Effect of magnesium and calcium on oxygen activity in model nickel melts at PAr = 0.1 MPa and analysis of nonmetallic inclusions

2021 ◽  
pp. 2-11
Author(s):  
V.T. Burtsev ◽  
◽  
E.B. Chabina ◽  
S.N. Anuchkin ◽  
◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Nonmetallic Inclusions ◽  
Oxygen Activity ◽  
Emf Method

The EMF method was used to study the oxygen activity in nickel melts during the deoxidation of Mg/Ca (up to 0.2 wt.%) in the atmosphere of ultrapure Ar. The logarithmic dependences were expressed in the change a[O] from the concentrations of deoxidizers. A significant increase in the deoxidation capacity of Mg and Ca was shown in comparison with Al at a content of 0.05 wt.% of the deoxidizers in the metal. The morphology and composition of nonmetallic inclusions after deoxidation were studied and complex configurations of nonmetallic inclusions from 2 to 100 microns located along the grain boundaries were shown.

Interaction of B and Hf with oxygen in a nickel melt at РAr = 0.1 MPa and analysis of nonmetallic inclusions

2021 ◽  
Vol 5 ◽  
pp. 49-59
Author(s):  
V. T. Burtsev ◽  
◽  
E.B. Chabina ◽  
Keyword(s):  
Dissolved Oxygen ◽  
Grain Boundaries ◽  
Nonmetallic Inclusions ◽  
Metallic Inclusions ◽  
Alloyed Nickel

The deoxidation of complex alloyed nickel-based alloys during melting in vacuum is carried out in the presence of aluminum with strong deoxidizers B and Hf, which requires additional knowledge about the activity of dissolved oxygen. For this, the activity was investigated in model melts Ni – O – (B/Hf, 0.001 – 0.1 wt. % of each) and Ni – O – Al (5 %) – (B/Hf, 0.001 – 0.1 wt. % of each) at 1560 °C and РAr = 0.1 MPa by the method of instantaneous EMF recording using certified sensors. It was shown that a[O] with the introduction of B into the melt without aluminum is 1.3 times less than with the introduction of Hf, and for melts with aluminum, a[O] decreased 1.6 times as compared with Hf. The study of the morphology and composition of non-metallic inclusions of the Ni – O – (B/Hf) systems showed that the inclusions are located along grain boundaries, have various complex configurations and sizes from 2 to 100 μm. These phases contain Ni, Fe, Zr, S, O, as well as Hf, Pb, Bi, Si, Mg after deoxidation of Hf and an increased content of Zr after deoxidation of B.

Interaction of La and Ce with O and S in nickel melts at PAr = 0.1 MPa

2020 ◽  
Vol 4 ◽  
pp. 72-79
Author(s):  
V.T. Burtsev ◽  
◽  
E.B. Chabina ◽  
V.V. Sidorov ◽  
◽  
...  
Keyword(s):  
Nonmetallic Inclusions ◽  
Oxygen Activity ◽  
Sem Investigation

The method of instant EMF fixation was used to determine the oxygen activity in model Ni melts containing up to 0.001-0.20 wt.% La and Ce. It was shown that at PAr = 0.1 MPa and 1560°C, the oxygen activity when cerium is introduced into the melt is 4.7 times lower than when it deoxidized with lanthanum. SEM investigation shows that the composition of nonmetallic inclusions in molten Ni deoxidized by La and Ce indicates a stronger bond of Ce with oxygen than La and a stronger bond of La with sulfur than Ce.

Analysis of Nonmetallic Inclusions on Grain Boundaries in Steel Hardened by Carbonitrides

2004 ◽  
Vol 46 (3/4) ◽  
pp. 103-105
Author(s):  
I. L. Brodetskii ◽  
V. P. Kharchevnikov ◽  
A. I. Trotsan
Keyword(s):  
Grain Boundaries ◽  
Nonmetallic Inclusions

Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 176-177
Author(s):  
D. E. Fornwalt ◽  
A. R. Geary ◽  
B. H. Kear
Keyword(s):  
Electron Microscope ◽  
Grain Boundaries ◽  
Volume Fraction ◽  
Rupture Life ◽  
Stress Rupture ◽  
High Volume ◽  
Precipitate Morphology ◽  
Stress Rupture Life ◽  
Nickel Base ◽  
Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

