Impulse pressuring diffusion bonding of a copper alloy to a stainless steel with/without a pure nickel interlayer

Impulse pressuring diffusion bonding of a copper alloy to a stainless steel was performed in vacuum. Using Ni interlayer of 12.5 μm, the joint produced at 825 °C under 5-20 MPa for 20 min exhibited lower strength, which could result from the insufficient thermal excitation and plastic deformation. At 850 °C under 5-20 MPa for 5-20 min, the strength of the joint improved with time. An optimized joint strength reached up to 217.2 MPa. Fracture occurred along the Cu-Ni reaction layer and the Ni layer and almost plastic fracture was confirmed by extensive dimples on the fracture surface. Using the interlayer of 50 μm, the fracture surface was similar. Without Ni assistance, under the same bonding condition, the joint strength was about 174.2 MPa. The lowered strength might be attributed to the appearance of some unbonded zones in the joint. Lots of brittle fracture areas appeared on the fracture surface.