Grain Size Optimization Using PSO Technique for Maximum Tensile Strength of Friction Stir-Welded Joints of AA1100 Aluminium

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.