Method for obtaining ingots of the A34 solder based on an investigation into the relation between the structure and properties of liquid and solid metals

A comparative analysis of the influence of the modifying method on the structure and phase composition of the ingots of the A34 solder is performed. Modification is performed by force of heating the melt to 1000°C and introducing the fine-crystalline remelt in an amount of 5% of the charge amount into the melt. The investigation is performed using DTA and metallographic analysis. The structure of the ingot of the A34 solder is additionally investigated at elevated temperatures (150 and 300°C) by the sc-AFM method using the NTEGRA Therma probe nanolaboratory, and recommendations are given to optimize the modes of casting and thermal treatment. © 2013 Allerton Press, Inc

Measurement of young's modulus and hardness of Al-50 wt % Sn alloy phases using nanoindentation

The nanoindentation method was used to measure the Young's modulus and hardness of the phases of the alloy Al-50 wt % Sn: α-aluminum and eutectic. Samples are obtained in different ways, i.e., traditionally via the transition of the melt into a homogeneous structural state by heating to a certain temperature, followed by cooling using the cooling rate greater by the order than that of the traditional method and via the addition of 0.06 wt % Ti and 1 wt % Zr to the binary alloy. It has been found that the most significant effect of the Al-50 wt % Sn phases on the Young's modulus is the transition of the melt into a homogeneous structural state and the introduction of Zr into the melt. As part of the mathematical theory of elasticity, a numerical evaluation of the interfacial pressure that arises due to the difference between Young's modulus of α aluminum and eutectic has been performed. The calculation has showed that the extra pressure is nine times less for the alloy formed through the transition of the melt into a homogeneous structural state than for the alloy produced via a traditional way. © 2013 Pleiades Publishing, Ltd

Viscosity and separation of Fe-Cu melts

A viscosimetric study of Fe-Cu melts is performed on heating and subsequent cooling of samples. The results of measurements in the above-liquidus part of the phase diagram are used to construct the boundaries of colloid-scale microheterogeneities in a melt. © 2013 Pleiades Publishing, Ltd

Influence of copper additives on the viscosity and stratification of iron melt

Viscosimetric data are obtained for Fe-Cu melts in heating and subsequent cooling of samples with 0-10 wt % Cu. Above the liquidus in the resulting phase diagram, the boundaries of the region where microheterogeneities of colloidal scale exist in the melt are found. © 2013 Allerton Press, Inc

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. © 2013 Allerton Press, Inc

Examining the structure of mill rolls made of 9X2MΦ and 8X3CΓΦ steels using the ultrasonic method for quality control

The microstructure of specimens of 9X2MΦ and 8X3CΓΦ steels taken from working rolls of a reversing mill was examined. A correlation between characteristics of the crystal structure of the metal and the intensified attenuation of ultrasonic waves was found. Ultrasonic inspection was carried out using an ultrasonic flaw detector (Krautkramer Co.). The microstructure was examined by means of traditional metallographic analysis methods, which were implemented using a scanning electron microscope; X-ray spectral microanalysis and electron backscatter diffraction were used. The morphology and elemental composition of discontinuity flaws were studied; as well, phase maps, crystallite misorientation histograms, and Taylor factor maps were plotted for specimens taken from the defect zone of a 9X2MΦ steel working roll. © 2013 Pleiades Publishing, Ltd

ИССЛЕДОВАНИЕ ВЛИЯНИЯ СТРУКТУРНОГО СОСТОЯНИЯ РАСПЛАВА НА КРИСТАЛЛИЧЕСКОЕ СТРОЕНИЕ И МЕХАНИЧЕСКИЕ СВОЙСТВА ФАЗ СПЛАВА AL-50 МАС.%SN МЕТОДОМ НАНОИНДЕНТИРОВАНИЯ

Nanoindentation is used to measure Young's modulus, the hardness, the plasticity, and the yield strength of the phases in Al-50 wt % Sn alloy samples prepared by a traditional method and using liquid-state homogenization. The effect of an increase in the cooling rate by an order of magnitude and alloying with 0.06 wt % Ti or 1 wt % Zr on the mechanical properties of the phases in the Al-50 wt % Sn alloy is studied. The most substantial effect on Young's modulus of the phases in the Al-50 wt % Sn alloy is found to be exerted by the homogenization of the metallic liquid and the introduction of zirconium in the alloy melt: the metal forming of an ingot is improved substantially. © 2013 Pleiades Publishing, Ltd

Когнитивное моделирование как инструмент отбора массовых открытых онлайн-курсов для самостоятельной работы студентов общеинженерных направлений подготовки по курсу физики

