Effect of H-doping on damping capacity of various NiTi-based alloys at kHz frequencies

The internal friction Q(-1) and the Young's modulus E of NiTi based alloys have been measured as a function of temperature after various thermomechanical and hydrogen-doping treatments given to the materials. Hydrogen is found to play a major role introducing tall damping peaks associated with Snoek-type and H-twin boundary relaxations. Levels of Q(-1) as high as 0.08 have been detected, which are among the highest to date measured in metal alloy systems. For appropriate alloy compositions, these peaks occur at around room temperature (for acoustical frequencies), thus providing a good opportunity to reduce machinery vibrations and noise pollution. In the paper the conditions are highlighted under which maximum efficiency can be reached in the, conversion of mechanical energy into heat.