Internal friction in a new kind of metal matrix composites

We have developed a new kind of metal matrix composites, based on powders of Cu–Al–Ni shape memory alloys (SMAs) surrounded by an indium matrix, specifically designed to exhibit high mechanical damping. The damping properties have been characterized by mechanical spectroscopy as a function of temperature between 150 and 400 K, frequency between 3 × 10−3 and 3 Hz, and strain amplitude between 5 × 10−6 and 10−4. The material exhibits, in some range of temperature, internal friction as high as 0.54. The extremely high damping is discussed in the light of the microstructure of the material, which has been characterized in parallel.