Mechanical spectroscopy of Al-Pd-Mn single quasicrystals

Internal-friction measurements were performed on icosahedral Al-Pd-Mn single quasicrystals in the temperature range from 100 to 1000K. At a frequency of 3Hz a prominent loss peak at 870 K and a second peak lower in intensity by about two orders of magnitude at 370 K were observed. The temperature positions of both peaks were found to shift with the measuring frequency, indicating thermally activated relaxation processes. The activation enthalpy of the low-temperature process was determined as H= 0.98 eV and that of the high-temperature process as = 4.0 eV. The values determined for the characteristic frequency constants were tau -infinity 1 = 4.5 1014 s-1 and - r 1= 3.0 1024 s- 1 respectively.