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This paper deals with the experimental analysis of Friction Stir Welding (FSW) of AA1100 aluminum alloy joined by means of a square pin tool. During the process, temperature measurement has been done by means of K-type thermocouples and it has been noticed that the temperature in the advancing side (AS) of the weld is about 20-25 °C higher than its retreating side (RS). The ultimate tensile strength (UTS) of the welded specimen is increased by 20% of the parent material due to the uniform dispersion of silicon particles present within the base material. Microstructural observations revealed finely arranged equiaxed grains in the nugget region of the weld. X-ray diffraction results showed the formation of alumina (Al2O3) in the weld nugget due to high heat generation and exposure to atmospheric oxygen during welding. Residual stress measurement exhibited a M-shaped distribution. The samples joined at low travel speed and high tool rotational speed showed compressive residual stress in the joint region. Residual stress of the material lying below the tool shoulder is found to be tensile in nature. Also, it has been noticed that the residual stress in the AS is superior in magnitude than the RS of the weld specimen. [ABSTRACT FROM AUTHOR]

An attempt has been made to characterize the friction stir-welded aluminium (AA 1100) joints in terms of the different processing parameters, like rotation speed of the tool (TRS), speed of welding (WS) and plunge depth (PD). In addition, the heat-affected zone (HAZ) has also been analysed in terms of the grain structure and grain orientation to throw light on the quality of the joint. The TRS is maintained at 1100–1500 rpm, WS at 20–60 mm/min and PD at 4.1–4.5 mm within a temperature range of 420–480 °C. Results show tensile and yield strength increase with increase in TRS and WS. Microhardness of the HAZ is the lowest among all the zones, indicating it to be the weakest region which represented the fracture location in the joint. Microstructural observations further reveal grain refinement at the joint and coarsening of grains away from the joint. Particle swarm optimization technique has been adopted for obtaining the optimal set of parameters to get suitable grain size for maximum tensile strength and ductility which govern the quality of welding. This research finds application in the automotive, ship building and aerospace industries as the optimization technique helps to achieve the best output with minimum supply of inputs without compromising the weld quality. [ABSTRACT FROM AUTHOR]