Fabrication of Invar/MnCu bimetallic structure by laser powder bed fusion: Microstructure, mechanical, thermal expansion and damping properties

Metallic bimetal structures that combine thermal stability and vibration damping are crucial for advanced structural–functional applications. Conventional joining methods restrict geometric complexity and can damage the interface. Laser powder bed fusion (LPBF) provides high spatial resolution and rapid solidification. Therefore, it is considered a promising technique for fabricating Invar/MnCu bimetals. However, the interfacial formation mechanism and the resulting properties are not fully understood. In this study, Invar/MnCu bimetallic structures with metallurgical bonding were fabricated by LPBF. Interface evolution and structure–property relationships were investigated. A stable build was achieved by tailoring the process strategy and parameters. A composition transition layer of approximately 91.39–96.12 μm was formed at the interface. Curved mixed grains were produced by elemental intermixing and sequential solidification driven by Marangoni convection. Mechanical tests showed a yield strength of 347.40 ± 2.5 MPa, an ultimate tensile strength of 399.95 ± 5.4 MPa, and an elongation of 28.73 ± 1.4 %. Fracture occurred within the Invar region rather than at the interface. Thermal expansion and damping behavior followed the rule of mixtures and no additional interfacial peaks were observed. These results indicate strong functional integration. This work fills a fundamental gap in the LPBF fabrication of Invar/MnCu systems and provides guidance for the design of high-performance, structurally integrated bimetallic components.