1. Materials Genome Institute, School of Materials and Energy, Yunnan University, Kunming 650500, China
2. State Key Laboratory of Precious Metal Functional Materials, Yunnan Precious Metal New Materials Holding Group Co., Ltd., Kunming 650106, China
3. School of Business and Information, Yunnan Land and Resource Vocational College, Kunming 652501, China
Cu/Al heterogeneous joints show significant application potential in new energy applications, but their prominent substantial physicochemical properties differences lead to the formation of brittle intermetallic compounds at the interface, compromising joint performance. Developing novel brazing filler metals and optimizing the process are key to achieving highperformance joints. Based on ThermoCalc thermodynamic calculations, this study designs and prepares a low-silver Al-Ge-Ag filler metal (AlGe255Ag5, at%). DSC results of the filler metal indicate solidus and liquidus temperatures of 417.26 and 436 ℃, respectively, with a narrow melting range, suitable for Cu/Al heterogeneous brazing. XRD，SEM and EDS analysis confirm that the as-cast alloy consists of Al, Ge and Ag2Al phases, consistent with predictions. Using this filler metal, successful vacuum brazing of Cu/Al is achieved, and the effect of brazing temperature (500, 520 and 540 ℃) is systematically investigated. Results show that joints brazed at 520 ℃ exhibit excellent interfacial integrity without defects, primarily forming Cu3Al2 and Al2Cu compounds and achieve the highest shear strength of 38.2 MPa. This study provides a novel mediumtemperature low-silver filler metal for Cu/Al heterogeneous joining and offers data support for brazing process optimization.