Optimizing joint efficiency in stainless steel-aluminum alloy FSW joints through advanced parameter control

The present work investigates the friction stir welding (FSW) of dissimilar materials, specifically stainless steel 304 and aluminum alloy AA2024-T3, to analyze their tensile strength behavior. The significant challenges inherent in joining these materials, stemming from their vastly divergent thermal and mechanical properties, are addressed through a structured experimental and statistical methodology. The L18 Taguchi mixed orthogonal array was employed to systematically evaluate the influence of three critical process parameters: tool rotational speed, welding speed, and tool pin offset. Eighteen experimental trials were conducted using a butt joint configuration. The analysis identified tool rotational speed as the most influential parameter affecting the joint integrity. A combination of 450 rpm rotational speed, 20 mm/min welding speed, and a 1.5 mm pin offset toward the aluminum side yielded the optimum results, achieving a peak ultimate tensile strength (UTS) of 344.7 MPa and a joint efficiency of 78.34%. Analysis of variance (ANOVA) quantified this influence, revealing that rotational speed accounted for 28.26% of the total variation in UTS, while the combined effect of welding speed and pin offset contributed 16.69%. These optimized parameters facilitated superior material mixing within the stir zone, producing a refined microstructure and a robust joint. Post-weld characterization via high-resolution microscopy and fractography confirmed a ductile mode of failure with no discernible defects, thereby validating the statistical findings. This work underscores the efficacy of the selected statistical technique and ANOVA for optimizing FSW parameters and provides a reliable framework for producing high-strength dissimilar metal joints for the automobile and transportation industries.