Internal friction in NiAl single crystals

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作者：

Max-Planck-Inst fuer Metallforschung, Stuttgart, Germany ^{[1
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来源：

Philos Mag Lett | / 3卷 / 189-194期

关键词：

Argon - Composition - Damping - Dislocations (crystals) - Enthalpy - Internal friction - Melting - Plastic deformation - Single crystals - Stoichiometry - Thermal effects - Vibrations (mechanical);

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摘要：

High-purity NiAl single crystals with a stoichiometric composition have been prepared by crucible-free inductive zone melting under an Ar atmosphere. The internal friction was investigated in the temperature range from 300 to 1400 K utilizing a low-frequency subresonance torsion apparatus operating in forced vibrations. In undeformed NiAl single crystals the internal friction exhibits above 1000 K a strongly increasing and frequency-dependent damping up to Q-1 = 0.3 at 1400 K. After plastic deformation a maximum at around 1250 K (0.1 Hz) is superimposed on this high-temperature damping. The activation enthalpy for the high-temperature increase was determined to be 2.65 ± 0.2 eV and for the superimposed maximum to be 2.9 ± 0.2 eV. The results are discussed in terms of the diffusion-controlled climb of dislocations by vacancies.

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