Changes in structural and dynamic characteristics of metal melts, glasses and nanocrystals depending on temperature and hydrogenation

N. A. Vatolin, V. A. Polukhin, N. I. Sidorov

ABSTRACT

Researchers conducted a comprehensive analysis of both the original material and the available information on phase-structural transformations during cooling, glass transition and crystallization of melts, with detailed tracking of their ordering methods using synchrotron X-ray diffraction, scanning electron microscopy, DSC calorimetric measurements, and interpretation of data by modeling and thermodynamic by calculations.

KEYWORDS

melts, amorphous alloys, vitrification, X-ray diffraction, DSC calorimetry, medium order, structural factor, heat capacity, hidden liquid transitions, viscosity, diffusion, crossover

DOI: 10.1134/S0235010619040121

Relaxation time to the steady-state growth of secondary dendritic branches

E. A. Titova, D. V. Alexandrov, P. K. Galenko

ABSTRACT

In this paper, the expression for the time of reaching the stationary mode of growth of secondary branches of dendritic crystals is theoretically determined. The dependences of the time of transition to the stationary mode on the Peclet growth number and the tip growth rate for nickel and succinonitrile dendrites are plotted. It was shown that during high-speed crystallization, the secondary branches of dendrites enter the steady-state growth mode faster than in the case of low-speed crystallization. The growth of the secondary branches of dendrites can almost always be considered stationary in cases of low-speed, moderate and high-speed crystallization.

KEYWORDS:

phase transformations, dendrites, supercooled melt

DOI: 10.1134/S0235010619020051

Bond energies in the molten M–Al–Zr–O–F systems (M = Li, Na, K)

A. S. Vorobiov, A. V. Suzdaltsev, A. E. Galashev

ABSTRACT

The bond energies in complex anions formed from the components Al–F, Zr–F, Al–OF, and Zr–OF were calculated in Siesta program using first-principle molecular dynamics. These anions are formed at the dissolution of ZrO2 and Al2O3 oxides in fluoride MFEAlF3 melts (where M = Li, Na, K). An influence of anions composition as well as the cation nature in the second coordination sphere on the bond energies in the anions was determined. It was shown that the Al O F2 and Zr O F2 anions are most stable among analyzed oxygen-containing anions. At the same time anions formed by zirconium have the lowest bond energies. Replacement of the cation in the second coordination sphere of the M2Al2O2F6 and M2Zr2O2F6 anions in the range from K to Li leads to a decrease in the bond energy.

KEYWORDS:

oxide-fluoride melt, anions, zirconium, aluminum, molecular dynamics simulation, bond energy, stability

DOI: 10.1134/S0235010619020063

Thermodynamics of rare earth chlorides in LiCl–KCl–CsCl eutectic based melts

E. A. Kharina, R. Yu. Kaychenkova, A. S. Dedyukhin,

A. V. Shchetinskiy, L. F. Yamshchikov, V. A. Volkovich

ABSTRACT

In this paper, the temperature dependences of formal standard potentials of some rare earth metals such as lanthanum, neodymium, praseodymium, gadolinium, holmium and erbium and the thermodynamic characteristics of the formation of their chlorides in molten eutectic mixture of lithium, potassium and cesium chlorides were calculated using the experimental data on determination of their equilibrium potentials.

KEYWORDS:

rare earth metals, melts, chlorides, quasi-standard potentiafls, emf method

DOI: 10.1134/S0235010619010079

Research of properties of oxide melts in model experiment

I. A. Babina, A. O. Babin

ABSTRACT

It is shown that the relative number of bridging oxygen atoms in the linkages Si–O–Si with linear decreases in the cases of all modifiers, the rapidity of the decline of the modifiers are arranged in order of MgO, Na2O, Li2O, CaO.

