Том 57, № 3 (2016)

Balance calculations of multicomponent equilibrium compositions in the gas–liquid–solid system under oxidizing smelting of the copper-free copper-electrolyte slime, during which sulfur, selenium, and tellurium dioxides transfer into the gas phase, while compounds of lead, copper, antimony, iron, and aluminum are concentrated in the composition of the silicate slag, are performed with the help of the Outotec’s Chemical Reaction and Equilibrium Software HSC Chemistry program. It is established that, under optimal conditions of oxidizing smelting of the charge (100 kg) of the electrolyte slime (O₂ ≈ 0.9 kg, SiO₂ ≥ 6%, CaO ~ 3%, t = 1200°C), lead, antimony, and arsenic almost completely transfer into the silicate slag, while copper and silver (above 91%) transfer into the matte. Selenium is distributed between the gas phase (49.8%), matte (24.1%), and metallic phase (26.1%), while tellurium is distributed between sublimates (14.4%), silicate slag (8.4%), and matte (77.2%).

Today, nuclear energy is considered as one of the most important energy sources. Thorium (Th) is also very important for nuclear energy because it can exist in nature spontaneously just as uranium (U) without depending on presence of another radioactive element. As plutonium and other trans-uranium elements are produced in lesser amounts compared to U in Th fuel cycle, Th is considered as the cleanest nuclear plant fuel. Bastnasite is one of the minerals which Th can be economically obtained. Bastnasite (Ce, La)FCO3, which is a rare earth fluorocarbonate, contains approximately 0.2–0.3% Th and 75% rare earth oxides. Within the scope of this study, dissolution behaviour of Th and rare earth element (REE) contents present in the bastnasite ores which is obtained from Eskisehir region of Turkey, with HCl leaching method was examined. In this context, the effects of different leaching parameters such as leaching time, HCl concentration and pulp temperature on Th and REE (Ce, Nd, La) dissolution efficiency and the best results have been obtained in the conditions of 5.48 M of HCl dosage, 220 min. of leach time and 70°C pulp temperature. In these optimum conditions, Th, Ce, Nd and La were obtained with dissolution efficiencies of 80.12, 77.12, 70.12 and 71.13%, respectively.

Tin bronzes have found wide application in various branches of industry to fabricate parts operating under the friction conditions. For example, the distribution of the eutectoid component is regulated for bronze BrO10C2N3 when producing important parts. In this study, the influence of ingot casting and solidification conditions on the distribution and amount of eutectoid in the alloy structure is investigated. Several types of bronze casting into the water-cooled and uncooled mold, as well as when applying ultrasonic waves and without them, are tried out. These trials result in the development of casting tin bronze BrO10C2N3 into a combined casting mold situated in the ultrasonic field. The mold itself is a steel mold placed into a graphite filler with a heat-insulating insertion in the upper mold part. The results show that the application of a new technology make it possible to fabricate ingots in complete correspondence with requirements of the normative documentation and a high product yield over 70%.

Silicon brass of LTs16K4 grade has found wide application in art castings due to its high process properties, beautiful gold-yellow color, and the possibility of deposing various decorative coatings. In this study, the possibility of increasing its fluidity by varying the chemical composition in terms of GOST (State Standard) 17711-93 is investigated. To measure fluidity, the method of vacuum suction is used. This method reveals the change in this characteristic upon adding from 0.1 wt % alloying element (Zn, Si, Al) and shows a high convergence of results. The experimental data are subjected to regression analysis. The quantitative evaluation of the degree of influence of zinc and silicon on the fluidity of silicon brass is found and an adequate mathematical model and the response surface of the fluidity function are constructed. The optimal overheating temperature providing the maximal alloy fluidity upon minimal zinc loss is determined. The results of this study can be used when fabricating art and industrial castings of silicon brass LTs16K4, as well as in other branches of metallurgy and foundry production.

