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Izvestiya. Non-Ferrous Metallurgy

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No 2 (2023)
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Metallurgy of Rare and Precious Metals

5-14 446
Abstract

This article discusses the physicochemical regularities of indium leaching from the surface of glass plates of used displays in various acids. The glass of used displays was pre-cleaned from polarizers and crushed. Their base is comprised of silicon and aluminum oxides. Indium is presented in the form of In2O3·SnO2. Indium content in the material obtained is 174.8 mg/kg. Individual solutions of sulfuric, hydrochloric and methanesulfonic acids were used as leaching agents. The influence of concentrations of the mentioned acids (0.1–1.0 N), leaching duration (10–60 min), temperature (298–353 K) and liquid-to-solid ratio (L : S = (7.5÷15.0): 1 cm3/g) on the degree of indium extraction into solution has been determined. Partial orders of reaction in terms of CH3SO3H, H2SO4, HCl are 0.69, 0.67 and 1.10, respectively. In the course of experiments an intensive increase in indium concentration was observed in the first 20–40 min f leaching in H2SO4 and HCl solutions. The process rate then decreased and indium extraction actually did not increase, due to a fall in the amount of non-reacted indium. During leaching in 0.1–0.4 N in CH3SO3H solutions, the rate of indium dissolution did not change throughout the experiment, since the amount of non-reacted indium gas decreased insignificantly. The acids considered here can be ranked in the following ascending order of their efficiency for indium dissolution: CH3SO3H, H2SO4, HCl, which corresponds to the growth of strengths of these acids. An increase in the temperature led to a significant increase in indium extraction. The apparent activation energies of In2O3 dissolution in CH3SO3H, H2SO4, HCl solutions have were calculated as equal to 51.4, 51.2, 43.4 kJ/mole, respectively. It was established that with the use of HCl as leaching agent, the increase in the fraction of liquid phase in the slurry from 7.5 : 1 to 15 : 1 cm3/g lead to fall in indium extraction by 2.4 times and the initial leaching rate by 3.2 times. It was demonstrated that an increase in L : S during indium dissolution in CH3SO3H (from 7.5 : 1 to 15 : 1 cm3/g) and H2SO4 (from 10 : 1 to 15 : 1 cm3/g) is accompanied by insignificant changes in extraction and initial leaching rate. Therefore, the studies performed demonstrated that indium leaching from glasses of spent displays flows in mixed mode upon the use of HCl and in kinetic mode in H2SO4 and CH3SO3H solutions.

Foundry

15-28 872
Abstract

The quality of cast parts produced by investment casting is largely determined by the quality of the ceramic molds. Currently, aircraft and engine building enterprises are switching to an environmentally friendly colloidal silica binders for the manufacture of ceramic molds. In this work, the dynamic and relative viscosity of slurries prepared using fused silica powder and colloidal silica binders of the VT13-02U (Vakuumteh LLC), Stavroform VS (Polymet LLC), UltraCast One + and UltraCast Prime (both Technopark LLC) manufacturers were determined. It is shown that the slurries prepared on the considered binders have similar viscosity values, and in their rheological properties they are close to Newtonian liquids. The values of dynamic and relative viscosity at a binder content of 400 mL per 1 kg of fused silica powder were ~732 mPa·s and ~380 s, respectively. With an increase in the binder content to 600 mL per 1 kg of fused silica powder, the dynamic and relative viscosity decreased to ~70 mPa·s and ~16 s, respectively. An equation was also found that relates the dynamic viscosity determined using a rotational viscometer and the relative viscosity determined using the VZ-4 viscosimeter. The mechanical properties were determined during three-point bending tests on ceramic samples obtained using slurries on the above-mentioned colloidal silica binders and fused silica stucco. Samples obtained on binders VT13-02U, Stavroform VS and UltraCast One+ showed very similar bending strength values, namely 3.5–4.3 MPa after drying and 5.8–6.1 MPa after firing. Due to the presence of a polymer addition in the binder, the ceramic samples obtained on the UltraCast Prime binder had higher values of bending strength after drying and after firing – 6.4 and 7.2 MPa, respectively. It was also shown that with an increase in the viscosity of the slurry and a decrease in the fraction of fused silica stucco, the strength of the samples increases. The lowest surface roughness was observed for samples obtained with UltraCast grade binders.