Measurement of the Displacement Across a Coincidence Grain Boundary

1977 ◽  
Vol 35 ◽  
pp. 124-125
Author(s):  
J. W. Matthews ◽  
W. M. Stobbs
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stacking Fault ◽  
The Other ◽  
Measuring Technique ◽  
High Angle ◽  
Twin Boundaries ◽  
Rigid Displacement ◽  
Cubic Crystals ◽  
Lattice Displacement

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

The Effect of Specimen Thickness and Probe Size on Aem Analysis of Cr-Depletion Profiles in Sensitized Stainless Steel

1982 ◽  
Vol 40 ◽  
pp. 518-519
Author(s):  
E. L. Hall
Keyword(s):  
Grain Boundaries ◽  
Boundary Region ◽  
Chromium Concentration ◽  
Foil Thickness ◽  
Specimen Thickness ◽  
Probe Size ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Sensitization Process ◽  
Compositional Gradients

Sensitization in stainless steels is caused by the formation of chromium-rich M23C6 carbides at grain boundaries, which depletes the adjacent matrix and boundary region of chromium, and hence leads to rapid intergranular attack. To fully understand the sensitization process, and to test the accuracy of theories proposed to model this process, it is necessary to obtain very accurate measurements of the chromium concentration at grain boundaries in sensitized specimens. Quantitative X-ray spectroscopy in the analytical electron microscope (AEM) enables the chromium concentration profile across these boundaries to be studied directly; however, it has been shown that a strong effect of foil thickness and electron probe size may be present in the analysis of rapidly-changing compositional gradients. The goal of this work is to examine these effects.

Electrolytic Isolation of Twin-Type Shock Deformation Structures

1967 ◽  
Vol 25 ◽  
pp. 318-319
Author(s):  
F. I. Grace ◽  
L. E. Murr
Keyword(s):  
Grain Boundaries ◽  
Thin Foil ◽  
Electrolyte Composition ◽  
Experimental Conditions ◽  
Average Current Density ◽  
Electron Transmission ◽  
Deformation Structures ◽  
The Matrix ◽  
Average Current ◽  
Specimen Edge

During the course of electron transmission investigations of the deformation structures associated with shock-loaded thin foil specimens of 70/30 brass, it was observed that in a number of instances preferential etching occurred along grain boundaries; and that the degree of etching appeared to depend upon the various experimental conditions prevailing during electropolishing. These included the electrolyte composition, the average current density, and the temperature in the vicinity of the specimen. In the specific case of 70/30 brass shock-loaded at pressures in the range 200-400 kilobars, the predominant mode of deformation was observed to be twin-type faults which in several cases exhibited preferential etching similar to that observed along grain boundaries. A novel feature of this particular phenomenon was that in certain cases, especially for twins located in the vicinity of the specimen edge, the etching or preferential electropolishing literally isolated these structures from the matrix.

Elucidation of block boundaries as the dissolution channels in hydrated cement

1978 ◽  
Vol 36 (1) ◽  
pp. 484-485
Author(s):  
N.V. Belov ◽  
U.I. Papiashwili ◽  
B.E. Yudovich
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Benzoyl Peroxide ◽  
Phase Contrast ◽  
Active Role ◽  
Point Of View ◽  
Hardened Cement ◽  
Hydrated Cement ◽  
Hardened Cement Paste

It has been almost universally adopted that dissolution of solids proceeds with development of uniform, continuous frontiers of reaction.However this point of view is doubtful / 1 /. E.g. we have proved the active role of the block (grain) boundaries in the main phases of cement, these boundaries being the areas of hydrate phases' nucleation / 2 /. It has brought to the supposition that the dissolution frontier of cement particles in water is discrete. It seems also probable that the dissolution proceeds through the channels, which serve both for the liquid phase movement and for the drainage of the incongruant solution products. These channels can be appeared along the block boundaries.In order to demonsrate it, we have offered the method of phase-contrast impregnation of the hardened cement paste with the solution of methyl metacrylahe and benzoyl peroxide. The viscosity of this solution is equal to that of water.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

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