科研之友
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摘要
The atomic diffusion of nanocrystalline metals showed significant difference in comparison to polycrystalline metals, this property is analyzed by considering the effect of temperature - time history on the interfacial structure. The interfacial structure is approximated by a dilated perfect crystal. Based on LeClair's diffusion theory, diffusion activation enthalpy in nanocrystalline metals was calculated. The results show that the change of diffusion activation enthalpy is closely related to the structure relaxation of the interfaces and the interfacial migration, the structure relaxation of the interfaces will increase the diffusion activation enthalpy when the crystallite growth can be negligible, whereas the migration of the interfaces will lead to the further increase of the diffusion activation enthalpy when crystallite growth proceeds rapidly. The theoretical prediction is found to be in accordance with experimental observations.
