Abstract
In this study, a Ga2O3 nano-particle was added into CsF-RbF-AlF3 flux to develop a highly active flux for brazing aluminum alloy to steel, and the spreadability and wettability of Zn-Al filler metal that matched the CsF-RbF-AlF3 flux-doped Ga2O3 nano-particle on the steel were investigated. The results showed that the spreadability and wettability of the CsF-RbF-AlF3 flux-doped Ga2O3 nano-particle could be remarkably improved when matching Zn-Al filler metals on both aluminum and low-carbon steel, for which the optimal content is in the range of 0.001–0.003 wt.% of Ga2O3. An investigation and analysis on the mechanism of reactions among CsF-RbF-AlF3-doped Ga2O3 nano-particle flux and filler metal or base metals showed that the Ga2O3 nano-particle is selectively absorbed by the interface of molten Zn-2Al filler metal and base metal, which released the surface-active element Ga to enrich the molten Zn-2Al filler metal and decreased the interfacial tension, so as to promote the enlargement of its spreading area during the brazing process. It was concluded that adding a trace amount of Ga2O3 nano-particle into CsF-RbF-AlF3 flux is a meaningful way to improve the activity of flux for brazing aluminum to steel compared with adding ZnCl2, which poses the risk of corrosion on aluminum.
Highlights
Brazing or welding Al to steel has become a hot subject in recent years because Al–steel composite metal materials have been found to have wide applications in industry
It was concluded that adding a trace amount of Ga2 O3 nano-particle into CsF-RbF-AlF3 flux is a meaningful way to improve the activity of flux for brazing aluminum to steel compared with adding ZnCl2, which poses the risk of corrosion on aluminum
CsF-AlF3 eutectic flux has been widely used in brazing aluminum alloys [1] and exhibits an excellent performance in brazing dissimilar metals matched with Zn-Al filler [2,3], such as brazing Al to Al [4] and Al to Cu [5]
Summary
Brazing or welding Al to steel has become a hot subject in recent years because Al–steel composite metal materials have been found to have wide applications in industry. CsF-AlF3 eutectic flux has been widely used in brazing aluminum alloys [1] and exhibits an excellent performance in brazing dissimilar metals matched with Zn-Al filler [2,3], such as brazing Al to Al [4] and Al to Cu [5]. CsF-AlF3 flux is not so good when brazing aluminum to steel, and the activity of removing the oxides on Al and steel simultaneously needs to be improved. It was reported that matching CsF-RbF-AlF3 flux and the 6061 aluminum alloy to 304 stainless steel can be executed [6]. According to Ref. [7], adding 6 mol.% of ZnCl2 enhanced the activity of
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