Vol 2018, No 3 (2018)

The damping capacity of a VT6 titanium alloy sample is shown to depend on the thickness of a new designed Al–Ni–Y alloy coating during vibrodynamic tests at the first flexural mode resonance frequency. The coating 20–100 μm thick is found to decrease the vibrostresses in the weakest section of the sample by 9–31% at a temperature of 20°C and by 40.6% at a temperature of 400°C and a coating thickness of 60 μm. The dependences of the damping capacity of the alloy–coating composition on high-temperature holding of coated samples in an atmospheric furnace (t = 400°C, τ = 500 h), the salt fog chamber conditions (t = 35°C, τ = 3 months), and the action of an abrasive flux (quartz sand, average particle fraction of 400 μm, particle velocity of 100 m/s) are studied.

The effect of annealing of a (Pr_0.41Ce_0.12Dy_0.47)_13.46(Fe_0.64Co_0.36)_80.3B_6.24 alloy at 1000°C on its microstructure and the properties of sintered magnets made of it has been studied. In the annealed state, the composition of the main magnetic phase (Pr,Dy)₂(Fe,Co)₁₄B changes sharply (dysprosium content changes), the residual induction of the sintered magnets made of the annealed alloy increases by 6%, and the coercive force determined from magnetization increases by 8.5%. The volume content of the main magnetic phase R₂(Fe,Co)₁₄B in sintered magnets (Nb,Dy)–(Fe,Co)–B and (Pr,Dy)–(Fe,Co)–B is found. The content of this phase in neodymium-based magnets is approximately half as much.

A setup is created to determine the main thermotechnical characteristics of copper alloys. At temperatures below 400°C, Cu–Fe alloys are found to have the thermal conductivity and the thermal diffusivity that are lower than those of pure copper by a factor of 1.5–2.0. As the temperature increases, these parameters become close to those of pure copper. The wall of a mold made of a copper alloy with 0.17–0.23 wt % iron has a satisfactory thermal conductivity upon heating to 250–300°C.

The effect of powerful pulsed fluxes of nitrogen plasma and nitrogen ions generated in the PF-4 Plasma Focus setup (LPI; energy flux density of plasma pulse was 10⁸–10¹⁰ W/cm²) on the modification of vanadium surface is studied. Melting and ultrafast solidification result in a fine cellular structure (cell size of 100–200 nm) in a thin surface layer in samples. There are irradiation regimes causing directional crack growth after solidification and cooling of the surface layer and the formation of a block microstructure with a block size of several tens of micrometers. The thickness of the melted layer in the samples is 2–4 μm. Cracks propagate to a depth of 5–20 μm. It is established that irradiation by pulsed nitrogen plasma and high-energy nitrogen ions changes the microhardness of the vanadium surface layers. The microhardness increases by a factor of three with the number of plasma pulses and the distance between a sample and the anode of the Plasma Focus (PF) setup. The increase in the microhardness is in agreement with the refinement of coherent scattering regions, the increase in lattice microstrain ε, and the formation of vanadium nitrides. Pulsed fluxes of nitrogen plasma and nitrogen ions decrease the lattice parameter much greater than cold working (rolling) does. The lattice parameter decreases when the total irradiation power is increased (the number of pulses increases or the distance between a sample and the anode of the PF setup decreases). Such changes seem to be caused by the action of the residual macrostresses induced by pulsed plasma irradiation. In addition, X-ray diffraction analysis showed a change in the texture of the surface layer after ion-plasma treatment of coldworked vanadium samples in the PF setup.

The laws of direct iron reduction by solid carbon are revealed. They open up fresh opportunities for the development of high-tech processes and the manufacture of high-purity and high-quality metal products at a substantial decrease in the gas yield and gas release to atmosphere. The existing (traditional and new) metallurgical technologies are based on the use of hot reducing gases (HRGs) according to the generally accepted scientific basis of an autocatalytic-adsorption mechanism. The use of the HRG potential at a level of 0.4–0.42 corresponds to HRG consumption of 2500–3000 m³/t per unit metal. The gas release to atmosphere is significant for such high HRG consumption, which complicates the worldwide ecological problem.