Russian Journal of Non-Ferrous Metals最新文献

The results of studies on the effect of the charge composition on the structure and mechanical properties of cast aluminum alloys of the Al–Si–Mg (AK9ch) and Al–Mg (AMg6l) systems are presented. It is shown that the contribution of deformed waste in the composition of the charge (electrical waste of aluminum and waste of beverage cans based on alloy 3104—for AK9ch; alloy plates AMg6—for AMg6l) contributes to the formation of dispersed micro- and macrostructure of working alloys in the solid state. The effect of modification (AlSr20 master alloy—for AK9ch; AlTi5 master alloy—for AMg6l) on the structure and mechanical properties of alloys obtained by various charge variants is investigated. Experiments on the effect of the charge composition on the modifiability of AK9ch and AMg6l alloys have shown that the structure of the deformed waste is partially inherited by working alloys through the liquid state. With similar chemical compositions, smaller micro- and macrostructure sizes and increased mechanical properties (tensile strength and elongation under tension) are characteristic of alloys obtained using an increased proportion of deformed waste in the composition of the charge. It was found that, in alloys with an increased proportion of deformed waste, exceeding a certain amount of the modifier element (0.06% Sr for the AK9h alloy; 0.04% Ti for the AMg6l alloy) causes the manifestation of the effect of overmodification. This is expressed in the enlargement of the parameters of the micro- and macrostructure, as well as a decrease in the tensile strength. The results obtained show that the optimal amount of the proportion of deformed waste in the composition of the charge will make it possible in practice to reduce the consumption of expensive modifying ligatures with a guaranteed effect of modification.

The effect of iron and silicon impurities on the phase composition and properties of the Al–4.3Cu–2.2Yb quasi-binary alloy has been determined. In the microstructure of the cast alloy, in addition to the aluminum solid solution and dispersed eutectic ((Al) + Al₈Cu₄Yb), in which about 1% of iron is dissolved, the Al₃Yb/(Al,Cu)₁₇Yb₂ and Al₈₀Yb₅Cu₆Si₈ phases are identified, which are not found in an alloy of a similar composition without impurities. After homogenization annealing at a temperature of 590°C for 3 h, the structure is represented by compact fragmented and coagulated intermetallic compounds 1–2 μm in size and a solid solution (Al) with a maximum copper content of 2.1%. The hardness of the deformed sheets significantly decreases after 0.5 h and changes slightly up to 6 h of annealing at temperatures of 150–210°C. After annealing at 180°C for 3 h, a substructure with a subgrain size of 200–400 nm is formed in the alloy structure. The softening after annealing of the rolled sheets at temperatures up to 250°C occurs owing to the recovery and polygonization processes and above 300°C owing to recrystallization. After annealing for 1 h at 300°C, the recrystallized grain size is 7 μm. The grain size increases to 16 µm after annealing for 1 h at 550°C. The Al–4.3Cu–2.2Yb alloy with impurities has a conditional yield strength of 205–273 MPa, a tensile strength of 215–302 MPa, and a relative elongation of 2.3–5.6% in the rolled alloy after annealing. Iron and silicon impurities do not lead to the formation of coarse lamellar intermetallic phases and do not reduce the ductility of the investigated alloy.

The thiosulfate system for silver extraction has numerous characteristics such as high efficiency, low consumption, and environmental protection, and it has good application prospects. However, the high cost of metal recovery in thiosulfate systems limits its industrial application. A previous study indicated that Ag₂S/Ag nanocomposite clouds were precipitated from silver thiosulfate complex (AgTS) through ultraviolet photolysis, whereas the semiconductor-metal nanopowders synthesized through the hydrothermal synthesis process are usually important composites that can be used in photocatalysis, broad-spectrum antibacterial, and other environmental fields. Therefore, this study aims to develop high-value utilization of AgTS hydrometallurgical systems based on the photocatalytic properties of nanocomposites, and proposes research on the visible-light photocatalytic activity of Ag₂S/Ag photocatalytic systems precipitated from AgTS through ultraviolet photolysis. First, the morphology and optical properties of the Ag₂S/Ag nanocomposite were investigated. Next, the visible light photocatalytic activity of the Ag₂S/Ag nanocomposite was evaluated, and finally, the new high-value utilization research method of “ultraviolet absorption → ultraviolet photolysis → photocatalysis” was proposed. In this study, we demonstrate a novel method of high-value utilization of silver thiosulfate lixivium with a high photocatalytic efficiency of the Ag₂S/Ag nanocomposite of up to 47.98% after three cycles.

The features of the extraction technology for the separation of rare-earth elements (REEs) of the yttrium group are considered with regard to the sharp reduction in the price of individual oxides. The price reduction has the same nature as the low prices of lanthanum and cerium oxides and is associated with a predominant increase in the consumption of praseodymium and neodymium and a slow increase in the consumption of other REEs, with the exception of terbium and dysprosium. Since all REEs are extracted from rare-earth concentrates, less in demand ones are stored or sold at very low prices. Elements such as samarium, europium, gadolinium, and dysprosium are used in high-tech instruments and devices. In this case, it is possible to allow the operation of low-profit production, but technological solutions must certainly be built taking into account the minimum costs and be the most economically effective. The authors propose a technology for separating elements of the yttrium group including the stages of isolation of yttrium in a single-stage mode by extraction with a mixture of three extractants (25 vol % trialkylmethylammonium nitrate–20 vol % tributyl phosphate–20 vol % higher isomeric carboxylic acid), followed by separation of the triad of elements samarium–europium–gadolinium by extraction with organophosphoric acids (30 vol % solution of di-2-ethylhexylphosphoric acid or 30 vol % solution of bis(2,4,4-trimethylpentyl)-phosphinic acid). In the last operation, concentrates of the yttrium group REEs are isolated simultaneously. The process is carried out in the mode of complete internal irrigation using a 30 vol % solution of bis(2,4,4-trimethylpentyl)-phosphinic acid as an extractant. First, all cells of the cascade are filled with the initial solution. Separation zones are formed in the cells of the cascade with the accumulation of terbium–dysprosium, holmium–erbium, and thulium–ytterbium–lutetium concentrates. After the accumulation of products, the solution of concentrates is drained from the cells and the process starts again. If there is a need for any element of the yttrium group, the corresponding binary or ternary concentrate is separated to isolate the required element.