Influence of dendritic chemical inhomogeneity on the structural recrystallization and properties of 38KhN3MFA steel

1989 ◽  
Vol 31 (3) ◽  
pp. 229-233
Author(s):  
N. N. Lipchin ◽  
A. N. Lipchina ◽  
I. E. Kosmatenko ◽  
G. S. Artem'ev ◽  
T. G. Tregubova
Keyword(s):  
Chemical Inhomogeneity ◽  
Structural Recrystallization ◽  
38Khn3mfa Steel

Local atomic structure of relaxor ferroelectric solids studied by pulsed neutron scattering

1994 ◽  
Vol 52 ◽  
pp. 554-555
Author(s):  
T. Egami ◽  
H. D. Rosenfeld ◽  
S. Teslic
Keyword(s):  
Neutron Scattering ◽  
Atomic Structure ◽  
Argonne National Laboratory ◽  
Relaxor Ferroelectrics ◽  
Relaxor Ferroelectric ◽  
Crystallographic Structure ◽  
Chemical Inhomogeneity ◽  
Distribution Analysis ◽  
Ferroelectric Transition ◽  
Pulsed Neutron

Relaxor ferroelectrics, such as Pb(Mg1/3Nb2/3)O3 (PMN) or (Pb·88La ·12)(Zr·65Ti·35)O3 (PLZT), show diffuse ferroelectric transition which depends upon frequency of the a.c. field. In spite of their wide use in various applications details of their atomic structure and the mechanism of relaxor ferroelectric transition are not sufficiently understood. While their crystallographic structure is cubic perovskite, ABO3, their thermal factors (apparent amplitude of thermal vibration) is quite large, suggesting local displacive disorder due to heterovalent ion mixing. Electron microscopy suggests nano-scale structural as well as chemical inhomogeneity.We have studied the atomic structure of these solids by pulsed neutron scattering using the atomic pair-distribution analysis. The measurements were made at the Intense Pulsed Neutron Source (IPNS) of Argonne National Laboratory. Pulsed neutrons are produced by a pulsed proton beam accelerated to 750 MeV hitting a uranium target at a rate of 30 Hz. Even after moderation by a liquid methane moderator high flux of epithermal neutrons with energies ranging up to few eV’s remain.

Effect of the shock-wave treatment on the dynamic strength of 38KhN3MFA steel

2000 ◽  
Vol 26 (8) ◽  
pp. 734-736 ◽  
Author(s):  
M. V. Sil’nikov ◽  
A. I. Mikhailin ◽  
A. V. Petrov ◽  
Yu. I. Meshcheryakov ◽  
V. A. Ermolaev ◽  
...  
Keyword(s):  
Shock Wave ◽  
Dynamic Strength ◽  
Wave Treatment ◽  
Shock Wave Treatment ◽  
38Khn3mfa Steel

scholarly journals On the question of using solid electrodes in the electrolysis of cryolite-alumina melts. Part 3. Electric field distribution on the electrodes

2021 ◽  
Vol 25 (2) ◽  
pp. 235-251
Author(s):  
E. S. Gorlanov ◽  
A. A. Polyakov
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Edge Effect ◽  
Current Density ◽  
Molten Salts ◽  
Functional Relationship ◽  
Electric Field Distribution ◽  
Chemical Inhomogeneity ◽  
Electrolytic Process ◽  
Solid Electrodes

