V. S. Tsepelev

Hysteresis properties of the amorphous high permeability Co66Fe3Cr3Si15B13 alloy

The scaling law of minor loops was studied on an amorphous alloy Co66Fe3Cr3Si15B13 with a very high initial permeability (more than 150000) and low coercivity (about 0.1 A/m). An analytical expression for the coercive force in the Rayleigh region was derived. The coercive force is connected with the maximal magnetic field Hmax via the reversibility coefficient μi/ηHmax. Reversibility coefficient shows the relationship between reversible and irreversible magnetization processes. A universal dependence of magnetic losses for hysteresis Wh on the remanence Br with a power factor of 1.35 is confirmed for a wide range of magnetic fields strengths.

Viscosity of high-entropy melts in Cu-Sn-Pb-Bi-Ga, G-Sn, Cu-Pb, Cu-Ga, and Cu-Bi equiatomic compositions

Temperature dependences of kinematic viscosity of high-entropy melts (HEM) of the composition, at %, Cu-20Sn-20Pb-20Bi-20Ga, Cu-50Sn, Cu-50Pb, Cu-50Ga, and Cu-50Bi are investigated in a temperature range from 1550 to 1300°C. It is shown that melt overheating above a definite temperature (thom) leads to the appearance of viscosity hysteresis, which indicates a variation in the structural state of the HEM. The values of thom for all studied samples are in limits of 925–1185°C. It is found that heating the HEM to definite temperatures (t*) leads to a variation in the activation energy of viscous flow (E) and entropy multiplier (A) in the Arrhenius equation: ν = Aexp[E/(RT)]. Entropy of viscous flow (ΔS#) for studied HEMs is investigated in terms of the Airing theory. It is revealed that the magnitude of ΔS# for a five-component Cu-Sn-Pb-Bi-Ga melt in a cooling mode is smaller than during heating by a factor of 2.6. The rheological characteristics of HEMs allow us to consider these melts promising functional materials: solders, heat carriers, and electric contacts.

Fast viscosity determination for high-temperature metal alloys

Methods for fast determination of the kinematic viscosity of high-temperature metallic melts are considered. The experiments may be standardized, simplified, and shortened, by using the parameters of two points on the oscillatory damping trajectory that differ by a factor e and also by means of bipolar synchronized torsion of a melt-filled crucible suspended on an elastic fiber. By measuring the parameters of metallic liquids, materials may be analyzed, and recommendations may be made for the production of alloys with specified characteristics. The feasibility of fast measurements with accuracy acceptable for most cases is analyzed. The potential for reducing the length of experiments, standardizing experiments, and reducing the subjective influence of the researcher is considered. Bidirectional torsion reduces the time for a single measurement cycle by a factor of 1.5 and reduces the total torsional time by a factor of 4. The accuracy of the proposed approach is acceptable.

Improvement of Low-Alloy Steel Quality by Forming an Equilibrium Melt Condition

A melt’s condition before solidification is important for improving low-alloy steel metal product quality. It depends on melting method, form or type of charge materials used, melting temperature and time parameters, mixing intensity during extra-furnace treatment, and other production methods. Improvement of the level of molten steel’s physical properties as a result of some action points to the formation of more equilibrium and homogeneous melt condition, and this has a marked effect on metal product structure, properties, and quality.

Influence of defects on the ductility of liquid 9X2MΦ and 75X3MΦ steel

Viscosimetric data on liquid 9X2MΦ and 75X3MΦ steel taken from working rollers of a reversible rolling mill with different ultrasonic behavior illustrate the influence of defects recorded in ultrasound monitoring on the temperature and time dependence of the liquid steel’s kinematic viscosity. A Krautkremer ultrasonic defectoscope is employed in monitoring. The viscosity of the liquid steel is measured by means of damping torsional oscillations of a crucible with melt in heating and subsequent cooling in the range 1500–1580°C.

Nanocrystalline Soft Magnetic Toroidal Cores of the Highest Relative Magnetic Permeability and Low Coercive Force

All the technologies of the melt quenching preparation ensure its time-temperature treatment to not only improve but also stabilize the metal structure and properties with every melt. The influence of annealing temperature of nanocrystalline alloy Fe72.5Cu1Nb2Mo1.5Si14B9 on the structure and magnetic properties has been investigated. The relation between numerical values of the coercive force, the initial magnetic permeability and the magnetic hysteresis loop rectangularity factor allows optimizing a mode of nanocrystalline alloy heat treatment.

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.

Similarity of Hysteresis Quantities

Based on the example of analyzing the Rayleigh equations for ascending and descending branches of the magnetic hysteresis loop, the dimensionless hysteresis quantities Br/Bmax, Wh/Wmax, Hc/Hmax, and BrHc/Wh, which have the same functional dependence on the external magnetic field Hmax, have been found. Hysteresis quantities proportional to the permeability μ or hysteresis loss Wh have been obtained. An analysis of the magnetically soft amorphous alloy Co66Fe3Cr3Si15B13 with very high initial permeability showed that the similarity of dimensionless hysteresis quantities takes place not only in the Rayleigh region, but also in a wider region of the magnetic field.

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.

The Structural and Magnetic Properties of the Amorphous and Nanocrystalline Alloys

An amorphous and nanocrystalline ribbon is produced applying the technology of rapid molten metal quenching. The chemical composition of the alloy is required to contain elements ensuring the amorphous structure formation in the course of quenching. A great number of various chemical elements in amorphous and nanocrystalline alloys contribute to the complex process of the structure formation in the course of heat treatment of the amorphous precursor. The results of an investigation into the melts’ property of iron-based amorphous and nanocrystalline alloys are presented in the paper. The structure has been shown to influence magnetic and mechanical properties of the material in preparing the melt before casting.