Effect of shear on interdiffusion in an Al-Cu binary couple: A molecular dynamics study

Shear between the particles can strongly influence diffusion-assisted mixing across dissimilar metal interfaces under thermomechanical conditions. In this study, classical molecular dynamics simulations were performed to quantify the effects of temperature and applied interfacial shear on interdiffusion in a binary Al–Cu couple. A Cu(100)/Al(100) interface model was employed to perform the simulations over a temperature range of 675–900 K, while shear was imposed through an applied interfacial shear velocity ranging from 3 to 15 m/s. The interdiffusion coefficients were then obtained from the Cu concentration profiles using the Boltzmann–Matano method. The interdiffusion followed thermally activated Arrhenius behavior across the studied temperature range corresponding to an effective activation energy of ∼0.38 eV. The calculated temperature-dependent interdiffusion coefficients are comparable to the range of experimentally reported values for Al–Cu intermetallic systems. With the applied shear, interdiffusion is accelerated compared to thermally activated diffusion, with larger shear velocities leading to higher interdiffusion coefficients. Our results show that the interdiffusion coefficients are at least one order of magnitude higher than those for thermally activated diffusion. Cross diffusion coefficients further reveal a higher Cu contribution than Al to the overall interdiffusion, indicating asymmetric atomic transport across the interface. The study highlights an important role of shear-driven effects in governing interdiffusion and provides atomistic insight into diffusion-assisted mixing in Al-Cu systems under thermomechanical conditions.