Vol 2016, No 3 (2016)

The results of kinetic studies on the removal of arsenic from scorodite using sulfidizing annealing are presented. The reaction order with respect to the reactant and the activation energy are established from the experimental data. The rate-determining step of the sulfidizing annealing process is determined. The main reactions that occur during the sulfidizing of arsenic in scorodite are proposed on the basis of the obtained results and confirmed by thermodynamic calculations and chemical analyses. The major results of testing this technology, as applied to the refractory oxidized ores in which arsenic is mainly concentrated in scorodite, are presented. Arsenic removal from this ore is confirmed by chemical and quantitative X-ray diffraction analyses and by qualitative phase analysis. Industrial use of this technology provides safe and efficient processing of refractory gold-containing ores, where arsenic is mainly concentrated in scorodite.

The structure and the mechanical properties of metastable austenitic steels after severe plastic deformation by four or six passes of equal-channel angular pressing (ECAP) at a temperature of 400°C are studied. It is shown that ECAP results in strain hardening mainly due to the formation of a submicrocrystalline structure, which is retained after subsequent heating to 500°C.

Transmission electron microscopy is used to study the formation of helium porosity in the nearsurface layer of ferritic–martensitic steels and vanadium irradiated by 40-keV He⁺ ions at a temperature of 923 K up to fluence of 5 × 10²⁰ He⁺/m² and, then, by 7.5-MeV Ni²⁺ ions at 923 K up to dose of 100 dpa. Large gas bubbles are found to form in the zone with the maximum concentration of radiation vacancies during He⁺ ion irradiation. Moreover, small bubbles form in some grains at the depths that are larger than the He+ ion range in the irradiated material. Sequential irradiation by He⁺ and Ni²⁺ ions leads to the nucleation of helium bubbles at still larger depths due to helium atom transport via recoil and/or ion mixing. The precipitation hardening of the steels by Y₂O₃ oxide nanoparticles is found to suppress helium swelling substantially.

The equation of coefficient of ultrasound absorption is substantiated in terms of classical and quantum theories. Polytherms for liquid gold, scandium, chromium, and rhenium in a wide temperature range have been obtained for the first time.

The Cu–Pb, Cu–Ga, Cu–Bi, Cu–Sn–In–Bi–Pb, and Cu–Sn–Ga–Bi–Pb melts of equiatomic compositions, i.e., high-entropy melts have been studied by the method of damped torsional vibrations of a crucible with a melt. The experiments are performed on heating with subsequent cooling of the samples in the maximum possible temperature range. The logarithmic decrement of the suspension system of the Shvidkovskii viscometer is measured. The results are used to determine the phase equilibrium temperatures.

The influence of intercrystalline internal yttrium or scandium adsorption on the internal friction of copper microalloyed by yttrium or scandium is studied. Grain-boundary and “impurity” grain-boundary internal friction peaks of relaxation nature are detected. The binding energies of yttrium and scandium atoms to grain boundaries in copper are estimated using the results of measuring the grain-boundary internal friction.

The phase compositions of solid Mg–Sm–Dy alloys corresponding to the magnesium-corner region of the phase diagram are studied by optical and scanning electron microscopy, electrical resistivity measurements, and electron microprobe analysis. The obtained results allowed us to determine the joint solubility of samarium and dysprosium in solid magnesium at 500, 400, and 300°C; it decreases with decreasing temperature. The magnesium solid solution is found to be in equilibrium only with the Mg₄₁Sm₅ and Mg₂₄Dy₅ compounds, which are in equilibrium with the magnesium solid solution in the binary Mg–Sm and Mg–Dy systems.

The process of coating of a steel wire with liquid copper at a high speed (>1 m/s) is considered. The results of long-term studies of copperizing under laboratory conditions and electron-microscopic investigation of the copper–steel adhesion are used to develop a mathematical model for coating of a steel wire with copper and to create a commercial setup to implement this process.