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Changes of Koiwa – hasiguti dynamic dislocation relaxation parameters in nanocrystalline and polycrystalline zirconium after severe plastic deformation and annealing

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Document pages: 12 pages

Abstract: The temperature dependence   K of the acoustic properties of nanostructures and polycrystalline zirconium was studied in the temperature range of 100-340. The effects of severe plastic deformation and subsequent annealing on the key parameters of Koiwa – hasiguti acoustic relaxation in zirconium were studied in detail. The results show that the relaxation strength of the sample increases significantly due to strong plastic deformation, and the temperature and width of the corresponding relaxation peak decrease systematically with the decrease of the average grain size in the sample. After annealing, the relaxation strength and peak temperature of the undeformed sample partially return to the initial value, but the width of the relaxation peak further decreases. majority effects observed can be explained by changes in dislocation subsystems of the samples during intensive plastic deformation and annealing. An influence of a random scatter of the relaxation time on the main parameters of the Koiwa–Hasiguti peak is established using the statistical analysis based on the lognormal distribution. It is shown that the parameter β of the lognormal distribution determines the width, height, and asymmetry of the peak and also allows estimating the relaxation strength from the peak height. An algorithm for retrieving the parameter β from experimental data is presented.

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