scholarly journals SHS Synthesis, SPS Densification and Mechanical Properties of Nanometric Tungsten

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 252
Author(s):  
Sarah Dine ◽  
Elodie Bernard ◽  
Nathalie Herlin ◽  
Christian Grisolia ◽  
David Tingaud ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cooling System ◽  
Second Phase ◽  
Alloying Element ◽  
Pure Tungsten ◽  
Powder Synthesis ◽  
Grain Sizes ◽  
Chromium Alloys ◽  
Current Production ◽  
Strength And Ductility

Recent studies have shown that low grain sizes are favorable to improve ductility and machinability in tungsten, as well as a resistance to ablation and spallation, which are key properties for the use of this material in a thermonuclear fusion environment (Tokamaks such as ITER). However, as one of the possible incidents during Tokamak operation is the leakage of air or water from the cooling system inside the chamber, resulting in the so-called loss of vacuum accident (LOVA), extensive oxidation may arise on tungsten components, and the use of an alloy with improved oxidation resistance is therefore highly desirable. As current production routes are not suitable for the fabrication of bulk nanostructured tungsten or tungsten alloys samples, we have proposed a new methodology based on powder metallurgy, including the powder synthesis, the densification procedure, and preliminary mechanical testing, which was successfully applied to pure tungsten. A similar study is hereby presented on tungsten-chromium alloys with up to 6 wt.% Cr. Results show that full tungsten densification may be obtained by SPS at a temperature lower than 1600 °C. The resulting morphology strongly depends on the amount of the alloying element, presenting a possible second phase of chromium oxide, but always keeps a partial nanostructure inherited from the synthesized powders. Such microstructure had previously been identified as being favorable to the use of these materials in fusion environments and for improved mechanical properties, including hardness, yield strength and ductility, all of which is confirmed by the present study.

Effect of Phosphorus on Microstructure and Properties of Al-Mg2Si Alloys Subjected to Electromagnetic Stirring

2011 ◽  
Vol 291-294 ◽  
pp. 652-657 ◽  
Author(s):  
Yu Yan Ren ◽  
Ying Min Li
Keyword(s):  
Mechanical Properties ◽  
Low Cost ◽  
Holding Time ◽  
Experimental Results ◽  
Electromagnetic Stirring ◽  
Low Density ◽  
Alloying Element ◽  
Manufacture Technology ◽  
Elastic Modules ◽  
Strength And Ductility

Al-Mg2Si composite has such advantages as low density, high elastic modules, simple manufacture technology and low cost. However, its strength and ductility need to be enhanced. Thus, the alloying element P was added to control the microstructure of Al-Mg2Si alloy and furthermore improve the mechanical properties of the composite. The experimental results show that the microstructure of the Al-Mg2Si alloys subjected to electromagnetic stirring can be significantly refined and the mechanical properties of the alloy get improved due to the addition of phosphorus. It is found that the best modification effect can be achieved when the adding amount of phosphorus is in the range from 0.7% to 1.1% and the holding time is about 15 minutes, and the mechanical properties of the Al-Mg2Si alloys get markedly enhanced.

Effect of Second Phase on Mechanical Properties of Bainite-Base Steels

2006 ◽  
Vol 15-17 ◽  
pp. 780-785 ◽  
Author(s):  
Hak Cheol Lee ◽  
Xiao Dan Wu ◽  
Young Min Kim ◽  
Nack J. Kim
Keyword(s):  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Retained Austenite ◽  
Fine Particles ◽  
Volume Fraction ◽  
The Other ◽  
Second Phase ◽  
Effective Grain Size ◽  
Hot Rolling Conditions ◽  
Strength And Ductility

Effects of acicular ferrite and retained austenite on the mechanical properties of bainite-base steels were investigated. Various morphology and volume fraction of constituent phases have been obtained by control of hot rolling conditions and alloy compositions. It has been shown that the steels containing retained austenite have better combinations of strength and ductility than the ones with no retained austenite. However, there is no noticeable change in DBTT by the incorporation of retained austenite in the microstructure since retained austenite exists as fine particles. On the other hand, DBTT of the steels are largely affected by the presence of acicular ferrite in the microstructure. EBSD analyses of fractured Charpy specimens show that cracks are deflected within the morphological packet of acicular ferrite, indicating its role in reducing the effective grain size of the steels.

