Characteristics of zinc-based brazing fillers for AA5083 alloy

The aim of this study was to develop low-melting-point brazing filler metals for marine aluminum alloy AA5083. Six Zn–Al–Cualloys with varying aluminum contents were designed and systematically investigated. Among the examined alloys, Zn-4Al-3Cu exhibited the lowest liquidus temperature of 397.5 °C, whereas Zn–14Al–3Cushowed a higher liquidus temperature of 435.5 °C. The Zn–14Al–3Cualloy demonstrated the smallest equilibrium contact angle and the longest flow distance at a joint gap of 0.8 mm. Calculations based on contact angle and surface tension data indicated that this alloy also possessed the highest capillary pressure. When the aluminum content was below 6 wt%, the microstructure consisted of η (Zn) dendrites and eutectic structures composed of layered η (Zn) and fine interlamellar eutectoid phases of η (Zn) and α (Al). With increasing aluminum content above 6 wt%, the microstructure evolved into dendritic eutectoid η + α structures together with lamellar eutectic phases. At the filler/base interface, zinc infiltration along the grain boundaries of the aluminum base metal was observed. The Zn–14Al–3Cualloy contained the fine eutectoid η + α structures, as well as the ε (CuZn 4 ) intermetallic compounds which contributed to strengthening of the filler alloy. Consequently, Zn–14Al–3Cuexhibited the highest shear strength and average hardness among the investigated fillers.