stir welding (FSW) has recently become one of the most intriguing areas in the joining technology, especially for the welding of aluminum alloys due to its numerous pluses over fusion welding processes such as low residual stresses [1], no weld porosity [2], better strength, and low distortion [3, 4]. As the modern automotive, aerospace, and defense materials are progressing toward high strength to weight ratio and improved corrosion resistance, the application of aluminum alloys has increased profoundly in these When the work was carried out, one of the authors (AKM) was with Defence Metallurgical Research Laboratory, Hyderabad. * A. N. Siddiquee [email protected] 1
Department of Mechanical Engineering, Jamia Millia Islamia, New Delhi 110025, India
Present Address: Hindalco Innovation Center, Hindalco Industries Limited, Navi Mumbai 410208, India
2
sectors and so this welding technology too [5–7]. FSW of thick rolled plates and extruded flats belonging to 5xxx and 6xxx series of aluminum alloys is further of current interest for the manufacture of structural components for high-speed trains [8]. During FSW, special tool geometry features impart limited but essential control over the extent of material mixing [9–11]. For 6-mm-thick AA7075 plates, Yeni et al. [12] demonstrated that conical pin with left-han
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