O. A. Chikova

Structure and nanomechanical characteristics of Al–Cu–Mg–Si alloy with partly liquated grain boundaries upon heat treatment

The microstructure, phase composition, and mechanical characteristics of the structural constituents of an Al–Cu–Mg–Si alloy in which the liquation of grain boundaries occurred during heat treatment have been studied. Bands of the (Al + Al15(Fe, Mn)3Si2) eutectics have been observed at the grain boundaries. An algorithm for calculating the additional pressure, which results from mechanical impact on the metal containing these bands has been described.

Microheterogeneity Domains in Cu—Pb Melts

The kinematic viscosites of chemically heterogeneous Cu—Pb melts were studied in to determine the temperature and concentration limits of the domains of their existence. Experiments are performed by heating and cooling samples in the temperature interval of 1050–1200°C. A quasi-chemical approximation of the irregular solution theory is used to consider the heterogeneous distribution of Cu and Pb atoms, and the short-range order parameter and characteristic enthalpy of mixing are estimated.

Relation between the Crystal Structure of 35KhGF Steel and the Viscous Flow Characteristics of the Forming Melt

The effect of the crystal structure of 35KhGF steel on the temperature dependence of the kinematic viscosity of the melt has been studied at temperatures of 1450–1780°C. The crystal structure of 35KhGF steel changes as a result of heat treatment, namely, normalizing and tempering. EBSD analysis is used to study the crystal structure of the steel. The kinematic viscosity of the liquid steel is measured by the oscillating crucible method during heating and subsequent cooling. The supercooling of the liquid metal before solidification and the activation energy of viscous flow are dependent on the heat-treatment conditions. This correlation is discussed in terms of metallurgical inheritance.

Structure and Nanomechanical Properties of the Al–Si–Fe Alloy Produced by Blowing the Melt with Oxygen

Abstract —The microstructure and nanomechanical properties of the Al–7% Si–1% Fe as-cast alloy produced by blowing oxygen into the melt have been studied. Blowing oxygen into liquid aluminum alloy results in the formation of Al2O3 nanoparticles, which increase the strength of the alloy after subsequent cooling and crystallization. Scanning electron and atomic force microscopy (EDS and EBSD analyses) have been used to examine the microstructure of the Al–7% Si–1% Fe alloy. The nanohardness and Young’s modulus of α-Al in microvolumes are measured using nanoindentation. Blowing oxygen into the melt has been found to significantly decrease the random scatter of Young’s modulus of α-Al. The results have been considered through the lens of modern knowledge of how composite materials of the aluminum matrix are strengthened.

Viscosity of liquid Cu–Sn alloys

ABSTRACT We investigated of the kinematic viscosity of liquid Cu–Sn alloys upon heating and subsequent cooling by the method of the oscillating cylinder. For the liquids alloys Cu75Sn25, Cu50Sn50, Cu48Sn52, Cu32Sn68, and Cu17Sn83, the temperature dependencies of the viscosity upon heating deviate from the Arrhenius relation. The temperature dependencies of viscosity show the Arrhenius-like behaviour upon cooling for all investigated alloys. A discrepancy between the temperature dependencies of viscosity obtained upon heating and cooling arised. We built the concentration dependences of the kinematic viscosity of liquid Cu–Sn alloys upon cooling. The increase of the values of viscosity and activation energy of viscous flow in the concentration range corresponding to the existence of intermetallic compounds Cu3Sn in the solid state was observed. These results were qualitatively interpreted using the concept of microheterogeneities of liquid alloys.

Microstructure and Mechanical Properties of Objects Prepared by Selective Laser Melting of AKD12 Powder

The morphology and elemental composition of Al–12% Si powder grade AKD12 of three fractions are studied. Powder is prepared in an original molten metal gas spraying unit UR-9 in a high-purity nitrogen atmosphere. Results are provided for measurement of mechanical properties, a study of outer surface morphology and the failure surface of objects prepared by selective laser melting from AKD12 powder fraction less than 45 μm. It is shown that the mechanical properties of these objects surpass these indices for analogs produced overseas, i.e., ultimate strength σu = 245 MPa with relative elongation δ = 12%.

Measurement of the electrical resistivity of liquid 32G2 and 32G1 steels by the rotating magnetic field method

The resistivity of liquid 32G2 and 32G1 steels are measured using the rotating magnetic field method to obtain information on their liquid structures. The technique of measurements is described and the influence of self-induction and viscosity on the resistivity is estimated. The results are discussed in the framework of a microheterogeneous structure of a metallic melt. A conclusion is made about the character of the influence of slag inclusions detected by magnetic powder and ultrasonic methods on the temperature dependences of the resistivities of liquid 32G2 and 32G1 steels. The change in the temperature coefficient of the resistivity of the melt on heating to 1700°C is interpreted using the Nagel–Tauc model.

Viscosity of the liquid Al–6Mg–1Mn–0.2Sc–0.1Zr alloy

The microstructure and the phase composition of as-cast Al–Mg–Mn–Sc–Zr alloy samples are studied by electron microscopy and electron-probe microanalysis. The processes of solidification and melting of this alloy are described. The temperature dependence of the kinematic viscosity of the Al–Mg–Mn–Sc–Zr melts is studied during heating and subsequent cooling of the samples. The measurement results are used to determine the temperature at which inherited microheterogeneities in the melts are destroyed irreversibly.

Effect of slag inclusions on the density and the surface tension of liquid 32G2 and 32G1 steels

The density and the surface tension of liquid 32G2 and 32G1 steels are experimentally studied. Samples are cut from oil-and-gas pipes having different degrees of imperfection. The experimental results are used to find the effect of the defects detected by magnetic-powder and ultrasonic inspection methods on the temperature dependences of the density and the surface tension of liquid 32G2 and 32G1 steels. The results obtained are interpreted in terms of the concepts of a microheterogeneous structure of metallic melts. Microheterogeneities are irreversibly destroyed when the liquid 32G2 steel is heated to 1700°C and the 32G1 steel, to 1750°C.

Estimating the parameters of the microheterogeneous structure of metal melts according to viscometric experimental data in terms of the absolute reaction rate theory

The temperature dependences of the viscosity of microheterogeneous metal melts are analyzed in terms of the Frenkel–Eyring theory. Using viscometric experimental data, the sizes of dispersed particles in metal melts whose components undergo eutectic and monotectic interactions are numerically estimated.