Comparative study on internal friction in an Al-Pd-Mn icosahedral quasicrystal and its crystal approximants

Abstract

The internal friction was measured for an Al-Pd-Mn icosahedral phase ͑i-phase͒ and its 1/1 and 2/1 approximant phases in an Al-Pd-Mn-Si system in a forced flexural-oscillation mode in a frequency range of 0.05-20 Hz and a temperature range of 300-873 K. For the i-phase, large and small absorption peaks were observed with Q −1 Ϸ 1.3ϫ 10 −2 and 8 ϫ 10 −4 , respectively. These two peaks were absent for the 1/1-phase, which showed two other peaks instead. The 2/1-phase exhibited the features of both the i and 1/1-phases; it showed two peaks of the i-phase and one of the two peaks of the 1/1-phase. All the observed peaks were of the thermally activated relaxation type, and their activation enthalpies and frequency factors were evaluated. The larger peak of the i-phase, which was absent for the 1/1-phase and present with a much reduced intensity for the 2/1-phase, was shown to result from a relaxation process involving collective atomic motion. Collective and correlated phason jumps were discussed as a possible mechanism for it. It was speculated that the other peaks observed only for the approximant phases are due to Zener relaxations by the reorientation of atom pairs involving Si.

Internal Friction of an Ag–In–Yb Icosahedral Quasicrystal

“…The peak heights of Q ¹1 experimentally obtained for AgInYb, AlPdMn 9) and AlCuFe 10) i-phases are summarized in Table 1. The effective elastic constants I, c and K change with changing the directions of the wavevector q and the wave polarization p of the elastic phonon wave given to the system.…”

“…Later, So and his coworkers 9) performed a comparative study on the internal friction of an i-AlPd Mn and its 1/1 and 2/1 crystal approximant phases. The results showed that the behavior of the internal friction systematically changes in the order of 1/1-, 2/1-and i-phases.…”