Vacuum diffusion brazing of Al5052 alloys using Ag-28Cu insert metal

In this study, we examined brazeability of Al5052 alloys using a Ag-28Cu insert metal in vacuum condition. A high frequency induction-heating vacuum hot press was used for the brazing. Under a static pressure of 0.5 MPa and a vacuum of 5 X 10-5 Torr, the temperature of hot press was raised up to brazing temperature (480-590 degrees C) at a speed of 10 degrees C/min and held at the brazing temperature for various times. Interface behaviors of the brazed joints were observed after brazing at 480-590 degrees C by optical microscopy and Electron Probe Micro Analyzer (EPMA). Also, bonding strength of the brazed joints was examined. During vacuum brazing of Al5052 alloys with Ag-28Cu insert metal, eutectic melts were formed by eutectic reaction between Al5052 and Ag-28Cu insert metal at about 490 degrees C. It was found that reaction layers of two phases are formed at the interface between Al5052 and Ag-28Cu insert. EPMA analysis revealed that two phases in the reaction layers consist of Ag-rich phase and Cu-rich phase. The bonding strength of the joints increased with brazing temperature and time. The highest bonding strength was 141 MPa at 580 degrees C, 10min.