Advances in laser additive manufacturing of copper/steel heterostructures

Copper/steel heterostructures demonstrate exceptional mechanical strength and superior physicochemical properties, positioning them as a transformative solution for transportation, energy infrastructure, and advanced construction systems. Conventional casting methods induce detrimental elemental segregation at copper/steel interfaces, which critically constrain property realization and industrial scalability. In contrast, laser additive manufacturing enables high-fidelity fabrication of geometrically intricate architectures. Its ultrashort thermal cycling helps to mitigate or eliminate metallurgical defects at the interface of dissimilar metals, thereby significantly enhancing the interfacial bonding strength and overall mechanical properties. This review synthesizes cutting-edge advancements in laser powder bed fusion and laser directed energy deposition for copper/steel systems through multiscale analysis. We rigorously decode the interplay between process dynamics, interfacial alloying mechanisms (Fe–Cu interdiffusion kinetics), and emergent microstructures (nanoscale intermetallic dispersion). Furthermore, a systematic comparison is specifically conducted on the process characteristics and application effectiveness of blue laser and green laser in the dissimilar material manufacturing of copper and steel. Building on these fundamentals, this work addresses prevalent challenges such as interface-localized chemical heterogeneity and abrupt grain size transitions. State-of-the-art mitigation strategies are critically evaluated, including stoichiometry-engineered Cu/Fe gradient zones and crystallographic confinement of brittle intermetallics (e.g., FeCu2, σ-phase) below critical size thresholds. These innovative strategies have reduced the density of interfacial defects and effectively enhanced the interfacial bonding state and mechanical properties of the material. Finally, this article provides an outlook on the future development directions of copper/steel heterostructures.