The damping behavior of a Ni-50 at.%Ti shape memory alloy

Abstract

In order to utilize the shape memory alloys (SMAs) for prospective damping applications, a near equiatomic NiTi alloy was investigated on a dynamic mechanical analyzer in the infrasonic frequency range. A high damping capacity stable to the variation of temperature can be obtained during a two-stage phase transformation and in the martensite state approaching to the martensite-parent phase transformation temperature in the NiTi SMA. The transient damping peaks associated with the phase transformation in the NiTi SMA shows a strong frequency dependence in both solutionized and annealed specimens. The frequency dependence parameter, n, was found to be in the range 0.3 – 0.6. For the applied strain amplitudes from 8.5 × 10 –6 to 5.0 × 10 –5 a clear strain amplitude dependence was not observed in the damping peaks, except for the solutionized specimens. While the damping capacity of the martensite state, characterized at 300 K, showed obvious frequency dependences in both the solutionized and annealed specimens, only the annealed specimens manifested the strain amplitude dependence. The different damping behavior was attributed to the internal structure of martensite, including dislocations, the twinning types and variant interfaces, changeable with the prior thermomechanical treatments.