Experimental Characterization and Microstructural Evaluation of Silicon Bronze-Alloy Steel Bimetallic Structures by Additive Manufacturing

Abstract

This paper proposes a novel and efficient preparation method for copper-steel bimetallic materials. A transition welding wire for copper-steel gradient connections was designed, and then gas metal arc welding (GMAW) additive manufacturing processes were explored. The effects of the process and material on the microstructure, interface characteristics, and mechanical properties of copper-steel bimetallic materials were systematically studied. The results show that copper-steel bimetallic thin-walled parts can be well formed, which confirms the possibility of the arc additive manufacturing of copper-steel bimetallic parts. With the direct deposition of silicon bronze on the surface of low-alloy steel, the melting unmixed zone (MUZ) appears at the bonding interface of low-alloy steel and silicon bronze, which is prone to produce microcracks, leading to fracture failure of the joint. However, with the addition of the Cu-Ni interlayer, the Fe, Ni, and Cu elements in the bronze interface between the low-alloy steel and silicon were continuously diffused, which improved the nonuniformity of the Fe-rich phase in silicon bronze matrix, and realized the gradient connection at the welding joint. Comparing the tensile properties and microhardness of the joints, it can be found that the tensile strength of the low-alloy steel/Cu-Ni/silicon bronze joint was 66.36 pct higher than that of the alloy steel/silicon bronze joint, which can reach approximately 345.2 MPa and shows a typical ductile fracture mechanism. Additionally, the microhardness of the transition zone in the low-alloy steel/Cu-Ni/silicon bronze joint was more uniform.