Impact of Stack Orientation on Self-Piercing Riveted and Friction Self-Piercing Riveted Aluminum Alloy and Magnesium All
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Impact of Stack Orientation on Self‑Piercing Riveted and Friction Self‑Piercing Riveted Aluminum Alloy and Magnesium Alloy Joints Yunwu Ma1,3 · Sizhe Niu1,2 · He Shan1,2 · Yongbing Li1,2 · Ninshu Ma3 Received: 31 March 2020 / Accepted: 1 July 2020 © China Society of Automotive Engineers (China SAE) 2020
Abstract Self-piercing riveting (SPR) is a mature method to join dissimilar materials in vehicle body assembling. Friction self-piercing riveting (F-SPR) is a newly developed technology for joining low-ductility materials by combining SPR and friction stir spot welding processes. In this paper, the SPR and F-SPR were employed to join AA6061-T6 aluminum alloy and AZ31B magnesium alloy. The two processes were studied in parallel to investigate the effects of stack orientation on riveting force, macro-geometrical features, hardness distributions, and mechanical performance of the joints. The results indicate that both processes exhibit a better overall joint quality by riveting from AZ31B to AA6061-T6. Major cracking in the Mg sheet is produced when riveting from AA6061-T6 to AZ31B in the case of SPR, and the cracking is inhibited with the thermal softening effect by friction heat in the case of F-SPR. The F-SPR process requires approximately one-third of the riveting forces of the SPR process but exhibits a maximum of 45.4% and 59.1% higher tensile–shear strength for the stack orientation with AZ31B on top of AA6061-T6 and the opposite direction, respectively, than those of the SPR joints. The stack orientation of riveting from AZ31B to AA6061-T6 renders better cross-section quality and higher tensile–shear strength and is recommended for both processes. Keywords Self-piercing riveting · Friction self-piercing riveting · Aluminum alloy · Magnesium alloy · Stack orientation Abbreviations SPR Self-piercing riveting F-SPR Friction self-piercing riveting FSSW Friction stir spot welding
1 Introduction To realize vehicle emission targets, traditional steels are being increasingly replaced with light metals, e.g., Al and Mg alloys, which is causing the demand for reliable Al–Mg join technologies [1–3]. To date, the most common solution to joining * Yongbing Li [email protected] 1
Shanghai Key Laboratory of Digital Manufacture for Thin‑walled Structures, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China
2
State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China
3
Joining and Welding Research Institute, Osaka University, Osaka, Japan
dissimilar metals in vehicle body assembling is self-piercing riveting (SPR). However, the use of SPR to join Al and Mg alloys has limitations. Mg alloys possess a hexagonal-closedpacked crystal structure with two basal slip systems at ambient temperature, resulting in their poor ductility [4]. Combined with the large and highly localized plastic deformation during the SPR process, this leads to inevitable cracking in Mg alloys. Other low-ductility metals, e.g.
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