Выявление магнитной анизотропии в аустенитной хромоникелевой стали после прокатки

Investigations of texture, phase composition and magnetic anisotropy in rolled samples of austenitic steel 09Kh17N5Yu were carried out. It has been shown that the method of magnetic nondestructive testing using measuring of magnetic fields from locally magnetized areas is sensitive to anisotropy of magnetic permeability. Anisotropy of magnetic properties is related to formation of mechanical rolling texture. FCC rolling texture {110}<111> was found in all the rolled samples. Rolling texture, common for BCC structure (strain-induced martensite in low-carbon austenitic steels), developed in the samples with 30% of deformation or higher. Formation of ferromagnetic strain-induced martensite in austenitic steel 09Kh17N5Yu was confirmed by magnetic force microscopy.

The estimation of energy and elastic properties of TiAlNb materials based on results of first principles calculations

The results of research of isolated TiAlNb clusters are presented. The models of isolated clusters of 27, 59, 65 atoms in size which is fragments of the bcc structure have been constructed. The models stoichiometry imitate α-, γ-, α+γ- and β-phase TiAlNb alloys. The structural, cohesive and electronic properties of these clusters have been investigated within the framework of electronic density functional theory with PBE0 functional with a set of MINI basis functions with application of Gaussian'03 and GAMESS software packages. It was found that upon transition of the cluster structure from the α- to the β-phase, the cohesion energy increases and the crystal lattice period decreases. This corresponds to an increase in the values of the structure strength and density. For the calculation of the bulk modulus were utilized value of changes in energy and volume of cluster, got in research. The bulk modulus of the isolated β-phase TiAlNb cluster is predicted. This bulk modulus near to 142.4 GPa. The result was extended to volumetric structures. The investigation showed that bulk modulus of Ti2AlNb materials near to 163.6 GPa. Comparison of calculation results with experimental values of elastic moduli of materials with similar structure and composition is carried out. The comparison revealed the agreement between the calculated values and the results of experiments. A method is proposed for evaluating the elastic properties of TiAlNb alloys based on the results of first principles calculations. Keywords: cluster, aluminide titanium, bulk modulus, computer material science.

Microstructure Characteristics and Strengthening Behavior of Cu-Bearing Non-Oriented Silicon Steel: Conventional Process versus Strip Casting

Based on conventional hot rolling processes and strip casting processes, Cu precipitation strengthening is used to improve the strength of non-oriented silicon steel in order to meet the requirements of high-speed driving motors of electric vehicles. Microstructure evolution was studied, and the effects of Cu precipitates on magnetic and mechanical properties are discussed. Compared with conventional processes, non-oriented silicon steel prepared by strip casting exhibited advantages with regard to microstructure optimization with coarse grain and {100} texture. Two-stage rolling processes were more beneficial for uniform microstructure, coarse grains and improved texture. The high magnetic induction B50 of 1.762 T and low core losses with P1.5/50, P1.0/400 and P1.0/1000 of 1.93, 11.63 and 44.87 W/kg, respectively, were obtained in 0.20 mm sheets in strip casting. Cu precipitates significantly improved yield strength over ~120 MPa without deteriorating magnetic properties both in conventional process and strip casting. In the peak stage aged at 550 °C for 120 min, Cu precipitates retained bcc structure and were coherent with the matrix, and the yield strength of the 0.20 mm sheet was as high as 501 MPa in strip casting. The main mechanism of precipitation strengthening was attributed to coherency strengthening and modulus strengthening. The results indicated that balanced magnetic and mechanical properties can be achieved in thin-gauge non-oriented silicon steel with Cu addition in strip casting.

