Influence of Welding Parameters and Tool Pin Profile on the Microstructure and Mechanical Properties of Dissimilar Friction Stir Welded AA2024-T3 to AA6061-T6 Alloys

Abstract

This study aims to produce joints from dissimilar Al alloys welded by the FSW process with a minimal defect rate. The investigation focuses on the mechanical behavior and microstructural characteristics of 2 mm-thick dissimilar Al alloys, AA2024-T3 + AA6061-T6. The parameters of the welding process were welding speed, tool rotation speed, tilt angle, and pin profile geometry. The experimental work was conducted to determine the optimal welding conditions for producing defect-free welds with superior mechanical performance. Three pin profiles (Triangle, square, and hexagon), three rotational speeds (620, 920, and 1500 rpm), and three feed speeds (13, 23, and 28 mm/min) were used. Tensile testing, microhardness testing, and microstructural examinations evaluated weld-joint quality. The results indicated that a rotational speed of 620 rpm and a feed ratio of 28 mm/min, combined with a triangular pin profile, provided the best welding conditions. Under these conditions, the welded joints exhibited the highest tensile strength and microhardness. The highest tensile strength under ideal conditions was 150 MPa, and the hardness value of a welded joint at the weld zone under ideal conditions was 160 HV. Furthermore, lower rotational speeds improved both the tensile and hardness properties of the dissimilar FSW joints. Microstructural observations revealed sound weld formation, with adequate material mixing and no visible welding defects. Fracture surface analysis indicated a predominantly ductile fracture mode