Characteristics of defects and tensile behaviors on friction stir welded AA6061-T4 T-joints

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 543; pp. 58 - 68
• Main Authors: Cui, Lei, Yang, Xinqi, Zhou, Guang, Xu, Xiaodong, Shen, Zhikang
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 01-05-2012; Elsevier
• Subjects: 6061-T4 aluminum alloy; Applied sciences; Defects; Exact sciences and technology; Fractures; Friction stir welding; Joining, thermal cutting: metallurgical aspects; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; T-joints; Tensile behaviors; Welding; T-joints; 6061-T4 aluminum alloy; Friction stir welding; Defects; Tensile behaviors; High strain; Aluminium base alloys; Tunnel effect; Rupture; Plastic deformation; Linear defect; T joint; Tension test; Welding parameter; Fractography; Formation mechanism; Defect formation; Fracture mode
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2012.02.045

From the figure, formation mechanisms of tunnel defect and kissing bond defect in FSW T-joints can be understood. Tunnel defect is actually an insufficient fulfilled cavity that delayed inner the weld after welding. Kissing bond is actually a new interface formed between the downward flowing materials of the skin and the deformed side surface of the stringer. [Display omitted]
► T-joints could be made by FSW in three combination ways of blanks. ► Tunnel, kissing bond, bonding line, and zigzag line were found in T-joints. ► Formations of defects were closed related to the material flow. ► Distributions of defects exhibited different features in different T-joints. ► Defects could decrease the tensile properties of T-joints to varying degrees.
In the present study, AA6061-T4 T-joints were successfully fabricated by friction stir welding (FSW) in three different combination ways of skins and stringers. Distributions and formation mechanisms of tunnel defects, kissing bond defects, original joint line with severe plastic deformation (OJLwSPD) defects, and zigzag line defects in T-joints were investigated by macro- and micro-observations. Influences of defects distributions and welding parameters on the tensile behaviors of T-joints were examined. To a better understanding of failure behaviors of T-joints, fracture locations and fracture surfaces of tensile samples were also investigated.