Influencing mechanism of Al-containing Zn coating on interfacial microstructure and mechanical properties of friction stir spot welded Mg–steel joint

Journal Article · Fri Jun 15 00:00:00 EDT 2018 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2018.04.011· OSTI ID:22805018

Xu, R. Z. ^[1]; Ni, D. R.; Yang, Q.; Xiao, B. L. ^[1]; Liu, C. Z. ^[2]

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1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)
2. College of Material Science and Engineering, Shenyang Aerospace University, 37 Daoyi South Street, Shenyang 110136 (China)

Highlights: • Al-containing Zn coating improved Mg–steel interfacial wettability during friction stir spot welding (FSSW). • Pre-existing Al{sub 5}Fe{sub 2} phase in coating on steel surface promoted Mg–steel metallurgical bonding. • A high tensile-shear load of 4.3 kN was obtained in FSSW AZ31–steel joint. - Abstract: 2.4 mm thick AZ31 Mg alloy sheet and 1.5 mm Q234 steel sheet with a hot-dipped Al-containing Zn coating were friction stir spot welded (FSSW) using a pinless tool. It was shown that the Al-containing Zn coating played a crucial role in joining the Mg alloy and steel during FSSW. The Zn coating observably improved the Mg–steel interfacial wettability during FSSW, and the Al{sub 5}Fe{sub 2} phase in the Zn coating on the steel substrate surface promoted the metallurgical bonding of Mg alloy and steel. It was confirmed that the Al{sub 5}Fe{sub 2} phase on the steel surface resulted from the reaction between the steel substrate and the Al in the Zn coating during hot-dipping, and was not related to the Al-containing Mg alloy substrate. The tensile-shear load of the FSSW Mg–steel joint reached 4.3 kN. The fracture of the joint occurred along the interface on the steel substrate side. The interface between the Al{sub 5}Fe{sub 2} layer and Mg alloy substrate was the weakest region of the Mg–steel joint.

• OSTI ID: 22805018
• Journal Information: Materials Characterization, Vol. 140; Other Information: Copyright (c) 2017 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
ALUMINIUM COMPOUNDS
INTERFACES
INTERMETALLIC COMPOUNDS
LAYERS
MAGNESIUM
MICROSTRUCTURE
STEELS
SUBSTRATES
WELDED JOINTS
ZINC COMPOUNDS