Effect of holding time on microstructure evolution and properties of T2Cu/Al1060 diffusion bonding layer

In this paper, the welding of T2 copper and Al1060 was realized by vacuum diffusion welding process. The microstructure evolution, mechanical properties, and corrosion resistance of Cu/Al diffusion bonding layer were explored. The results show that intermetallic compounds Al₂Cu, AlCu, and Al₄Cu₉ generate at the joint under the welding condition of holding for 60 min at 530 °C. When the holding time reaches 90 min, a new phase of Al₂Cu₃ generates, and the diffusion bonding layer evolves into a four-layer structure. The thickness of diffusion layer increases with the extension of holding time and is affected by the body diffusion. The shear strength of the joint increases first and then decreases with the extension of holding time. The maximum shear strength of 20.91 MPa can be obtained under the holding time condition of 60 min, and fracture mainly occurs between Al₂Cu and AlCu phases. Nanoindentation hardness and elastic modulus of intermetallic compound phase are much higher than those of copper and aluminum matrix. Specifically, Al₄Cu₉ phase exhibits the largest nanoindentation hardness and elastic modulus of 11.062 GPa and 132.8 GPa. The corrosion resistance of diffusion bonding layers is significantly different from that of the base material. Compared with copper, the corrosion potential of each diffusion layer and aluminum matrix is relatively lower. The corrosion rates of diffusion layers and base materials are in descending order of Al > Al₂Cu > AlCu > Al₄Cu₉ > Cu.