Abstract
Ti-Ni shape memory alloy is one of the most promising materials among high damping alloys. Ti-Ni alloys show a transient damping peak due to martensitic transformation and an almost temperature independent damping in the martensitic phase. Since the transient damping peak is useless due to many limitations, we can utilize only the damping capacity of martensitic phase. In the present work, we doped hydrogen into a ternary Ti-Ni-Cu alloy, which is known to exhibit higher damping capacity than binary Ti-Ni alloy, to improve further the damping capacity. Ti50Ni25Cu25 alloy was produced by a lamination process from a high workability point of view. As a result of hydrogen doping, a new damping peak occurred at around 260 K. The temperature of damping peak was shifted with change in oscillation frequency. The activation energy (H) and relaxation time constant (τ0) of the damping peak were calculated according to the Arrhenius plot as H=57.5 kJ/mol. τ0=2.2×10-13 s. The damping capacity due to hydrogen doping increased with increasing hydrogen concentration up to 0.45 at% hydrogen showing tan φ=0.05, but thereafter decreased. On the other hand, the peak temperature increased monotonously with increasing hydrogen concentration, and the peak shape was broader than single Debye relaxation peak.
From these results, we conclude that this damping peak is not the Snoek peak but the Snoek-Koster peak possibly caused by hydrogen and dislocation interaction effect; G. Schoecks theory for Snoek-Koester peak may be applicable.
