Process Parameter Optimization of Ti-6Al-4V Laser Beam Welds Through RSM-Based NSGA-II Analysis

Abstract

Laser beam welding of Ti-6Al-4V alloy requires precise control of process parameters to achieve sufficient penetration while limiting thermal damage. In this study, a hybrid response surface methodology (RSM)–NSGA-II–TOPSIS framework was applied to optimize laser power, welding speed, focal diameter, and shielding gas flow rate with respect to fusion zone width (FZ), heat affected zone width (HAZ), total weld width (TWW), and depth of penetration (DOP). ANOVA results revealed that laser power and welding speed were the dominant factors, jointly contributing more than 50% of the total variation in all responses. DOP ranged from 2.68 to 3.52 mm and exhibited the lowest variability is C.V. = 8.25%. The developed RSM models showed strong predictive capability with R² values above 0.95 and adequate precision exceeding 16. Pareto analysis demonstrated a clear trade-off between penetration and weld geometry. TOPSIS identified a best compromise condition, achieving an 8.6% increase in DOP while achieving 32.0% reduction in TWW and 22.3% reduction in FZ, confirming the effectiveness of the proposed optimization approach for Ti-6Al-4V laser welding.