The aim of this work is to identify the theoretical limitations of molten salts electrolysis using solid electrodes to overcome these limitations in practice. We applied the theory of electric field distribution on the electrodes in aqueous solutions to predict the distribution of current density and potential on the polycrystalline surface of electrodes in molten salts. By combining the theoretical background of the current density distribution with the basic laws of potential formation on the surface of the electrodes, we determined and validated the sequence of numerical studies of electrolytic processes in the pole gap. The application of the method allowed the characteristics of the current concentration edge effect at the periphery of smooth electrodes and the distribution of current density and potential on the heterogeneous electrode surface to be determined. The functional relationship and development of the electrolysis parameters on the smooth and rough surfaces of electrodes were established by the different scenario simulations of their interaction. It was shown that it is possible to reduce the nonuniformity of the current and potential distribution on the initially rough surface of electrodes with an increase in the cathode polarisation, alumina concentration optimisation and melt circulation. It is, nonetheless, evident that with prolonged electrolysis, physical and chemical inhomogeneity can develop, nullifying all attempts to stabilise the process. We theoretically established a relationship between the edge effect and roughness and the distribution of the current density and potential on solid electrodes, which can act as a primary and generalising reason for their increased consumption, passivation and electrolytic process destabilisation in standard and low-melting electrolytes. This functional relationship can form a basis for developing the methods of flattening the electric field distribution over the anodes and cathodes area and, therefore, stabilising the electrolytic process. Literature overview, laboratory tests and theoretical calculations allowed the organising principle of a stable electrolytic process to be formulated -the combined application of elliptical electrodes and the electrochemical micro-borating of the cathodes. Practical verification of this assumption is one direction for further theoretical and laboratory research.

scholarly journals Designing order–disorder transformation in high-entropy ferritic steels

2021 ◽  
Author(s):  
Prashant Singh ◽  
Duane D. Johnson
Keyword(s):  
Short Range ◽  
Density Functional ◽  
Short Range Order ◽  
Range Order ◽  
Atomic Scale ◽  
Atomic Fraction ◽  
Compositional Variation ◽  
Ferritic Steels ◽  
Chemical Inhomogeneity ◽  
High Entropy

AbstractOrder–disorder transformations hold an essential place in chemically complex high-entropy ferritic steels (HEFSs) due to their critical technological application. The chemical inhomogeneity arising from mixing of multi-principal elements of varying chemistry can drive property altering changes at the atomic scale, in particular short-range order. Using density-functional theory-based linear-response theory, we predict the effect of compositional tuning on the order–disorder transformation in ferritic steels—focusing on Cr–Ni–Al–Ti–Fe HEFSs. We show that Ti content in Cr–Ni–Al–Ti–Fe solid solutions can be tuned to modify short-range order that changes the order–disorder path from BCC-B2 (Ti atomic-fraction = 0) to BCC-B2-L21 (Ti atomic-fraction > 0) consistent with existing experiments. Our study suggests that tuning degree of SRO through compositional variation can be used as an effective means to optimize phase selection in technologically useful alloys. Graphic abstract

Confocal Raman Microscopy. Thomas Dieing, Olaf Hollricher, and Jan Toporski (Eds.)

2012 ◽  
Vol 18 (6) ◽  
pp. 1494-1494
Author(s):  
Sebastian Schlücker
Keyword(s):  
Raman Spectroscopy ◽  
Rapid Development ◽  
Optical Microscope ◽  
Small Sample ◽  
Raman Microscopy ◽  
Chemical Information ◽  
Chemical Inhomogeneity ◽  
Confocal Raman Microscopy ◽  
Noninvasive Technique ◽  
Confocal Raman

Confocal Raman Microscopy. Thomas Dieing, Olaf Hollricher, and Jan Toporski (Eds.). Springer, New York, 2011, 289 pages. ISBN 978-3642125218Raman microscopy is the combination of Raman spectroscopy with optical light microscopy and was first presented in the mid-1970s. It combines the advantages of vibrational Raman spectroscopy as a noninvasive technique providing a wealth of chemical information on the properties of molecules and solids with the imaging capabilities and small sample volume requirements of an optical microscope. “Seeing is believing”: Raman microscopy can visualize the inherent chemical inhomogeneity of a sample without the need of external labels, information that cannot be obtained from simply looking at an unstained sample in the standard optical microscope. During the last decade, confocal Raman microscopy has gone through a rapid development with respect to instrumentation and software as well as the diversity of applications.

