1829 ISSN 1063-7842, Technical Physics, 2015, Vol. 60, No. 12, pp. 1829–1841. © Pleiades Publishing, Ltd., 2015. Original Russian Text © B.K. Kardashev, V.I. Betekhtin, M.V. Narykova, 2015, published in Zhurnal Tekhnicheskoi Fiziki, 2015, Vol. 60, No. 12, pp. 94–106. Elastoplastic Properties of Micro- and Submicrocrystalline Metals and Alloys B. K. Kardashev*, V. I. Betekhtin, and M. V. Narykova Ioffe Physical Technical Institute, Russian Academy of Sciences, Politekhnicheskaya ul. 26, St. Petersburg, 194021 Russia *e-mail: B.Kardashev@mail.ioffe.ru Received May 18, 2015 Abstract—The problem of application of physical acoustic methods to studying the mechanisms that control plastic deformation and fracture is considered using micro- and submicrocrystalline materials (Be, Al, Ti, Al–Sc alloy, Cu–Nb laminated material) as examples. The influence of grain boundaries on the acoustic (elastic, inelastic) properties of polycrystalline micro- and nanostructured metallic materials is analyzed. Experimental results are presented for a wide oscillating-stress amplitude range, from 0.2 to 50 MPa. The experimental data are discussed in terms of the theoretical concepts of oscillatory dislocation mobility, which depends on both the short-range stress fields around point defects and the long-range fields of internal stresses. It is shown that various types of discontinuities, such as pores and microcracks, noticeably influence the acoustic properties. The aspects of the relation, similarity, and difference between acoustic and mechan- ical (plasticity, strength) tests of polycrystalline materials with micro- and nanosized structural elements are discussed. DOI: 10.1134/S1063784215120063 INTRODUCTION Practical interest in microcrystalline and nano- structured materials is mainly evoked by the fact that they have substantially different mechanical properties as compared to the corresponding coarse-grained polycrystals. These properties and the specific features of a defect structure that determine them were studied in numerous works described in reviews [1–5]. The traditional characteristics of mechanical properties, such as microhardness, yield strength, ultimate tensile strength, and macroplasticity (i.e., the elongation of a sample during tension until failure), are usually inves- tigated and analyzed in those works. However, the acoustic (elastic and macroplastic properties, including internal friction) characteristics of such materials have received little attention. Young’s modulus was only mentioned in review [2] in the context of nanoindentation. Nevertheless, despite the simplicity and convenience of this method, it should be noted that its reliable application requires an optimal load and a proper state of the sample surface. Moreover, in nanoindentation, it is difficult to esti- mate the effect of some factors, such as porosity and phase composition, on Young’s modulus. Available acoustic data were published in various scientific journals and proceedings of scientific con- ferences. The purpose of this review is to collect avail- able experimental data on the microplastic properties of fine-grained (down to nanosized) polycrystalline metals and alloys and to analyze them using the exist- ing theoretical models. In this review, we present the experimental possi- bilities of application of physical acoustic methods to study the mechanisms that control the plasticity and strength of micro- and submicrocrystalline metals and alloys. 1. STUDY OF THE MECHANICAL PROPERTIES BY ACOUSTIC METHODS The existing dislocation concepts that can be used to adequately describe the mechanical and acoustic properties of single crystals and coarse-grained poly- crystals appeared a long time ago [6–9] and have been developed for more than eighty years. The acoustic properties (elastic modulus, absorption of the energy of elastic vibrations (or internal friction)) and the mechanical properties (plasticity, strength) were com- pared in a number of works (see, e.g., [9–17]). The physical dislocation mechanisms that substan- tially control plastic deformation and fracture can be reliably detected by a nondestructive acoustic tech- nique. The stress vibrations that induce certain ampli- tude-dependent internal friction (ADIF) are usually compared with yield strength or characteristic plastic flow stress as functions of temperature [11–14]. In essence, the micro- and macroplastic characteristics that reflect the behavior of crystalline materials at the SOLID STATE