Diffusion bonding of copper to titanium using CoCrFeMnNi high-entropy alloy interlayer

Copper and titanium was bonded in this work by utilizing vacuum solid-state diffusion method with an interlayer of CoCrFeMnNi high entropy alloy, the effect of temperature on the diffusion reaction mechanism was investigated. At the interface of Cu/CoCrFeMnNi, only FCC type solid solution formed in the reaction layer, and the diffusion interface was well bonded. At the interface of CoCrFeMnNi/Ti, solid solution structure and intermetallic Mn2Ti and Cr2Ti phases formed. At the diffusion temperature range of 800 °C–900 °C, the Cu/CoCrFeMnNi/Ti joint was bonded firmly. The diffusion coefficients of the component elements were calculated, and followed the rate of Mn > Cr > Fe > Co > Ni. The standard activation energy of atoms in CoCrFeMnNi high entropy alloy is higher than that of Cu atom. It is investigated that CoCrFeMnNi high entropy alloy can be used as an effective diffusion barrier for dissimilar materials bonding of Cu/Ti.