Ductility Limit Diagrams for Superplasticity and Forging of High Temperature Polycrystalline Materials

Bi–Ca–Co–O polycrystalline materials with a layered structure were prepared. The synthesis of the sintered specimens from two starting compositions, Bi1.8Ca2Co2Oxand Bi2.5Ca2.5Co2Ox, revealed the latter is preferentially formed at high temperature(850 °C). The increase in sintering time was shown by growth of large platelike grains (up to 50 μm in diameter and several micrometers in thickness). The reaction mechanisms during the heat treatment and the preferential formation of the Bi2.5Ca2.5Co2Ox phase were observed by x-ray diffraction, thermogravimetry–differential thermal analysis, and scanning electron microscopy. These techniques supposed the presence of a liquid phase at high temperature, origin of a highly kinetic phase formation, and the growth of large grains. Interestingly the liquid phase reaction promotes an efficient stacking and sliding of grains during hot-forging treatment, and highly (00l) oriented materials were prepared. A relationship between thermoelectric performance, texture strength, and microstructure is clarified.

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Corrosion of Polycrystalline Fe-Si Alloys Studied by TMS, CEMS, and XPS

CORROSION ◽

10.5006/2676 ◽

2018 ◽

Vol 74 (6) ◽

pp. 623-634 ◽

Cited By ~ 2

Author(s):

Rafał Idczak ◽

Karolina Idczak ◽

Robert Konieczny

Keyword(s):

Mössbauer Spectroscopy ◽

High Temperature ◽

Photoelectron Spectroscopy ◽

Mossbauer Spectroscopy ◽

High Temperature Corrosion ◽

Polycrystalline Materials ◽

Metal Interface ◽

Mößbauer Spectroscopy ◽

Segregation Process ◽

Strong Segregation

The high-temperature corrosion behavior of three polycrystalline Fe-Si alloys containing approximately 4, 5, and 10 at% Si was studied using transmission Mössbauer spectroscopy (TMS), conversion electron Mössbauer spectroscopy (CEMS), and x-ray photoelectron spectroscopy (XPS). The XPS measurements reveal the strong segregation process of silicon atoms to the surface. Moreover, the obtained XPS results suggest that the presence of adsorbed oxygen on the Fe-Si surface effectively enhances the silicon segregation process. On the other hand, the obtained TMS and CEMS spectra show that even 10% of silicon atoms dissolved in the iron matrix do not prevent high-temperature corrosion of the studied Fe-Si alloys. During exposure to air at 870 K, a systematic growth of an α-Fe2O3 compound was observed. Finally, the Mössbauer results show that, during exposure to air, oxygen atoms diffuse to the studied polycrystalline materials not only through the oxide/metal interface on the surface but also along the grain boundaries. Such effects result in the formation of iron oxides in deeper parts of the alloy.

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Effect of HPHT processing on the structure, and thermoelectric properties of Co4Sb12 co-doped with Te and Sn

Journal of Materials Chemistry A ◽

10.1039/c4ta05477f ◽

2015 ◽

Vol 3 (8) ◽

pp. 4637-4641 ◽

Cited By ~ 38

Author(s):

Hairui Sun ◽

Xiaopeng Jia ◽

Le Deng ◽

Pin Lv ◽

Xin Guo ◽

...

Keyword(s):

High Pressure ◽

High Temperature ◽

Thermoelectric Properties ◽

Polycrystalline Materials ◽

X Ray Diffraction ◽

X Ray ◽

Temperature Method ◽

Co Doped

Te–Sn co-doped Co4Sb12 bulk polycrystalline materials Co4Sb11.7−xTexSn0.3 have been prepared using a high pressure and high temperature method and then characterized using X-ray diffraction.

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Powder Diffractometry at the Tsukuba Photon Factory

Australian Journal of Physics ◽

10.1071/ph880133 ◽

1988 ◽

Vol 41 (2) ◽

pp. 133 ◽

Cited By ~ 14

Author(s):

R Uno ◽

H Ozawa ◽

T Yamanaka ◽

H Morikawa ◽

M Ando ◽

...

Keyword(s):

High Pressure ◽

High Temperature ◽

Molten Salts ◽

Amorphous Solids ◽

Sufficient Accuracy ◽

Polycrystalline Materials ◽

Photon Factory ◽

Main Work ◽

Basic Features ◽

Work Done

Powder dift"ractometry at the Photon Factory has been carried out with a diffractometer specially designed for measurements on molten salts, liquids, amorphous solids and polycrystalline materials. The main work done with the diffractometer has been structure analysis, and the study of phase transitions at high pressure and high temperature on Ge02' In 1986 a new powder diffractometer was designed and constructed. The aims of the new diffractometer are to allow easy alignment and provide sufficient accuracy for measurements taking advantage of anomalous dispersion and also to provide for energy dispersive diffractometry. The basic features are described.

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Effect of Thermomechanical Processes on Σ3 Grain Boundary Distribution in a Nickel Base Superalloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.2333 ◽

2010 ◽

Vol 638-642 ◽

pp. 2333-2338

Author(s):

Nadia Souaï ◽

Roland E. Logé ◽

Yvan Chastel ◽

Nathalie Bozzolo ◽

Vincent Maurel ◽

...

