Development of Zn-15Al-xZr filler metals for Brazing 6061 aluminum alloy to stainless steel

Brazing of a 6061 aluminum alloy to 304 stainless steel has been conducted using a Zn-15Al-xZr filler metal and the effects of Zirconium (Zr) addition on the properties and microstructures of Zn-15Al filler metals were investigated. The experimental results indicated that the liquidus temperature of Zn-15Al-xZr was approximately 445 °C and Zr addition had little influence on the melting point of the Zn-15Al-xZr filler metal. Moreover, adding an appropriate amount of Zr appeared to refine the η-Zn dendrites and improve the microstructure of the filler metal. However, an excessive amount of Zr led to the formation of Zr-bearing compounds in the Zn-15Al-xZr alloy. The results also indicated that the thickness of the intermetallic compound layer of Fe4Al13 along the brazed seam/stainless steel interface was significantly reduced and a layer as thin as 0.93 μm was observed at the interface of Zn-15Al-0.2Zr brazed joint. This imparted a 10% increase to the average shear strength of the joints brazed with Zn-15Al-0.2Zr in comparison to the Zn-15Al filler metal.