Baikov Institute of Metallurgy and Materials Science

The effect of preliminary irradiation with argon ions (energy of 20 keV, dose of 2.0 × 1022 m–2, Tirr ∼ 700 K) and subsequent exposure to pulsed laser radiation (LR) with a power density of q ∼ 1.2 × 1012 W/m2, pulse duration τ0 = 50 ns, and the number of pulses from 1 to 4 on the morphology and microhardness of the surface of V–10Ti–6Cr–0.05Zr–0.1Si vanadium alloy is studied. It is found that implantation of Ar+ ions in the specified mode leads to the formation of a porous (spongy) structure in the surface layers. It is shown that, as a result of the impact of pulsed LR, a common feature of the destruction of the surface layer of both the initial sample and the sample preliminarily irradiated with argon ions is the formation of a crater surrounded by a parapet. However, in the second case, the parapet is a ring-shaped rim, and there is practically no splashing of metal out of the crater. It is found that, as a result of ultrafast melting and crystallization, a fine-cell structure with a cell size of ∼200 nm is formed in the near-surface layers of samples implanted with Ar+ in the region of the crater. Behind the crater, there is a heat-affected zone (HAZ), into which the plasma cloud transfers part of its energy. It is established that, as a result of the combined effect of argon ions and pulsed laser radiation, typical structures are formed in the HAZ, being observed both for this alloy and for vanadium arising under the influence of LR under various modes of preliminary ion implantation. It is found that the microhardness of the surface layers after implantation of Ar+ ions into alloy increases slightly. After the impact of pulsed LR on both the initial and preliminarily implanted (by Ar+) alloy samples, the microhardness in the crater area first decreases, and then, with an increase in the number of pulsed impacts, a tendency towards its increase is observed. The mechanisms of the observed phenomena are discussed.

The electrochemical oxidation process of W-Re alloy waste (using VR-26 alloy (weight %: 74 W, 26 Re) as an example) under the action of direct and symmetrical sinusoidal alternating current of industrial frequency (50 Hz) with changing current density (0,5 ÷ 2,0 A/cm2) and electrolyte temperature (20 ÷ 50 °C) in an aqueous solution of ammonium carbonate (0,5 ÷ 1,0 M) was investigated. It was found that the use of direct current under optimal conditions ensures high-speed dissolution of the alloy (~22 kg/m2·h), while the use of alternating current makes it possible to synthesize microdispersed tungsten-rhenium oxide powder. A fundamental process flowchart for producing W-Re powder using an electrochemical method is proposed. The fundamental process flowchart ensures a ~50% recovery of tungsten and rhenium from waste into powder.

Results of the Rietveld X-ray diffraction analysis are presented for PbZr0.53Ti0.47O3, Pb0.95Sr0.05Zr0.53Ti0.47O3, PZT-19, and PZT-23 samples along with the results of studying their dielectric, piezo-, and pyroelectric properties. The samples are found to consist of a mixture of solid solutions having the perovskite structure with tetragonal (T), monoclinic (M), and rhombohedral (R) crystal lattices. Their weight fractions are 48T/39M/13R, 39T/61M, 49T/51M, and 72T/28M in the samples respectively. Main structural parameters of the phases are determined (unit cell symmetry and parameters of the phases, atomic coordinates and isotropic thermal displacements). The effect of the phase compositions of the samples on their electrophysical properties is discussed. Based on the results of the theoretical-group analysis, the conclusion is drawn that the observed differences in the ferroelectric and related (dielectric, piezoelectric) properties of the studied samples are due to: 1) concentration of monoclinic phase Cm, 2) structural parameters of the Cm phase.

Abstract—This work is devoted to the study of the influence of complex modification on the microstructure of complex-alloy hypereutectic silumin of the Al–Si–Cu–Mg–Ni–Mn system. The task of the work was to determine the phase composition of the alloy in the cast state. The analysis of literature and multicomponent phase diagrams was carried out. The phase composition was studied using scanning electron microscopy (SEM), energy-dispersive X-ray spectral microanalysis, and X-ray phase analysis (XRD) of the studied alloy. Various modifying elements and their modifying mechanisms are considered. For modification of complex-alloy hypereutectic silumin the following additives were used: K2TiF6 and K2ZrF6 salts, complex-modifying fluxes (CMFs), a tableted refining-modifying preparation (RMP), and a phosphorus-containing ligature. The effect of complex modification on the coefficient of thermal linear expansion (CTLE), hardness, and microhardness of primary silicon of complex-alloy hypereutectic silumin was assessed. Microstructural studies of the effect of complex modification on the sizes of primary and eutectic silicon were conducted. The studies showed that the use of complex modification is a relevant direction for improving the structure of complex-alloy hypereutectic silumins and increasing their properties.

Abstract—The parameters of micromodules for thermoelectric generators used at low heat fluxes have been calculated. For the branches of micromodules, our own developments of fine-crystalline materials based on the Sb2Te3–Bi2Te3 solid solution of p-type conductivity and the Bi2Te3–Bi2Se3 solid solution of n-type conductivity obtained by hot pressing and extrusion of powders prepared by grinding an ingot and by the melt rapid crystallization methods, that is, by melt spinning and crystallization of melt in a liquid, are considered. Calculations of the dependence of micromodule power on the temperature difference, thermoelectric properties (the Seebeck coefficient, specific electrical conductivity, and thermal conductivity) of p- and n-branch materials, their number, cross-section, and height at the cold junction temperature of 17°C have been carried out. It was found that the generated power of the module is directly proportional to the cross-sectional area and inversely proportional to the height of the module branches.