Molecular Dynamics Study of Impurity Effects on Grain Boundary Grooving

Impurity effects on grain boundary grooving in crystalline aluminum are studied using computer molecular-dynamics simulation. We use a Morse potential that includes equilibrium spacing (v A1 ) and potential well depth (|(u A1 |) to characterize aluminum/aluminum interaction, and a two-body interatomic potential that includes equilibrium spacing (v m ) and potential well depth (|u min |) to characterize aluminum/ impurity interaction. Simulations show that when v m is smaller than v A1 and when |u min | is close to |u A1 | (within ±20% of it), grain boundary grooving is prevented. This is effect is explained by a decrease in the ratio of grain boundary diffusion to surface diffusion. Diffusion coefficients obtained in our simulations show that impurities at grain boundaries which satisfy the above conditions (e.g. copper) strengthen surface diffusion without strengthening grain boundary diffusion.