Isotropic elasticity of the Al-Cu-Li quasicrystal

The elasticity tensor of a single-grain quasicrystal of composition ${\mathrm{Al}}_{5.1}$ ${\mathrm{CuLi}}_3$ has been determined. The longitudinal and transverse mode velocities have been obtained at ultrasonic frequencies (20 MHz) for several propagation and polarization directions. We find that the quasicrystal is elastically isotropic within the experimental uncertainty of 2%. This finding supports hydrodynamic analyses which predict isotropy. At 300 K, the measurements yield 6.4×${10}^5$ cm ${\mathrm{s}}^{\mathrm{-}1}$ and 3.8×${10}^5$ cm ${\mathrm{s}}^{\mathrm{-}1}$ for longitudinal and transverse velocities, respectively, and a Debye temperature FTHETA of 493 K.