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The aim of this work was to provide a guidance to the prediction and design of high-entropy alloys with good performance. New promising compositions of refractory high-entropy alloys with the desired phase composition and mechanical properties (yield strength) have been predicted using a combination of machine learning, phenomenological rules and CALPHAD modeling. The yield strength prediction in a wide range of temperatures (20–800 °C) was made using a surrogate model based on a support-vector machine algorithm. The yield strength at 20 °C and 600 °C was predicted quite precisely (the average prediction error was 11% and 13.5%, respectively) with a decrease in the precision to slightly higher than 20% at 800 °C. An Al13Cr12Nb20Ti20V35 alloy with an excellent combination of ductility and yield strength at 20 °C (16.6% and 1295 MPa, respectively) and at 800 °C (more 50% and 898 MPa, respectively) was produced based on the prediction.

The present study aimed to discover the effect of cold swaging reduction on the bulk gradient structure formation and mechanical properties of a 316-type austenitic stainless steel. The initial rod was subjected to radial swaging until 20–95% reduction of initial rod diameter, at room temperature. According to finite element simulation, higher plastic strain was accumulated in the surface layer compared to the center region during swaging. Microstructural investigations revealed three-stage gradient structure formation in the center and edge regions of the deformed rod. Meanwhile, cold swaging resulted in the development of strong 111ǁBA, 001ǁBA, and weak 111ǁBA texture components in the center and edge, respectively. Significant tensile strengthening was observed after cold swaging. For instance, the yield strength (YS) increased from 820 MPa to 930 MPa after 40–80% reduction respectively, without the loss of ductility (δ–14%). This unique aspect of the mechanical behavior was attributed to the gradient structure of the cold swaged material and explained in detail.

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Multilayer composites with a layer thickness on a nanometer scale are called nanolaminates [1-3] and have good prospects for application as both structural and functional materials possessing special mechani cal, magnetic, and electrical properties due to unique combinations of characteristics of the component lay ers, in particular, metals. This stimulates investigations of various characteristics of nanolaminates, including the structural parameters, thermal stability, ultimate strength, flow stress, microhardness, etc. [4]. The elasto plastic properties of these multilayer compos ites with nanodimensional layers have been studied to a much lesser extent.In this work, acoustic measurements were used to determine the elasto plastic characteristics of q nano laminate of the Cu-Nb system, including the charac teristics of elastic deformation (Young's modulus E) and reversible microplastic deformation (amplitude independent decrement δ and microplastic flow stress σ) related to the oscillatory motion of dislocations. A special feature of the acoustic experiment is that, at moderate amplitudes, the dislocation structure of samples is retained and the density of dislocations in the metal remains unchanged [5].The samples were studied by a resonant method of a composite vibrator, which is described in much detail elsewhere [5]. Using this technique, it is possible to determine the Young's modulus E and study the absorption of ultrasound (i.e., internal friction) and inelastic (microplastic) properties of samples. The data on inelastic properties are obtained by measuring the E and δ values in a wide range of amplitudes of vibrational strain ε. At sufficiently large ε, a sample material exhibits nonlinear amplitude dependent absorption δ h = δ -δ i and amplitude dependent shift of the Young's modulus, which is defined as (ΔE/E) h = (E -E i )/E i , where E i and δ i are the Young's modulus and decrement determined at small amplitudes (for which both E and Δ are independent of ε).Using the results of acoustic measurements per formed in a wide range of vibration amplitudes, it also possible to evaluate the mechanical (microplastic) characteristics of materials in the conventional mechanical testing coordinates of stress versus inelas tic strain, where the ordinate represents the amplitude of vibrational stress σ = Eε and the abscissa represents the nonlinear inelastic strain ε d = ε(ΔE/E) h .The samples for acoustic measurements were rod shaped with a 2 × 0.5 mm rectangular cross section and a length of l = 20 mm, which corresponded to reso nance frequency longitudinal oscillations close to f 1 00 kHz. The Young's modulus was defined as E = 4ρl 2 f 2 , where ρ is the material density.The Cu-Nb nanolaminate was obtained by com plex rolling of copper and niobium sheets and repre sented a sandwich of these metals, in which the thick ness of each layer (see Fig. 1) was about 10 nm. The boundaries of these layers were oriented in the direc tion of propagation of a longitudinal acoustic wave. The effective density of the nanola...