Modification of the structure of the hypereutectic silumin alloy Al-44Si under the action of compression plasma flows

Effects of the high-energy compression plasma flows on the structure, elemental composition, and phase state of Al-44 at.% Si hypereutectic silumin alloy have been investigated. Using scanning electron and optical microscopy it was found decreasing in grain size of both primary silicon particles and Al-Si eutectic parts with increase of absorbed energy density of compression plasma flows. The primary silicon crystals were dispersed down to 300 nm in the result of high cooling rate of the melted layer after its homogenization by means of hydrodynamic mixing. It was found that increase in the absorbed energy density, homogenization of elemental composition in the modifies layer occurs due to increase in lifetime of the melted state and more efficiency mixing process.

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Diagnosing collisions of magnetized, high energy density plasma flows using a combination of collective Thomson scattering, Faraday rotation, and interferometry (invited)

Review of Scientific Instruments ◽

10.1063/1.4890564 ◽

2014 ◽

Vol 85 (11) ◽

pp. 11E502 ◽

Cited By ~ 32

Author(s):

G. F. Swadling ◽

S. V. Lebedev ◽

G. N. Hall ◽

S. Patankar ◽

N. H. Stewart ◽

...

Keyword(s):

Energy Density ◽

Faraday Rotation ◽

Thomson Scattering ◽

High Energy ◽

High Energy Density ◽

Plasma Flows ◽

Collective Thomson Scattering ◽

Density Plasma

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Formation and Investigation of Plasma Powder Coatings Made of Oxide Ceramics Modified with High-Energy Effects

Science & Technique ◽

10.21122/2227-1031-2018-17-5-378-389 ◽

2018 ◽

Vol 17 (5) ◽

pp. 378-389 ◽

Cited By ~ 1

Author(s):

V. A. Okovity ◽

F. I. Panteleenko ◽

V. V. Okovity ◽

V. M. Astashinsky ◽

V. V. Uglov ◽

...

Keyword(s):

Surface Layer ◽

Zirconium Dioxide ◽

Composite Coatings ◽

High Energy ◽

Morphological Properties ◽

Multilayer Composite ◽

Plasma Flows ◽

Near Surface ◽

Compression Plasma Flows ◽

X Ray

The paper presents results of studying structure and properties of multilayer composite coatings optimized for their composition based on zirconium dioxide materials used for deposition of plasma coatings on the models of elements for anti-meteor shielding screens. The influence of plasma jet parameters (current, distance of sputtering, consumption of plasma-forming nitrogen gas) and fractional composition of an initial powder on characteristics of two-layer composite coatings based on nickel-chromium-aluminum-yttrium and zirconium dioxide on the elements of protective screens has been analyzed in the paper. Optimization has been carried out on the basis of obtaining maximum coefficient of powder utilization. The investigations have made it possible to ascertain specific features of elemental and phase composition, surface morphology, microstructure multilayer composite coatings on the basis of a solid layer of metal oxides and a viscous transition sub-layer subjected to compression plasma flows. The investigations have been executed with the help of scanning electron microscopy, energy dispersive x-ray spectral microanalysis, and x-ray diffraction analysis. It has been shown on the basis of the obtained results that the effect of compression plasma flows on multilayer composite coatings leads to a modification of a near-surface layer with a thickness up to 15 μm that presupposes its melting and subsequent high-speed crystallization which together provide an increase in its density, decrease in porosity while maintaining the initial phase state. Liquid-phase processes in the molten phase of the near-surface layer permit to modify morphological properties of the surface which are associated with its smoothing and lowering of roughness.

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MULTILAYER COMPOSITE PLASMA COATINGS ON SCREEN PROTECTION ELEMENTS BASED ON ZIRCONIUM DIOXIDE

Science & Technique ◽

10.21122/2227-1031-2017-16-5-422-431 ◽

2017 ◽

Vol 16 (5) ◽

pp. 422-431 ◽

Cited By ~ 2

Author(s):

V. A. Okovity ◽

F. I. Panteleenko ◽

V. V. Okovity ◽

V. V. Astashinsky ◽

P. P. Hramtsov ◽

...

Keyword(s):