Pressing of preliminarily heated billets of aluminum alloys on hydraulic presses of the “heating–pressure treatment” industrial complex is investigated. The heating stage is implemented in a multisectional inductor providing the specified temperature drop over the billet length. To form the most favorable conditions of isothermal pressing, a special problem of the parametric optimization of pressing to the accuracy maximum of approaching the temperature in a matrix die to its maximally admissible value according to production requirements is formulated and solved. The temperature state of a billet after its loading into the press container is considered as a controlling effect at the pressing stage. To solve the problem, a special alternance method for the optimization of systems with the distributed parameters is used. This method is implemented based on the developed mathematical models of billet temperature fields at heating and pressing stages.

The microstructure of polycrystalline alloys of titanium with chromium (2, 4, and 5.5 wt %), cobalt (2 and 4 wt %), and copper (2 and 3 wt %) is investigated. Series of prolonged isothermal annealing of these materials are performed in a temperature range from 600 to 850°C (in vacuum). Annealing temperatures fall in two-phase regions α(Ti,Me) + β(Ti,Me) of phase diagrams Ti–Cr, Ti–Co, and Ti–Cu. Temperature dependences of the fraction of grain boundaries β(Ti,Me)/β(Ti,Me) completely “wetted” by interlayers of the second solid phase α(Ti,Me) and average contact angle are measured. The results of microstructural investigations showed that the type and concentration of the second component in the alloy strongly affect the formation of equilibrium grain-boundary interlayers. A nonmonotonic temperature dependence of the fraction of grain boundaries completely wetted by interlayers of the second solid phase in the absence of ferromagnet–paramagnet phase transformations in the volume is revealed for the first time.

Regularities of the dissolution, the phase formation, and the structure formation implemented under the contact interaction conditions of titanium carbide of various compositions with Ni and Ni–(5–25%)Mo melts are investigated. It is originally established that the dissolution of carbide TiC_x in nickel-based melts is incongruent. Preferentially, carbon transfers into the melt at x ≥ 0.9 and titanium at x ≤ 0.8. The limiting stage of the dissolution is diffusion of metal atoms in the liquid phase. The formation regularities of carbide Ti_1–nMo_nC_x (K-phase)—the main product of the contact interaction in the TiC/Ni–Mo system—are revealed. It is established that the K-phase is formed under the relative excess conditions of the Ni–Mo melt preferentially according to the dissolution–isolation mechanism. The composition of autonomous isolations of the K-phase depending on the experimental conditions (1450°C, 0–25 h) varies in limits from Ti_0.4Mo_0.6C_0.7 (a = 4.27 Å) to Ti_0.7Mo_0.3C_0.6 (a = 4.29 Å). It is determined by the molybdenum concentration in the melt at the unsteady dissolution stage and by the concentration ratio between titanium and carbon in it at the steady-state dissolution stage.

Experimental data on the influence of irradiation by high-current pulsed electron beams (HCPBs) on the physicochemical state of surface layers and operational properties of the blades of gas-turbine engines made of heat-resistant materials are analyzed. It is shown that the microsecond HCPB is a high-efficient tool for modifying the surface of turbine and compressor blades providing high-speed thermal treatment (quenching), material recrystallization in 20–30-μm-thick surface layers, and surface cleaning and smoothing. These processes determine the increase in the fatigue strength of blades (by 10–30%), heat resistance (by a factor of 2–4), and salt corrosion resistance (up to a factor of 6).

Titanium aluminides (TiAl₃, TiAl, Ti₃Al) fabricated by powder metallurgy were used as alloying electrodes for the formation of electric-spark coatings. Intermetallic coatings were deposited on steel substrates in argon or nitrogen. The microstructure and composition of fabricated coatings were investigated by scanning electron microscopy, X-ray structural analysis, and electron probe microanalysis. It is established that initial Ti–Al intermetallic phases are present in fabricated coatings; however, the ratio between Ti and Al concentrations is shifted to aluminum compared with the stoichiometric one. When depositing titanium aluminide in the nitrogen medium, titanium nitride is additionally formed in surface layers. Thermal and tribotechnical tests showed that the Ti₃Al coating deposited in nitrogen possesses high wear resistance and heat resistance.