Steel Hot Deformation Flow Stress: Artificial Neural Network Computation

Построена математическая модель, основанная на искусственной нейронной сети, позволяющая с высокой точностью определять напряжение течения сталей в широком диапазоне их химического состава и условий горячей пластической деформации. Проверка построенной модели на независимых экспериментах для стали Fe–30Mn–10Al–1,1C–4Mo показала ее высокую точность в прогнозировании кривых деформации.An artificial neural network model has been constructed for the prediction of the steel flow stress during hot deformation. The model shows high accuracy in a wide range of steel chemical composition and hot deformation conditions. Verification of the constructed model using independent experiments for Fe–30Mn–10Al–1,1C–4Mo steel has shown its high accuracy in predicting the deformation curves.Pабота выполнена при финансовой поддержке Российского научного фонда (проект № 18-79-10153-П).The work was carried out with the financial support of the Russian Science Foundation (project No. 18-79-10153-P)

HOT DEFORMATION BEHAVIOR AND MICROSTRUCTURE OF THE STAINLESS HEATRESISTANT STEEL AISI 310

Experimental investigation of hot deformation behavior and fracture of AISI 310 steel was conducted using thermomechanical simulator Gleeble 3800. The hot deformation and fracture under the torsion with tension conditions was simulated by FEM. Dynamic recrystallization during the deformation atthe temperatures above 1100 °C leads to significant grain refinement.С использованием комплекса физического моделирования термомеханических процессов Gleeble 3800 проведено исследование и построена конечно.элементная модель поведения жаропрочной стали 20Х18 Н23 в процессе горячей пластической деформации. Показано, что в результате пластической деформации при температуре более 1100 °C в стали происходят процессы динамической рекристаллизации, приводящие к значительному измельчению зерна.Работа выполнена при финансовой поддержке Российского научного фонда (проект № 18-79-10153)

Exploration of spectra of periodic Comet 153P/Ikeya−Zhang

We present preliminary results of study of middle-resolution optical spectra of Comet 153P/Ikeya–Zhang obtained on May 5, 2002 with the help of the 2.12-m reflector of the Guillermo Haro Astrophysical Observatory. Emission lines of the molecules C₂, C₃, CN, NH₂, CO (Asundi and triplet bands), and H₂O⁺ are identified in these spectra. On the basis of the intensity distribution along the slit of the spectrograph in C₂, C₃, CN emission lines we determined the velocities expansion and life times of these molecules

Study of Amorphous Allos (Fe1-xNix)79P5B12Si3C1 System

In this work, magnetically soft amorphous alloys of the Fe–Ni–P–B–Si–C system. The crystallization kinetics of alloys has been investigated different thermal analysis by means of isothermal heating and continuous heating. As a result of isothermal annealing, Avrami exponents were found and mechanisms of crystallization were determined. Using continuous heating, the activation energy was found by the Kissinger method.В работе исследовались магнитомягкие аморфные сплавы системы Fe–Ni–P–B–Si–C. Была изучена кинетика кристаллизации сплавов с использованием термического анализа при режимах: изотермической выдержки и непрерывного нагрева. В результате проведения изотермического отжига были найдены показатели Аврами и определены механизмы кристаллизации. По методу Киссинджера при непрерывном нагреве определена энергия активация

ИССЛЕДОВАНИЕ И МОДЕЛИРОВАНИЕ ПРОЦЕССОВ КРИСТАЛЛИЗАЦИИ ОБЪЕМНЫХ МЕТАЛЛИЧЕСКИХ СТЕКОЛ НА ОСНОВЕ ЦИРКОНИЯ

The article describes the investigation and simulation of Zr-based bulk metallic glass crystallization kinetics using DSC and DIC techniques. The investigation of the kinetics of crystallization processes may eventually provide deeper understanding of the bulk metallic glass crystallization mechanism and promote the evidence-based selection of heat treatment to form desired structure and properties of bulk metallic glasses based composites.Работа посвящена исследованию и моделированию кинетики кристаллизации объемных металлических стекол на основе циркония при нагреве с постоянной скоростью, а также при изотермической выдержке при повышенной температуре. Исследование кинетики процессов кристаллизации со временем может обеспечить более глубокое понимание механизма кристаллизации объемных металлических стекол и способствовать научно обоснованному выбору режимов термической обработки для формирования желаемых структуры и свойств композиционных материалов на их основе

