The research investigated primarily three critical issues in TIG welding-brazing of aluminum-stainless steel dissimilar metals, which consisted of the guarantee of stable weld formation, the control of intermetallic compounds (IMCs) and the mechanism of interfacial reaction between the solid steel and molten aluminum.
The joints of excellent weld formation were achieved by employing a modified flux and a twin hot wire feeding system. The suppression of the IMCs and improvement of joints’ strength can be realized by two different approaches to control the IMCs, which are inhibiting the IMC growth by decreasing heat input with ER2319 filler and promoting IMC dissolution by adjusting the welding procedures with ER1100 filler respectively. The results of mechanical tests suggested that the joint with ER2319 filler had a higher tensile strength of 283 MPa but more brittle, while the joint with ER1100 filler exhibited better comprehensive mechanical properties. The microstructure characteristics of the joints including both the interfacial IMCs and precipitates in the weld have been investigated and analyzed. After identification of the fracture behaviour, the relationships between welding procedure, microstructure and weld properties were established. Finally, the mechanisms of the formation of interfacial IMC layers were revealed based on the theory of thermodynamics and kinetics and the simulation result of interfacial temperature field.