Russian Physics Journal最新文献

The features of microstructure and mechanical properties of yttrium-modified low-activation austenitic steel after high-temperature aging at 700 °C during 100 h are investigated. Using transmission and scanning electron microscopy, it is shown that aging results in the precipitation of dispersed particles of M₂₃C₆ carbides (M–Cr, Mn, Fe). These particles are found along the grain boundaries and inside the grains in the form of shells on dispersed particles of MC carbides (M–Ti, Ta, V), as well as at the boundaries of micro- and nanotwins. The strength properties of the steel are studied in tensile tests at 20, 650 and 700 °C. It is shown that an intense precipitation of carbides has a significant effect on the mechanical properties of this steel. After aging of the quenched state, the yield strength increases at all test temperatures used in this study, while the elongation to failure decreases by a factor of 1.6. This is due to the precipitation of carbide particles. After aging of the cold-rolled state, the yield strength decreases by 1.3–2 times, while the values of elongation to failure do not practically change. This is due to the intensive recovery of the dislocation substructure and the prevailing precipitation of carbides along the boundaries of micro- and nanotwins under aging of the cold-deformed state.

The paper studies the influence of the chromium and boron powder mixture on the structure and wear resistance of the 0.12 C-18Cr-9Ni-Ti steel after electron-beam surfacing. Electron-beam surfacing of powder mixtures provides hardening of 4‑mm thick coatings deposited onto the steel surface. Electron-beam surfaced coatings contain chromium boride. Powder mixtures are selected to gain the wear resistance 2 and 4 times higher than that of the hardened steel in friction against rigidly and non-rigidly fixed abrasive particles, respectively.

The wear resistance of copper-steel composites is studied and found to be quite satisfactory. A significant orientation dependence of their tribological properties is observed. The contact characteristics of the specimens with a high steel content are slightly better than those with a high copper content in the composite. This effect is due to a smaller role of frictional setting and plastic pushing of the specimen material out of the frictional contact zone.

The results of mechanical interactions between tungsten carbide tools and technically pure titanium blanks during friction stir welding are considered. An adhesive layer formed as a result of this contact is described. The tool geometry resulting from the tool wear is shown and compared with the initial tool geometry.

In the current paper, Galilean relativism with coupled parameters is discussed, which, in the special case of non-relativistic conditions, transitions into the well-known Galilean relativity. The extension of the principles of Galilean relativity is considered, which includes the application of proper time and proper coordinates, connected through a hyperbolic function of rapidity. Relativistic Galilean coordinates have been obtained. The results show that the proper relativistic Galilean coordinates are invariant under Lorentz transformations with respect to the proper Galilean interval. An extension of the Jacobi theorem, formulated by Einstein for dynamic functions with coupled parameters, is presented in the form of the Jacobi–Milekhin theorem. Invariants with respect to the proper coordinates have been derived from the Jacobi equation. The motion of a relativistic particle is demonstrated through the Galilean and Lorentz coordinates in a one-dimensional laser pulse with linear polarization.

The paper presents calculation of current–voltage characteristics of Me-i-Me HR-GaAs:Cr structures compared with the experimental data. With respect to the voltage redistribution to an extremely high resistance of the i-layer, the current flow is limited by processes in the space charge region of the reverse-biased Schottky barrier formed at the i-Me interface.

The paper deals with the direct synthesis of titanum borides from lanthanum hexaboride layers deposited onto a titanium substrate followed by processing with a microsecond low-energy high-current electron beam (LEHCEB). It is shown how the electron-beam energy density affects the structure and properties of the obtained surface layer. The latter consists of 54 to 41 at.% B, depending on the LEHCEB processing mode. Microstructure investigations show that the surface layer is a nanostructured composite consisting of a mixture of TiB and TiB₂ particles distributed in the submicrocrystalline α‑Ti matrix. The boride particle size ranges between 10 and 70 nm, depending on the synthesis modes. It is shown that the formation of the composite nanostructure improves the nanohardness and wear resistance of the synthesized surface layer. When the content of boride phases is the highest, the nanohardness grows up to 12.5 GPa or by 3.9 times, while the wear resistance becomes more than 5 times higher than in the initial titanium substrate.

The paper presents research results of the evolution of dislocation structures in low-stability Cu–Mn alloys deformed at different temperatures. The dislocation structure evolution in these alloys indicates to an important process during a transfer from one deformation stage to another. Each stage is characterized by its own strain carrier in the form of the specific dislocation structure with the highest volume fraction at the given stage. The strain carrier from the preceded stage gradually dissapears at the given stage with increasing deformation, and the strain carrier from the successive stage appears. Thus, in a certain strain range, there are strain carriers from the preceded stage, given stage, and successive stage. It is supposed that the formation of the cellular structure corresponds to the kinetic diffuse first-order phase transition to the dislocation structure.

The paper presents a methodology for comparing the integral structural characteristics of a carbon fiber material (CFM) under static and cyclic loading. The aim is to identify the damage evolution scenario using micro-computed tomography (MCT) data. Bayesian threshold segmentation based on Gaussian mixtures and cluster analysis are applied to detect small and large pores associated with mechanical loads. These findings contribute to a deeper understanding of the CFM composite behavior under loading and facilitate the development of more accurate damage models.

The paper studies the layer degradation on the nozzle and electrode surface of plasma torches operating at a current with applied reverse polarity. AA5056 and AA2024 aluminum alloy sheets are used for plasma cutting. It is demonstrated that the surface of the nozzle channel and discharge chamber of the plasma torch are covered with the aluminum layer, that can be attributed to its evaporation in the cutting zone. Copper oxides and insignificant aluminum traces are observed on the surface of the discharge chamber and electrode channel. These copper oxides can almost completely block the water injection in the channel making it unusable.