An atomic insight into effect of grain boundary on diffusion behavior of Cu/Al dissimilar materials undergoing ultrasonic welding

JW Yang and CH Xie and J Zhang and ZY Ding and J Qiao, JOURNAL OF IRON AND STEEL RESEARCH INTERNATIONAL, 31, 2555-2567 (2024).

DOI: 10.1007/s42243-024-01349-5

The diffusion processes in bicrystalline Cu/Al joints, characterized by typical high-angle grain boundaries (GBs), were investigated using molecular dynamics simulations. It was found that GBs facilitated the diffusion of both Cu and Al atoms, predominantly enhancing the migration of Cu atoms into Al matrix. According to mean squared displacement results, the movement of Al atoms within Al matrix was more vigorous than that of Cu atoms. The mechanisms of atomic rearrangement, dislocation movement, stacking fault formation, and dynamic recrystallization were analyzed. During the compression and initial welding stages, the mismatch in lattice constants and the twisting of grains initiated a squeeze-induced rearrangement of Al atoms at the interface, leading to the formation of dislocations and vacancies. During the advanced stages of welding, the plastic deformation primarily occurred within Al matrix, marked by the emergence of dislocations, stacking faults, and GB sliding. Particularly, the shearing effect during the ultrasonic welding process, combined with GB sliding, collectively induced grain recrystallization at the interface. Furthermore, the diffusion between Cu/Al joints could be enhanced by increasing the vibration frequency, due to a significant rise in the number of amorphous regions.

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