The damping behavior in torsion of single phase β-In3Sn has been evaluated at room temperature over a broad range of frequencies (10-4 to 103 Hz) and as a function of various mechanical and thermal treatments. The results are consistent with a model for the power-law (tan δ α f-n), high-temperature-background absorption being effected by diffusional processes on grain and, particularly, on subgrain boundaries. The results are compared/contrasted with those for damping in single-phase γ-InSn4 and in the two-phase β-γ eutectic. Failure of the eutectic material to follow a composite model for damping, combined with a thermal aging effect that lowers damping only for certain frequencies, shows that the boundary-based absorption model for the high-temperature background applies, too, to phase boundaries.
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We thank Mark Ludwigson for preparing the β samples; we thank, too, Joe Bunton for his advice and assistance in all areas of microstructural specimen preparation and analysis. The microtome is housed in the UW–Madison Integrated Microscopy Center; Randy Massey provided both access and assistance. This work was financially supported, in part, by grants from the National Science Foundation (CMS-9896284 to RSL and EAR-0106620 to RFC).