Grain boundary internal friction in bicrystals with different misorientations

The grain boundary (GB) internal friction peak has been observed in pure aluminum bicrystals containing 〈1 0 0〉 and 〈1 1 2〉 tilt GBs with different misorientations. It is found that the apparent activation parameters are different among low-angle, high-angle random and special GBs, and different extents of coupling effect are involved in different types of GBs. The results reveal that the basic mechanism for low-angle GBs can be attributed to dislocation climb, while that for high-angle GBs can be attributed to GB diffusion. The previously puzzling behaviors (apparent high activation energy and broad peak-width) of GB internal friction in polycrystals can also be explained in the light of the coupling model.