Butt Joining of Bi-Layered Aluminum Sheets through Friction Stir Welding: Tensile Stresses, Bending Stresses, Residual Stresses, and Fractrography

Abstract

Laminated metals sheets have been used widely in various sectors including the optoelectronics, aerospace, ship, and automotive industries because of their desirable mechanical properties. Therefore, techniques for successful joining of such laminates are a focus of study. The objective of this study was to perform butt-welding of bi-layered aluminum laminated sheets using the friction stir welding (FSW) technique. The tensile properties, flexural properties, residual stress distribution, and fractured surfaces of the final weldments were analyzed. The effects of the process parameters on the mechanical properties of the weldments were also investigated. Mixing defects (voids and cracks) were observed in the stir zone (SZ) at the following combinations: low rotational speed (ω) and low tool traverse speeds (v) and also at high ω and high v, which substantially decreased the tensile and bending strength of the weldments as well as % elongation. Moreover, the sample welded at ω = 1500 rpm and v = 47.5 mm/min showed the best performance under mechanical loading: with a % elongation and tensile strength of 24.72% and 79.10 MPa, respectively. Similarly, the sample welded at ω = 750 rpm and v = 118 mm/min showed the highest flexural strength of 3.15 MPa. Finally, the suitable parameters are proposed for the joining of bi-layered aluminum laminated sheets.