Microstructure and strength of graphite and copper brazed joints in vacuum

The vacuum brazing of graphite to copper was carried out by Ag-Cu-Ti brazing filler metal,and the microstructures and strength of the joints were also investigated by means of SEM,XRD and shearing test.The experimental results show that the bonding of graphite to copper can be performed by Ag-Cu-Ti filler metal in vacuum.The interfacial microstructure of the joint is graphite/TiC/Ag-Cu eutectic+Cu solid solution/Cu solid solution/copper.With increasing of the brazing temperature and holding time,TiC layer became thicker,but thickness of layer could not continuously increase.The maximum shear strength of the joint,which was brazed at 870℃ for 15 min in vacuum,was up to 17 MPa.The brazed specimens fractures occurred at the graphite near the interface between graphite and filler metal.