Microstructure and Microhardness of Interfaces of High Thermal Conductivity Ag-Cu Dissimilar Metals Fabricated by Laser Powder Bed Fusion Additive Manufacturing

Ag and Cu are widely used in key fields such as smart electronics, wearable devices, and healthcare due to their excellent high electrical and thermal conductivity (HETC) properties. The laser powder bed fusion (LPBF) technology is an innovative technology for high-precision manufacturing of dissimilar metals, which can expand the application of Ag-Cu in the emerging high-tech fields. In this study, we have pioneered the successful fabrication of Ag7.5Cu/Cu10Sn/Ag7.5Cu dissimilar metal samples without macroscopic defects using LPBF technology. The effect of microstructure on microhardness of the Ag7.5-Cu/Cu10Sn (A/C) and Cu10Sn/Ag7.5Cu (C/A) interfaces is investigated. The results show that the high thermal conductivity substrate promotes the molten pool convection in the A/C and C/A interface fusion zones, which can help reduce the porosity and crack defects and improve the interface bonding strength. The gradient grain in the fusion zone prevents the propagation of the microcracks, and facilitates the reduction of crack defects. The isotropy of the interface results in a good combination of macroscopic mechanical properties for the both interfaces. The more intense Marangoni convection at the A/C interface causes a wider fusion zone, which promotes the extensive elemental migration and reduces the macroscopic segregation, and makes the average hardness (183.34HV) in the fusion zone higher than that (134.27HV) at the C/A interface. This study provides theoretical guidance and process reference for the fabrication of HETC dissimilar metals by LPBF.