The Friction Stir Welding (FSW) process, employed for joining aluminium alloys, particularly the 5xxx and 6xxx series, is widely utilized in various applications, notably within the automotive industry. These alloy series exhibit properties that render them ideal for manufacturing components such as frames, chassis, and pistons due to their lightweight, strength, and corrosion resistance. FSW is especially advantageous as it presents an environmentally friendly alternative for aluminium welding, characterized by its low melting point, which facilitates precise thermal control during the welding process. This investigation focuses on the impact of FSW process parameters on the microstructure and mechanical properties of 5083-O and 6061-T6 aluminium alloys, Optimal welding conditions were determined to be a tool rotational speed of 1400 RPM, a travel speed of 30 mm/s, and a tool tilt angle of 1°. Under these parameters, a tensile strength efficiency of 75% relative to the 5083-O base material was achieved, with a maximum tensile strength recorded at 203.8449 MPa and a hardness range of 70.1-70.5 HV. Microstructural analysis reveals a clean weld surface devoid of significant defects that could compromise weld quality. The material exhibited equiaxed recrystallized grains in the WN zone under optimal parameters. Conversely, the most vulnerable aspect of the welded joint was consistently identified within the Heat Affected Zone (HAZ) of the 6061-T6 side across all parameter configurations. This susceptibility is attributed to grain growth and the dissolution of Mg2Si precipitates induced by the thermal effects during the FSW process, as corroborated by microphotographic analysis.