A. G. Tyagunov

Production of heat-resistant EP220 and EP929 alloys by high-temperature treatment of melt

Analysis of samples of EP220 and EP929 alloys in the liquid and solid state permits the determination of the parameters for high-temperature melt treatment in their production. On heating to specific temperatures, the structure of the liquid alloys moves closer to equilibrium. In the solidification of such melt, the cast metal formed is characterized by finer grain structure, greater dispersity of the dendrites, and greater density and microhardness of the matrix. Industrial adoption of high-temperature melt treatment will improve plasticity, increase the long-term strength, and boost the product yield. The proposed technology does not fully utilize the potential of the alloy structure obtained after high-temperature melt treatment. The effect may be amplified by more prolonged holding of the melt at 1650°C and by optimization of the vacuum-arc heating, deformation, and heat treatment, in the light of the structural changes in the experimental samples of solid metal.

Multilayer perceptron, generalized regression neural network, and hybrid model in predicting the spatial distribution of impurity in the topsoil of urbanized area

The study is based on the data obtained as a result of soil screening in the city of Noyabrsk, Russia. A comparison of two types of neural networks most commonly used in this type of research was carried out: multi-layer perceptron (MLP), generalized regression neural network (GRNN), and a combined MLP and ordinary kriging approach (MLPRK) for predicting the spatial distribution of the chemical element Chromium (Cr) in the surface layer of the urbanized territory. The model structures were developed using computer modeling, based on minimizing of a root mean squared error (RMSE). As input parameters, the spatial coordinates were used, and the concentration of Cr - as the output. The hybrid MLPRK approach showed the best prognostic accuracy.

Chromium distribution forecasting using multilayer perceptron neural network and multilayer perceptron residual kriging

It is known that combination of geostatistical interpolation techniques (e.g. kriging) and machine learning (e.g. neural networks) leads to better prediction accuracy and productivity. The paper deals with application of the artificial neural network residual kriging (ANNRK) to the spatial prediction of soil pollution by Chromium (Cr). In the work, we examined and compared two neural networks: Multilayer Perceptron (MLP) and Multilayer Perceptron Residual Kriging (MLPRK). The case study is based on the survey on surface contamination by Cr at the subarctic Noyabrsk, Russia. The proposed models have been built, implemented and validated using ArcGIS and MATLAB software. The models frameworks have been developed using a computer simulation based on a minimization of the root mean squared error (RMSE). Both models showed almost identical results.

Forecasting of heavy metal distribution based on co-kriging and generalized regression neural network with co-elements concentration as input data

In this paper, we examined and compared a generalized regression neural network (GRNN), a GRNN with co-elements (co-GRNN) and a geostatistical method: co-kriging for modeling the chemical elements surface distribution. The study is based on data of surface contamination by Chromium (Cr) in subarctic Noyabrsk, Russia. The proposed models were built, implemented and tested using ArcGIS and MATLAB software. The model structures were developed using computer modeling, based on minimizing of the root mean squared error (RMSE). Co-GRNN showed the best predictive accuracy.

