Acoustic quality factor of titanium from 50 mK to 300 K

The amplitude-independent mechanical quality factor Q of grade 1 commercially pure polycrystalline titanium has been measured in the temperature range from 50 mK to 300 K. Data were obtained from a torsional mode of a mechanical resonator at about 1 kHz. Maximum Qs of 2–3 million were observed below 30 K in thermally stress-relieved material. A recrystallizing anneal led to reduced Qs. High-resolution frequency measurements gave the temperature dependence of the dynamic shear modulus. From 2 to 35 K, the modulus is shown to correspond to a superposition of electron-gas and phonon contributions. From 50 mK to 2 K, anomalies in both Q and the shear modulus do not exhibit the temperature dependence expected for superconductivity. This study is part of the continuing work in this laboratory on acoustic losses in high-Q materials at low temperatures, of particular interest for the construction of sensitive detectors of gravitational radiation.