Vol 2018, No 7 (2018)

The recovery of cobalt, copper, zinc, and manganese ions from technical solutions by the modified natural zeolites of the Aidag deposit (Azerbaijan) is experimentally studied. The results obtained show that the zeolite modified with monoethanolamine can be used as an efficient sorbent for the recovery of Co²⁺, Cu²⁺, Zn²⁺, and Mn²⁺ ions from technical solutions. The adsorption ability of the metal ions depends strongly on the pH of the solution and the initial concentration of the metal ions. The order of selectivity of the metal ions on the zeolite modified with amines is as follows: Co²⁺ > Cu²⁺ > Zn²⁺ > Mn²⁺. The data on the adsorption of the studied systems are interpreted on the basis of the Langmuir and Freundlich isotherms. The results obtained show that the Langmuir regions are consistent with the experimental data.

The mechanical properties of as-cast Mg–Dy–Sm alloys additionally alloyed with zirconium to refine grains in the as-cast state have been studied. The dysprosium and samarium contents are close to their mutual solubility in a magnesium-based solid solution at a homogenization temperature of 515°C, and their total content is 4–12 wt %. The mechanical properties of the alloys have been determined in the states homogenized after casting and aged after homogenization. It is found that the strength properties of the alloys increase to σ_u ≈ 290 MPa and the plasticity decreases to lower values at a relative elongation δ ≈ 3% as the total content of the rare-earth metals in the alloy increases. The Mg–Dy–Sm–Zr alloys are significantly hardened upon aging, and the age hardening effect increases with the rare-earth metal content in them.

The influence of aerothermoacoustic treatment on the formation of the microstructure and the mechanical properties of cast aluminum alloys (silumins) is considered. The experimental data demonstrate that this treatment, which is included in the technological cycle of standard heat treatment or partly replacing it, increases the strength of the alloys by 35–40% at a retained or slightly decreased plasticity.

The influence of cobalt (5 and 16 at %) and chromium (4.25 at %) on the structure of a (β-NiAl + γ'-Ni₃Al + γ-Ni) alloy with 27 at % Al of the Ni–Al–Co system, which is chosen as the basis of alloys with given physicochemical properties, in particular, moderate density (≤7.2 g/cm³) and sufficient heat resistance at 1100–1300°C, is studied. A high stability of the high-temperature γ phase is found. It forms upon solidification according to the reaction L\( \rightleftarrows \) β + γ and is nonequilibrium at 1200 and 1300°C (below the temperatures of the transformations β + γ \( \rightleftarrows \) β + γ + γ' \( \rightleftarrows \) β + γ'). The volume fraction of the γ-Ni phase increases with the cobalt content or upon chromium addition in comparison with its fraction in the base alloy. The influence of alloying on the cobalt and chromium distribution in alloy phases is estimated. Additional alloying increases the differences in the phase compositions in cobalt and chromium.

Atomistic computer simulation is used to calculate the Gibbs energy at 300 K in the α and γ modifications of Nb₅Si₃, which are reinforcing phases in in situ composite materials based on the Nb–Si system. The calculations are carried out for boron and carbon atoms at interstitial sites. The calculated change in the Gibbs energy ΔG_300 K and crystal chemistry analysis are used to conclude about the referred localization and solubility of boron and carbon atoms in the structures of the α and γ modifications of Nb₅Si₃.

The relation between the physical parameters of nondestructive testing (coercive force, eddy current parameter, self-magnetic field, acoustic emission parameters) and the characteristics of real damage (relative damaged surface area, concentration criterion), which were estimated during the tension of grade 20 and 45 steel specimens with stress concentrators, is studied.