Microstructure and Mechanical Properties of Butt Joints between Stainless Steel SUS304L and Aluminum Alloy A6061-T6 by TIG Welding.

The tungsten inert gas (TIG) welding method most commonly used to weld ferrous metals, nonferrous metals, and other metals since it is simple, easily implemented, and achieves consistent high-quality welds. In this study, butt joints produced between aluminum alloy A6061-T6 and stainless steel SUS304L have been achieved by using TIG welding with ER4047 filler metal. The macrostructure and microstructure of the resulting specimens were analyzed by means of an optical microscope (OM), a scanning electron microscope (SEM), and an energy dispersive X-ray spectrometer (EDS). A uniform intermetallic layer was found at the interface between the stainless steel and the weld seam having a thickness of 2 µm, and the intermetallic compound (IMC) includes Fe₄Al13, Fe₂Al₅, and FeAl₃ phases. The micro-hardness and tensile strength of the weld joints were also investigated. Due to Si content in the compensating metal, there was a prevention of iron diffusion into the aluminum, thus hindering the development of the IMC layer and reducing its thickness in such a way that the weld joint strength increases. The analyzed results show that the average micro-hardness of the stainless steel, weld seam, aluminum alloys, and IMC layer were 218 HV, 88.3 HV, 63.3 HV, and 411 HV, respectively. The fracture occurred at the brazed interface, and the ultimate tensile strength value reached 225 MPa.