Interfacial Behavior of Copper/Steel Bimetallic Composites Fabricated by CMT-WAMM

Copper/steel bimetallic composites were made by using cold metal transfer wire and arc additive manufacturing (CMT-WAAM) with 1.2 mm diameter ER120S-G high-strength steel and 1.2 mm diameter ERCuSi-A silicon bronze welding wires. Based on the optimal tensile strength, the optimal CMT additive parameters of the copper layer were determined by the single-factor method under the conditions of the fixed steel layer process parameters of a 100 A welding current and 550 mm/min welding speed. The interfacial behavior of copper/steel bimetallic composites with the optimum parameters was investigated in particular. The results show that the optimum CMT additive process parameters for depositing a copper layer on a steel layer are a welding current of 100 A and a welding speed of 500 mm/min. The steel side consists mainly of martensite and ferrite, and the copper side consists of α-Cu matrix, Cu3Si, and Cu15Si4 reinforcing phases. The composite interfacial region is mainly composed of the FeSi2 reinforcing phase. At the optimum parameters, the ultimate tensile strength of the composites can reach 404 MPa with a ductile fracture on the copper side. Under the optimum parameters, the microhardness of the composites declines gradually from the steel side to the copper side, and the microhardness at the interface is higher than that at copper side, reaching 190 HV. In addition, the corrosion current density of the copper-side metal is 2.035 × 10−6 A·cm−2, and the corrosion current density of the steel-side metal is 7.304 × 10−6 A·cm−2. The corrosion resistance of the copper-side metal is higher than that of the steel-side metal. The CMT-WAAM process can produce copper/steel bimetallic composites with excellent comprehensive performance. The advantage of material integration makes it a broad application prospect.