International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 12 Issue: 04 | Apr 2025
p-ISSN: 2395-0072
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A Parametric Study on the Influence of Welding Speed and Axial Force in Friction Stir Welding of High-Strength Aluminum Alloys Prakash Singh-Madhur Srivastava 1M.Tech (CAD CAM) Scholar, Department of Mechanical Engineering, Ambalika Institute of Management &
Technology, Lucknow, Uttar Pradesh, India
2 Assistant Professor, Department of Mechanical Engineering, Ambalika Institute of Management & Technology,
Lucknow, Uttar Pradesh, India ---------------------------------------------------------------------***--------------------------------------------------------------------Traditional arc welding techniques often degrade the Abstract- Friction Stir Welding (FSW) offers a promising
mechanical properties of these alloys by dissolving strengthening precipitates and inducing defects such as hot cracking and voids due to their high thermal conductivity and low solidus temperature.
solid-state joining method, particularly for high-strength aluminum alloys like AA7075-T6, which are prone to welding defects under conventional fusion methods. This research evaluates how variations in welding speed (50– 100 mm/min) and axial force (4–10 kN) influence mechanical performance and microstructural features of FSW joints. Using a systematic design of experiments, joints were evaluated via tensile testing, Vickers microhardness, and optical microscopy. Optimal results were found at 60 mm/min and 6 kN, yielding a tensile strength of 420 MPa and refined, defect-free grains. These findings provide actionable insight into parameter selection for advanced aerospace and automotive applications.
FSW provides an effective solution by joining the material in the solid state, preserving its metallurgical integrity and reducing heat-affected damage. Nevertheless, the mechanical and microstructural quality of the FSW joint is highly sensitive to process parameters. Among the critical variables in FSW, welding speed (traverse speed) and axial force (downward pressure) play vital roles. These parameters control heat input, material flow, toolworkpiece interaction, and recrystallization behavior, all of which influence the final joint strength and quality.
Key Words: Friction Stir Welding (FSW), Welding Speed and Axial Force, tensile strength, etc.
i.
Welding speed affects the time available for frictional heat generation and plastic flow. Higher speeds reduce heat input, potentially leading to defects such as tunnel voids due to inadequate stirring. Conversely, slower speeds increase heat, which can cause grain coarsening or excessive flash.
ii.
Axial force governs the depth of tool penetration and material consolidation. Insufficient axial force may lead to incomplete bonding or void formation, while excessive force can cause flash defects and increase tool wear.
1. INTRODUCTION Tungsten Friction Stir Welding (FSW) is a solid-state joining process that has revolutionized the way engineers and manufacturers approach the welding of non-ferrous metals, especially aluminum alloys. Developed by The Welding Institute (TWI) in 1991, the technique involves the use of a specially designed rotating tool with a pin and shoulder that is plunged into the abutting edges of the workpieces to be joined. As the tool traverses along the joint line, frictional heat and plastic deformation soften the material without reaching its melting point. The softened material is stirred and forged under axial pressure, resulting in a high-integrity, fully consolidated weld. This method eliminates common fusion welding defects such as solidification cracking, porosity, and metallurgical discontinuities.
While previous studies have addressed these variables independently, limited research has examined their combined effects on the FSW of AA7075-T6, especially under industrially relevant conditions. Moreover, the interaction between these parameters remains underexplored in terms of how they affect joint efficiency, hardness gradients, and microstructural transformation zones, such as the nugget zone (NZ), thermo-mechanically affected zone (TMAZ), and heat-affected zone (HAZ).
High-strength aluminum alloys such as AA7075-T6, which are precipitation-hardened and belong to the 7xxx series, are essential in high-performance applications due to their excellent strength-to-weight ratio, fatigue resistance, and corrosion behavior. These alloys are widely used in aerospace structures, automotive crash components, defense systems, and marine applications. However, their inherent weldability issues pose significant challenges.
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The present study aims to bridge this gap by conducting a comprehensive parametric investigation into how varying welding speeds and axial forces influence the mechanical properties and internal structure of AA7075-T6 FSW joints. Through systematic experimentation and
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