Papers by Keyword: Liquid Metal

Abstract: The objective of this study is to suggest a method for judging jumping periods, which means an atom moves significantly in a short time in liquid metal. In this study, molecular dynamics (MD) simulation of liquid Pb at 773 K was performed. The self-diffusion coefficient was calculated to confirm that the simulation adequately reproduces liquid Pb and was almost consistent with the reliable experimental data. In the evaluation of jumping period, atomic motion during jumping was considered. A method for estimating jumping period by using each atomic speed and 1st-peak of pair distribution function was suggested by using a time when speed is at a local minimum value.

Abstract: It is demonstrated that using the mathematical formalism of the interaction parameters for multicomponent metallic solution, it is possible to predict mass transfer in a system consisting of two dissimilar metals separated by low-melting one containing non-metallic impurities. The calculation of the interaction parameters in three-and four-component systems was carried out using the equations of the coordination-cluster model. Comparison between theory and data reported in the literature for corrosion in sodium loop led to the conclusion about the most probable mechanism of the influence of the oxygen impurity content on the corrosion rate of iron under non-isothermal conditions.

Abstract: A review of publications on metallurgical and foundry production showed that many authors, when analyzing the properties of liquid metals and alloys, proceed from the concept of their cluster structure. The cluster structure of a liquid is a hypothesis, but it is confirmed by studies of diffraction of X-rays, electrons and neutrons reflected from its surface. This paper considers the existing concept that a cluster is a crystal-like concentration of atoms. Around the clusters there is a weakened zone, which consists of disordered atoms, the volume of which does not exceed 3 ... 5%, and this provides the fluidity of many melts. The authors of the publications have achieved success in explaining the forming structure of ingots, proceeding from the cluster mechanism of the crystallization of liquid metals and alloys. The authors of this work suggested that the superheated liquid metal in the head of the bath, which has smaller clusters, moves under the action of magnetic fields to its tail, and provides refinement of the weld metal structure during welding with the action of a control transverse magnetic field.

Abstract: This Article Presents the Results of the Development of Multilayer Ceramic Coatings to Protect Metal Products from Corrosion in Aggressive Liquid Metal Environments. the Development is Based on the Integrated Use of Low-Temperature Heterophase Transfer and Microarc Oxidation Methods. the Results of Corrosion Tests of Coatings in the Interaction with Molten Lead in the Temperature Range of 400-600°C are Presented. the Structural Characteristics of the Coatings are Considered.

Abstract: The aim of this investigation is to provide theoretical justification of the crystallizing nucleus formation in liquid iron. To solve this problem, the authors put forward the fluctuation hypothesis: short range order region formation in liquid metal takes place due to temperature fluctuations, and the temperature of the short range order is the temperature fluctuation around Kelvin scale zero in the course of crystallization time. The investigations were carried out for liquid state of the substance, in particular, for iron in paramagnetic state at the melting temperature. Analytical derivation of the temperature fluctuation value was given. Analytical expressions were obtained to define the average number of atoms in the short range order region for crystallizing iron. The investigation results show that short range order contains enough atoms to provide interaction with pulsed magnetic field resulting in the increase in the number of crystallization nuclei and in the decrease of their size. The obtained results can be used in the decision-making process concerning some manufacturing operations aimed at providing homogeneous structure of metals, particularly, in ferrous and non-ferrous metallurgy.

Abstract: Studies of the properties steels and alloys in the liquid and solidity conditions bear witness that the technical peculiarities of the receipt liquid metal in particular overheating have influence on the its properties and structure. The time-temperature treatment of the liquid metal influence on the structure of the liquid metal. The structure of the liquid metal influence on the character hardening and properties of the solidity samples in the one's turn. It should be noted the fact that place the just regularity take place: than extent of the melt equilibrium before crystallization is higher the solid metal distinguish oneself the better figures of the quality.

Abstract: Developments in synchrotron and home laboratory X-ray sources and fast low noise X-ray imaging detectors over the last 15-20 years has enabled real time X-radiography of alloy solidification from the melt. These investigations have been an important tool for in–situ investigations of dendrite-, eutectic and monotectic growth, dendrite fragmentation etc. At the same time, the techniques have allowed studies of phenomena in the melt such as convection, formation of solute boundary layers and minority phase droplet interactions. The article will review the X-radiography techniques and some of the results with emphasis on studies of phenomena in alloy melts.

Abstract: The developments of the high power proton accelerators become a worldwide interest to provide various applications, where the targets are demanded to efficiently produce secondary beams and to survive intensive MW class proton beam power supplied by the accelerators. Solid metal targets might be melted by very high heat flux that is caused by the intensive proton beam bombardment. In fact, the incident occurred at J-PARC (Japan Proton Accelerator Research Complex), in which the gold solid target was locally melted to explosively jet molten gold. The molten gold jet collided with a structural beryllium flange plate that has a function of vacuum boundary. Some parts of molten gold were splashed and the other stuck on the flange plate. The relationship between the impact velocity and the morphology of the sticking pattern on the plate was quantitatively evaluated by introducing fractal analysis. It was found that the fractal dimension is correlated with the impact velocity and might be a useful factor to indicate the localized impact force and behavior.

Abstract: The improvement of mathematical models for semisolid alloy flow properties requires profound understanding of the underlying physical nature. To date, it is commonly accepted that the shear thinning behaviour of these suspensions is caused by the solid phase microstructure, while the liquid phase is assumed to be Newtonian with a viscosity in the lower mPas-range. Recent measurements however, demonstrate non-Newtonian behaviour of fully liquid metals with pronounced shear thinning and high viscosities (multiple Pas) in the low shear-rate range. By gathering and analysing rheological measurement data of various alloys (Sn14.2%Pb, A356 and X210CrW12), the relevance of the new findings for semisolid metals is investigated. The results indicate that the previously unexamined non-Newtonian flow behaviour of the liquid matrix has, besides the solid fraction, the most dominant influence on the shear thinning behaviour of semisolid alloys. The influences of shear-rate and solid fraction are nearly independent of each other which allow the construction of master-curves; a general flow curve for the suspension where the solid fraction is considered by a scaling factor. Consequently, a modelling approach is suggested in which the dependency of solid fraction is considered independently of the shear-rate.

Abstract: This numerical study examines a three-dimensional liquid-metal magnetohydrodynamic flow in a hairpin-shaped electrically-conducting duct with a square cross-section under a uniform magnetic field applied perpendicular to the flow plane. Predicted is detailed information on fluid velocity, pressure, current, and electric potential in the magnetohydrodynamic duct flow. Higher velocities are observed in the side layers in the inflow and outflow channels, yielding M-shaped velocity profiles. More specifically, in the present study the axial velocity in the side layer near the partitioning wall is higher than that near the outer walls because of the current features therein. In the turning segment, a large velocity recirculation is observed at the entrance of the outflow channel caused by the flow separation, yielding complicated distributions of the electric potential and current therein. The pressure almost linearly decreases along the main flow direction, except for in the turning segment.