Mechanical spectroscopy of i-Al–Pd–Mn and d-Al–Ni–Co

Mechanical spectroscopy was applied for the study of defect properties in i-Al–Pd–Mn and d-Al–Ni–Co by applying measuring frequencies between 10−2 and 104 Hz in the temperature ranging from 200 to 1220 K. i-Al–Pd–Mn single quasicrystals exhibit two mechanical loss peaks at 370 (peak A) and 870 K (peak B) for f=3 Hz. Peak A with an activation enthalpy of H=0.98 eV and an attempt frequency τ∞−1=2×1015 s−1 is attributed to atomic jumps enabled by phason flips or vacancies. Peak B (H=4 eV, τ∞−1=3×1024 s−1) shows nonlinear Arrhenius behaviour for higher frequencies (f>1 kHz) and is attributed to a relaxation process in which dislocation movement is controlled by creation and movement of phason defects. First measurements on Al–Ni–Co alloys (decagonal or with fivefold symmetry) show a loss maximum at 870 K (f=2 kHz) indicating reorientation of atomic defects. A high temperature background (H=2.3 eV) is assigned to diffusion controlled deformation.