Molecular Dynamics Study of Impurity Effects on Grain Boundary Grooving

Grain boundary grooving in crystalline aluminum is simulated by computer molecular dynamics, and impurity effects are investigated. We use a Morse potential that includes equilibrium spacing, γA1, and potential well depth, |uA1| to characterize aluminum-aluminum interaction. We also use a two-body interatomic potential that includes equilibrium spacing, γm, and potential well depth, |umin| to characterize aluminum-impurity interaction. The simulations show that when γm is smaller than γA1 and when |umin| is close to |uA1| (with the relative difference smaller than 20%), grain boundary grooving is prevented. This effect is explained by a decrease in the ratio of grain boundary diffusion to surface diffusion. Diffusion coefficients obtained by these simulations show that impurities at the grain boundaries which satisfy the above conditions (e. g., copper) strengthen surface diffusion without strengthening grain boundary diffusion.