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 1000 K. At a frequency of 3 Hz 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 H = 4.0 eV. The values determined for the characteristic frequency constants were tau(r infinity)(-1) = 4.5 x 10(14) s(-1) and tau(r infinity)(-1) = 3.0 x 10(24) s(-1) respectively.