Dissimilar low-temperature diffusion bonding of copper and titanium using a Zn interlayer: Interfacial microstructure and mechanical properties

Abstract

In this study, a zinc (Zn) interlayer was applied in the diffusion bonding of pure copper (Cu) and titanium (Ti). The interfacial microstructure evolution and metallurgical reaction mechanisms of Cu/Ti joints with Zn interlayer were investigated by SEM, EDS and TEM. The addition of the Zn interlayer facilitated metallurgical bonding between Cu–Zn and Ti–Zn at low temperatures. The shear strength of joints exhibited a gradual increase followed by a sharp decline as the bonding temperature increased. An intimate bonding between Cu and Ti was achieved at 450 °C, and the highest average shear strength of 106.82 MPa was obtained at 490 °C. The weld seam is primarily composed of a β′-CuZn layer, which exhibited excellent plasticity and hindered the formation of brittle Cu–Ti intermetallic compounds. The τ1-Cu2TiZn layer, adjacent to β′-CuZn, demonstrated stronger resistance to crack propagation compared to the brittle TiZn3 and TiZn2 layers. Furthermore, the predominant β′-CuZn layer and τ1-Cu2TiZn layer formed a coherent interface, ensuring a reliable bonding. These results demonstrate that the addition of Zn interlayer is an effective strategy for preparing highly reliable Cu/Ti joints at low temperatures.