Influence of welding parameter on mechanical properties and fracture behavior of friction stir welded Al–Mg–Sc joints

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2014-08, Vol.612, p.236-245
• Main Authors: Tao, Y., Zhang, Z., Ni, D.R., Wang, D., Xiao, B.L., Ma, Z.Y.
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum alloys; Applied sciences; Bonded joints; Cross-disciplinary physics: materials science; rheology; Elasticity and anelasticity; Exact sciences and technology; Fracture; Fracture mechanics; Fractures; Friction stir welding; Joining, thermal cutting: metallurgical aspects; Kissing; Materials science; Mechanical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Microstructure; Physics; Treatment of materials and its effects on microstructure and properties; Welding; Welding parameters
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2014.06.051

8.1-mm thick Al–Mg–Sc plates were friction stir welded (FSW) at tool rotation rates of 400–800rpm and welding speeds of 100–400mm/min to investigate the effect of welding parameter on the microstructure, mechanical property and fracture behavior of joints. The lazy S and kissing bond, with quite different morphologies, were observed in the stir zone at 400 and 600rpm, attributing to insufficient material flow. However, neither of them were detected at 800rpm. Ultimate tensile strength of the joints was nearly equal to that of the base metal with the joint efficiency being 97–99%. Facture behavior of the joints changed with the welding parameter and it was strongly affected by the lazy S and kissing bond. For the joints at 400 and 600rpm, fracture occurred partially along the lazy S at 100mm/min or initiated at the kissing bond at 400mm/min. However, the joints at 800rpm exhibited a fracture independent of the lazy S or kissing bond. Furthermore, the present observations were compared with those made by other researchers and the reasons for insufficient material flow at lower rotation rates of 400 and 600rpm were discussed.