Vol 125, No 5 (2024)

The study is devoted to the theoretical analysis of noncollinear magnetic structures of charge-ordered manganites with a doping level x=3/4, 4/5. The reasons for canted and perpendicular magnetic structures to form as a result of the competition between the orbitally dependent exchange interaction in different crystallographic directions and the influence of single-ion anisotropy are considered. The mechanism of formation of predominantly noncollinear magnetic structures is shown. Trimer stripe magnetic structures with ordering along pseudo-perovskite axes x_p, y_p, z_p = b are predicted. The presence of magnetic structure components aligned with the b axis is assumed and methods for checking the presence of such components based on field dependencies of magnetization and antiferromagnetic resonance frequencies are proposed.

the dependence of the differential magnetic susceptibility c_ac(T) of metallic biaxially textured NiW_x ribbons with a tungsten content x = 5.5, 6.0, 7.4, 7.7 at% on plane mechanical tension and compressive stresses has been studied in the temperature range 50–350 K. To create the tensile and compressive stresses, the thermal cycling procedure is applied to the ribbons glued to the substrates made of Si and aluminum alloy D16T, respectively. It is shown that the main peculiarities of the magnetic susceptibility behavior can be explained by magnetic orientation transitions and the occurrence of internal stresses s(T) that exceed the elastic limit of NiW_x.

the possibility of the existence of a spin nematic state a strong magnetic field in a ferromagnetic substance, which exhibits large biquadratic exchange interaction and has a magnetic ion with spin S = 1, is investigated within the mean field approximation. The case of both isotropic and anisotropic ferromagnet beyond the Heisenberg model is studied. The transformation of the geometric projection of a spin nematic with respect to the magnetic field strength has been studied.

A study has been conducted on the hydro-vacuum dispersion process of metal melts using gray cast iron SCh20 (in Russian nomencluture; 3.3–3.5C, 1.4–2.4Si, 0.7–1Mn, <0.15S, <0.2P in wt %)—an analogue of GG20. It has been revealed that the main factor conditioning the mechanoactivation of formed particles is their solidification in a fibrous non-equilibrium structural-tensioned state. This state is achieved by flattening and asymmetric twistedness of droplets that are detached from the liquid metal in the disperser under volumetric impact of shock-pulsating waves of hydraulic discharge. The degree of particle activation was found to depend exponentially on their dispersion and specific surface area. These parameters determine the degree of asymmetry of shear deformations and the amount of accumulated energy. In turn, the size dispersion and specific surface are significantly influenced by physical and technological factors such as the specific flow rate and pressure of injected water, the thickness and the elevation angle of the hydro shell of the vacuum diffusion funnel, the diameter of the dispersed melt jet passed through it, and its superheating temperature. The control of these parameters makes it possible to smoothly adjust the key ratio “liquid metal: water” and set up the dispersion process with the highest possible degree of size dispersion and activation of the resulting powder.

The investigation is focused on the impact of hydrogen on the physical and mechanical properties of 316L austenitic stainless steel (67.5Fe, 17.7Cr, 10.6Ni, 2.6Mo, 1.2Mn, 0.4Si in wt %) processed by selective laser melting (SLM). The study also determined the kinetic parameters of hydrogen interaction with 316L-SLM steel at temperatures ranging from 300 to 700°C. It has been demonstrated that the plasticity characteristics are highly sensitive to the impact of hydrogen within the temperature range from 20 to 600°C. At 600°C, the maximum degree of hydrogen embrittlement is ≈30%. However, the elongation to failure and reduction of area remain at a sufficiently high level. Reduction in strength characteristics is only observed at 600°C and does not exceed 10%. Prolonged thermal impact and resulting structural changes do not affect the kinetic parameters of hydrogen interaction with 316L-SLM. The hydrogen solubility in SLM-processed 316L steel and 12Cr18Ni10T steel produced by conventional technology is nearly identical.

New data on phase states and structural phase transitions in alloys Fe₇₃Ga₂₇ alloys doped with Dy, Er, Tb, and Yb in an amount of ~0.5 at% are presented. Structural data were obtained in neutron diffraction experiments performed with high resolution and in continuous temperature scanning mode during heating to 850°C and subsequent cooling at a rate of ±2°C/min. It has been established that both the sequence of forming and disappearing structural phases and the final state of the alloy depend on the type of rare earth element. Phase transitions in the alloy with Dy are similar to those in the initial Fe₇₃Ga₂₇ alloy, excluding the final state. The procedure of doping with Er and Tb leads to the formation of disordered A1 and A3 phases instead of the L1₂ and D0₁₉ ordered close packed phases, respectively. In the case of doping with Yb, neither of the above phases is observed. The formation of the L60 (m-D0₃) and D0₂₂ tetragonal structural phases previously discovered in similar alloys by the electron diffraction method is not confirmed.

Methods to simulate the grain growth in alloys considering the inhibition of this growth by second-phases particles have been proposed. The presented approaches are primarily focused on low-alloyed steels with carbonitride strengthening. The calculation results have been compared with the experimental data available in the literature and their satisfactory agreement has been shown.

X-ray diffraction analysis, ellipsometry and optical microscopy have been used to study aluminum alloys samples (Al and Al–2.3% V) fabricated by 3D printing using selective laser melting. The mechanical properties of the resulting products have been compared. The strength and plastic properties of parts made from pure Al and Al–2.3% V alloys have been found to be insensitive to heat treatment. The addition of vanadium to pure Al showed that the Al–2.3% V alloy has significantly improved performance properties compared to those of primary aluminum, without affecting its initial plasticity.