Russian Metallurgy (Metally)最新文献

The mechanical properties and structure of the joints of cast aluminum alloys made by friction stir welding (FSW) are studied. The processes of intense plastic deformation during FSW influence the formation of the weld microstructure, on which its strength properties depend; however, the determining factor is represented by the specific temperature–time FSW conditions. The study of the structure of the weld core revealed a special layered metal structure consisting of recrystallized grains separated by high-angle boundaries. The average grain size in the stir zone is shown not to depend on the average grain size in the initial casting: it is determined by the FSW parameters. A fully recrystallized structure with an average grain size of 3.9–5.3 μm is found to form in the weld core during FSW of cast aluminum alloys. The strength coefficients of the FSW welded joints of VAL10, AL19, and VAL16 alloys are 79.2, 81.3, and 96.7%, respectively.

The study is aimed at developing and determining parameters of the preparation under laboratory conditions of an optimum composition of a biocompatible powder material of a CaO–MgO–SiO₂ system that stimulates and activates cell recovery, growth, and differentiation of bone tissue. The patterns of the transformations and formation of akermanite Ca₂Mg(SiO₇), merwinite Ca₃Mg(SiO₄)₄, larnite Ca₂(SiO₄), bredigite Ca₇Mg(SiO₄), and olivine (Mg,Fe)₂SiO₄ in this system are presented. The molecules are identified by vibrational (IR) spectroscopy and Raman spectroscopy. The quantitative ratio of the indicated chemical compounds in the powders is found by phase X-ray diffraction (XRD) analysis. The transformation patterns of these compounds during annealing in a temperature range of 1000–1500°C for holding times of 1–10 h are experimentally determined. Since the akermanite concentrations higher than 55 wt % are achieved in the CaO–MgO–SiO₂ system in the experimentally obtained one-stage mode or theoretically calculated sequential annealing mode, a powdered conglomerate with a high content of the biocompatible component in the calcium–magnesium–silicate mixture can be prepared. The calcium–magnesium–silicate mixture is designed for studying biocompatible properties of coatings of titanium endoprostheses under artificial conditions (in vitro).

The authors identify patterns and assess the competitive advantages of the development of Russian business in the country’s metallurgical sector; moreover, they carry out a comparative analysis of the domestic steelmaking production with analogous production in the leading countries in the world metallurgy. Based on an analysis of retrospective information on market concentration and liquid steel production indicators in the TOP-10 countries, as well as the gross domestic product of these states for 2009–2023, they obtained data to assess the potential opportunities for business development in the metallurgical sector of the domestic and global economies. Estimated indicators of competitive relations between the Russian steelmaking sector and the corresponding production in the TOP-10 countries are determined using a direct competition indicator, namely, absolute entropy, and an indirect indicator, namely, the Herfindahl–Hirschman index, for 2009–2023. A general trend toward monopolization in the production and economic sphere of the metallurgical sector of the global economy has been revealed, and the prospects for a positive positioning of the domestic steelmaking cluster in the global development of metallurgy are evaluated.

The influence of the parameters of laser treatment performed for marking on the roughness and structure of the surface layers and the corrosion resistance of implants made of a Ti–55.8 wt % Ni titanium nickelide-based alloy is studied. Laser treatment at a radiation power of 4–6 W and a modulation frequency of 170 kHz is found to form a TiO₂ oxide layer 40–52 nm thick, which provides satisfactory color saturation of the treated surface at a remelted layer thickness not exceeding 2 μm, and to preserve the high pitting and fretting corrosion resistance of the material.

Friction stir treatment of aluminum alloys performed without introducing high-strength particles is investigated. Rational friction stir parameters, including a tool rotation speed of 850 rpm and a linear speed of 25–40 mm/min, are determined experimentally. The influence of the tool pin length on the required sizes of the heat-affected and deformation zones is studied. A tool pin length of 1.5–2.0 mm is identified as the most effective. During friction stir treatment, a bowl-shaped treatment zone with uniformly expanding boundaries toward the workpiece surface forms. This treatment results in the fragmentation and uniform distribution of primary intermetallic phase particles. An ultrafine-grained structure with an average grain size of (2.30 ± 0.05) μm is observed in the stir zone. For flat specimens, an overlap of 0.25–0.33 for adjacent passes is recommended.

Particles of titanium powder prepared by the electrodispersion of VT20 titanium alloy wastes in distilled water are experimentally found to be spherical and elliptical in shape or exist as agglomerates. The average volumetric particle diameter is 26.3 μm, and the particle surface is cladded with oxygen. An analysis of the phase composition shows the presence of the main phases α-Ti and TiO and minor amounts of Ti₂O₃ and Ti₃Al. The new electroerosive titanium spherical powder materials can efficiently be used for additive technologies.

The possibility of hydrogen treatment of alloys based on titanium and its intermetallics is analyzed. The introduction of hydrogen is shown to increase the technological ductility of commercial hard-to-deform titanium alloys and alloys based on the Ti₃Al and Ti₂AlNb intermetallics. As the degree of aluminum alloying of the alloys increases, the hydrogen plasticization effect is found to occur at lower concentrations of introduced hydrogen. Subsequent vacuum heat treatment of the alloys is shown to remove hydrogen from the material to safe concentrations for preventing hydrogen embrittlement and to form a set of mechanical properties not inferior to those after traditional types of treatment.

An overview of the origin, classification, modern production technologies, chemical compositions, and physicomechanical properties of precipitation hardening steels are presented. 17-4RN steel is shown to be the most in-demand precipitation hardening martensitic steel in the domestic industry at present; it has no analogs in the practice of Russian metallurgical production. The technological process at AO Petrostal Metallurgical Plant, under which 07Kh16N4D4B steel is produced, is described.

The EAF dust formed during steel making from metal scrap is studied. When the EAF dust is processed to produce Waelz oxide, an iron-containing clinker is an additional by-product. Briquetting of the EAF dust to form briquettes before Waelz processing is proposed. After Waelz processing, metallized briquettes can be used to produce powders of alloys PK10D2F, PK10F, and PK40D3KF and steels AS45G2, A40G, and 110G13L.

The formation of a multicomponent composite heat-resistant Ni–Cr–Al coating alloyed with tantalum, tungsten, and hafnium using the methods of vacuum carburizing, gas circulation aluminizing, vacuum plasma cathode deposition, and thermobaric treatment is considered. The laws of formation of the chemical composition, structure, and state of stress in a Ni–Cr–Al–Ta–W–Hf–Y composite coating are established. Yttrium is shown to play a positive role as a deoxidizer of condensate coatings, and thermobaric treatment is found to decrease the microporosity and the grain size in the deposited composite coating.