A Study in Friction Stir Welding on Marine Grade Dissimilar Metals

Abstract

Friction Stir Welding is an advanced technique for joining dissimilar materials, mitigating traditional welding issues like solidification cracking and distortion. This study explores friction stir welding for marine-grade Aluminium Alloy 6063-T4 (AL6063-T4) and Magnesium Alloy AZ31B (MG AZ31B), highlighting their lightweight and corrosion-resistant properties suitable for marine environments. Chapter 1 provides a comprehensive background, goals, and benefits of the study. It includes detailed analyses of relevant journal articles and modifications of general articles pertinent to this project. To improve both the weld quality and the efficiency of the friction stir welding process. Chapter 2 goes into detail about Tool geometry which is critically examined to enhance weld quality and friction stir welding efficiency. Steady-state temperature analysis identifies the optimal tool shape using "SolidWorks" for superior mechanical and thermal performance. The tool assembly includes a high-speed steel (HSS) drill bit and an H13 tool steel shoulder. In Chapter 3 a custom vertical milling machine welds two alloy plates, modelled independently in ANSYS for thermal analysis. The study uses SOLID70 elements for three dimensional thermal analysis, with precise boundary conditions to ensure accurate predictions. A tetrahedral mesh captures high-temperature gradients and stress concentrations, providing insights into deformation, stresses, temperature, and welding properties. In Chapter 4, AL 6063-T4 and MG AZ31B alloys are joined using friction stir welding, with specific surface preparation and butt joint configurations. Mechanical testing includes Vickers microhardness and tensile tests, revealing variations in joint hardness and intricate stress-strain behaviours. Failure analysis identifies TMAZ as the primary failure site, emphasizing its diverse texture structures and fracture initiation. Chapter 5 focuses on optimizing hardness and tensile strength through experimental and Computational Fluid Dynamics (CFD) analysis. ANOVA assesses the impact of rotational and travel speeds on tensile strength, finding rotational speed significantly influences tensile strength. Verification runs confirm the effectiveness of optimized parameters, with minor discrepancies suggesting areas for CFD model improvement. Lastly, friction stirs welding successfully welds 6063 T4 and AZ31B alloys at 430–490°C, enhancing microhardness and joint integrity. While joint tensile strength is lower than base materials, optimization at 1120 rpm and 63 mm/min improves yield strength. Future research should explore microstructural analysis, material innovation, application-specific studies, environmental impact, and standardization, underscoring friction stir welding's potential across various sectors.