Abstract: This paper explores the feasibility and effectiveness of friction stir pinless spot welding (FSPSSW) for joining dissimilar aluminium alloys. The absence of a traditional pin in the tool design reduces material deformation, improves surface finish, and eliminates exit hole defects. Experimental trials were conducted on various aluminium alloy combinations, optimizing parameters such as rotational speed, plunge depth, and dwell time. Results indicated strong metallurgical bonding with refined microstructures and minimal intermetallic formation. Mechanical testing showed high tensile shear strength and ductility, validating the quality of the welds. The process proved advantageous in enhancing joint integrity while being cost-effective and energy-efficient. This study confirms the suitability of pinless FSSW for lightweight applications in automotive and aerospace industries, offering an innovative alternative to conventional welding techniques.

Keywords: Friction Stir Welding (FSW), Pinless Tool, Dissimilar Aluminium Alloys, Spot Welding, Solid-State Joining, Weld Strength, Microstructure, Heat-Affected Zone (HAZ), Lightweight Materials, Aerospace Applications.

| DOI: 10.17148/IARJSET.2025.12312