Diffusion activation enthalpy of nanocrystalline metals
(Non-equilibrium Materials Research Institute; Central South University of Technology; Changsha 410083; P. R. China；
Institute of Materials Science; Guangxi University; Nanning 530004; P. R. China)
Institute of Materials Science; Guangxi University; Nanning 530004; P. R. China)
Abstract: The atomic diffusion of nanocrystalline metals showed significant difference in comparison to poycrystalline 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 diffusi on theory, diffusbo activation enthalpy in nanocrysta1line meta1s 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 rapid1y. The theoretical prediction is found to be in accoedance with experimental observations.
Key words: diffusion activation enthalpy; structure relaxation; interfacial migration