Low Temperature Physics: 37, 625 (2011); https://doi.org/10.1063/1.3645026 (7 pages)
Fizika Nizkikh Temperatur: Volume 37, Number 7 (July 2011), p. 792-799    ( to contents , go back )

Statistical analysis of the low-temperature dislocation peak of internal friction (Bordoni peak) in nanostructured copper

E.N. Vatazhuk1 and V.D. Natsik1,2

1B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
E-mail: vatazhuk@ilt.kharkov.ua

2V. Karazin Kharkov National University, 4 Svobody Sq., Kharkov 61077, Ukraine
pos Анотація:

Received February 25, 2011

Abstract

The temperature-frequency dependence of internal friction in the nanostructured samples of Cu and fibred composite C–32 vol.%Nb with the sizes of structure fragments ~ 200 nm is analyzed. Experiments are used as initial information for such analysis. The characteristic for the heavily deformed copper Bordoni peak, located nearby a temperature 90 K, was recorded on temperature dependence of vibration decrement (frequencies 73–350 kHz) in previous experiments. The peak is due to the resonance interaction of sound with the system of thermal activated relaxators, and its width considerably greater in comparison with the width of standard internal friction peak with the single relaxation time. Statistical analysis of the peak is made in terms of assumption that the reason of broadening is random activation energy dispersion of relaxators as a result of intense distortion of copper crystal structure. Good agreement of experimental data and Seeger’s theory considers thermal activated paired kinks at linear segments of dislocation lines, placed in potential Peierls relief valley, as relaxators of Bordoni peak, was established. It is shown that the registered peak height in experiment correspond to presence at the average one dislocation segment in the interior of crystalline grain with size of 200 nm. Empirical estimates for the critical Peierls stress σР ≈ 2·107 Pа and integrated density of the interior grain dislocations ρd ≈ 1013 m–2 are made. Nb fibers in the composite Cu–Nb facilitate to formation of nanostructured copper, but do not influence evidently on the Bordoni peak.

75.50.Tt Fine-particle systems; nanocrystalline materials;
PACS: 62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances.

Key words: nanostructured metals, low temperatures, acoustic vibrations, internal friction, Bordoni peak, dislocations.

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