ИССЛЕДОВАНИЕ ЭВОЛЮЦИИ СТРУКТУРЫ ДВУХФАЗНОГО ТИТАНОВОГО СПЛАВА В ПРОЦЕССЕ ТЕРМОДЕФОРМАЦИОННОЙ ОБРАБОТКИ

This paper studies Ti–3,5Fe–4Cu–0,2B two-phase titanium alloy behavior during its thermal deformation processing under uniaxial compression. Boron was added to obtain a fine-grained structure in the cast state. Samples of alloys 6 mm in diameter were obtained by melting pure components in a vacuum induction furnace with their subsequent crystallization into a solid copper mold. Uniaxial compression tests with a true strain of 0,9 were performed using the Gleeble 3800 thermal-mechanical physical simulation system at 750, 800 and 900 °C and strain rates of 0,1; 1 and 10 s–1. Scanning electron microscopy was used to study the microstructure of the alloy in its initial and deformed states. A model of flow stress dependence on temperature and strain rate was built as a result of the tests. It is shown that pressure treatment involves recrystallization of the initial cast structure containing solid solutions based on α-Ti, β-Ti and titanium diboride aggregates. During the deformation process, the volume fraction of α-titanium solid solution grains decreases with rising temperature, and the fraction of the β phase, on the contrary, increases. In this case, the average grain size of solid solutions based on α-Ti and β-Ti varies insignificantly after deformation in almost all of the studied modes. It is shown that the preferred mode of hot pressure treatment for obtaining a high complex of mechanical properties in the investigated alloy is a temperature range of 750– 800 °C, since α-phase grain sizes increase from 2,2 to 4,5 μm with an increase in temperature to 900 °C.Исследовано поведение двухфазного титанового сплава Ti–3,5Fe–4Cu–0,2B в процессе термодеформационной обработки на одноосное сжатие. Бор вводили для получения в литом состоянии мелкозернистой структуры. Образцы сплавов диаметром 6 мм получали путем сплавления чистых компонентов в вакуумной индукционной печи и последующей ускоренной кристаллизации в массивной медной изложнице. Испытания на одноосное сжатие с истинной деформацией 0,9 проводили на комплексе физического моделирования термомеханических процессов «Gleeble 3800» при температурах 750, 800 и 900 °С и скоростях деформации 0,1; 1 и 10 с–1. Микроструктуру сплава в исходном и деформированном состояниях изучали с помощью сканирующей электронной микроскопии. В результате испытаний построена модель зависимости напряжения течения от температуры и скорости деформации. Показано, что в процессе обработки давлением происходит рекристаллизация исходной литой структуры, содержащей твердые растворы на основе α-Ti, β-Ti и колонии диборида титана. В процессе деформации с повышением температуры объемная доля зерен твердого раствора на основе α-титана уменьшается, а доля β-фазы, наоборот, возрастает. При этом средний размер зерен твердых растворов на основе α-Ti и β-Ti меняется незначительно после деформации почти по всем исследованным режимам. Показано, что предпочтительным режимом горячей обработки давлением для получения высокого комплекса механических свойств в изучаемом сплаве является диапазон температур 750–800 °С, так как размер зерен α-фазы увеличивается с 2,2 до 4,5 мкм при повышении температуры до 900 °С

Rejuvenation of metallic glasses by non-affine thermal strain.

When a spatially uniform temperature change is imposed on a solid with more than one phase, or on a polycrystal of a single, non-cubic phase (showing anisotropic expansion-contraction), the resulting thermal strain is inhomogeneous (non-affine). Thermal cycling induces internal stresses, leading to structural and property changes that are usually deleterious. Glasses are the solids that form on cooling a liquid if crystallization is avoided--they might be considered the ultimate, uniform solids, without the microstructural features and defects associated with polycrystals. Here we explore the effects of cryogenic thermal cycling on glasses, specifically metallic glasses. We show that, contrary to the null effect expected from uniformity, thermal cycling induces rejuvenation, reaching less relaxed states of higher energy. We interpret these findings in the context that the dynamics in liquids become heterogeneous on cooling towards the glass transition, and that there may be consequent heterogeneities in the resulting glasses. For example, the vibrational dynamics of glassy silica at long wavelengths are those of an elastic continuum, but at wavelengths less than approximately three nanometres the vibrational dynamics are similar to those of a polycrystal with anisotropic grains. Thermal cycling of metallic glasses is easily applied, and gives improvements in compressive plasticity. The fact that such effects can be achieved is attributed to intrinsic non-uniformity of the glass structure, giving a non-uniform coefficient of thermal expansion. While metallic glasses may be particularly suitable for thermal cycling, the non-affine nature of strains in glasses in general deserves further study, whether they are induced by applied stresses or by temperature change.This research was supported by the World Premier International Research Center Initiative (WPI), MEXT, Japan, by NSF China and MOST 973 China, and by the Engineering and the Engineering and Physical Sciences Research Council, UK (Materials World Network project). Y.H.S. acknowledges support from a China Scholarship Council (CSC) scholarship.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nature1467

Prediction of True Stress at Hot Deformation of High Manganese Steel by Artificial Neural Network Modeling

The development of new lightweight materials is required for the automotive industry to reduce the impact of carbon dioxide emissions on the environment. The lightweight, high-manganese steels are the prospective alloys for this purpose. Hot deformation is one of the stages of the production of steel. Hot deformation behavior is mainly determined by chemical composition and thermomechanical parameters. In the paper, an artificial neural network (ANN) model with high accuracy was constructed to describe the high Mn steel deformation behavior in dependence on the concentration of the alloying elements (C, Mn, Si, and Al), the deformation temperature, the strain rate, and the strain. The approval compression tests of the Fe–28Mn–8Al–1C were made at temperatures of 900–1150 °C and strain rates of 0.1–10 s−1 with an application of the Gleeble 3800 thermomechanical simulator. The ANN-based model showed high accuracy, and the low average relative error of calculation for both training (5.4%) and verification (7.5%) datasets supports the high accuracy of the built model. The hot deformation effective activation energy values for predicted (401 ± 5 kJ/mol) and experimental data (385 ± 22 kJ/mol) are in satisfactory accordance, which allows applying the model for the hot deformation analysis of the high-Mn steels with different concentrations of the main alloying elements