Friction stir welding (FSW) has an advanced technique in solid-state conditions that joins from different materials compared to the fusion welding process and is eco-friendly. This  ignificant advancement involves aluminium (Al) alloys which facilitate the FSW of distinguished flow patterns in the weld zone. Technically, heat energy and stirred material resulted in softening areas, affecting joint efficiency, mechanical properties, and metallurgical characterisation. This paper has concerns comprehensively covering and summarising the development and application of the topic in different aspects of the performance and quality of the FSW welded joint. The proper tools can create sufficient heat under the shoulder for excellent performance to deal with the welding parameter. All these tools have their literature and journal, which extensive discussion.Furthermore, alloy positioning, defect formation,rotational speed and transverse feed are essential analytical tools for FSW to control the significant weld quality. Furthermore, the mechanical properties associated with microstructural evolution highly dependent on welding technique have remarkably contributed to product development. Finally, a previous study has shown the interest in the topic to enhance the knowledge for further investigation with emerging technology for future recommendations in the FSW discipline.

Water cooling has the potential to improve the mechanical qualities of weldment joints in butt welding configurations. However, the joining procedure on such a configuration faces a challenging defect-free joining issue with the standard approach. This project investigates the effect of welding conditions on the joint quality using three different tool pin profiles (cylindrical straight, cylindrical threaded and tapered cylinder) during dissimilar underwater friction stir welding of a 6 mm thick plate. An experimental method following Taguchi parametric design is carried out to optimise the technique on hardness and microstructure at the weld nugget. ANOVA is used to assess the effect of each process parameter, namely tool pin profiles, welding speed, welding speed, and hardness responses. The water environment approach lowers thermal flow by maintaining consistent temperature from tool pin profiles. The combination of ongoing process parameters and fast-cooling rate induced heat input improves the welded joint's mechanical characteristics and microstructural grain. The experiment revealed the appropriate process parameters of 900 rpm, 60 mm/min, and tapered cylinder pin profile. Consequently, water-cooling significantly contributes to welded joints' mechanical properties and microstructure at the optimal parameter level, resulting in improved strength performance.