Damping Capacity of Ni–Mn–Ga–Gd High-Temperature Shape Memory Thin Film

Abstract

The damping capacity of Ni–Mn–Ga–Gd films annealed for different durations has been investigated by dynamic mechanical analysis (DMA) measurement. The DMA results show that the internal friction peaks are absent in the IF curves, due to very low transformation rate and low transformation strain in the films. With the increase of annealing time, the value of tan delta in martensite first increases then decreases due to the combined effect of grain size and martensite structure change. Owing to the occurrence of high-temperature creep behavior, an abrupt increase of tan delta takes place over 400 °C in the film annealed for 10 h. The film annealed for 5 h shows good thermal stability of phase transformation and keeps a high damping capacity in martensite after ten times of repeated DMA measurement. In terms of the high damping capacity (tan δ = 0.046) in martensite, high transformation temperature (As = 292 °C), and good thermal stability, the film annealed for 5 h can be used as a damping material for MEMS devices in elevated temperature.