Optimization of friction stir welding parameters for dissimilar aluminium alloys using RSM-GRA and RSM-TOPSIS: Towards sustainable manufacturing in industry 4.0

Friction Stir Welding (FSW) have highlighted the importance of process parameter optimization to enhance joint performance in dissimilar aluminium alloys. This study focused on optimizing process parameters, specifically tool shoulder-to-pin diameter ratio (SP), Tool rotational speed (RS), and Tool travel feed (TF) for dissimilar aluminium alloys Al 2024 and Al 7050. A hybrid optimization approach was implemented by Response surface methodology (RSM) with two decision-making techniques Grey Relational Analysis (GRA) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The experimental matrix was developed using a Face-Centered Box-Behnken Design (FBBD). ANOVA results revealed that RS and its interaction with TF had the most substantial effect on Ultimate Tensile Strength (UTS). RSM-TOPSIS approach identified optimal process parameters As sp of 2.5, TF of 40 mm/min, and RS of 1200 rpm, yielding a UTS of 509.6 MPa, elongation of 11.9 %, and hardness of 109.2 Hv. SEM analysis for this optimized parameter confirmed the integrity of the welds, revealing fewer voids and microstructural defects, which directly correlate with the observed high tensile strength. Conversely, the RSM-GRA method suggested optimal values A. sp ratio of 2.5, RS of 900 rpm, and TF of 50 mm/min, resulting in a UTS of 508.3 MPa, elongation of 12.1 %, and hardness of 114.9 HV. Although both methods produced comparable tensile strength, the RSM-GRA approach demonstrated superior results in terms of elongation and hardness, indicating enhanced ductility and surface integrity. The results support sustainable manufacturing and also provide valuable insights for optimizing FSW in industrial applications.