Tribological Properties of High-Entropy Alloys under Dry Conditions for a Wide Temperature Range—A Review

High-entropy alloys (HEAs) are composed of multiple elements with equimolar or near equimolar composition that have superior mechanical and tribological properties. In this article, we present a review on the tribological performance of HEAs. The tribological properties of different HEAs systems have been evaluated, and it has been found that the wear rate strongly depends on the crystal structure of the phases. The most common structures are face-centered cubic (FCC), body-centered cubic (BCC), and dual-phase (FCC + BCC) alloys due to the high entropy of mixing instead of forming intermetallic phases. In general, HEAs with a BCC structure showed superior hardness and wear properties compared to FCC and FCC + BCC alloys. The lesser wear rate of HEAs with a BCC structure is attributed to the reductions in ductility, resulting in strong but brittle alloys. In addition to the crystal structure, the effect of temperature on the tribological performance of the HEAs is also discussed, which highlights their potential applications for high temperatures. Moreover, various other factors such as grain size, formation of an oxide layer, and wear mechanisms are discussed.

Microstructure and Corrosion Properties of AlCrFeCoNi High-Entropy Alloy Coatings Prepared by HVAF and HVOF

High-entropy alloys (HEAs) represent an innovative development approach for new alloy systems. These materials have been found to yield promising properties, such as high strength in combination with sufficient ductility as well as high wear and corrosion resistance. Especially for alloys with a body-centered cubic (bcc) structure, advantageous surface properties have been revealed. However, typical HEA systems contain high contents of expensive or scarce elements. Consequently, applying them as coatings where their use is limited to the surface represents an exciting pathway enabling economical exploitation of their superior properties. Nevertheless, processing conditions strongly influence the resulting microstructure and phase formation, which in turn has a considerable effect on the functional properties of HEAs. In the presented study, microstructural differences between high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) sprayed coatings of the alloy AlCrFeCoNi are investigated. A metastable bcc structure is formed in both coating processes. Precipitation reactions are suppressed by the rapid solidification during atomization and by the relatively low thermal input during spraying. The coating resistance to corrosive media was investigated in detail, and an improved passivation behavior was observed in the HVAF coatings.

Microstructure and Hydrogen Storage Properties of the Multiphase Ti0.3V0.3Mn0.2Fe0.1Ni0.1 Alloy

The hydrogen storage properties of a multi-component alloy of composition Ti0.3V0.3Mn0.2Fe0.1Ni0.1 were investigated. The alloy was synthesized by arc melting and mechanical alloying, resulting in different microstructures. It was found that the as-cast alloy is multiphase, with a main C14 Laves phase matrix along with a BCC phase and a small amount of Ti2Fe-type phase. The maximum hydrogen storage capacity of the alloy was 1.6 wt.%. We found that the air-exposed samples had the same capacity as the as-cast sample but with a longer incubation time. Synthesis by mechanical alloying for five hours resulted in an alloy with only BCC structure. The hydrogen capacity of the milled alloy was 1.2 wt.%, lower than the as-cast one. The effect of ball milling of the as-cast alloy was also studied. Ball milling for five hours produced a BCC structure similar to the one obtained by milling the raw materials for the same time.

Template-Assisted Iron Nanowire Formation at Different Electrolyte Temperatures

We studied the morphology, structure, and magnetic properties of Fe nanowires that were electrodeposited as a function of the electrolyte temperature. The nucleation mechanism followed instantaneous growth. At low temperatures, we observed an increase of the total charge reduced into the templates, thus suggesting a significant increase in the degree of pore filling. Scanning electron microscopy images revealed smooth nanowires without any characteristic features that would differentiate their morphology as a function of the electrolyte temperature. X-ray photoelectron spectroscopy studies indicated the presence of a polycarbonate coating that covered the nanowires and protected them against oxidation. The X-ray diffraction measurements showed peaks coming from the polycrystalline Fe bcc structure without any traces of the oxide phases. The crystallite size decreased with an increasing electrolyte temperature. The transmission electron microscopy measurements proved the fine-crystalline structure and revealed elongated crystallite shapes with a columnar arrangement along the nanowire. Mössbauer studies indicated a deviation in the magnetization vector from the normal direction, which agrees with the SQUID measurements. An increase in the electrolyte temperature caused a rise in the out of the membrane plane coercivity. The studies showed the oxidation resistance of the Fe nanowires deposited at elevated electrolyte temperatures.