Russian Metallurgy (Metally)最新文献

For the first time, an intermetallic 2Ni–Mn–Al-based alloy is prepared by self-propagating high-temperature synthesis (SHS) combined with centrifugal casting. According to X-ray diffraction data, the main phase of the SHS product is the (Ni,Mn)₃Al nickel aluminide solid solution with the partial substitution of manganese for nickel. The study of the microstructure shows a low aluminum content at the boundaries of the (Ni,Mn)₃Al main phase. The averaged microhardness of the synthesized alloy is 8500 ± 45 MPa and the peak hardness is 11500 MPa. The alloy exhibits soft magnetic properties. The maximum magnetization in a field of 796 kA/m (10 kOe) is J_s = 1.1 (A m²)/kg (emu/g) and the coercive force is H_c = 14.3 kA/m (179.7 Oe).

The interaction of gaseous chlorine with granules based on zirconium dioxide and carbon-containing material was studied. The most probable chemical processes occurring in the ZrO₂–C–Cl₂ system. The interaction of granules with gaseous chlorine was analyzed on the basis of ideas about the chain mechanism of chlorination.

The possibility of using the fractional precipitation of rare-earth metals (REMs) and manganese from hydrochloric acid solutions by ammonium carbonate is considered. Specific features of the behavior of elements during precipitation, which are necessary to know when preparing selective REM and manganese concentrates, have been revealed. At pH 5.25, 85% ΣTR₂O₃ pass to a deposit (in the oxide formula, ΣTR is the commonly accepted international designation of REMs), and the REM content is 60.5%. At pH 5.25–7.4, 92% manganese are extracted to a manganese concentrate, and the MnO content in the concentrate reaches 70.7%. The complicated chemical composition of the solution requires three-stage fractional precipitation for preparing qualitative selective concentrates: iron and thorium should be precipitated as a cake at the first stage, and REMs and manganese should be precipitated at the second and third stages, respectively. This makes it possible to form deactivated concentrates in the form of carbonates suitable for the further extraction of REMs and manganese by the well-known methods.

Magnetron sputtering and subsequent annealing are used to form nano- and micron-sized cerium dioxide (CeO₂) surface layers on a VT6 titanium alloy base. The structure of samples is studied by scanning electron microscopy, Auger-electron spectroscopy, energy dispersive spectroscopy, and X-ray diffraction analysis. We detected a linear dependence of the surface layer thickness on the deposition time, a nonlinear increase in the thickness with the supply power, an increase in the surface roughness, and delamination and surface layer loosening, which are likely to be related to annealing. For samples with a surface layer less than 750 nm in thickness, the formation of a TiO₂, Al₂O₃, and CeVO₄ sublayer is found; at a layer thickness of less than 300 nm, the entire cerium dioxide is consumed to form vanadate from vanadium dioxide.

The factors affecting iron(III) adsorption by strongly acidic Dowex G-26(H) cation-exchange resin are studied. These factors include the adsorbent dose, pH of the solution, contact time, initial Fe(III) concentration in the solution, and temperature. Langmuir and Freundlich adsorption isotherms are constructed from the experimental results. Both isotherms quite satisfactorily describe Fe(III) adsorption by the Dowex G-26(H) adsorbent, which is indicated by high (close to unity) coefficients of determination (R²). The calculated capacity of the adsorbent ranges from 166.6 to 196.1 mg g^–1 at different temperatures (T = 293–313 K). The kinetic and thermodynamic parameters of the process (ΔH°, ΔS°, ΔG°) have been determined. The positive calculated standard entropy (ΔS°) and enthalpy (ΔH°) changes suggest that the adsorption of Fe(III) ions on the resin is endothermic and spontaneous.

Abstract—The deformation behavior of an ultrafine-grained (UFG) 08Kh18N10T steel at elevated temperatures (450–900°C) has been studied. The maximum elongation to failure (~250%) is detected at a temperature of 750°C. The deformation of the UFG steel at elevated temperatures is controlled by the intensities of simultaneous processes of grain-boundary sliding and power-law creep. The contribution of each mechanism depends on the grain growth rate under superplasticity conditions, which affects the rate of defect accumulation at migrating grain boundaries. The fracture of the UFG steel has a cavitation character: the fracture and specimen surfaces after high-temperature tests contain large elongated pores having formed on nonmetallic inclusions and submicron pores having formed on σ-phase particles.

Abstract—The possibility of increasing the hardness of a Co–Cu binder in single-stage production of WC–Cu–Co composites using pre-solidification low-frequency vibration (LFV) is investigated. Cu–Co and WC–Cu–Co alloys are fabricated by reactive infiltration of liquid copper into uncompacted WC and Co powders under LFV of their compositions (80 Hz for 10 min at 1300–1350°C). Their phase and chemical compositions, structure, and hardness have been studied. We are the first to experimentally show that metastable formations (frozen immiscibility regions of two liquids) are the precursors of (Co) dendrites and have the same composition with them. The cobalt distribution over the height of Cu–Co alloy ingots and over phase components is shown to depend on the cobalt content, the effect of vibration, the geometric arrangement of initial component layers, and the temperature. The optimum conditions for achieving a uniform cobalt distribution over the melt have been determined. Cobalt is shown to ensure precipitation hardening of the Cu–Co metal binder due to the formation of (Cu) solid solutions already at the stage of synthesis of Cu–Co and WC–Cu–Co alloys. Moreover, the potential for additional hardening by subsequent heat treatment or by changing cooling conditions is still incompletely fulfilled.

The effect of impurities on the structural and physicochemical properties of melts is considered in order to improve the service properties of cast high-temperature alloys. The changes in the state of nickel melts depending on the tin impurity content and the temperature are studied using the parameters of such structurally sensitive properties as density and surface tension. When the tin content in nickel melts increases to several hundredths of a percent, their density and compression effect are found to increase; however, a further increase in the tin content to 0.6 wt % is accompanied by a significant decrease in these properties. A stable nickel-based cluster solution is shown to form when the density and the surface tension increase at 0.02 wt % tin. When the temperature increases to 1650°C, the properties of the melts are characterized by a slight decrease in the surface tension and the density at a retained type of dependences.

X-ray diffraction is used to determine the influence of the reduction during cold rolling of wedge steel 20Kh15AN3MD2 samples on the quantitative phase composition, the texture, and the residual macrostresses in the α and γ phases. When the reduction increases, the fraction of the γ phase decreases from 82% in the initial hot-rolled state to 74% at a 10% reduction and to 60% when the reduction increases to 70%. The type of austenite texture is characterized by the components typical of the rolling texture of fcc metals, namely, the “brass” texture ({110}〈112〉). It does not change at a 10% reduction, then increases significantly at a 20% reduction, and remains the same up to a 70% reduction. The texture of the α phase is characterized by three components, namely, {110}〈110〉, {211}〈110〉, and {001}〈110〉. The first two components are the transformation textures, which dominate in the initial state; after a reduction of 30%, the third component, which corresponds to the rolling texture of the bcc α phase, increases. The estimation of residual stresses shows that compressive stresses of 600–1100 MPa form in the γ phase and tensile stresses of 1200–1600 MPa form in the α phase.

Interaction of gaseous chlorine with granules based on zirconium dioxide and carbon-containing material has been studied. It was found that the degree of formation of zirconium tetrachloride significantly depends on the chlorination temperature. It is shown that an increase in the carbon content in the granules favours the opening of zirconium dioxide.