Vol 2017, No 11 (2017)

The structure and the properties of an Mg–Y–Nd–Zr alloy (WE43) are studied after high pressure torsion (HPT) in the temperature range 20–300°C. Structure refinement proceeds mainly by deformation twinning with the formation of a partial nanocrystalline structure with a grain size of 30–100 nm inside deformation twins. The WE43 alloy is shown to be aged during heating after HPT due to the decomposition of a magnesium solid solution. HPT at room temperature and subsequent aging causes maximum hardening. It is shown that HPT significantly accelerates the decomposition of a magnesium solid solution. HPT at all temperatures considerably increases the tensile strength and the yield strength upon tensile tests and significantly decreases plasticity. Subsequent aging additionally hardens the WE43 alloy. A potentiodynamic study shows that the corrosion resistance of this alloy after HPT increases. However, subsequent aging degrades the corrosion properties of the alloy.

The structural changes in the vanadium sample surface are studied as functions of the conditions of irradiation by pulsed high-temperature deuterium plasma and deuterium ion fluxes in the Plasma Focus installation. It is found that processes of partial evaporation, melting, and crystallization of the surface layer of vanadium samples take place in the plasma flux power density range q = 10⁸–10¹⁰ W/cm² and the ion flux density range q = 10¹⁰–10¹² W/cm². The surface relief is wavelike. There are microcracks, gas-filled bubbles (blisters), and traces of fracture on the surface. The blisters are failed in the solid state. The character of blister fracture is similar to that observed during usual ion irradiation in accelerators. The samples irradiated at relatively low power density (q = 10⁷–10⁸ W/cm²) demonstrate the ejection of microparticles (surface fragments) on the side facing plasma. This process is assumed to be due to the fact that the unloading wave formed in the sample–target volume reaches its irradiated surface. Under certain irradiation conditions (sample–anode distance, the number of plasma pulses), a block microstructure with block sizes of several tens of microns forms on the sample surfaces. This structure is likely to form via directional crack propagation upon cooling of a thin melted surface layer.

The surface tension and the density of the nickel melts with introduced ZrO₂ nanoparticles are studied by the sessile drop method using a digital camera and computer processing of images. The revealed differently directed effects of nanoparticles on the surface tension in the Ni–Sn and Ni–S systems points to a change in the structure of the melt–gas surface layer. The nanoparticles are shown to affect the adsorption of surfactants, and the surface layer is likely to consist of adsorbed Ni + (ZrO₂–surfactant) ensembles. The ZrO₂ content in a metal is determined using the technique of separate determination of the zirconium content dissolved in a metal and zirconium in the form of ZrO₂. It was found that, at 0.10 wt % ZrO₂ initially present in a metal, 0.021–0.031 wt % ZrO₂ are retained in samples; that is, about 70 rel % ZrO₂ are removed to the interface in the form of ensembles. Auger spectroscopy analysis of the Ni–Sn–ZrO₂ surface film detected 5–10 rel % Zr in the surface layer.

The electrochemical behavior of amorphous and nanocrystalline soft magnetic Fe₇₉P₁₃Si₅V₃ alloy in a 0.1 M Na₂SO₄ solution has been studied. Mössbauer studies show that the electrochemical characteristics of the alloy are comparable with those of an Finemet Fe₇₇Si₁₃B₇Nb_2.1Cu_0.9 alloy, whereas the studied alloy is inexpensive and can be prepared using natural alloy ferrophosphorus containing vanadium and silicon.

The effect of the initial structure of 38KhN3MFA steel on the mechanical properties of heattreated seamless pipes is studied. It is found that satisfactory macrostructure, strength, and plastic characteristics are insufficient to achieve the required set of service properties of the end product in the presence of a structural heterogeneity in tubular billets. A banded structure can cause a substantial scatter of the mechanical properties of the end product and a decrease in the impact toughness of the steel. It is shown that, in the presence of a banded structure, the required mechanical properties of the end product made of 38KhN3MFA steel can be achieved by correcting the final heat treatment conditions.

The factors that affect the relation between ultimate tensile strength σ_u and hardness HB of gray cast iron with flaked graphite are studied. The scatter of the ultimate tensile strengths at a given hardness is shown to be caused by one of the primary structure parameters, namely, the volume fraction of primary austenite dendritic crystals. The dependences derived in this work can be used to increase the accuracy of a rapid estimation of the quality of cast iron ingots.

For the first time, the electronic properties of liquid metals (charge carrier concentration, relaxation frequency, effective concentration of conduction electrons), including all groups of the periodic system (Na, Mg, La, Hf, Nb, Cr, Mn, Fe), have been studied in wide temperature range using acoustic data.