Basic mechanism of grain-boundary internal friction revealed by a coupling model

Abstract

By taking into account the mutual interaction among relaxation species, the data of grain boundary (GB) internal friction of Al bicrystals obtained in our previous works [Phys. Rev. B 71, 060101(R) (2005); Phys. Rev. B 72, 174118 (2005)] are further analyzed based on a coupling model. It is found that the high-angle GBs exhibit a strong coupling; while the low-angle GBs exhibit a weak coupling. It is shown that the basic mechanism of GB internal friction is GB diffusion for high-angle GBs, and dislocation climb for low-angle GBs. The previously puzzling behaviors (measured high activation energy and broad peak width) of GB internal friction in bicrystals with high-angle GBs and in polycrystals are satisfactorily explained in the light of the coupling model.