Study on Lead Segregation Control and Tribological Property Improvement of Copper–Steel Bimetallic Melting‐Casting Materials

High‐lead copper alloy exhibits excellent lubrication property and finds application in copper–steel bimetallic. However, lead tends to segregate at grain boundaries, which impairs mechanical and tribological properties. To resolve this, this study employs the rare‐earth Ce—characterized by high chemical activity and strong grain boundary segregation tendency—as a modifier. Copper–steel bimetallic materials are prepared using melting‐casting process, and the influence of Ce on the microstructure and tribological properties of the bimetallic materials is investigated. The mechanisms for inhibiting lead segregation and improving tribological properties are revealed. Results show that adding Ce can refine particles and suppress the segregation of Pb. With increasing the content of Ce, the particle size of Pb first decreases and then increases, while the mechanical and tribological properties of the composite initially improve and then deteriorate. During the melting‐casting process, the refractory CePb 3 phase, formed by Ce and Pb, serves as heterogeneous nucleation sites that refine the matrix's grain structure by providing additional nucleation points. This process divides more Pb melt pools, preventing coalescence and segregation. The dispersed lead enhances the stability of the Pb lubrication film, thereby improving the tribological performance.