Introduction. The article is devoted to the development of an adaptive mechanism for managing the independent work of students of general engineering areas when studying a physics course by using massive open online courses based on cognitive modeling technology. Purpose setting. The problem of choosing the factors that determine the feasibility of choosing massive open online courses for self-study of physics is being studied, and the sensitivity of the educational result to changes in influencing factors has been experimentally assessed. Methodology and methods of the study. The complex and weakly structured task of assessing the feasibility of using massive open online courses in teaching physics to students is formalized by constructing cognitive maps that allow modeling changes in the academic result with an impulsive change in factors and in the formation of scenarios. The research methodology is based on the qualitative principles of graph theory, PEST methodology and SWOT analysis. Results. A cognitive model is presented in the form of a functional graph and a simulation experiment was carried out to test the adequacy of the formed cognitive model. Conclusion. The results obtained should subsequently become the ground for the formation of a scientific basis for managing the quality of education in terms of selecting massive open online courses for independent work of students and increasing its both internal and external efficiency.Введение. Статья посвящена разработке адаптивного механизма управления самостоятельной работой студентов общеинженерных направлений при изучении курса физики путем использования массовых открытых онлайн-курсов на основе технологии когнитивного моделирования. Постановка задачи. Изучается проблема выбора факторов, определяющих целесообразность выбора массовых открытых онлайн-курсов для самостоятельного обучения физике, экспериментальным путем проведена оценка чувствительности образовательного результата к изменениям влияющих факторов. Методика и методология исследования. Сложная и слабоструктурированная задача оценки целесообразности применения массовых открытых онлайн-курсов в обучении студентов физике формализована путем построения когнитивных карт, позволяющих провести моделирование изменения академического результата при импульсном изменении факторов и при формировании сценариев. Методология исследования базируется на качественных положениях теории графов, методике PEST и SWOT-анализа. Результаты. Представлена когнитивная модель в виде функционального графа и проведен имитационный эксперимент для проверки адекватности сформированной когнитивной модели. Выводы. Полученные результаты должны стать впоследствии основой для формирования научной базы управления качеством образования в части отбора массовых открытых онлайн-курсов для самостоятельной работы студентов, повышения ее как внутренней, так и внешней эффективности

Термодинамическая устойчивость микрогетерогенных состояний в расплавах Fe – Mn – C

The probability of the existence of microheterogeneous states in Fe - Mn - C melts has been analyzed in accordance with the concepts of chemical thermodynamics. The microheterogeneous state of a chemically heterogeneous Fe - Mn - C melt was understood as the presence of dispersed Fe - C particles in it. These are suspended in the Mn - C medium and separated from it by an interface. The microheterogeneous state in Fe - Mn - C melts is destroyed as a result of heating to a temperature specific for each composition. The hypothesis of the microheterogeneous state of Fe - Mn - C melts is supported by a wide range of numerous experimental data on their thermodynamic and physical properties. The identification of anomalies in temperature dependences of physical properties of Fe - Mn - C melts has allowed for temperature values above which the melt superheating treatment (MST) causes destruction of microheterogeneity to be determined, i.e., liquid - liquid structure transition (LLT) in the melt. LLT is understood by the authors as a structural transition "microheterogeneous melt - homogeneous solution". This is expressed as the destruction of the microheterogeneous state when the Fe - Mn - C melt is heated to a temperature specific for each composition (MST). The authors have previously analyzed the effect of LLT in Fe - Mn - C melts on the microstructure, crystal structure and mechanical properties of solid metal in submicrovolumes. This paper describes a method of theoretical determination of the temperature range where the microheterogeneous state of the Fe - Mn - C melt is thermodynamically stable. The thermodynamic stability of dispersed Fe - C particles in the Mn - C medium has been estimated according to the equations proposed by G. Kaptay for a regular solution. It was assumed that the interface between the dispersed particle (Fe - C) and the dispersion medium (Mn - C) is enriched with carbon. The paper demonstrates the possibility of existence in the Fe - Mn - C melt of dispersed Fe - C particles with sizes from 2 to 34 nm, distributed in the Mn - C dispersion medium and separated from it by an interface with increased carbon content. The estimated result is consistent with the data on the size of structural units of a viscous flow, obtained earlier within the framework of the theory of absolute reaction rates. © 2022 National University of Science and Technology MISIS. All rights reserved

Microstructure and mechanical properties of Al-12Si produced by selective laser melting

Al-12Si specimens are produced by selective laser melting (SLM) from gas atomized powders. Installation for the production of powder is original. All specimens were prepared using the EOSINT M 280 device. A fine cellular structure is observed with residual free Si along the cellular boundaries. Room temperature tensile tests reveal remarkable mechanical behavior: the samples show yield and tensile strengths of about 102 MPa and 425 MPa, respectively, along with fracture strain of 12%. The study of crack surface morphology was shown by the example of a sample. Except the spherical pores, the interface of the molten pool also appears on the fracture surface, which indicates a mixture of fragile and ductile fracture. Additionally, the agglomerated silicon group appears also on the fracture surface. © Published under licence by IOP Publishing Ltd