Microstructure and mechanical properties of aluminum/stainless steel brazed joint with torch brazing

The wettability, microstructure, intermetallic compound (IMC) layer and mechanical properties of aluminum/stainless steel joints brazed with Zn-xAl filler metals were investigated by means of scanning electron microscope, energy dispersive X-ray spectrometer and X-ray diffraction. The results indicate that the oxide film on the base metal could be effectively removed by the modified CsF-RbF-AlF₃ flux, and the excellent mechanical properties of the brazed joints were obtained. The spreading area as well as the clearance filling ability of Zn-xAl filler metal was both improved with by increasing the content of Al in the filler metals. However, the shear strength of the joint increased first and decreased afterwards, and the best mechanical property of brazed joint is obtained when the content of Al is 15%. It has been found that when the content of Al is low, the interfacial layer is composed of Zn-rich and Fe₄Al₁₃ phase. As for the excessive amount of Al, additional Fe₂Al₅ phase is visible at the interface.