Effects of tool geometry on the weld quality of friction stir welded ultra-thin 1060 aluminum alloy plate

Abstract

Friction Stir Welding (FSW) has gained widespread application in aluminum alloy joining due to its ability to produce high-strength, defect-free welds. However, welding ultra-thin aluminum alloy plates (thickness <2 mm) presents challenges such as joint softening, surface thinning, and warping. In this study, 1.4 mm-thick 1060 aluminum alloy plates were friction stir welded using tools with varying geometric parameters—including shoulder diameter, concave angle, and stir pin taper—under fixed welding conditions of 3000 r/min rotation speed and 300 mm/min welding speed. Through metallographic observation, Vickers microhardness testing, and tensile strength evaluation, it was found that the tool with a conical stir pin (Tool No. 2), featuring a 5 mm flat shoulder, root diameter of 2 mm, and end diameter of 1 mm, produced the highest-quality weld. The resulting joints exhibited a smooth surface finish, minimal internal defects, and a maximum tensile strength of 131.80 MPa–99.55 % of the base material strength (132.40 MPa). The fracture consistently occurred in the base material region, indicating excellent joint integrity. Additionally, the weld zones demonstrated fine-grained microstructures and maintained or exceeded the base material's hardness across all regions. This research confirms that by optimizing stir tool geometry, FSW can effectively eliminate defects such as thinning, grooves, and warping in ultra-thin aluminum sheets. The findings offer practical guidance for the reliable application of FSW in high-precision, lightweight structures such as aerospace components and new energy vehicle battery trays.