Grain Boundary Diffusion in Copper under Tensile Stress

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Stress enhanced self-diffusion of Copper on the Σ3 twin grain boundary was examined with molecular dynamics simulations. The presence of uniaxial tensile stress results in a significant reduction in activation energy for grain-boundary self-diffusion of magnitude 5 eV per unit strain. Using a theoretical model of point defect formation and diffusion, the functional dependence of the effective activation energy Q on uniaxial tensile strain ε is shown to be described by Q(ε)=Q₀-E₀V*ε where E₀ is the zero-temperature Young's modulus and V* is an effective activation volume. The simulation data agree well with this model and comparison between data and model suggests that V*=0.6Ω where Ω is the atomic volume. V*/Ω=0.6 is consistent with a vacancy-dominated diffusion mechanism.