High viscoelastic damping is observed in InZn materials over ranges of composition, frequency,
temperature and annealing time. Microscopy reveals InZn when cast segregates into a
heterogeneous micro-structure resembling an in situ composite consisting of a zinc matrix with
soft indium platelet inclusions. This morphology is predicted to be advantageous for maximizing
the damping figure of merit Etan! by viscoelastic composite theory. InZn is found to be
linearly viscoelastic, unlike other high damping metals. The damping of InZn varies little over
a substantial range of temperature, in contrast with polymers. For 5% In material, the optimal
composition, Etan! is 2.8 GPa at 10 Hz, compared to a peak of 0.6 GPa for high damping
rubbers. After annealing for 13 years, Etan! was still high at 1.9 GPa. InZn demonstrates high
damping under a wide range of conditions.
keywords: Complex modulus, Dynamic mechanical properties, Linear viscoelasticity, Solid,
Structure, Dynamic moduli