Russian Physics Journal最新文献

The scope of application of ceramic materials is increasingly widening. Additive manufacturing techniques assist in the production of ceramic materials. Photopolymerization 3D printing technology is one of the most widespread processes of manufacturing articles of complex forms. In this paper, the dilatometric analysis is used to study the shrinkage process of green bodies manufactured from zirconia on a 3D printer. It is shown that shrinkage of green bodies is characterized by the same properties as shrinkage of powder compacts obtained by a conventional ceramic method. After the removal of the polymer binder, the maximum shrinkage rate is observed at the heating stage between 1223 and 1239 °C. The shrinkage process intensively continues during the successive isothermal sintering. Shrinkage grows with increasing sintering temperature and exposure time. Porosity of the green body gradually reduces while sintering. Density, porosity and microhardness of zirconia ceramics sintered from the green body at 1550 °C annealing for 6 h, are detected as 4.7 g/cm³, 12.5% and 4.3 GPa, respectively. The obtained results can be used to fabricate zirconia ceramics with specified density and porosity in certain engineering applications.

The results on upgrading the Synchrotron Radiation Technological Station of the SR beamline from the VEPP‑4 storage ring are presented with an aim of developing a method for X‑Ray fluorescence analysis using SR for detecting light elements in the samples of strawberry plants. An experimental setup for detecting such elements as Al, Si, P, S, Cl, K, Ca, and Ti is described, an estimation of their minimum detection limit is performed, and an application of this technique to studying the influence of a silicon-chelate-based biostimulant on the plant development is reported using the example of common strawberry.

Evaluation of tribological characteristics of coatings at elevated temperatures is important for predicting their wear and heat resistances. The paper presents the results of experimental studies of dry sliding friction at different temperatures for a single-component CrN coating and multilayer coatings of the ZrN/CrN system. As a result of high-temperature sliding friction, the wear of the multilayer coatings is 15 times lower, and the friction coefficient is by a factor of 1.6 lower than that of the single-component CrN coating, respectively. The research results show the feasibility of using the multilayer ZrN/CrN coatings in tribosystems operating at elevated temperatures in pairs with steel parts.

The changes in internal stresses and mechanical properties of V‑Nb-Ta-Ti alloys manufactured by arc melting after irradiation with He²⁺ ions (40 keV) to a fluence of 2 ⋅ 10¹⁷ cm⁻² are studied. The irradiation of V, VNb, and VNbTa alloys is shown to decrease the compressive macrostresses in the pre-peak region and increase them for V and VNbTa in the peak region of helium implantation. The irradiation of a VNbTaTi high-entropy alloy increases the compressive macrostresses by 44% and 50% in the two regions, respectively. The dislocation density is observed to increase significantly. The elastic modulus of VNbTa and VNbTaTi was stable, but decreased for V and VNb. The degree of hardening is the highest for V and VNb (99% and 52%, respectively) and the lowest—for VNbTa and VNbTaTi (29% and 45%, respectively). The influence of macrostresses and dislocation density on the hardness of V‑Nb-Ta-Ti alloys irradiated with He is established. VNbTaTi shows a higher radiation resistance compared to that of V, VNb, and VNbTa.

The friction stir welding of dissimilar joints between aluminum alloy AA7075 and titanium alloy Grade 5, utilizing an overlapping configuration with liquid cooling and varying tool rotation speeds, is studied. A metallographic analysis of the resulting joints reveals a mutual penetration of the dissimilar alloys during welding. Mechanical testing of the joints allowed for an evaluation of how the tool rotation speed affects the weld strength.

The paper presents molecular dynamics simulation of the radiation dose effect on mechanical properties of the Fe-10Ni-20Cr alloy samples having different grain size. It is shown that plastic strain of irradiated samples always nucleates in clusters of point defects locating near grain-boundary triple point intersections and caused by the stacking fault generation. It is found that the elastic limit in the fine grain sample, is higher and reduces more slowly with increasing irradiation dose than in the coarse grain sample.

A comparison of the structure and properties of 47HNM, 40HNU and 67KN5B alloys possessing superplasticity is performed. It is shown that during superplastic deformation in the grain-boundary layers of these alloys the systems of tetrahedral close-packed clusters with Frank-Kasper structures are formed. The use of cluster models allows attributing the manifestation of ferromagnetic properties in superplastic materials to a change in the electron density. A qualitative agreement with the experiment is confirmed by the calculation of the spectra of spin-polarized electrons performed for the cluster structures.

The paper focuses on the evolution of the dislocation structure in Cu-Аl and Cu-Мn polycrystalline alloys in the low-stability state. Experiments conducted at different temperatures, show that the main structure of alloys having different content of Al and Mn alloying elements, changes insignificantly with increasing temperature in contrast to the density of dislocation barriers, dislocation clusters, dissociated dislocations, and stacking faults. Dislocation parameters of Cu-Mn alloys decrease with increasing temperature, while Cu-Al alloys manifest another behavior.

The temperature effect on the dislocation structure parameters is different in Cu-Аl and Cu-Мn alloys. With increasing strain temperature, the average dislocation density in Cu-Mn alloys decreases, and grows in Cu-Al alloys. Misorientations in the structure, density of extinction contours and subboudaries reduce in Cu-Mn alloys and grow in Cu-Al alloys. It is found that the behavior of the dislocation structure parameters depends on temperature and is different in Cu-Аl and Cu-Мn alloys.

The excitation of electron shell of a daughter atom in a neutrinoless ββ decay changes the shape of the total energy peak of β electrons at the endpoint of the energy spectrum. The main parameters of the modified distribution are the average energy and the variance of the electron shell excitation energy. An expression is derived for the variance taking into account exchange effects, and numerical estimates of the average excitation energy and variance are made based on the non-relativistic Roothaan–Hartree–Fock method and the relativistic Dirac–Hartree–Fock method implemented in the General Relativistic Atomic Structure Package (Grasp2018). The estimates are made for eleven isotopes, the two–neutrino double–β decay of which is observed experimentally. The results are determined by the first two negative moments of the electron radii in the parent atom. The values obtained can be used to parameterize the energy distribution of β electrons, taking into account the electron shell excitation of the daughter atom.

In this work, the structural-phase state of TiNi-based alloy samples printed by electron beam wire-feed additive manufacturing method on a VT1‑0 substrate is studied. It is shown that the printed samples have a columnar, coarse-grained microstructure. Using the X‑ray diffraction method, it has been established that at room temperature, the studied samples have a B2 phase structure with the presence of no more than 10 vol.% of the Ti₂Ni (or Ti₄Ni₂(O,N,C)_x) phase. It is shown that when printing the TiNi-based alloy samples on the VT1‑0 substrate using EBAM, the samples are alloyed with titanium atoms from the substrate.