Development of ZrF4-containing CsF–AlF3 flux for brazing 5052 aluminium alloy with Zn–Al filler metal. (15th January 2016) - Xiao, Bing
Abstract: Intermediate-temperature brazing of the 5052 aluminium alloy was conducted using Zn– x Al ( x = 8, 15, and 22 wt.%) filler metals with a ZrF4 -containing CsF–AlF3 flux developed in this study. The microstructure and mechanical properties of the brazed joints as well as the oxide-film removal behaviour during brazing were analysed. The results show that the ZrF4 -containing CsF–AlF3 flux improved the wettability of the Zn–Al filler metals on the surface of the 5052 aluminium alloy. Because the Zr produced by the chemical reaction between Zr 4 + and the Al substrate did not block the continued occurrence of this reaction under the oxide film, the activity of the flux was enhanced. The 5052 aluminium alloy was brazed successfully with Zn–15Al and Zn–22Al filler metals and CsF–AlF3 flux containing 4–6 mol% ZrF4 . Microstructural observations of the brazing seam showed that it was composed of the α-Al phase, eutectoid structure, β-Zn phase, and a Zn–Al eutectic structure. The strength of the Zn–15Al brazing joint was higher than that of the Zn–22Al brazing joint, because the relatively low heating temperature used during brazing with the Zn–15Al filler metal resulted in reduced softening of the base metal. Graphical abstract: Highlights: A novel CsF–AlF3 flux containing ZrF4 was developed. The 5052 aluminium alloy was brazed using Zn–Al filler metals and the developed flux. The oxide-film removal behaviour of the developed flux was clarified.