KEYWORDS:

melt, modifier, complexes

DOI: 10.1134/S0235010619010043

Computer simulation of multicomponent melts of metallurgical slags

E. V. Dyul’dina, B. R. Gelchinski, V. N. Selivanov

ABSTRACT

Based on the experimental data on the density, the molecular dynamics simulation of multicomponent oxide-fluoride metallurgical slag-forming systems: SiO2–CaO–Al2O3–MgO–CaF2–Na2O–K2O–FeO was carried out for the first time in the approximation of the ionic bond model. The results were discussed and compared with literary experimental and calculated data. The obtained model indicates a weak temperature dependence of the structure of the melt. An increased diffusion mobility of fluorine ions as well as ions of alkali metals in comparison with other elements has been revealed.

KEYWORDS

melt, metallurgical slag, computer simulation, structure, properties

DOI: 10.1134/S0235010618050055

Model investigation of liquid interaction metal and dispersed steel inclusions in castingon gasificable models

B. S. Vorontsov, N. V. Nesterov

ABSTRACT

A mathematical model for the interaction of liquid metal with metallic inclusions embedded in the foam polystyrene, reflecting the filling of molds, the effect of thermal decomposition of expanded polystyrene and heat exchange of the base alloy and filler material, is developed. The resulted results of the experiment on obtaining prototypes by casting on gasified models, confirming the predictions of mathematical modeling.

KEYWORDS

mathematical model, interaction of metal particles with melt, local alloying, casting for gasified models, composite materials

DOI: 10.1134/S0235010618050158

Corrosion of various types of stainless steels in chloraluminate melts

V. V. Karpov, A. V. Abramov, K. V. Dedov, A. V. Shak, A. Yu. Zhlyakov,

I. B. Polovov, S. V. Belikov, O. I. Rebrin

ABSTRACT

In the present work the corrosion behavior of 08Kh17T (analogue of AISI 439) ferritic steel, 12Kh13 (analogue of AISI 410) and 16Kh12MVSFBR ferritic-martensitic steels, and AISI 316L (analogue of 03Kh16N15M3), 12Kh18N10T (analogue of AISI 321) and 06KhN28MDT austenitic alloys was studied at 550°C in fused KCl–AlCl3 mixture with the initial AlCl3EtoEKCl ratio of 1.1. The corrosion rates of the studied materials in the KCl–AlCl3 were determined. The corrosion processes in all the studied iron-based steels were caused by the red-ox reactions resulting in dissolution of the most electronegative alloy components (Cr, Fe and Mn), that indicate the electrochemical nature of corrosion phenomena.

KEYWORDS

corrosion, stainless steel, chloraluminate melts, intergranular corrosion, molten salt reactor

DOI: 10.7868/S0235010619010067

Thermodynamic parameters anomalies of the heterogeneous system Li2CO3–Na2CO3–K2CO3–nanopowder MgO

I. D. Zakiryanova, I. V. Korzun

ABSTRACT

The method of the differential scanning calorimetry (DSC) has received data on thermodynamic parameters of the heterogeneous system Li2CO3–Na2CO3–K2CO3–nanopowder MgO. Abnormal reduction of temperature and the relative enthalpy of melting of a salt phase at increase in contents in a magnesium oxide composite is established.

KEYWORDS

heterogeneous systems, nanopowder MgO, carbonates of alkaline metals, composite

DOI: 10.7868/S0235010619010249

On the separation of uranium and zirconium: electrochemical properties of zirconium in 3LiCl–2KCl melt

D. S. Maltsev, V. A. Volkovich, E. V. Raguzina, K. E. Strepetov, A. A. Kozlova, M. N. Soldatova

ABSTRACT

Electrochemical properties of zirconium in lithium and potassium chlorides eutectic melt was studied employing solid (tungsten) and liquid (gallium, indium, zinc) cathodes in temperature range 550–750°С.

KEYWORDS

uranium, zirconium, separation, cyclic voltammetry, chloride melts, deposition potentials

DOI: 10.7868/S0235010619010109