Papers by Keyword: Scandium

Abstract: The demand for structural lightweight in a variety of industries, particularly the automobile industry, has driven the development of heat-free die-cast aluminum alloys with excellent properties. Utilizing lightweight materials, such as Al-Si alloys has several benefits, including higher overall performance in automobiles and other industries, increased heat resistance efficiency, decreased emissions, and reduced weight. The purpose of this study is to modify the microstructure and enhance the mechanical properties of high-pressure die-casting (HPDC) AlSi10MnMg foundry alloy by incorporation of TiB₂ and Sc without any heat treatment. The results showed that the HPDC process significantly refines the grain structure and AlSiMnFe intermetallic compounds, transforming the eutectic morphology from sharp to rounded, and 93% enhancement in elongation at the optimum content (0.018 wt.%) of TiB₂. While the hardness of the alloy was improved by 15.7% with the addition of 0.03wt.% TiB₂. TiB₂ incorporation refines the grain structure and AlSiMnFe phases, while depressing externally solidified crystals (ESCs). The HPDC process refines Al₃Sc phases as well as AlSiMnFe phases while increasing yield strength due to Al₃Sc strengthening effects. After 0.5wt.% Sc addition in 0.018wt.% TiB₂-AlSi10MnMg alloy, the YS, and EL reached the maximum of 196MPa and 9.93% respectively.

Abstract: This study continues and develops approaching of bauxite residue treatment and associated waste for extracting highly valuable metals and scandium recovery by optimizing a hydrometallurgy method for process intensification. Laboratory-scale experiments were conducted in a nitric acid medium on electrostatic precipitator dust (ESPD) received in bauxite sintering. The method includes prior water-leaching of ESPD and subsequent asid leaching experiments at different liquid-to-solid ratios, leaching times and temperatures. The maximum extraction of the scandium was around 76.5 % at pH=0.2. Experimental design based on response surface methodology was used for obtained values optimization. Researches have shown that the optimization of the conditions for the transfer of scandium from red mud to the leaching solution mainly depends on the pH that have to be adjusted in range 0.5-1.7. The pH should not be too low, since Sc does not have time to go into solution in the presence of iron and other elements, as well as too high, because high values lead to re-precipitation of Sc from the filtrate. Complete study for Sc recovery is under progress and is not elaborated here.

Abstract: Objective of the study: study of various homogenization modes effects on mechanical and corrosive properties of rolled sheets from Al-Mg system alloy 1570 with additions of zirconium and scandium transition metals. The sheets were produced in laboratory conditions from the ingot, cast in production DC mold based on the commercial production practices and treatment modes. 4 homogenization modes, 2 tempers H12 and H321, and several modes of stabilization annealing in the temperature range from 240 °C to 325 °C have been reviewed. The samples have been comprehensively examined using optic and electron scanning microscope, mechanical properties were achieved by break test in compliance with ISO 6892-1, corrosion was examined using ASTM G66 and G67 standards. The curve of 1570 alloy sheets softening as the function of annealing temperature was constructed. It was demonstrated that the increasing temperature effect during homogenization leads to strength properties decrease and corrosion resistance improvement due to interdendritic segregation elimination. Among analyzed homogenization modes, 360 - 380 °C - 6 h mode is established as the most practical, and the sheets. produced without stabilization annealing, occurred to be the most resistant to exfoliation corrosion. The sheets, subjected to annealing at 260 °C - 2 h, show no traces of layer corrosion, but have pit corrosion locations rated as «PC» based on ASTM G-66 classification, such rating is unacceptable for the manufacture of products for use in the marine environment.

Abstract: Synthesis of YSAG:Yb ceramic powders with different stoichiometry by chemical precipitation method was carried out. It has been established that scandium can replace both dodecahedral and octahedral positions of garnet. It is shown that scandium is embedded in those positions that become available to it when the YAG:Yb composition deviates from stoichiometric. Thus, scandium can compensate for the lack of one of the components of the oxide composition Y₂O₃, Yb₂O₃, and Al₂O₃ during the formation of the garnet phase.

Abstract: The results of studies on the production of welding wires with a diameter of 2.5 and 3.3 mm from alloy 1580 are presented. To compare the manufacturability of the processing, various methods were used to obtain billets for drawing with a diameter of 8-12 mm: the traditional method of direct hot extruding (discrete); combined rolling-extruding method; and ingotless rolling-extruding method (continuous). The developed modes of bar rolling, drawing and annealing made it possible to obtain prototypes of wire in laboratory and industrial conditions. It was found that alloy 1580 is highly manufacturable both with the traditional method of pressure treatment (extruding) and with combined rolling-extruding methods. It was revealed that the application of all methods makes it possible to obtain billets with the level of mechanical properties necessary for further multi-operation processing. Based on the results of research obtained in laboratory conditions, rational drawing modes for industrial wire production have been developed. As a result of bay drawing, pilot batches of welding wire with a diameter of 3.26 and 2.47 mm from alloy 1580 were obtained, which was successfully used for welding sheet metal.

Abstract: The crystal structure of the new ternary aluminide Sc_1.33Pd₃Al₈ was refined by the Rietveld method from X-ray powder diffraction data. It crystallizes with a Gd_1.33Pt₃Al₈-type structure: hR51-14.00, R-3m, a = 4.29142(4), c = 38.1638(4) Å, R_B = 0.0344. The main feature of the structure is the statistical distribution of Sc atoms and Al₃ triangles within atomic layers of composition Sc₂Al₃ (Sc_0.67Al within the translation unit here), which is likely to correspond to stacking disorder of ordered layers. During the final cycles of the refinement, the occupancies of the corresponding sites were fixed at occ. = 2/3 for Sc in Wyckoff position 6c and occ. = 1/3 for Al in 18h. The unit cell of Sc_1.33Pd₃Al₈ contains six Sc_0.67Al layers, nine Pd and eighteen Al atom layers along the crystallographic direction [001]. Together with the structure types Tb_0.67PdAl₃, Y₂Co₃Ga₉, Sc_0.67Fe₂Si₅, Er₄Pt₉Al₂₄, Yb_0.67Ni₂Al₆, and ErNi₃Al₉, the structure type Gd_1.33Pt₃Al₈ forms a family of intergrowth structures built up of three kinds of similar monoatomic layer.

