Loading frequency and temperature-dependent damping capacity of NiTiHfPd shape memory alloy

Superelastic shape memory alloys with ultra-high-strength, large mechanical hysteresis, and the ability to recover large deformations are promising materials for damping applications. In this study, the superelastic response and damping capacity of quaternary Ni45.3Ti39.7Hf10Pd5 polycrystalline alloys are investigated in terms of temperature and loading frequency dependency. It is shown that this alloy can show fully recoverable superelastic behavior with strain amplitude of 6-7% from -40 degrees C to 80 degrees C after heat treatments. The damping capacity of 550 degrees C-3h aged alloy at 20 degrees C was 22.5 J/cm(3) for quasi-static loading which decreased to 12.5 J/cm(3) under 1 Hz loading frequency. At the high temperature of 80 degrees C the damping capacity was determined 9.2 J/cm(3) under quasi-static loading and 4 J/cm(3) under 1 Hz loading frequency. The decrease in damping capacity with loading frequency and temperature is linked to: the changes in local temperature of the specimen which significantly increases critical stress for reverse transformation while not affecting the critical stress for forward transformation, improved compatibility of transforming phases, and decrease in the contribution of superelastic strain to the total recovered strain.