Abstract
The novel low-silver 12AgCuZnSn filler metals containing In and Pr were used for flame brazing of copper and 304 stainless steel in this study. The effects of In and Pr content on the melting temperature, wettability, mechanical properties and microstructure of 12AgCuZnSn filler metal were analyzed. The results indicate that the solidus and liquidus temperatures of filler metals decrease with the addition of In. Trace amounts of Pr have little impact on the melting temperature of the low-silver filler metals. In addition, the spreading area of filler metals on copper and 304 stainless steel is improved. The highest shear strength of brazed joint is 427 MPa when the content of In and Pr are 2 wt.% and 0.15 wt.%, respectively. Moreover, it is observed that the trace amount of Pr significantly refines the microstructure of brazed joint matrix. A bright Pr3Cu4Sn4 phase is found in filler metal and brazing seam when the contents of In and Pr are 5 wt.% and 0.5 wt.%, respectively.
Highlights
Silver-based filler metals have a diverse range of applications in aerospace, electrical appliances, automobile industries, refrigeration applications navigation and military application in view of their distinguished brazing properties, such as, low melting point, high joint strength, excellent liquidity, strong corrosion resistance and other positive features [1,2]
The fumes produced by cadmium-containing silver brazing filler metals during brazing processes are highly toxic to humans, which has caused the application of AgCuZnCd series brazing alloys to be greatly restricted [5]
The differential thermal analysis (DTA) curves of 12AgCuZnSn-xIn-yPr brazing filler metals are shown in Figure 1, and the solidus temperatures (Ts) and liquidus temperatures (Tl) are marked by arrows in DTA traces
Summary
Silver-based filler metals have a diverse range of applications in aerospace, electrical appliances, automobile industries, refrigeration applications navigation and military application in view of their distinguished brazing properties, such as, low melting point, high joint strength, excellent liquidity, strong corrosion resistance and other positive features [1,2]. In the past few decades, AgCuZnCd series alloys have been used for brazing dissimilar joints of ferrous metals and copper alloys due to their excellent comprehensive properties [3]. The fumes produced by cadmium-containing silver brazing filler metals during brazing processes are highly toxic to humans, which has caused the application of AgCuZnCd series brazing alloys to be greatly restricted [5]. It is of interest to develop cadmium-free and low-silver brazing filler metals as the alternatives [6,7]
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