The viscoelastic behavior of β-In₃Sn and the nature of the high-temperature background

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.