Russian Metallurgy (Metally)最新文献

The thermodynamics of the sublimation process of zirconium tetrachloride has been studied. The possibility in principle to purify ZrCl₄ from the accompanying niobium pentachloride is shown. Part of niobium in zirconium tetrachloride can be contained in the form of niobium oxytrichloride. Niobium oxytrichloride is virtually non-volatile over the entire temperature range and will concentrate in the char.

Polycrystalline samples of the Li–Mn–Eu–O system were obtained by preliminarily ball-milled precursor mixtures annealing in air (700, 800, 900, 1000, and 1100°C). The obtained products were studied by X-ray powder diffraction and thermogravimetry (TG-DSC). The possibility of substituting Mn with Eu for spinel LiMn_2–xEu_xO₄ was assessed. Within the framework of the Li–Mn–Eu concentration triangle, a subsolidus isobaric diagram and a projection of the liquidus surface of the Li–Mn–Eu–O system were constructed using models of polythermal phase diagrams of the LiEuO₂–LiMnO₂ and LiEuO₂–LiMn₂O₄ sections. The temperatures of eutectic equilibria involving three crystalline phases and a melt were determined.

The combined deoxidation of Fe–Ni melts by manganese and aluminum at 1873 K is thermodynamically analyzed. The dependences of oxygen solubility on the manganese and aluminum content are calculated for the Fe–40% Ni melt. The combined deoxidation of the Fe–40% Ni melt by manganese and aluminum is experimentally studied in the range 0.1–0.3% Mn and 0.0005–0.056% Al at 1873 K. The oxygen concentration is found not to depend on the manganese content in the manganese content range under study (0.1–0.3%). The experimental data obtained are in good agreement with the results of thermodynamic analysis, from which it follows that the effect of manganese on the deoxidation ability of aluminum in the Fe–40% Ni melt in the range 0.1–1% Mn can be significant if the aluminum content is lower than 0.0005%.

Abstract—The influence of annealing at 600°C on the mechanical and thermomechanical characteristics of a Ti₅₀Pd₃₀Ni₂₀ alloy with high-temperature shape memory effect (SME) is studied. The best strength (σ_u = 1030 ± 140 MPa) and plastic ((varepsilon _{0}^{{max }}) = 11.5 ± 6.0%, δ_res = 6 ± 4%) characteristics have been obtained after annealing at 600°C. The maximum thermally recoverable strain (ε_SME = 4.3%) and the maximum degree of shape recovery (η_SME = 67%) are achieved after annealing at 600°C after preliminary induced tensile deformation at temperatures t_d =235–230°C and a strain rate (dot {varepsilon }) ≈ 2.8 × 10^–3 s^–1; in this case, the reverse martensitic transformation temperatures characterizing the main shape recovery are A_sSME = 220°C and A_fSME = 249°C. Taking into account the studies carried out before, we found that the martensitic transformation temperatures increase almost linearly and, conversely, the SME and the degrees of shape recovery decrease as the titanium nickelide is alloyed with palladium in the content range from 30 to 50 at %. Linear regression equations are derived. The results obtained are used for designing safety devices of, e.g., crosscutting and pushing types.

Abstract—Data on the physicochemical properties of the sulfur allotropes in the temperature range used in autoclave processes are presented. Elemental sulfur is shown to have an enhanced sensitivity to a temperature change. The chemical activity of sulfur can change by several orders of magnitude in a range of 30°C, and the viscosity changes by several thousands of times. The oxidation leaching of sulfides, sulfur hydrolysis, sulfidizing, and precipitation of nonferrous metals are considered. The laws according to which the leaching processes occur depending on the allotropic composition of sulfur are revealed. The activators capable of decreasing the temperature range of the transformation of cyclic sulfur molecules into chain molecules are considered. The yield of elemental sulfur is explained using the polysulfide mechanism of oxidation of sulfides and the physicochemical properties of sulfur allotropes.

