Papers by Keyword: Alloy

Abstract: In the article, the authors examined the technological aspects of obtaining a functional alloy based on silver alloyed with chromium, zirconium, rhenium and rare earth elements (cerium, lanthanum, yttrium). A technology has been developed for producing powder from this alloy and nanostructured functional coatings based on it using the method of cold gas-dynamic spraying.

Abstract: The spheroidization mechanism from different initial microstructures during spheroidizing heat treatment was studied in Fe-0.68C-2.33Mn alloy. Two types of initial microstructures, i.e. pearlite and martensite, were obtained by varying the cooling rate. The microstructure and property evolution during spheroidizing annealing was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The DICTRA software, assuming local equilibrium conditions, was used to simulate the carburizing process of different initial microstructures through different cooling rate. The results indicate that the spheroidization mechanism of cementite was related to the initial microstructures and the smaller lamellar spacing of pearlite inhibited the coarsening of cementite, resulting in the size of cementite smaller than that of martensite as the initial structure.

Abstract: A method for the preparation and properties of an alloy based on nickel is discussed. An electrolyte for the deposition of a tin-nickel alloy has been developed. The influence of electrolysis regimes and electrolyte composition on the physical and mechanical properties (microhardness, spreading coefficient of solder, transient electrical resistance, coating ability to soldering, phase composition, porosity, adhesion, corrosion resistance) of an electrolytic coating based on nickel-tin alloy precipitated from a chloride electrolyte. The possibility of using a tin-nickel alloy as a solderable coating instead of gold and silver is shown.

Abstract: The paper gives an assessment of the possibility of using local mineral raw materials to create foundry alloys that are operated under natural low temperatures. The feasibility of using iron ores of the Lena ore field (Yakutia, North-East of Russia) for the development of new cold resistant and high strength steels is analyzed. The chemical composition and microstructure of the melted alloy were studied. Also the phase composition of the alloy by X-ray diffraction method is analyzed. The alloy with respect to the chemical composition is naturally doped Mn, W, V, which are well preserved in the preparation of the iron semi-finished product by direct reduction technology. The obtained sample after processing has acquired a uniform structure, typical for tool carbon steel after forging. Elemental analysis data indicate a uniform distribution of iron, carbon, manganese, sulfur and phosphorus in the alloy.

Abstract: Directional solidification is a paradigm process to gain the desired microstructure via certain applied solidification parameters. A thorough understanding of the diffusion-limited solid-liquid interface morphology evolution from initial transient to steady state is of uppermost importance to optimize the solidification processes. The rapid development of quantitative phase-field model provides a feasible computational tool to explore the underlying physics of the morphological transition at different stages. On basis of the diffusion-limited quantitative phase-field simulations using adaptive finite element method, the directional solidification of Al-4wt.%Cu alloy is characterized and both the solid interface propagation speed and solute profile are analyzed. The simulations are then compared with the in situ and real-time observation by means of synchrotron radiation x-ray radiography image. Good agreements are obtained between simulations and experimental data. Detailed mechanism that controls the morphological instability and transition are then addressed.

Abstract: The complex approach to the microstructure and microhardness parameter of BrOCS 5-5-5 changing dependences out of hardening degree are presented. The acquired results correlate with the earlier research, but give us new knowledge about the microstructure and microhardness parameter value changes depending of the deformation degree. That allows predetermining the accumulated deformation degree at bush type hardening process, for example – plain bearing liners or structural elements in the form of axial symmetry tybes. The prediction of the microstructure and mechanical parameters – microhardness parameter value in dependence of accumulated degree in particular becomes possible. The microstructure research carried out allows predetermining the necessary deformation degree for the studied material for its further application.

Abstract: The results of the course of martensite transformation in steel under the action of the magnetic field are presented. These results indicate that the formation of stress-assisted martensite in the temperature interval M_d-M_s (where superplasticity was observed) is possible. It was found that during hardening of steel products in magnetic field, martensite can be formed not only below M_s, but higher than this point (in the temperature range). The significant structural transformations and steel properties improvement under thermal treatment in a magnetic field depend on the catalytic effect of a field on the transformation development. This effect occurs when the initial phase is paramagnetic, and the product of the transformation is ferromagnetic. Stress-assisted martensite and cooling-induced martensite are formed in the superplastic temperature range of the austenite. This makes it possible for the undeformation hardening of steel products in a magnetic field. The undeformation hardening is caused by a magnetic field holding the product and the formation of martensitic structure oriented predominantly towards the magnetic field vector.

Abstract: In this paper weldability study of low-alloyed thermal resistant conductor alloys of Al-Cu-Mn and Al-Mg-Si alloying systems with different content of B, Sc, Fe, Zr and ability to resist corrosion in the welding area is presented. The effect of large intensive deformation in the welding area on the phase composition and the size of phases was determined.

Abstract: The structural, electronic, dynamical and thermodynamical properties of binary Zr-Al alloy (Zr₃Al) with its end members are studied using the first principles calculations based on density functional theory. We have employed the Perdew-Zunger local density approximation as the exchange correlational functional in these calculations. There is a good agreement between present and available and experimental and other theoretical data. The calculated electronic band structure and density of states suggest that the Zr-Al alloy and its end members are metallic in nature consistent with earlier studies. Full phonon dispersion curves and phonon density of states are also calculated which show the dynamical stability of these compounds at zero pressure. The temperature dependence of the thermodynamical functions are also presented.

Abstract: Hydrometallurgical routes of copper recovery from smelted low-grade e-waste are presented. Electronic scrap was smelted to produce Cu–Zn–Ag-Sn alloys of various phase compositions. The alloys were then treated in the following ways: (a) anodic dissolution with simultaneous metal electrodeposition using ammoniacal solutions with various ammonium salts (chloride, carbonate, sulfate). This resulted in the separation of metals, where lead, silver and tin accumulated mainly in the slimes, while copper was transferred to the slime, electrolyte and then recovered on the cathode. (b) leaching in ammoniacal solutions of various compositions and then copper electrowinning. Alloy was leached in chloride, carbonate, sulfate and thiosulfate baths. This resulted in the separation of the metals, wherein copper and zinc were transferred to the electrolyte, while metallic tin and silver as well as lead remained in the slimes. Copper was selectively recovered from the ammoniacal solutions by the electrolysis, leaving zinc ions in the electrolyte. The best conditions of the alloy treatment were obtained, where the final product was copper of high purity (99.9%) at the current efficiency of 60%. Thiosulfate solution was not applicable for the leaching of the copper alloy due to secondary reactions of the formation of copper(I) thiosulfate complexes and precipitation of copper(I) sulfide.