Russian Physics Journal最新文献

The paper studies ferrite pastes based on lithium-containing ferrite (Li_0.4Fe_2.4Zn_0.2O₄). A selection of the binder composition is described herein. Pastes based on the binding terpineol with polyethylene glycol demonstrate the best porosity and application quality. The frequency response of the microstrip transmission line with a ferrite sublayer is studied. As a result, the determined parameters of the ferrite layer are determined to be the dielectric permittivity (ε = 16), loss-angle tangent (tanδ = 0.3) and magnetic permeability (μ = 40).

Using molecular dynamics simulation, this paper studies structural changes in the nanocrystalline Fe-10Ni-20Cr alloy at different irradiation doses. The alloy structure tends to recrystallize with increasing irradiation dose. The main recrystallization mechanism is the interaction of grain boundaries with atomic displacement cascades, generated point defect clusters and neighboring grain boundaries.

The friction stir welding is performed on rolled sheets of titanium alloy Ti-6Al-4V and aluminum alloy Al-6Zn-2Mg-2Cu, using an overlapping technique, implementing liquid cooling of the welded joints and applying various axial loads. The interaction between the two alloys within the stir zone of the joints is examined using metallographic analysis. The results demonstrate that a variation of the axial load parameters during friction stir welding significantly influences the strength properties of the joints.

The microstructure of 12% chromium ferritic-martensitic steel EK-181 formed during thermomechanical treatment with deformation at 900 °C is investigated. It is shown that this treatment leads to a refinement of the parameters of the steel microstructure and an increase in the dislocation density and the magnitude of microdistortions of the crystal lattice, compared to the state after quenching. Plastic deformation at 900 °C followed by tempering allows reducing the average sizes of the prior-austenite grains by 2 times, the width of martensite laths by almost 4 times, and the particles of the carbide phase M₂₃C₆ by 2 times, compared to the state after traditional heat treatment. In this case, the density of dislocations and the degree of lattice microdistortions increase by 2 times. The microhardness of EK-181 steel is also studied. It is shown that plastic deformation at 900 °C leads to a 15% increase in the steel microhardness in the quenched state and by 10% after additional tempering.

The microstructural features and mechanical properties of the Mg-1Zn‑0.15Ca alloy after homogenization annealing at T = 450 °C are investigated. The annealing is shown to result in a homogeneous distribution of zinc in the grain volume. The stabilization of the grain size after annealing for 4–12 h is attributed to the influence of globular particles at the boundaries. The equal channel angle pressing reduced the average size from 300 μm to 3 μm. This provided an increase in strength and elongation to 270 MPa and 13%, respectively.

The structure and mechanical properties of the sintered Al-7Fe-38Sn composite sample after its processing by forging in a closed die by 50% have been studied. It has been established that the homogeneity of the sample flow is determined by the value of friction forces of its ends against the punches and channel walls of the die. The forging temperature has a significant effect on the value of the friction forces. The application of back pressure does not affect the nature of the plastic flow of the material, but allows one to avoid cracking of the samples.

The influence of the degree of plastic deformation by cold rolling on the microstructure and mechanical properties of high-nitrogen austenitic steel VNS-53-Sh‑M is studied by scanning and transmission electron microscopy. It is shown that under the experimental deformation conditions the initial austenitic grains are stretched in the rolling direction. The packets of microtwins and increased density of dislocation substructures are formed inside the grains. At a rolling strain of 20%, these packets are observed along several twinning systems. When the deformation degree is increased up to 60%, the formation of deformation localization bands of the shear band type is detected. The intersection of microtwins in different crystallographic orientations with shear bands leads to the formation of submicrocrystalline scale fragments. The changes of microstructure under plastic deformation conditions causes an increase in strength and a decrease in plastic properties compared to those in the quenched state. At room tensile test temperature, the yield strength increases by a factor of 1.5 and 1.9 relative to the quenched state at the strain rates of 20 and 60%, respectively. At the same time, the elongation to fracture remains at a fairly good level within 7.4–12.6%.

The structural features of the Al–40Sn composite that are formed when part of the tin is replaced by lead have been studied. It was found that the sintered composite has a 3-phase structure consisting of Al, α‑Pb and β‑Sn phases. Lead poorly wets aluminum, and their interphase boundaries are weaker than Al–Sn boundaries. As a result, the strength and wear resistance of the sintered lead-alloyed composite are lower than those of the base material.

The paper deals with molecular dynamics simulation of the evolution of atomic displacement cascades in pure iron initiated by accelerated iron ions with energies of 10 and 30 keV up to their thermalization or thermal spike formation. The paper compares calculated results and thermal radiation spectra obtained for targets irradiated with Ar⁺, Kr⁺ and Xe⁺ of inert gases with energies of 5 to 20 keV.

The results of a theoretical study of the Fe₃SiTe₂ compound, belonging to a promising class of the van der Waals systems with high Curie temperature and gigantic magnetoresistance, are presented. It is found out that Fe₃SiTe₂ represents a ferromagnetic metal characterized by high spin-polarization values at the Fermi level. It is shown that the charge transport occurs due to a contribution from the spin-down electrons and is formed prevailingly in the plane of five-layer blocks.