Surface Layer ◽

Zirconium Oxide ◽

Zirconium Dioxide ◽

Fractional Composition ◽

Lattice Parameter ◽

Plasma Formation ◽

Plasma Flows ◽

Compression Plasma Flows ◽

Melted Layer ◽

Scanning Electron

The paper contains results of investigations pertaining to an influence of plasma jet parameters (current, spraying distance, consumption of plasma formation gas (nitrogen)), fractional composition of initial powder and degree of cooling with compressed air on anti-meteoric coating characteristics. Optimum modes (arc current 600 A; spray distance of 110 mm; consumption of plasma formation gas (nitrogen) – 50 l/min; fractional composition of zirconium dioxide powder <50 μm; compressed air consumption for cooling – 1 m3/min; p = 4 bar) make it possible to obtain anti-meteoric coatings based on zirconium dioxide with material utilization rate of 62 %, total ceramic layer porosity of 6 %. After exposure of compression plasma flows on a coating in the nitrogen atmosphere a cubic modification of zirconium oxide is considered as the main phase being present in the coating. The lattice parameter of cubic zirconium oxide modification is equal to 0.5174 nm. Taking into consideration usage of nitrogen as plasma formation substance its interaction with zirconium coating atoms occurs and zirconium nitride (ZrN) is formed with a cubic crystal lattice (lattice parameter 0.4580 nm). Melting of pre-surface layer takes place and a depth of the melted layer is about 8 μm according to the results of a scanning electron microscopy. Pre-surface layer being crystallized after exposure to compression plasma flows is characterized by a homogeneous distribution of ele-ments and absence of pores formed in the process of coating formation. The coating structure is represented by a set of lar- ge (5–7 μm) and small (1–2 μm) zirconium oxide particles sintered against each other. Melting of coating surface layer and speed crystallization occur after the impact of compression plasma flows on the formed coating. Cracking of the surface layer arises due to origination of internal mechanical stresses in the crystallized part. While using a scanning electron microscopy a detailed analysis of the surface structure has permitted to reveal a formation of a cellular structure with an average cell size of less than 1 μm in the crystallized portion and formation of the cells can be caused by speed crystallization of the melted layer.

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Structure and phase composition of hypereutectic silumin alloy Al – 20Si after compression plasma flows impact

Journal of the Belarusian State University. Physics ◽

10.33581/2520-2243-2021-2-25-33 ◽

2021 ◽

pp. 25-33

Author(s):

Vitali I. Shymanski ◽

Antons Jevdokimovs ◽

Nikolai N. Cherenda ◽

Valiantsin M. Astashynski ◽

Elizaveta A. Petrikova

Keyword(s):

Phase Composition ◽

Method Development ◽

Diffraction Method ◽

High Energy ◽

High Rate ◽

X Ray Diffraction ◽

Plasma Flows ◽

Silicon Phase ◽

Compression Plasma Flows ◽

Si Content

The results of structure and phase composition investigation in hypereutectic silumin alloy with 25 at. % Si content after high-energy pulsed compression plasma flows impact are presented in the work. The compression plasma flows impact with an absorbed energy density 25 – 40 J/cm2 allows to modify the sub-surface layer with a thickness up to 30 – 32 µm due to its melting and high rate solidification. By means of X-ray diffraction method, it was found the formation of two silicon phases with different grain sizes. The high-dispersed structure of silicon is presented in the Al-Si eutectic while the silicon phase with coarse grains exists in the primary crystals. The obtained results are the basis for a new method development for nanostructuring of the surface layers of hypereutectic silumin alloys increasing its wear resistance.

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Мechanochemically synthesized nickel-containing aluminosilicate modifiers for tribotechnical aluminum alloys

Physics and Chemistry of Materials Treatment ◽

10.30791/0015-3214-2021-4-50-57 ◽

2021 ◽

Vol 4 ◽

pp. 50-57

Author(s):

S. A. Kovaleva ◽

◽

T. F. Grigoreva ◽

P. A. Vitiaz ◽

V. I. Zhornik ◽

...

Keyword(s):

Mechanical Activation ◽

Structural Changes ◽

Primary Silicon ◽

High Energy ◽

Micro Hardness ◽

Composite Powders ◽

Oh Groups ◽

Silicon Crystals ◽

Nickel Composites ◽

Wear And Corrosion Resistance

Silumins are promising antifriction alloys for the manufacture of friction units. They have a low density, high wear and corrosion resistance. However, they own low hardness and strength, which leads to the need to develop modifying and strengthening additives. Aluminosilicates have a density close to silumin and can be used for its strengthening, but they are characterized by low wettability by metals. To improve wettability, it is necessary to modify the aluminosilicates with metals. The aim of this work is to study the mechanochemical synthesis of aluminosilicate/Nickel composites and modification of silumin using them. Structural changes in powder mixtures of natural aluminosilicates with Nickel during high-energy mechanical processing in a planetary ball mill, as well as in alloys of the composition silumin + potassium fluoroborate and silumin + potassium fluoroborate + aluminosilicate/Nickel obtained by hot pressing of mechanoactivated powders, were studied using Fourier-infrared spectroscopy and x-ray diffraction analysis. It is shown that mechanical activation of a mixture of silumin + potassium fluoroborate powders leads to a redistribution of silicon during sintering with the formation of large primary silicon crystals and a decrease in micro hardness by ~ 20 %. Mechanical activation of aluminosilicates with Nickel leads to the formation of composite powders with the removal of OH groups and the formation of SiO2 framework structures. The use of such a modifier during sintering of the silumin alloy leads to the formation of a homogeneous fine structure of the alloy with the grinding of eutectic and primary silicon grains, which increases the micro hardness of the alloy by 1.5 times.

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