ASA 125th Meeting Ottawa 1993 May

1pPA2. A comparison of elastic constants of the quasicrystalline and cubic approximant phases of AlCuLi, using resonant ultrasound spectroscopy.

P. S. Spoor

M. J. McKenna

J. D. Maynard

Dept. of Phys., Penn State Univ., University Park, PA 16802

The anisotropy (epsilon)=|1-2c[sub 44]/(c[sub 11]-c[sub 12])| of a sample of quasicrystalline (T[sub 2]-phase) AlCuLi has been measured in our laboratory to be 0.0020(plus or minus)0.0004; since a perfect quasicrystal should be isotropic, this could signify deviation from perfect icosahedral order. A comparison with the closely related R-phase cubic approximant, which is often present when macroscopic quasicrystals are grown, may provide a better basis for interpreting such measurements. Among the various methods of determining elastic properties, only resonant ultrasound spectroscopy, which uses the normal mode resonance frequencies to retreive the complete elastic tensor in one measurement, offers the necessary sensitivity to resolve such small anisotropies. Results on a recently received R-phase sample, and on its neighboring icosahedral grains, will be compared with the results mentioned above. [Work supported by NSF Grant No. DMR-9000549 and by the Office of Naval Research.]