The creep of β-Sn single crystals oriented for slip in the (100)〈010〉 system is investigated in the temperature range 0.45–4.2 K. A transient creep, decaying in time by a logarithmic law, is registered both above and below 1 K. The temperature dependence of the coefficient of logarithmic creep is studied in detail, and the existence of two qualitatively different regions of its behavior is established: in the interval 4.2–1.2 K the coefficient increases linearly with decreasing temperature, while below 1 K the creep acquires an athermal character and the coefficient remains constant. It is shown that the regularities observed in the experiment are in accord with the idea that the kinetics of creep in pure β-Sn is governed by the motion of dislocations in the Peierls potential relief by a mechanism of nucleation of kink pairs on the dislocation lines. This process entails the overcoming of a small effective potential barrier of the order of 0.001 eV: in the temperature region T<1 K the nucleation of kink pairs occurs by a quantum tunneling effect, and the creep is of a purely quantum character; at higher temperatures the leading role is played by thermal fluctuations, and the deformation kinetics corresponds to the classical ideas of thermally activated creep. Empirical estimates are obtained for the density of mobile dislocations and the work hardening coefficient.
A first-time presentation of a wide range of charts imaging the stretch of amorphous polyimide (PI) film samples in the 300–1.6 K temperature range and an analysis of how temperature affects the conditional limit of fluidity, strength, and deformation of this film at the indicated temperatures. The athermal character of the breaking stress below the temperature of liquid nitrogen and its thermally activated behavior above 80 K are demonstrated. We also analyze the features of the behavior of glassy PI film samples that are stretched at low temperatures and then unloaded and warmed up to room temperatures.
The detailed study begun earlier (V. P. Soldatov et al., Fiz. Nizk. Temp. 27, 1421 (2001) [Low Temp. Phys. 27, 1048 (2001)]) on the kinetics of transient creep stimulated by the n–s superconducting transition in single crystals of pure β-Sn is continued. The samples are oriented for slip in the (100)〈010〉 system. In that case the kinetics of creep is governed by the motion of dislocations through the barriers of the Peierls potential relief. Experiments are carried out at temperatures of T1=1.6 K and T2=3.2 K, which are lower than the critical temperature of tin, Tc=3.72 K; the n–s and s–n transitions are brought about by turning a magnetic field off and on. The staged character of the creep curves δεns(t) after an n–s transition is confirmed: at T1=1.6 K one can distinguish a transient, a dynamic, and a fluctuation stage, and at T2=3.2 K, a transient and a fluctuation stage. The quantitative characteristics of each stage are investigated as functions of the creep rate at the time of the n–s transition and the total prestrain of the sample. The method of small loads is used to construct the macroscopic stress–strain diagram of β-Sn for the temperatures indicated and the work-hardening coefficients characterizing the intensity of the hardening on a macroscopic scale are determined. In the Appendix a theory of low-temperature creep in metals is set forth which involves the quantum (tunneling), dynamic, and thermally activated motion of dislocations in the Peierls potential relief. The features and characteristics of the dynamic and fluctuation stages of the experimental creep curves δεns(t) of tin are compared with the theory. It is established that the fluctuation stage of creep in tin is of a quantum character in the temperature interval studied. An analysis of the creep curves allows estimation of the work-hardening coefficient on the macro- and microscopic scales. It is found that the transient creep of β-Sn at temperatures in the liquid-helium region is due to low-energy dislocation processes involving a tunneling through effective potential barriers of the order of 10−3 eV in height.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.