A stepwise vacuum diffusion bonding method was used to fabricate Cu/Al joint with varied thickness of Ni intermediate layer.The interfacial microstructure and metallurgical reaction between Cu and Al were investigated.The morphology and phase composition of heterogeneous composite interface were analyzed by scanning electron microscopy（SEM）and energy disperse spectroscopy（EDS）.The shearing strength and the micro-hardness of the joint were measured by shearing experiment and hardness testing.The results reveal that

Ni intermediate layer can prevent effectively generation of brittle intermetallic compound phase in the Cu and Al.Compound phase of two layer Al

3

Ni and Al

3

Ni

2

can be observed in Ni/Al interface

and there exists solid solution phase with clear elemental composition gradient in the Cu/Ni interface.When Ni foil thickness is 20μm

Ni foil just be completely consumed

so obvious defects are absent in interface

and the interface shear strength reaches maximum value.