Abstract: The isothermal section at 800°C of the phase diagram of the ternary system Sc–Cu–Al was constructed in the whole concentration range using X-ray powder diffraction data. The existence of eight ternary compounds was confirmed: ScCu_4.9‑6.0Al_7.1‑6.0 (structure type ThMn₁₂, Pearson symbol tI26, space group I4/mmm), Sc₆Cu_24.1Al_11.9 (own structure type, cI176, Im-3), Sc₂Cu_6.25Al_4.75 (own structure type, oS108, Cmmm), Sc₃Cu_7.5Al_7.5 (Sc₃Ni₁₁Ge₄, hP38, P6₃/mmc), ScCu₂Al (MnCu₂Al, cF16, Fm-3m), ScCu_0.8Al_0.2 (CsCl, cP2, Pm-3m), ScCu_0.6Al_1.4 (MgNi₂, hP24, P6₃/mmc), and ScCuAl (MgZn₂, hP12, P6₃/mmc), and the existence of a continuous solid solution ScCu_1-xAl_x (x = 0-1), based on the binary compounds ScCu and ScAl with CsCl-type structure (cP2, Pm-3m), was established. The investigation of the Ti–Cu–Al system at 800°C confirmed the existence of four ternary compounds: TiCu_0.25Al_2.75 (ZrAl₃, tI16, I4/mmm), TiCu_0.3-0.6Al_2.7-2.4 (Cu₃Au, cP4, Pm-3m), TiCu_2-2.7Al_1-0.3 (MnCu₂Al, cF16, Fm-3m), and TiCu_0.54-1.16Al_l.46-0.84 (MgZn₂, hP12, P6₃/mmc). Electrical resistivity measurements were performed for three compounds in the Sc–Cu–Al system and confirmed metal behavior in the temperature range 5-290 K.

Abstract: When bauxites from the Middle Timan and Severouralsk deposits are processed into alumina by the low-temperature sintered process the high-iron content red mud can be obtained. The red mud contain up to 58 % of iron and are a potential raw material for ferrous metallurgy. Rare earth elements (REEs) such as Sc, Y and La are converted from bauxites to red mud in the form of hydroxides during processing and are easily leached by weak acid solutions. In this work, the red mud is treated with a solution of sulfuric acid (pH = 2.5–5), the REEs pass into solution, and then the solution is neutralized to obtain a precipitate, i.e. a concentrate of rare elements. The recovery of REEs is about 75–90 % (Sc, Y, La). The high-iron content red mud is converted to the naturally-doped cast iron and titanium slag (up to 50 wt.% TiO₂). As a result of processing bauxite, alumina (Al₂O₃), the naturally-doped cast iron, concentrate of REEs (Sc, Y, La, etc.) and titanium slag (TiO₂) are obtained. The flowsheet of the proposed complete processing of the high-iron content red mud is given.

Abstract: This article presents a study of Tomtor rare earth ore decomposition. This material contains a lot of valuable components such as REE and niobium (mas., %: 12,8 ΣREO (rare earth oxides), 0.039 Sc, 18.4 P₂O₅, 9.9 Fe, 9.0 Al, 0.24 ThO₂, 8.2 Nb₂O₅). The study aims to find efficient ways of processing this deposit. Technologies using the sulfuric acid as the main reagent to leach are described in this article. Investigation has three trends. The first trend is agitation leaching at low sulfuric acid concentrations, temperatures up to 95 °C and atmospheric pressure. The second trend is pressure leaching at low sulfuric acid concentrations, high temperatures (up to 180 °C) and high pressure. The third trend is high temperature sulfatization with concentrated sulfuric acid at elevated temperature (up to 180 °C) and atmospheric pressure followed by aqueous leaching. The dependence of target components (rare earth elements, scandium, phosphorus) and the impurity (iron, aluminum, thorium) extractions into solution from major factors was studied.

Abstract: Results of researches of process of hot rolling of ingots from the experimental aluminum alloy which is economically alloyed by scandium are given. The computer model of process of hot rolling with the use of which the straining, temperature and speed processing modes conditions is calculated and also power parameters of processing is calculated in applied to industrial conditions. It is shown that the use in the model of a certain shape of the ingot faces (Petrov's lock) and indirect rolling action in the edging stand is made it possible to reduce the likelihood of the formation and further development of micro cracks on the edges of rolled metal. The adequacy of results of modeling was confirmed by carrying out pilot-industrial tests when rolling large-size ingots from the experimental alloy and obtaining batches of hot-rolled plates and sheets of various sizes. The tensile test was used to study deformed samples after rolling and samples obtained on five regimes of heat treatment with varying heating temperatures of 300, 350 and 380 oС and holding time in the furnace for 1 and 3 hours. The results of the studies on samples of hot-rolled sheets 10 mm thick showed that, compared with the initial state, the strength characteristics of the metal after heat treatment are reduced by an average of 12-20%, and plastic characteristics increase by 50-65%. In this case, the heat treatment regimes 1 - 3 give a good ratio of the ductility and plastic properties of the metal.