Effect of cyclic solution treatment on microstructure and mechanical properties of friction stir welded 7075 Al alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 649; pp. 293 - 300
• Main Authors: Bayazid, S.M., Farhangi, H., Asgharzadeh, H., Radan, L., Ghahramani, A., Mirhaji, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2016
• Subjects: 7075 Al alloy; Aging; Aluminum base alloys; Cyclic solution treatment; Dimpling; Friction stir welding; Heat treatment; Mechanical properties; Microstructure; Scanning electron microscopy; Tensile strength; Aging; Mechanical properties; Cyclic solution treatment; 7075 Al alloy; Microstructure; Friction stir welding
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2015.10.010

7075-T6 aluminum alloy plates were prepared by friction stir welding (FSW) followed by age hardening. A novel solutionizing method, namely cyclic solution treatment (CST), comprising of a repeated heating between 400 and 480°C for 0.25h was employed. The microstructure of the joints was studied by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The effect of CST on mechanical properties was assessed by means of tensile test and microhardness measurement. A significant grain size refinement is taken place by FSW whilst the grain size is not considerably changed after CST. The results show that precipitate particles of the welding area before and after heat treatment are MgZn2 and MgAlCu/Al7Cu2Fe, respectively. CST improves tensile strength and elongation while homogenizes the hardness distribution of the FSWed joint. A noteworthy enhancement in the hardness (~45%) and tensile strength (~33%) of the FSWed sample is achieved after CST and aging at 130°C for 24h. The tensile fracture surface of the Al alloy joint demonstrates fine dimples after CST while less-developed dimples are detected after aging.