Defects and Diffusion in d-AlNiCo-Quasicrystals - Application of Mechanical Spectroscopy

Abstract:

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Mechanical loss (internal friction) measurements were applied to polycrystalline d- AlNiCo quasicrystals for compositions ranging from Al72.8Ni7.5Co19.7 to Al71.1Ni18Co10.9 and to an Al71.3Ni13.4Co15.3 mono-quasicrystal The measurements were carried out in the temperature range from 290 K up to 1220 K for measuring frequencies between 0.1Hz and 10 kHz. A loss maximum of Debye type is observed at ≈ 700 K (2Hz) for both the I-phase and the bCo-phase, which is attributed to local rearrangement of point defects. The activation enthalpy of the peak of H = 1.9 - 2.4 eV is in the range of values obtained from tracer diffusion experiments. This indicates that local defect rearrangement and self diffusion are governed by the same atomic diffusion process.. A high temperature viscoelastic damping background is only observed in polycrystalline samples with H = 2.4 – 3 eV. The background is assigned to viscolealastic relaxation based on intergranular diffusion.

Info:

Periodical:

Defect and Diffusion Forum (Volumes 237-240)

Edited by:

M. Danielewski, R. Filipek, R. Kozubski, W. Kucza, P. Zieba, Z. Zurek

Pages:

322-327

DOI:

10.4028/www.scientific.net/DDF.237-240.322

Citation:

M. Weller et al., "Defects and Diffusion in d-AlNiCo-Quasicrystals - Application of Mechanical Spectroscopy", Defect and Diffusion Forum, Vols. 237-240, pp. 322-327, 2005

Online since:

April 2005

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$35.00

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