Establishing an Empirical Relationship to Predict the Tensile Strength of a FSSW-AA7075 Aluminum Alloy with Mild Steel

In this study, an investigation was conducted on friction stir spot-welded AA7075 aluminum alloy with mild steel. Fusion welding of these two materials presents challenges because of differences in melting points and metallurgical incompatibility. To overcome these challenges, friction stir spot welding was employed for joining these materials. Trial runs were conducted based on a central composite rotatable design matrix, which encompassed four factors at five levels: tool rotational speed, plunge rate, dwell time, and tool diameter ratio. Shear tests were conducted to evaluate the joint strength, and subsequently, an empirical equation was developed via analysis of variance. Notably, a joint fabricated under specific conditions demonstrated exceptional strength, with the highest fracture load of 9.56 kN. These optimal parameters included the tool rotational speed, plunge ratio, dwell time and diameter ratio of 1000 rpm, 4 mm/min, 5 sec and 3.0. This achievement underscores the critical role of meticulous parameter optimization in achieving superior weld quality and mechanical properties in dissimilar material joints.