Microstructure and Diffusion Mechanism of CoCrCuFeNi HEA Joints Diffusion Welded Using Co Filler

Abstract:

A CoCrCuFeNi high-entropy alloy (HEA) was diffusion welded using a Co filler at 850, 950, 1050, and 1100 °C, and the microstructure and diffusion mechanism of the joints were examined. Results show that firm connections are achieved at each temperature, no intermetallic compound forms in the joints, and some Kirkendall voids are remained on the HEA side around the interface. The diffusion coefficients of Cr, Fe, Ni, and Cu in the Co filler at 850 and 950 °C are calculated, ranked as follows: Cu>Cr>Fe>Ni. The diffusion rates of all elements are at the same level. The diffusion between the CoCrCuFeNi HEA and Co filler occurs under the combined action of the vacancy and grain boundary diffusion mechanisms.

Key words:high-entropy alloy;diffusion welding;microstructure;diffusion coefficient;diffusion mechanism