Dynamics of domain walls in Ti-Ni-Cu alloy

The internal friction for Ti-Ni-Cu shape memory alloys (SMAs) was measured in the Hz and kHz range. The peak temperature in the Hz range is independen t of the measuring frequencies. Only in the tens of kHz range does the peak temperature shift with the frequencies, showing a thermally activated prog ress with tau = tau(0)e(-B/Tc-T), characteristic of viscous motion of domai n walls, instead of the Arrhenius relation. Taking into account the change of the density of the domain walls during the phase transformation, we modi fied the Q(-1)-formula by using a model of viscous motion of domain walls, obtaining a good result in agreement with the experimental data. Additional ly, corresponding parameters, which play a key role in the shape memory eff ect, such as the viscosity coefficient and the effective pinning force cons tant, were obtained.