Interfacial behaviour of the high-entropy alloy CuCoCrFeNi and TC4 joint obtained by vacuum diffusion welding

In this work, good bonding between the high-entropy alloy (HEA) CuCoCrFeNi and TC4 titanium alloy was obtained through vacuum diffusion welding at a joining temperature of 1000 °C for 60 min under a pressure of 5 MPa. The results showed that the typical interfacial microstructure of the CuCoCrFeNi/TC4 joint was TC4/diffusion layer/island structure/dendritic structure/diffusion layer/HEA. Compared with Ti atoms, atoms such as Cr and Co from the CuCoCrFeNi substrate were prone to diffuse into the other material. Intermetallic compounds Cu 0.5 Fe 0.5 Ti and Co 0.15 Ni 0.85 Ti, solid solutions Ti(Fe, Cr)ss and amorphous materials were produced in the joint. The self-diffusion activation energy formula [see formula in PDF] can be used to approximate the order of diffusion capacity of elements, which follows in Cr >Fe> Co > Ni.