Physics of Metals and Metallography最新文献

Abstract—Ultrafine ZnO–ZnS powder with d-metal oxide additions, namely, V₂O₅, MnO, Fe₂O₃, CoO, NiO, and CuO are studied. The alloying of the ZnO–ZnS system with d metals changes the morphology of the synthesized powders. The particle size distribution obeys a lognormal law. An addition of d metal oxide upon the synthesis of ZnO–ZnS composite shifts the maximum of the particle-size distribution to the larger sizes. The more probable particle size in the samples alloyed with iron and cobalt (530 nm) exceeds that of unalloyed samples (320 nm) by more than 1.6 times. All the synthesized samples are found to be characterized by excess oxygen. The zinc, sulfur, and oxygen contents in the unalloyed ZnO–ZnS compositions is 48.0, 12.8, and 39.2 at %, respectively. The synthesis of the ZnO–ZnS composition together with transition metal oxides does not change the hexagonal and cubic symmetry of zinc sulfide and hexagonal symmetry of the zinc oxide. The presence of iron leads to an increase in the coherent domain size of the ZnS phase.

Abstract

Methods to simulate the grain growth in alloys considering the inhibition of this growth by second-phase 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.

Abstract

The possibility of existence of a spin nematic state under 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 ferromagnets 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.

Abstract—

The dependence of differential magnetic susceptibility χ_ac(T) of metallic biaxially textured NiW_x ribbons with a tungsten content of x = 5.5, 6.0, 7.4, 7.7 at % on planar mechanical tensile and compressive stresses has been studied in the temperature range of 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 σ(T) that exceed the elastic limit of NiW_x.

Abstract—

New data on phase states and structural phase transitions in alloys Fe₇₃Ga₂₇ doped with Dy, Er, Tb, and Yb in an amount of about 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.

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X-ray diffraction analysis, ellipsometry, and optical microscopy have been used to study aluminum alloy samples (of Al and Al–2.3% V) fabricated by 3D printing using selective laser melting. The mechanical properties of the resultant 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.

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The chemical composition, surface morphology, and electrochemical properties of Ti–Al–V alloys in the initial state and after irradiation with О⁺ ions and alternating irradiation with О⁺ and N⁺ ions differing in the irradiation dose of N⁺ ions are studied. Under irradiation with О⁺ ions, the active oxidation of Ti atoms is shown to occur, which is accompanied by the formation of titanium oxides and hydroxides. In the course of subsequent irradiation with N⁺ ions, the accumulation of nitrogen and formation of titanium nitride TiN are found to occur to lower concentrations as compared to those observed without the preliminary irradiation with О⁺ ions. It is assumed that this is due to the higher chemical activity of oxygen with respect to titanium atoms, as compared to that of nitrogen.

Abstract

The paper examines the impact of interparticle interactions on the superparamagnetic relaxation of ultrasmall nanoparticle ensembles, using Fe₂O₃∙nH₂O iron oxyhydroxide (ferrihydrite) nanoparticles as an example. Two samples were analyzed: ferrihydrite of biogenic origin (with an average particle size of (leftlangle d rightrangle ) ≈ 2.7 nm) with a natural organic shell, and a sample (with (leftlangle d rightrangle ) ≈ 3.5 nm) that underwent low-temperature annealing, during which the organic shell was partially removed. The DC and AC magnetic susceptibilities (χ′(T), χ′′(T)) in a small magnetic field in the superparamagnetic (SPM) blocking region of the nanoparticles were measured. The results show that an increase in interparticle interactions leads to an increase in the SPM blocking temperature from 28 to 52 K according to DC magnetization data. It is shown that below the SPM blocking temperature, magnetic interactions of nanoparticles lead to the formation of a collective state similar to spin glass in bulk materials. The scaling approach reveals that the dynamics of correlated magnetic moments on the particle surface slow down with increasing interparticle interactions. Simulation of χ′′(T) dependence has shown that the dissipation of magnetic energy occurs in two stages. The first stage is directly related to the blocking of the magnetic moment of nanoparticles, while the second stage reflects the spin-glass behavior of surface spins and strongly depends on the strength of interparticle interactions.

Abstract

The influence of the degree of dispersion of a nickel–zinc ferrite powder of a Ni_0.7Zn_0.3Fe₂O₄ composition on its magnetic properties has been considered. The material has been synthesized using the ceramic technology with preliminary mechanical activation of precursors. The degree of dispersion has been varied using different modes of its dry grinding in a ball mill. The patterns of the changes in saturation magnetization and the coercive force as a function of grinding modes and a specific surface area of the ferrite powder have been established. The changes in the pattern of the magnetic phase transition in the region of the Curie temperature of materials with different degrees of dispersion have been determined.

Abstract—

The study investigates carbon-containing coatings of 3d-metals (Ni, Co, Fe) produced by chemical deposition method using arabinogalactan. The coatings were analyzed using X-ray diffraction, FMR, and M(H) magnetometry. Measurement of M(H) in plane and perpendicular to the plane of the magnetic coatings allowed determining the distribution of demagnetizing factor in the studied coatings. The obtained distributions of the demagnetizing factor were used to analyze the angular dependences of the ferromagnetic resonance field. The values of magnetization and perpendicular anisotropy field were estimated. The paper illustrates the effect of texture on the magnetic parameters.