Abstract: The friction stir technique was used to connect copper and aluminum with low melting points. The diffusion ability of copper and aluminum atoms at the interface affects the mechanical properties of the interface. Molecular dynamics was used to study the diffusion behavior of atoms at the Cu/Al interface during friction stir welding, and the mechanical properties of the interface were assessed under different strain rates. The results showed that the quantity of copper atoms diffusing into the aluminum lattice is much larger than that of aluminum atoms diffusing into the copper lattice. The atom diffusion is dominated by the nearest-neighbor hopping mechanism with diffusion activation energies of 0.58, 0.75 eV for Cu and Al atoms, respectively. The thickness of the interface transition layer is mainly controlled by the holding temperature with the optimal thickness interface at 800 K. The maximum interfacial tensile strength is 3.19 GPa at the tensile strain rate of 1×10¹⁰s^－1. Plastic deformation primarily occurs within the aluminum side with minimal plastic deformation on the copper side. Dislocation reaction during the deformation process includes the decomposition of perfect dislocation and the formation of stair-rod dislocation. The dislocation energy decreases with the Shockley dislocation being the main slip dislocation.

Key words: molecular dynamics, Cu/Al interface, diffusion, strain rate, mechanical property