Recrystallization Mechanisms in Severely Deformed Dual-Phase Stainless Steel

2010 ◽  
Vol 638-642 ◽  
pp. 1905-1910 ◽  
Author(s):  
Andrey Belyakov ◽  
Rustam Kaibyshev ◽  
Yuuji Kimura ◽  
Kaneaki Tsuzaki
Keyword(s):  
Stainless Steel ◽  
Large Strain ◽  
Austenite Phase ◽  
The Other ◽  
Dual Phase ◽  
Austenite Stainless Steel ◽  
Ultrafine Grained ◽  
Continuous Recrystallization ◽  
Ultrafine Grained Microstructure ◽  
Structural Recrystallization

The structural recrystallization mechanisms operating in an Fe – 27%Cr – 9% Ni dual-phase (ferrite-austenite) stainless steel after large strain processing to total strain of 4.4 were investigated in the temperature range of 400-700oC. The severe deformation resulted in the development of an ultrafine grained microstructure consisting of highly elongated grains/subgrains with transverse dimensions of 160 nm and 130 nm in ferrite and austenite, respectively. The annealing mechanism operating in ferrite phase was considered as continuous recrystallization, which involved recovery leading to the development of essentially polygonized microstructure. On the other hand, the mechanism of discontinuous nucleation took place at an early recrystallization stage in austenite phase.

scholarly journals Differential abundances of open clusters and their tidal tails: Chemical tagging and chemical homogeneity

2020 ◽  
Vol 635 ◽  
pp. A8 ◽  
Author(s):  
L. Casamiquela ◽  
Y. Tarricq ◽  
C. Soubiran ◽  
S. Blanco-Cuaresma ◽  
P. Jofré ◽  
...  
Keyword(s):  
High Precision ◽  
Synthetic Data ◽  
Chemical Species ◽  
Open Clusters ◽  
Solar Neighborhood ◽  
High Signal ◽  
Chemical Inhomogeneity ◽  
Differential Analysis ◽  
Chemical Homogeneity ◽  
Chemical Signature

Context. Well studied open clusters (OCs) of the solar neighborhood are frequently used as reference objects to test galactic and stellar theories. For that purpose, their chemical composition needs to be known with a high level of confidence. It is also important to clarify if each OC is chemically homogeneous and if it has a unique chemical signature. Aims. The aims of this work are (1) to determine accurate and precise abundances of 22 chemical species (from Na to Eu) in the Hyades, Praesepe, and Rupecht 147 by using a large number of stars at different evolutionary states, (2) to evaluate the level of chemical homogeneity of these OCs, and (3) to compare their chemical signatures. Methods. We gathered ∼800 high resolution and high signal-to-noise spectra of ∼100 members in the three clusters, which were obtained with the latest memberships based on Gaia DR2 data. We built a pipeline, which computes atmospheric parameters and strictly line-by-line differential abundances among twin stars in our sample. With this method, we were able to reach a very high precision in the abundances (0.01–0.02 dex in most of the elements). Results. We find large differences in the absolute abundances in some elements, which can be attributed to diffusion, non-local thermodynamic equilibrium (non-LTE) effects, or systematics in the analysis. For the three OCs, we find strong correlations in the differential abundances between different pairs of elements. According to our experiment with synthetic data, this can be explained by some level of chemical inhomogeneity. We compare differential abundances of several stars from the Hyades and Praesepe tails: The stars that differ more in chemical abundances also have distinct kinematics, even though they have been identified as members of the tail. Conclusions. It is possible to obtain high precision abundances using a differential analysis even when mixing spectra from different instruments. With this technique, we find that the Hyades and Preasepe have the same chemical signature when G dwarfs and K giants are considered. Despite a certain level of inhomogeneity in each cluster, it is still possible to clearly distinguish the chemical signature of the older cluster Ruprecht 147 when compared to the Hyades and Praesepe.

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