Pressure Treatment of Metals

29-37 591
Abstract

The structure of insufficiently deformed areas at the non-steady phase of extrusion was studied. The tests at Kamensk Uralsky Metallurgical Works using a 120 MN press and 800 mm dia. container, in order to extrude a 355.6 mm dia. Bar was performed. The bar material is the Al–Mg–Si AD33 aluminum alloy (GOST 4784), similar to ASTM 6061. The percentage reduction was 80 %, and the reduction ratio was 5.06. After that, the macrostructure, microstructure, and average grain size along the radius, mechanical properties at room and elevated temperatures were investigated. It was found that the extruded bar macrostructure is fine-grained, homogeneous, and dense, with no nonmetallic or intermetallic inclusions. The cross-section contained several structures. The central part is weakly deformed preserving the dendritic cell structure inherited from the casting. At the circumference, a streaked structure is formed. Its components are crushed and uniformly distributed. We measured the strength at elevated temperatures and compared the results to the data available in the literature. The tested material strength almost doubled, thus indicating its incomplete softening. The ductility was also performed. The DEFORM-2D software, in order to simulate the low reduction of extrusion was used. The metal at the circumference is exposed to a greater strain from the extrusion beginning. A step-by-step analysis indicated that at the first step, the strain is localized near the die hole. In the second step, a rigid area is formed in the vicinity of the die/container liner interface. The circumference layer of metal with a 1.75–2.00 reduction of area is formed. At the bar center, this range is 0.75–1.00 (half of the circumference value). In the third step, the circumference layer with an elevated strain has a wedge-like shape. In the fourth step, the circumference layer (with elevated strain) has an equal thickness along the extrusion axis. This indicates the steady phase. The plastic strain at the bar front end is higher at the circumference than in the center. This confirms the structural analysis results. They show that the central part of the bar may retain its cast structure, while the circumference is deformed. If the bar central part is required to have some specific properties, the bar has to undergo another manufacturing operation to increase the accumulated strain. Re-extrusion processes the areas insufficiently deformed during the first extrusion.

Physical Metallurgy and Heat Treatment

38-48 362
Abstract

This article presents experimental results of resistance against fracture upon static tension of cast aluminum matrix composites based on aluminum with various content of Al2O3 strengthening phase. The cast aluminum matrix composite materials were produced by the technology based on burnout of aluminum melt upon interaction with oxygen. Two batches of ingots with various content of solid phase were smelted for tests of static strength. The average particle size of strengthening phase of predominantly prismatic morphology was 60–80 μm, and their content varied from 15 to 25 %. The fracture surfaces obtained upon static uniaxial tension of the considered samples were studied on the samples destroyed at maximum stress. The fracture surfaces were analyzed using an optical microscope with expanded options due to improved long-focus system and digital processing of images based on unique procedure of 3D structure analysis. For indepth analysis of characteristic fracture region a scanning electron microscope was used equipped with energy and wavelength dispersive elemental analyzers. It was established in the studies that in the samples with lower content of dispersed phase, the fracture is characterized by mixed heterogeneous in terms of macrogeometry pattern. This can be interpreted as dry fibrous fracture with visible crystalline pimples and breakaways. With an increase in the solid phase, a mixed, sufficiently homogenous in terms of macrogeometry, fracture pattern of fanlike fibrous structure can be observed. Crystalline pimples were also detected of a different fracture surface area, as well as breakaways of other geometrical sizes. The features of changes in the relief of fracture surface and the fracture mechanisms of the obtained composites have been detected and described.

