Vol 2019, No 1 (2019)

The bloomery reduction roasting of oxidized magnesia nickel ores with flux additions, which is intended to manufacture ferronickel, is studied. The influence of the charge composition, the roasting temperature, and the iron content in slag on the technological properties of slag and the coarsening of metallic particles with the formation of ferronickel balls is investigated. The challenging problems related to the characteristic features of bloomery process, in particular, the formation of slag skull in the temperature range 1000–1250°C during reduction roasting in a rotary kiln, and approaches to their elimination are discussed in detail.

Thermodynamic calculations are used to study the phase compositions of Al–Si–X and Al–Cu–X alloys, where X is a low-melting metal (Sn, Pb, Bi, Cd, In). Poly- and isothermal sections are used to determine the temperatures of invariant monotectic reactions. The formation of globular low-melting phase inclusions in heating at 500°C is found by experimental techniques.

A rapidly quenched intermetallic VTI-4 titanium alloy, which is based on the orthorhombic Ti₂AlNb phase and is formed by extraction from a molten hanging drop, has been hydrogenated. The phase composition and the microhardness of the alloy saturated to various hydrogen contents are studied. To study the opportunities of producing a fine alloy powder, fibers are ground in a ball mill. The alloy in the rapidly quenched β single-phase state is found to exhibit a high plasticity and is not fragmented upon ball milling, and sharp fiber embrittlement is observed as the alloy is saturated to a high hydrogen content (0.88 wt %). In this hydrogenated state, the alloy has a high hardness and its phase composition consists of the hydrogen-rich Ti₂AlNb phase.

The steel 316L plates formed by selective laser melting of a powder are found to have a sharp texture, which is close to the {001}\(\left\langle {100} \right\rangle \) cube texture, and the texture intensity and the deflection of texture from external plate directions change across the plate width differently in plates of different thicknesses. The mechanical properties determined by nanoindentation are also nonuniform over the plate width. The nonuniformity of texture and microhardness is assumed to be related to the changes in the plate growth conditions in printing, such as the heating and cooling rates, the direction of laser beam action, the heat removal direction in plates of different thicknesses, and the shape of the molten pool. The crystallographic texture is shown to be a sensitive indicator of all plate growth processes; therefore, it can be used to optimize the parameters that determine the properties of the plates.

The structure of “thick” (up to 100 μm) condensed ion-plasma multicomponent coatings deposited from a two-phase vacuum-arc metallic plasma flow containing “liquid” and “solid” microdroplets of an evaporated material has been studied. The structure of the coatings is shown to be dependent on the operating conditions of the vacuum-arc evaporator cathode (radiative or forced cathode cooling), the evaporator current, the bias voltage, and the substrate temperature. The existence of solid microdroplets of the evaporated material in a plasma flow leads to the formation of growth defects in the condensate and, hence, open microporosity in the coatings. A number of techniques, which enable a significant decrease in the microporosity of the ion-plasma coatings, have been proposed.

The chemical compositions of the films on the nickel surface are examined by X-ray photoelectron spectroscopy during direct current polarization in aqueous and acidic electrolytes, which determine the mechanism of nickel electrode passivation.

The laws of changing the presolidification supercooling of bismuth drops during continuous thermal cycling were studied by thermal analysis in the temperature–time coordinates. A sawtooth cyclic dependence of the supercooling on the sequence of heating and cooling cycles, which is described by a Fourier function, is detected. An expression is derived for the energy of coagulation of nuclei, and it is used to find a relation between the experimental and calculated supercoolings. The obtained results are interpreted in terms of a cluster-coagulation solidification model and the anomalous properties of bismuth in melting and solidification.