Vol 2016, No 1 (2016)

An addition of the polydisperse Yakovlevo deposit sintering ore on the efficiency of pelletizing and, hence, the gas permeability of a sintering mixture containing fine concentrates is studied. This sintering ore is found to have unique properties, which make it possible to increase the iron content in a sinter and to improve the gas permeability of a sintering mixture significantly (by a factor of 2–4). As a result, the sintering machine capacity can be substantially increased, the strength of the sinter can be increased at a lower fuel flow rate and lower lime consumption, and the blast furnace capacity can be substantially improved at lower consumption of expensive coke. Therefore, this version of using the Yakovlevo deposit sintering ore has a high economic efficiency.

The macrokinetic regularities of the reactivity of synthesized Ni–Re (20 and 60 wt %) alloys in a sulfuric acid solution (100 g/L, 25–40°C) during direct current polarization are studied using physicochemical methods. The phase composition of the synthesized alloys is determined by the formation of solid solutions as a function of the initial Ni/Re weight ratio. These are two types of nickel solid solutions (Ni₁₆Re_0.2 and Ni₁₄Re_0.9) and one rhenium solution (Ni_1.1Re). These solid solutions are anodically oxidized in the sequence of their structural rearrangement Ni₁₆Re_0.2 → Ni₁₄Re_0.9 → Ni_1.1Re with a combined transition of the metals into an electrolyte solution. These solid solutions provide the reduction of Ni³⁺ to Ni²⁺ due to the depolarization ability of rhenium, being their component.

The deformation and fracture localization characteristics are estimated by the methods of replicas, acoustic emission, metal magnetic memory, ultrasonic attenuation, microhardness, and electrical resistance. The relation between the estimated physical parameters on the one hand and the plastic zone size and the microcrack concentration in this zone, on the other, is considered.

The effect of the vacancy migration energy in austenitic steels on their resistance to irradiation-induced swelling is studied. ChS68 and EK164 steels, whose energies of vacancy migration differ by 0.1 eV from each other, are used to show that the steady-state vacancy concentration in the EK164 steel is less than that in the ChS68 steel. This difference explains why the critical pore nucleus diameter (after which pore grows owing to an unbalanced vacancy flow) in the EK164 steel is larger than that in the ChS68 steel. As compared to the ChS68 steel, a larger number of helium atoms and, correspondingly, a longer incubation swelling time are required for such a pore nucleus to form in the EK164 steel.

The structure of the surface layer in high-nitrogen 05Kh22AG15N8M2F steel workpieces subjected to face turning is studied by electron microscopy. It is found that improved machinability by VK8 alloy cutting tools is achieved at a cutting depth of 0.25 mm and that the cutting-tool life decreases sharply when the cutting depth increases to 1 mm. A nanocrystalline structure with nanocrystal sizes from several to several tens of nanometers forms in the surface layer upon face turning in the as-cast, hot-rolled, and thermally deformed states. The structure of the surface layer is characterized by a high dislocation density and large austenite fragments with broad subgrains and deformation twins.

A in-situ composite Nb–Si–Ti–Hf–Cr–Mo–Al composite material alloyed with yttrium and zirconium is studied. The evolution of the structure–phase state of the alloy during oxidation under dynamic and isothermal conditions is considered on samples prepared by vacuum remelting and directional solidification. The phase composition and the microstructure of the alloy are examined by the methods of physico-chemical analysis, and the distribution of alloying elements in initial samples and the products of oxidation is estimated. Thermogravimetric experiments are performed on powders and compacted samples during continuous (in the range 25–1400°C) and isothermal (at 900 and 1100°C) heating in air. The directional solidification of an Nb–Si–Ti–Al–Hf–Cr–Mo–Zr–Y is found to cause the formation of an ultradispersed eutectic consisting of α-Nb_ss and γ-Nb₅Si_3ss cells. The as-cast sample prepared by vacuum remelting has a dendritic structure and contains Nb₃Si apart from these phases. Oxidation leads to the formation of a double oxide layer and an inner oxidation zone, which retain the two-phase microstructure and the ratio of alloying elements that are characteristic of the initial alloy. Diffusion redistribution is only detected for molybdenum. The cyclicity of heating at the initial stage of oxidation weakly influences the oxidation resistance of the alloy.

The assimilation of a number of rare-earth metals (REM = praseodymium, neodymium, erbium) in a cast high-temperature nickel aluminide–based intermetallic alloy and the effect of REM alloying of the alloy on the critical temperatures, the high-temperature strength, and the heat resistance (time to failure) of the structural alloy are studied. It is shown that the heat resistance and the time to failure of the alloy at 1200°C can be increased by microalloying of the intermetallic alloy with REM.