Abstract
A new thermodynamic and kinetic calculation method to be applied to nanocrystalline materials is proposed. The diffusion behavior of Ti atoms in pure nanocrystalline Fe is described by our vacancy model, first-principles calculations, and experimentally. First principles calculation results showed that the diffusion barrier in a one-vacancy structure was 0.659 eV, and in a two-vacancy structure it was 0.353 eV. The diffusion temperature of Ti atoms in pure Fe nanocrystalline was 400 °C, which was significantly lower than the corresponding value in bulk. Pure Fe surface mechanical attrition treatment (SMAT) was performed to increase the surface vacancy concentration and depress the Debye temperature. Experimental results were in good agreement with the theoretical calculations.
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