Microstructure and properties of brazed graphite and copper joints

Graphite was joined to copper using amorphous TiZrNiCu filler foil by vacuum brazing. Joint interface was analyzed by several methods, such as optical microscope, SEM, EDS and EPMA. The results showed that Cu-Ti, Cu-Zr and Ni-Ti compounds distributed on the interface and cracks tended to occur at large-size compounds. Cu-based solid solution can prevent or slow down the crack propagation, which is favorable for the joint strength. When the joint is brazed at 950°C for 5 min, the resistance of joint is below 5 mΩ and the average resistance is 3.3 mΩ, while the joint shear strength reaches 16.34 MPa. All of these meet the demand of the joint as a diverter.