Formation and properties of aluminum-steel transition joints processed by friction stir additive manufacturing

Considering the difficulties of low strength and limited application of aluminum-steel joining, a wire-based friction stir additive manufacturing method was proposed and utilized for the aluminum-steel transition joints. 5B06 aluminum alloy wires and 3 mm 316L stainless steel sheets were used as feedstock and substrate, respectively. Aluminum-steel transition joints with good forming and excellent mechanical performance were manufactured with laser texture assistance at a deposition efficiency of 3.0 kg/h and a single-layer thickness of 1.0 mm. The wires were thermo-plasticized and filled into the textured groove. No defect was observed along the interface. Metallurgical bonding was achieved by Al/Fe intermetallic compounds (IMCs) layers with a thickness of 1.8 μm. The shear strength of the joint reached 110.0 MPa ± 4.7 MPa, which increased by 18% relative to the joints with untreated surfaces. Aluminum alloys and IMCs (Fe₂Al₅ and Fe₄Al₁₃) were noticed on the fracture of the steel side, indicating that sound bonding was achieved by mechanical and metallurgical joining. The fracture mode of the joints was tough-brittle composite fracture. This method showed great potential in manufacturing aluminum-steel transition joints.