Deformation and fracture of diffusion-bonded Cu-Ni-Zn/Cu-Cr layered composite

Mechanical performances and fracture behavior of serial-type and parallel-type Cu-Ni-Zn/Cu-Cr composites prepared by diffusion bonding were investigated. One advantage of Cu-Ni-Zn/Cu-Cr joining is the good bondability with no detrimental interfacial compounds. The conductivity of Cu-Ni-Zn/Cu-Cr composites reached 59-63% IACS (International Annealed Copper Standard) with aging. In the serial-type Cu-Ni-Zn/Cu-Cr composite (with the loading axis perpendicular to the interface), deformation is concentrated in the weaker side of the two joined alloys and no interface fracture occurred at a stress as high as 290 MPa if the strength difference is appreciable. Interfacial fracture occurred in the serial-type composite as the strain is concentrated and the slip incompatibility developed near-interface region when the strengths of two alloys become comparable by aging. In the aged parallel-type Cu-Ni-Zn/Cu-Cr composite (with the loading axis parallel to the interface), strain accommodation across the interface was difficult because of the high strength of aged Cu-Cr and interface debonding occurred as the lateral stress developed across the interface with strain. Strain concentration and strain incompatibility at the interface is the necessary requirement for interface fracture of composite.