Influence mechanism of copper interlayer on the interface bonding during wire and laser additive repair of TA1/Q235 bimetallic sheets

Titanium/steel bimetallic sheets are extensively employed in engineering applications due to their excellent cost performance and high corrosion resistance. However, the interface defect is easy to form due to significant differences in physical and chemical properties between titanium and iron, which need to be improved through effective repair techniques. The wire and laser additive manufacturing (WLAM) method is implemented to repair TA1/Q235 bimetallic sheets. The addition of a copper interlayer plays a crucial role in the repair process. According to the results, S201 copper wire is used as the interlayer material, while TA1 wire serves as the deposit material in the repair process using the WLAM technique. Under the conditions of a laser power setting of 1500 W, a defocusing amount of −40 mm, a deposition speed of 1 mm/s and an argon flow rate of 23 L/min, the interface defects are effectively addressed, leading to successful repair. The WLAMed copper interlayer avoids direct contact between the titanium repaired layer and the steel base layer, improving the interface bonding characteristics. The interior of the repair region of TA1-Q235 bimetallic sheets is made of the pure copper layer, Cu₂Ti + Cu₄Ti₃ layer, CuTi layer, CuTi₂+β-Ti layer and pure titanium layer. The copper-titanium compound region exhibits a pronounced increase in hardness, with the repair region achieving a tensile strength of 436 MPa. Notably, the fracture position occurs within the repair region, with the titanium side exhibiting brittle fracture and the steel side displaying ductile fracture.