Effect of process parameters on weld geometry and mechanical properties in friction stir welding of AA2024 and AA7075 alloys

Abstract

FSW joints are promising because they have a minimal heat input in welding and can limit the amount of intermetallic compound formation in dissimilar metals. Solid-state welding processes, particularly friction stir welding (FSW), are preferred for welding aluminium alloys due to their low heat input and ability to minimize intermetallic compound formation. This study conducted FSW trials on AA7075 and AA2024 alloys, each 4 mm thick. Parameters such as axial force, rotational speed, and traverse feed were adjusted while keeping other factors constant. The study analyzed weld geometry characteristics, including bead width and penetration depth. Angle distortions during FSW of thin plates in a butt joint were investigated. Additionally, the study examined the effects of FSW parameters on mechanical properties such as tensile strength and hardness immediately after welding. Microstructures of the welds were observed using optical microscopy (OM). The optimal mechanical properties are achieved at a rotational speed of 1000 rpm, a traverse feed of 30 mm/min, and an axial force of 10 kN. This optimal condition facilitates material flow around the pin at an ideal speed, ensuring adequate material filling and preventing tunnel formation. The stir zone's microstructure under these parameters exhibits a finely recrystallized structure with a significantly smaller grain size than the base material. Consequently, this enhances the joint's microhardness and tensile strength.