Process Parameter Effects in Friction Stir Welding of High Strength Aluminum Alloys

Abstract

Friction stir welding (FSW) has emerged as a highly effective solid-state joining technique for high-strength aluminum alloys, offering superior mechanical properties, minimal distortion, and reduced residual stresses compared to traditional fusion welding methods. This study investigates the influence of key process parameters including tool rotation speed, welding speed, and tool shoulder-to-pin diameter ratio on the mechanical performance and microstructural characteristics of AA7075-T651 aluminum alloy butt joints. A series of experimental welds were performed using varying combinations of parameters under controlled conditions. The welded joints were evaluated for tensile strength, hardness distribution, and microstructural evolution using optical microscopy and scanning electron microscopy (SEM). Results demonstrate that optimized process parameters significantly enhance joint strength and uniformity by promoting defect-free weld zones and refined grain structures in the stir zone. Deviations from optimal conditions led to defects such as voids, tunnel formation, and incomplete material flow. The study provides comprehensive guidelines for selecting FSW parameters to maximize joint quality in high-strength aluminum alloys, supporting industrial applications in aerospace, automotive, and defense sectors.