Experimental and computational analysis of thermal and mechanical characteristics in friction stir welding of dissimilar aluminum alloys with varying tool pin geometries

This study investigates friction stir welding (FSW) of dissimilar aluminum alloys AA6061-T6 and AA7075-T6, focusing on tool pin profile geometries and their mechanical performance. ABAQUS finite element analysis revealed complex energy dissipation characteristics, with the hexagonal pin profile demonstrating superior thermal and mechanical behavior. Frictional energy analysis showed the hexagonal profile generated 15% lower frictional heat compared to cylindrical profiles, while plastic dissipation energy measurements indicated 22% more uniform energy distribution. Peak plastic strain reached 0.68 at the weld interface, with the hexagonal pin profile exhibiting more consistent strain localization. At an optimal rotational speed of 1200 rpm, the hexagonal pin profile achieved the highest tensile strength of 608.12 MPa, representing a 33.5% improvement over cylindrical profiles. Microstructural analysis exposed refined grain structures and reduced intermetallic formation, while macrostructural examination highlighted improved joint integrity. These results provide critical insights for high-reliability dissimilar metal joining in aerospace and automotive industries, demonstrating the hexagonal pin's potential for enhanced welding performance.