Role of interfacial reaction on the mechanical performance of Al/steel dissimilar refill friction stir spot welds

ABSTRACT

Al/steel welds were successfully fabricated by refill friction stir spot welding. The welding parameters were optimised based on the clamping ring temperature and weld strength. 85.7% of welds achieve a strength which exceeds the American Welding Society requirement when the clamping ring temperature ranges from 230 to 265°C. Cracks are formed under the pin and sleeve in the Al substrate at the Al/steel interface, which are associated with the tool sleeve plunging period and attributed to the α-Al + Al–Zn eutectic structure. The interdiffusion between Al and Zn at the steel surface produced an Al–Zn eutectic structure layer at the Al/steel interface, while part of the zinc coating materials is squeezed out of the sleeve periphery, leading to a brazing effect which contributes to weld strength. Nanoscale discontinuous Fe₄Al₁₃ and FeAl intermetallics form as a layer localised at the Al–Zn layer/steel substrate interface.

KEYWORDS:

• Refill friction stir spot welding
• aluminium alloy
• zinc-coated steel
• interfacial reaction
• mechanical performance

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

B. Shalchi Amirkhiz http://orcid.org/0000-0002-6756-0278

A. P. Gerlich http://orcid.org/0000-0003-0270-7475

Additional information

Funding

This work has been supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canadian Foundation for Innovation (CFI).