Internal friction peak in pure Al bicrystals with ⟨100⟩ tilt boundaries -: art. no. 174118

A substantial internal friction peak associated with grain boundary (GB) has been observed in pure aluminum bicrystals with < 100 > tilt GBs, which is similar to that observed for < 112 > tilt GBs in the previous work [Phys. Rev. B 71, 060101(R) (2005)]. The peak is suggested to be induced by GB sliding, but with different mechanisms in microscopic scale for different types of GBs by considering their difference in relaxation parameters. The relaxation parameters for low-angle GBs with a < 100 > tilt axis are at the same level as those with a < 112 > tilt axis, and can be interpreted by the glide and climb of dislocations composing the GB, but controlled by climb. The studied high-angle high Sigma (Sigma=29) < 100 > tilt GB behaves similarly to high-angle general and high Sigma < 112 > GBs; their mechanism is possibly associated with a local rearrangement of disordered atom groups. The studied low Sigma (Sigma=5) < 100 > tilt GB exhibits a special behavior (i.e., high activation energy and low relaxation strength), which is attributed to its low free volume. The < 100 > tilt GBs with angular deviations from exact Sigma 5 but within the near-CSL (coincidence site lattice) limit also exhibit some special behavior, but to a lesser extent.