Development and Assessment of Friction Stir Welding Strategy for Similar and Dissimilar Joints

Friction Stir Welding (FSW) is a solid-state joining process invented at The Welding Institute (TWI), UK, in 1991. It produces defect-free, high-strength welds without melting the base material, eliminating fusion welding defects such as porosity, hot cracking, and solidification distortion. This paper presents the development and assessment of an FSW strategy applicable to similar joints (AA5083–AA5083) and dissimilar joints (AA5083–AA7039 and aluminium–mild steel). The study examines the influence of critical process parameters—rotational speed, traverse speed, plunge depth, tool tilt angle, and tool geometry—on joint quality, microstructure, and mechanical properties. AA5083 (marine-grade, non-heat-treatable) and AA7039 (defence-grade, heat-treatable) were selected as base materials with H-13 tool steel used for the FSW tool. The paper consolidates findings from 21 peer-reviewed references and presents a four-stage welding strategy covering tool design, parameter optimisation, weld zone qualification, and service performance validation including corrosion and fatigue. Results confirm that controlling the rotation-to-traverse speed ratio (n/v) and tool shoulder-to-pin geometry is central to achieving consistent mechanical properties across both similar and dissimilar joint configurations.