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Advanced Approach to Modify Friction Stir Spot Welding Process Behrouz Bagheri1   · Mahmoud Abbasi2 · Amin Abdollahzadeh1,3 · Hamid Omidvar1 Received: 22 April 2019 / Accepted: 30 July 2019 © The Korean Institute of Metals and Materials 2019

Abstract Nowadays, friction stir spot welding (FSSW) is used in automotive, rail vehicle construction, the aerospace industry, and electrical industry. In the current research, a modified version of the FSSW process entitled friction stir spot vibration welding was introduced to join Al5083 specimens. The joining specimens were vibrated normal to the tool movement direction, while the joint position cooled by passing coolant through the fixture. Different characteristics of developed joint namely microstructure, mechanical properties, corrosion behavior were studied. The results showed that stir zone grain size decreased significantly as the vibration was employed and the joint position was cooled. It was found that vibration enhanced the dynamic recrystallization and coolant decreased the grain growth. Both led to enhanced grain refinement in the stir zone. The results also indicated that shear strength and hardness of the weld region increased as the modified version of FSSW was applied. Corrosion tests revealed that corrosion resistance increased as the modified method was applied. Keywords  Friction stir spot welding · Vibration · Coolant · Microstructure · Corrosion List of Symbols FSSW Friction stir spot welding FSSVW Friction stir spot vibration welding BM Base metal WN Weld nugget SZ Stir zone EBSD Electron backscatter diffraction TEM Transmission electron microscopy SEM Scanning electron microscopy TMAZ Thermo-mechanical affected zone HAZ Heat-affected zone SEM Scanning electron microscopy UFSW Underwater friction stir welding SFSW Submerged friction stir welding TC Thermo-couple VMM Vision measuring machine Icorr Corrosion current density Ecorr Corrosion potential C.R Corrosion rate * Behrouz Bagheri [email protected] 1



Department of Mining and Metallurgy, Amirkabir University of Technology, Tehran, Iran

2



Faculty of Engineering, University of Kashan, Kashan, Iran

3

Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran



Rp Polarization resistance NAMLT Nitric acid mass loss test IGC Intergranular corrosion

1 Introduction Friction stir spot welding (FSSW) is known as a solid-state joining process to weld structural components in different configurations [1–5]. It has been originated from friction stir welding (FSW). FSSW has been utilized to replace conventional spot welding methods to reduce joining steps and lower costs in different industries [6, 7]. Tool in FSSW, unlike the FSW method, is not traversed and the joint is obtained by forcibly plunging a rotating tool into the joining sheets in the lap joint until the shoulder is in contact with the surface of the top sheet. The frictional heat, due to contact between the tool and workpiece, softens the material around the tool, so that the