49-56 369
Abstract

Aluminum alloys alloyed with rare earth and transition metal are promising materials for electric energy transportation due to their high properties of strength, thermal stability, and electrical conductivity. The features of strengthening, their mechanical properties and electrical conductivity of Al–0.2Y–0.2Sc–0.3Er alloy after cold rolling have been established. The alloy as a cast structure is presented by aluminum solid solution (Al) and dispersed eutectics with τ2 (Al75-76Er11-17Y7-14) phase upon complete dissolution of scandium in (Al), and a content of yttrium and erbium at the level of 0.2–0.3 % each. Cold rolling the ingot accelerates strengthening upon annealing at 270 and 300 °C, reducing the time of achieving peak hardness. The maximum strengthening due to precipitation of L12 dispersoid of Al3(Sc,Y,Er) phase with the average particle size up to 10 nm is achieved after 7 h of annealing at 300 °C after cold rolling. This shows the prevailing heterogeneous mechanism of nucleation due to defects accumulated during cold rolling which stimulates strengthening. The eutectic particles are located mainly along the boundaries, elongated in the rolling direction. Irrespective of the mode of sheet fabrication, the alloy demonstrates high thermal stability up to 400 °C. During annealing of the sheets to 450 °C, their non-recrystallized structure is retained. Ingot annealing at t = 300 °C in 7 h and cold rolling with subsequent annealing under the same conditions provide a high level of mechanical properties and electrical conductivity: σ0.2 = 194 MPa, σu = 210 MPa, δ = 12.1 % and IACS – 60,1 %. The alloy has demonstrated high yield stress up to 100 h of annealing at t = 300 °C.

57-73 506
Abstract

Ti2AlNb-based alloys are promising materials for operation at high temperatures in aerospace industry. Meanwhile, the existing difficulties of weldability restrict opportunities of their application. This work is devoted to studies of welded joints from Ti2AlNb-based VTI-4 alloy, obtained using pulsed laser welding (PLW). The optimum PLW modes have been determined providing uniform faultless joint. The features of formation of external defects, internal pores, cracks and non-uniform penetration depth were detected depending on welding conditions. The main PLW parameters influencing on formation of welded joint are voltage and duration of laser pulse. It was demonstrated that at insufficient medium and high peak powers sawtooth seam roots and internal pores can be formed. However, at higher rates of energy input thermal hydraulic processes in welding bathe are violated, accompanied by metal splashing (spattering), heterogeneity of pulse imposition is observed. This leads to formation of cracks, higher porosity, heterogeneity of melting zone, and as a consequence, poor mechanical properties. Microstructure analysis of the welded joints obtained by means of PLW has demonstrated that the melting area is comprised of long dendritic grains of β phase, and the heat affected zone from two regions of β + α2 phases and β + α2 + O phases. Herewith, the achieved joint strength equals to ~80 % of the base metal produced using the optimum PLW mode.

74-82 362
Abstract

We conducted a study on fatigue in flat samples of the VT3-1 titanium alloy using “soft” cyclic beam bending tests. For this purpose, we developed an innovative electromagnetic test bench. The test bench's electromechanical system induces mechanical vibrations at a frequency that matches the eigenfrequency of the sample, ensuring that the cyclic load frequency remains constant. The electromagnetic force bends the sample while the elastic force unbends it, producing a quasi-sinusoidal cyclic load. Through our investigation, we determined the impact of this cyclic loading on both cyclic strength and durability. Our findings indicate that the VT3-1 titanium alloy possesses high resistance to fatigue and an endurance limit. Furthermore, we observed a low variability of the experimental fatigue resistance in relation to the approximating fatigue curve, suggesting the alloy has high structural stability. This finding indicates that the VT3-1 titanium alloy possesses high structural stability. To assess eigenfrequency stability, we subjected the alloy samples to cyclic tests, interrupting them at a reference number of 50 million cycles to evaluate changes in eigenfrequencies and stability under loads close to the fatigue limit. The results showed that the titanium alloy has a high level of eigenfrequency stability. Interruptions in cyclic tests resulted in jump-like increases in eigenfrequencies, which was not observed in continuous tests. Nevertheless, the total eigenfrequency deviations from the initial value at the end of the tests were similar in both cases



ISSN 0021-3438 (Print)
ISSN 2412-8783 (Online)