Transmission electron microscopy methods are used to analyze the changes in the structure, phase composition, and dislocation substructure in the head of long differentially hardened special-purpose DT400IK rails made of E90KhAF steel along the radius of fillet rounding at the surface and at a distance of 2 and 10 mm from it after a passed tonnage of 187 mln t during field tests. Bend extinction contours, which indicate an elastic-stressed state of the rail head as a result of long-term operation, are found to form. The sources of lattice curvature torsion are revealed. The mechanisms of destruction of cementite lamellae and repeated precipitation of carbide-phase nanoparticles are considered.

Cu/graphene metal matrix composite is promising for a wide range of applications. However, the important problems in the synthesis of the Cu/graphene composite exist, associated with the poor dispersion of the graphene in the matrix and weak interfacial bonding. High pressure torsion processing supplies a possibility to obtain bulk samples with a nanocrystalline structure, without pores and contamination from dissimilar materials. This processing was successfully used for fabrication of the Cu/graphene composite out of thin copper foils coated with a monolayer of graphene. Microstructural characterization of the processed disks demonstrated microstructure with an equiaxed grain size of about 300 nm. The process significantly increased microhardness of Cu/graphene composite. The tensile tests showed the value of the tensile strength reached 670 MPa at room temperature.

The kinetics of atmospheric hydrochloric acid leaching of the iron-containing slime formed during quartz–leucoxene sandstone beneficiation is studied. The calculated activation energies indicate two temperature ranges of the slime leaching: a diffusion kinetic region at 40–70°C (E_a = 35.79–36.56 kJ/mol) and a kinetic region at 70–80°C (E_a = 48.68 kJ/mol). A steplike character of the development of slime during the leaching of iron-containing minerals from it is revealed, which is caused by the consecutive processes of siderite and hematite decomposition and a change in the process rate as the solution is saturated with iron ions.

A comparative analysis of changes in structure and ambient temperature mechanical behavior of pure FCC metals—Al, Ni and Cu, due to high-dense electropulsing (HDEP) of isothermally cryorolled at liquid nitrogen temperature sheets, has been carried out. Processes, driving forces and factors controlling the nature and kinetics of transformation of the deformation structure during HDEP are discussed. Temperature ranges of activation of recovery and recrystallization in the cryorolled metals under pulsing of different capacity are determined. It is shown that the processing allows controlling strength of metals within a wide range owing to formation of homogeneous and/or heterogeneous structures with different crystallite size, dislocation density and grain boundary spectrum, involving ultra-fine grained and nanostructured ones. It is concluded that the phenomenology and nature of metal softening under electric pulsing are similar to those, occurred at conventional furnace annealing.

The use of modern automated control systems in the production of cathode copper provides the possibility of remote access to resources for monitoring and regulating the parameters of the electrolytic process, which determines the efficiency of production while reducing energy costs. Important parameters in the electrolytic refining of copper are the temperature and composition of the electrolyte, the circulation rate of the electrolyte, the level of sludge, the frequency of short circuits between the electrodes, and the current density, which directly affect the quality of the volume of the cathode deposit at the bottom of the electrolytic cell. The presence of short circuits in the bath is due to the growth of dendrites, which entails the need to control the voltage, composition, and temperature of the electrolyte, and to periodically analyze their composition and the accumulation of the volume of sludge sediment at the bottom of the electrolyzer. The intensification of the electrolysis process occurs mainly due to an increase in the current density, a decrease in the interelectrode distance, an improvement in the quality of the electrodes, an improvement in the electrolyte circulation system, with further mechanization and automation of the process itself and its auxiliary operations, leading to an increase in productivity. The purpose of this work is to expand the functions of the APCS by introducing sludge level control sensors to reduce irrecoverable losses in the presence of short circuits of dendritic sediment on the electrodes in the lower bottom of the electrolyzer using new software. A method for controlling the level of sludge sediment to prevent short circuits is considered, and a control program is developed using float-type level sensors for electrolyte and sludge sediment. This measure, when implemented, will reduce energy consumption by 15–20%, which can be useful for implementation in the electrolytic copper production shops at the Copper Smelting Plant (Lao Cai City, Socialist Republic of Vietnam).