Temperature and strain-amplitude dependent variations of logarithmic decrement () in
a high damping Mn-20Cu-5Ni-2Fe (at pct) alloy are compared for 4 different
processing conditions. The primarily cold-rolled sample shows  above 0.08 in a wide
temperature range of about 100ºC, while solution treating the as-casted sample obtains
a strain-amplitude sensitive damping behavior, as high as 0.25 at the strain of 2.0×10-4.
The chemical inhomogeneity in primarily casted alloy is reflected by the flattened
changes of Young’s modulus (E), broadened x-ray patterns, and the co-existence of
twin plates and tweed microstructure. While the strain-amplitude sensitive damping
behavior is related to the large fraction of Mn-rich Mn phase, the thin (011) twin plates,
intersected with the traces of stacking faults, is considered to be the products of
dislocation reaction at the conjunction of intersected (111) plane. Such twins may
possess a low activation energy for cyclic movement, and therefore cause a stable
damping behavior in the vicinity of room temperature.