Russian Physics Journal最新文献

In this work, plastic deformation localization regularities in pure aluminum polycrystals are studied using speckle photography technique. It is shown that at the parabolic work hardening stages in the temperature range of 170 < T < 350 K, the temperature effect upon the emergence of a stationary dissipative structure is determined by the change in the autowave length of localized plasticity at the macroscale level and the cell size of the dislocation substructure at the microscale level.

In this work, the deformation behavior of porous ceramics ZrO₂–5.5 wt.% Y₂O₃ with different morphology of the pore space under axial quasi-static compression is studied by the digital image correlation (DIC) method. Two stages of the deformation behavior of the ceramics have been identified, namely, the controlled accumulation of microcracks and the formation of block structures. It has been found that an increase in the average pore size leads to a decrease in the tensile strength, a decrease in the effective elasticity modulus, and an increase in the ultimate deformation, while the nature of the deformation macrolocalization changes from ordered to chaotic one. It is shown that the rate of accumulation of local deformations in the central part of the deformable sample with a pore size of 68 μm is several times higher than in the sample with a pore size of 29 μm.

The development of inelastic and plastic strains is studied for Ti_49.3Ni_50.7 (at.%) alloy samples with the structure of high-temperature B2 phase in the state as received from the manufacturer under torsion. It has been established that when the strain of the samples, specified by torsion, is equal to 10.6%, the value of the accumulated plastic strain is 0.35%. Therefore, the actual yield stress of the Ti_49.3Ni_50.7 (at.%) alloy samples is localized at the end of the pseudo-yield plateau on the stress-strain dependence rather than at the end of the strain hardening stage, as previously thought. The results presented in the work should be taken into account in the practical use of the alloy with this composition as products for technical and medical purposes that experience tensile, bending, and torsional deformations.

Additive manufacturing (3D printing) is one of the most promising methods for creating complex metal parts and structures. It has already become a widespread industrial method in the production of coatings or various details of constructions and mechanisms made of pure metals and alloys. In this work, the mechanisms of the formation of intermetallic compounds based on nickel, aluminum and chromium by a dual-wire electron beam additive manufacturing were studied. The microstructure, phase composition, and microhardness of the intermetallic material strongly depend on the ratio of NiCr and Al wires deposited during the electron-beam melting. The intermetallic material based on the NiAl phase was obtained by the deposition of wires in the equal ratio NiCr:Al = 1:1. In the material obtained with a wire ratio of NiCr:Al = 3:1, ordered Ni₃Al(Cr) and disordered Ni₃Cr(Al) intermetallic compounds are predominantly observed, but the fraction of the Ni₃Cr-based phase prevails. The microhardness of the NiAl-based alloy turns out to be higher (5.1 GPa) than that of the Ni₃Al(Cr)-based material (4.3 GPa). These intermetallic alloys are developed for the production of intermetallic coatings using electron beam additive manufacturing method.

Using the method of hot compaction (HC) of mechanically activated powder mixtures of titanium and carbon (carbon black) in an ethanol medium, titanium-matrix composites with a carbide strengthening phase were obtained. To obtain a composite with different content of titanium carbide, the amount of carbon was varied within the range of 0–1 wt.%. The mechanically activated carbon-doped titanium powder mixtures, as well as the mechanically activated titanium powder subjected to HC (temperature of 900°C and holding time of 15 min) and additional annealing at different temperatures and holding times are studied by optical metallography, scanning electron microscopy, and X-ray diffraction and chemical analysis. According to the metallography and X-ray diffraction results, the TiC content in the HC composite has been found to be significantly higher than the estimated value. The reason is a destruction of ethanol molecules during mechanical activation resulting in the release of carbon and hydrogen. To obtain the targeted (no more than 10 vol.%) TiC content in the titanium matrix composite, it is necessary to establish a specific technological mode for the mechanical activation of the titanium powder.

The effect of heat treatment on the structural evolution, phase transformation, and mechanical strength of Al–12Si obtained using wire electron beam additive manufacturing has been investigated. The as-built Al–12Si alloy was characterized by structural inhomogeneities in the form of interlayer bands with coarsened Si particles resulted from cyclic reheating of the solidified metal. Quenching the as-built samples resulted in the increase of the volume fraction of Al/Si eutectics by 9% with simultaneous refinement of Fe-containing particles. This structure allows obtaining the combination of strength and plasticity better than that of the asbuilt sample. Annealing leads to coarsening of both Si and Fe-containing particles, thereby increasing the Al/Si volume fraction and impairing the mechanical characteristics.

A novel double-negative metamaterial-inspired structure is proposed. Using the NRW method, the permittivity and permeability of the presented metamaterial unit cell is determined. The metamaterial structure is analyzed and characterized in the frequency range from 2.28 to 3.00 GHz, and the real ε_r is found to be negative. The results imply that the proposed metamaterial-inspired structure exhibits double-negative characteristics from 2.28 to 2.70 GHz; with a negative peak around 2.4 GHz.

In the present work, we synthesized ZnO–Ag heterophase nanoparticles and ZnO–Ag modified polypropylene (PP) granules toward the degradation of dye under visible light irradiation. The nanoparticles (NPs) were produced by electrical explosion of zinc and silver twisted wires in oxygen-containing atmosphere. The heterophase structure of ZnO–Ag nanoparticles plays an important role in the enhancing the photocatalytic dye removal through the localized surface plasmon resonance effect of silver. In our investigation, the 0.5 wt.% NPs on the PP granule surface are the best composite samples to achieve the best methylene blue dye degradation (99.7%). The ZnO–Ag heterojunction retains an excellent performance of 46.4% even after being used repetitively for 4 cycling tests. This is the first report on the ZnO–Ag–ZnO/polypropylene granules to advance polymer technology for food storage and self-cleaning coating in the near future.

The paper studies the influence of the spectral composition of accelerated radiation on the radiation intensity of a relativistic charged particle based on its equation of motion in the field of the amplitude-modulated electromagnetic wave. Equations are suggested for the phase and phase-angular distributions of the particle radiation. The dependence between the radiation and modulation coefficient are presented herein.