Dissimilar joining of stainless steel and aluminum using twin-wire CMT

The twin-wire CMT with Al-Si filler was used as weld/brazing process for dissimilar joining of stainless steel and aluminum. It is shown that this approach can ensure a satisfactory performance of the joint and the dissimilar joint exhibits typical characteristics of common known steel/aluminum weld brazing joints. Intermetallic compounds (IMCs) were detected next to the steel as a layer of Fe2Al5, as a layer of Fe3Al2Si4 adjacent to the aluminum side and as a scattered phase of Fe4Al13 in between. The total thickness of the IMCs was determined with 2-4 mu m. The maximum tensile strength of the weld joints without reinforcement was up to 96 MPa and cross tensile test specimens fractured at the brazing interface at about 35% of the strength of the aluminum. An increase of the wire feeding rate and decrease of the welding speed thereby outperform beneficial in respect to wetting characteristics. However, excessive heat input (e.g., wire feeding rate larger than 7.5 m/min) causes a reduction of the mechanical properties. A groove gap about 1 mm ensures furthermore a good back appearance.