Keyword(s):

High Temperature ◽

Grain Boundary ◽

Polycrystalline Materials ◽

Nickel Base Superalloy ◽

Grain Boundary Engineering ◽

Thermomechanical Process ◽

Grain Boundary Character ◽

Nickel Base ◽

Thermomechanical Processes ◽

Base Superalloy

According to various studies, Grain Boundary Engineering (GBE) is likely to enhance mechanical properties of polycrystalline materials. The present investigation highlights some relationships between thermomechanical process (TMP) parameters of a commercial nickel-base superalloy PER72, supplied by Aubert & Duval (equivalent to Udimet®720™) and the resulting microstructure. The long-term goal is to develop TMPs that modify the Grain Boundary Character Distributions (GBCD) in order to improve high temperature properties. In this context, Grain Boundary Engineering (GBE) techniques are considered, thinking of replacing standard forming processes by optimised thermomechanical treatments. Mechanical testing at high temperature (compression and torsion tests) has been carried out and it is shown that multi-step treatments promote twinning. Some clues are then presented in an attempt to explain when and how twins are created.

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Structure and phase composition of aluminosilicate-based microspheres

Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel nogo universiteta JOURNAL of Construction and Architecture ◽

10.31675/1607-1859-2020-22-4-140-146 ◽

2020 ◽

Vol 22 (4) ◽

pp. 140-146

Author(s):

V. A. Vlasov ◽

V. V. Shekhovtsov ◽

O. G. Volokitin ◽

N. K. Skripnikova ◽

G. G. Volokitin ◽

...

Keyword(s):

Phase Composition ◽

High Temperature ◽

Condensed Phase ◽

Amorphous State ◽

Amorphous Structure ◽

Strength Properties ◽

Polycrystalline Materials ◽

Alumina Powder ◽

X Ray ◽

Α Al2o3

The paper focuses on aluminosilicate-based microspheres, whose shell represents an X-ray amorphous state, which significantly reduces their strength properties. However, a number of technological characteristics used in industry provide the formation of glass-ceramic and crystalline states of the condensed phase, which is the shell microsphere. Presently, the formation of the structure and phase composition during the interaction between aluminosilicates (the SiO2/Al2O3 ratio varies between 0−100 %) and high-temperature (≥ 5000 K) plasma is most interesting. This paper presents the research results of the structure and phase composition of the aluminosilicate-based condensed phase during the microsphere production. The X-ray phase analysis shows that after cooling, the structure and phase composition of the microsphere shells based on refractory polycrystalline materials promotes the formation of the X-ray amorphous structure at SiO2 ≥ 60 wt. % in the initial powder and the transition of γ-Al2O3 cryptocrystalline phase to high-temperature α- Al2O3 phase with the use of the initial alumina powder.

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Ductility limit diagrams for superplasticity and forging of high temperature polycrystalline materials

Acta Materialia ◽

10.1016/j.actamat.2020.04.050 ◽

2020 ◽

Vol 194 ◽

pp. 378-386 ◽

Cited By ~ 1

Author(s):

Wei Zhang ◽

Yanfei Gao ◽

Zhili Feng ◽

Xin Wang ◽

Siyu Zhang ◽

...

Keyword(s):

High Temperature ◽

Polycrystalline Materials

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Influence of Thermo-Mechanical Processing on the Microstructure of Beryllia Dispersed Nickel Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071363 ◽

1973 ◽

Vol 31 ◽

pp. 184-185

Author(s):

M.S. Grewal ◽

S.A. Sastri ◽

N.J. Grant

Keyword(s):

High Temperature ◽

Nickel Alloys ◽

Thermomechanical Processing ◽

Cold Work ◽

High Temperature Strength ◽

Strengthening Effect ◽

Mechanical Processing ◽

Uniform Dispersion ◽

Oxide Particles ◽

Nickel Base

Currently there is a great interest in developing nickel base alloys with fine and uniform dispersion of stable oxide particles, for high temperature applications. It is well known that the high temperature strength and stability of an oxide dispersed alloy can be greatly improved by appropriate thermomechanical processing, but the mechanism of this strengthening effect is not well understood. This investigation was undertaken to study the dislocation substructures formed in beryllia dispersed nickel alloys as a function of cold work both with and without intermediate anneals. Two alloys, one Ni-lv/oBeo and other Ni-4.5Mo-30Co-2v/oBeo were investigated. The influence of the substructures produced by Thermo-Mechanical Processing (TMP) on the high temperature creep properties of these alloys was also evaluated.

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Application of TEM to Deformation, Wear, and Fracture of Ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052377 ◽

1974 ◽

Vol 32 ◽

pp. 472-473

Author(s):

B. J. Hockey

Keyword(s):

Wear Resistance ◽

High Temperature ◽

Mechanical Behavior ◽

Brittle Materials ◽

High Temperature Strength ◽

Wide Range ◽

Corrosive Environments ◽

Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

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Lattice Imaging of Grain Boundaries in Ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078171 ◽

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.

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