Investigation of the Impact of Tool Pin Geometry and Feed Rate Speed in Friction Stir Lap Welding of 7075 and 5182 Aluminum Alloys

Abstract

7075 and 5182 aluminum alloys are crucial for aerospace and automotive applications, receptively. Joining these alloys can enable more economical and efficient structures. Therefore, weldability of these materials by friction stir lap welding (FSLW) was studied based on investigating influence of tool pin geometry (conical and cylindrical screw) and welding speed (22, 37 and 51 mm min-1) on weld microstructure and mechanical properties. Strong welds were acquired with both tools. However, stronger ones were made employing conical pin tool thanks to having a deeper weld penetration and denser microstructure. Weld strength improved with increasing tool advancing speed for conical pin tool since welded area width and vertical downward penetration increased while opposite of this occurred for cylindrical screw pin. While by conical pin, the strongest weld having 13033 N tensile load was made at 51 mm min-1, by cylindrical screw pin, the strongest weld with 12162 N was obtained at 22 mm min-1. It was an indication of a stronger weld formation for both tools when the lines formed through tool shoulder on top surface of upper sheet were broken into small particles and disappeared. Proper tool advancing speed value can show considerable variability depending on tool pin geometry.