In this research, the impact of changes to a few variables on joint properties like ultimate tensile strength (UTS), yield tensile strength (YTS), and elongation (EL) are investigated. Examples of such variables are shoulder diameter (SD), shoulder flatness (SF), pin profile (PP), pin diameter (PP), weld passes (NP), and weld speed (WS). From the trials done to optimise the process parameters, the SD, PP, SF, and WS for comparable FSW of AA6061 and AA5083 are chosen. Modifying the Rotational Speed (RS), Welding Speed (WS), and tilt angle (TA) of the tool allows for the creation of a wide variety of FSW joints. There is a total of three experimental groups examined: those with FSWs that are comparable to AA6061, those that are similar to AA5083, and those that are dissimilar to AA6061 and AA5083. The tests are arranged using "Minitab" and the RSM (response surface methodology) approach. The dissimilar FSW of AA6061 and AA5083, all three factors, i.e. Rotational speed, Welding speed and Tilt angle and their interactions are revealed as significant through ANOVA. In multi-objective optimization results, RS of 1440 rpm, WS of 32 mm/min and TA of 2.40 are suggested as optimal setting of these parameters for dissimilar FSW which is found in well agreement with predicted results of tensile properties within ± 10%. © 2024 Elsevier B.V., All rights reserved.