Microsclerometry as Applied to Studying Rehbinder Effect. Review
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Microsclerometry as Applied to Studying Rehbinder Effect. Review E. D. Shchukina and V. I. Savenkoa, * aFrumkin
Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, 119071 Russia *e-mail: [email protected] Received June 26, 2020; revised June 30, 2020; accepted July 2, 2020
Abstract—Works devoted to studying the effect of active environments on damageability of surfaces of solid bodies and materials upon contact actions (Rehbinder effect) have been briefly reviewed. A novel procedure, which combines microscratching and electrochemical reduction of an active component on a studied material surface, has been described. This procedure enables one to simulate and study the liquid-metal embrittlement of the material in the absence of a liquid metal phase on its surface. DOI: 10.1134/S1061933X20060149
INTRODUCTION Fracture of a solid begins, as a rule, from its surface. The friction of contacting and mutually displaced elements of machines and devices, as well as the wear thereof, are exclusively surface phenomena. This circumstance makes it necessary to use precise analytical methods for studying their micromechanisms. Such methods enable one to monitor initial stages of the surface damage of solid bodies and materials, especially the stages associated with the manifestation of the effect of an active environment on the mechanical properties of studied objects [1–3]. Microindentation is traditionally used to study mechanical properties of near-surface layers of structural materials and industrial gods. This method has been investigated in detail both theoretically and experimentally; it has been supplied with a set of modern instruments, including those of the nanoscopic level [4–8], at which this method joins with the contemporary methods of tunnel and atomic force microscopy [9, 10].
Results of experiments on the microindentation of the (001) surfaces of NaCl single crystals under different boundary conditions [13] may be presented as an example. Path ratios θ = le/ls between the edge and screw dislocations were compared for rosettes resulting from tests performed in an inert environment (thoroughly dehydrated heptane) and in a humid air atmosphere. The magnitude of the effect was determined using parameter R = (θ – θ0)/θ0, where θ0 is the constant value of θ at high loads P, for which R ≈ 0 (see Table 1).
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MAIN RESULTS Microindentation was employed to obtain important experimental data on the sensitivity of mechanical properties of solid bodies and materials to environmental effects. The studies of indentation-induced rosettes of dislocation, which are revealed after selective etching of a sample surface (Fig. 1); measurements of the paths of edge (le) and screw (ls) dislocations with account of differences in their energies; determination of their starting stresses; etc. [11–13]; are among such studies. 627
30 µm Fig. 1. The appearance and geometric characteristics of dislocation rosettes formed on a single-crystalline NaCl surface as a result of indentation in
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