THE OBSERVATION OF MECHANICAL RELAXATION IN A QUASI-CRYSTALLINE AL75CU15V10 ALLOY

We measured dynamic mechanical properties, such as the storage modulus E' and loss tangent tan 6, i.e. the internal friction, a quasicrystal line Al75Cu15V10 alloy between 393 and 773 K by a forced oscillation m ethod. A tan delta peak appears distinctly at 439 K in the temperature -dependent measurements for a frequency of 62.8 rad s-1. The loss peak exhibits frequency dependence which is a feature of relaxation. We ha ve thus confirmed experimentally the existence of the mechanical relax ation system at high temperatures in quasicrystals for the first time. The activation energy for the relaxation obtained from the frequency- dependent measurements is 110 kJ mol-1. The distribution of the relaxa tion time is much broader than that of the Debye peak of the single re laxation time. The occurrence of relaxation is ascribed to phasons.