Polytherms of the physical properties of metallic melts

The temperature dependence of the kinematic viscosity, electrical resistivity, surface tension, and density of liquid steels and alloys on heating and subsequent cooling is analyzed. On that basis, the polytherms of the physical properties of steels and alloys are systematized. On heating to certain critical temperatures, changes occur in the structure of the melt. Consequently, the cooling polytherms take a form more closely resembling the equilibrium classical laws and do not match the heating polytherms. Branching or hysteresis of the temperature dependences is only irreversible on heating to critical temperatures. Otherwise, partial or complete return to the primary melt structure is possible. That affects the degree of hysteresis of the polytherms. The degree of hysteresis and the data regarding the properties provide qualitative information regarding the transition of the melt structure from the equilibrium to the microhomogeneous state. The uniformity of the distribution of atoms of the alloying elements in microgroupings or clusters indicates the equilibrium of the structure, while the uniformity of the distribution of clusters that differ in structure over the melt volume reflects structural microhomogeneity. Data on the properties of multicomponent metals indicate that, after melting, the variation in melt properties on isothermal holding takes the form of familiar damping oscillations. With increase in temperature, the damping becomes aperiodic, and the relaxation time declines. The processes responsible for the isothermal variation in melt properties occur at the microscopic level. Nonequilibrium industrial metal usually contains inclusions inherited from the initial materials, such as insoluble graphite particles in the cast iron or associations and aggregations of carbide and nitride type. The melt takes a long time to reach equilibrium—usually longer than the time for diffusional mixing of the atoms within the nonequilibrium regions. With more complex chemistry and structure of the solid metal, the distance of the melt from equilibrium will be greater. In this system, new correlations are formed and broken more intensely. Cooperative interactions of the new spatial and time structures with those inherited from the initial materials occur here, as indicated by oscillating behavior of the properties of the metallic melts. Information regarding the state of the melt before solidification permits scientific analysis of the melting points and melting times of the steels and alloys. Such preparation of the melt affects its supercooling, its solidification rate, the formation of hardening phases and eutectics, the segregation of the elements, the dendrite and zonal; structure of the castings, and the overall product quality and production efficiency.

Effect of Secondary Melt Refining on the Properties of an EP602 Nickel Superalloy

The influence of argon blowing of the EP602 alloy melt in a ladle is considered. Ladle treatment during the manufacture of nickel superalloys is shown to form a more equilibrium and homogeneous structure of a melt, which leads to changes in the structure and properties of the solid metal.

Influence of the chromium concentration on structure formation in liquid chromonickel alloys

The electrical resistivity of liquid nickel–chromium alloys is studied as a function of the temperature and concentration. Experimental data indicate that the dependence of the alloys’ electrical-resistance isotherms on the concentration is nonlinear. On the basis of the temperature and concentration dependence of the electrical resistivity of nickel and chromium alloys, the optimal conditions for the formation of microhomogeneous and equilibrium structure in the melt may be determined. The electrical-resistance isotherms of chromonickel alloys may be qualitatively explained on the basis of percolation theory and a quasi-chemical model of the microheterogeneous structure of molten metal alloys. The structure formation of chromonickel melts with increase in chromium concentration is characterized by the successive formation of clusters with different structure and dimensions.

ВЛИЯНИЕ КОНЦЕНТРАЦИИ ХРОМА НА ПРОЦЕСС СТРУКТУРООБРАЗОВАНИЯ ЖИДКИХ ХРОМОНИКЕЛЕВЫХ СПЛАВОВ

The temperature and concentration dependences of the electrical resistivity of the nickel-chromium alloys in the liquid state have been studied. Experimental data suggest a nonlinear concentration dependence of the electrical resistivity isotherms of the studied alloys. The results of studies of the temperature and concentration dependencies of the electrical resistivity of nickel-chromium alloys allow determining the optimal conditions for the formation of microhomogeneous and the equilibrium structure of the melt. Using of percolation theory and quasichemical model of microheterogeneous structure of liquid metal alloys gives the possibility to explain the nature of the isotherms of the electrical resistivity of nickel-chromium melts. The process of structure formation of nickel-chromium melts with increasing chromium concentration has been presented in the form of schemes, reflecting the gradual formation of different clusters, featuring by their structure and size.

Production feature of soft magnetic amorphous alloys

Methods for making nanocrystalline alloys have been discussed. Temperature dependences of the surface tension (σ), electric resistivity (ρ), magnetic susceptibility (χ) and kinematic viscosity (ν) have been obtained. Comparison of the properties of amorphous ribbons obtained by the pilot and serial technologies has been conducted. Science-based technology of multi-component alloy smelting makes it possible to prepare equilibrium smelt, the structure of which has a significant effect on the properties of the amorphous ribbon before spinning and kinetics of its crystallization has been offered.