scholarly journals Effect of Pretreatment and Cryogenic Temperatures on Mechanical Properties and Microstructure of Al-Cu-Li Alloy

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4873
Author(s):  
Cheng Wang ◽  
Jin Zhang ◽  
Youping Yi ◽  
Chunnan Zhu
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Hot Deformation ◽  
Electron Backscatter Diffraction ◽  
Coarse Grained ◽  
Second Phase ◽  
Strengthening Effect ◽  
Cryogenic Temperatures ◽  
Transmission Electron ◽  
Strength And Ductility

The mechanical properties of Al-Cu-Li alloys after different pretreatments were investigated through tensile testing at 25 and −196 °C, and the corresponding microstructure characteristics were obtained through optical metallography, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. An increasing mechanism of both strength and ductility at cryogenic temperatures was revealed. The results show that the hot deformation pretreatment before homogenization promoted the precipitation of Al3Zr particles, improved particle distribution, and inhibited local precipitation-free zones (PFZ). Both hot deformation pretreatment before homogenization and cryogenic temperature were able to improve strength and ductility. The former improved strength by promoting the precipitation of Al3Zr particles while enhancing the strengthening effect of the second-phase particles and reducing the thickness of the coarse-grained layer. Meanwhile, the increase in ductility is attributable to the decrease in thickness of the coarse-grained layer, which reduced the deformation incompatibility between the coarse and fine grains and increased the strain-hardening index. The latter improved the strength by suppressing dynamic recovery during the deformation process, increasing the dislocation density, and enhancing the work hardening effect. Additionally, the increase in ductility is attributable to the suppression of planar slip and strengthening of grain boundaries, which promoted the deformation in grain interiors and made the deformation more uniform.

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

Atomic structure of interface of intermetallic compound TiAl and nitride Ti2AIN using HREM and image processing

1991 ◽  
Vol 49 ◽  
pp. 570-571
Author(s):  
E. Sukedai ◽  
H. Mabuchi ◽  
H. Hashimoto ◽  
Y. Nakayama
Keyword(s):  
Mechanical Properties ◽  
Image Processing ◽  
Composite Material ◽  
Intermetallic Compound ◽  
Side Surface ◽  
High Resolution Electron Microscopy ◽  
Hexagonal Structure ◽  
Second Phase ◽  
Resolution Electron ◽  
Compound Tial

In order to improve the mechanical properties of an intermetal1ic compound TiAl, a composite material of TiAl involving a second phase Ti2AIN was prepared by a new combustion reaction method. It is found that Ti2AIN (hexagonal structure) is a rod shape as shown in Fig.1 and its side surface is almost parallel to the basal plane, and this composite material has distinguished strength at elevated temperature and considerable toughness at room temperature comparing with TiAl single phase material. Since the property of the interface of composite materials has strong influences to their mechanical properties, the structure of the interface of intermetallic compound and nitride on the areas corresponding to 2, 3 and 4 as shown in Fig.1 was investigated using high resolution electron microscopy and image processing.

scholarly journals Novel Co-Cu-Based Immiscible Medium-Entropy Alloys with Promising Mechanical Properties

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 238
Author(s):  
Sujung Son ◽  
Jongun Moon ◽  
Hyeonseok Kwon ◽  
Peyman Asghari Rad ◽  
Hidemi Kato ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Binary System ◽  
Design Methodology ◽  
Miscibility Gap ◽  
Face Centered Cubic ◽  
Solid Solution Strengthening ◽  
Solution Strengthening ◽  
Face Centered ◽  
Strength And Ductility ◽  
Cobalt Copper

New AlxCo50−xCu50−xMnx (x = 2.5, 10, and 15 atomic %, at%) immiscible medium-entropy alloys (IMMEAs) were designed based on the cobalt-copper binary system. Aluminum, a strong B2 phase former, was added to enhance yield strength and ultimate tensile strength, while manganese was added for additional solid solution strengthening. In this work, the microstructural evolution and mechanical properties of the designed Al-Co-Cu-Mn system are examined. The alloys exhibit phase separation into dual face-centered cubic (FCC) phases due to the miscibility gap of the cobalt-copper binary system with the formation of CoAl-rich B2 phases. The hard B2 phases significantly contribute to the strength of the alloys, whereas the dual FCC phases contribute to elongation mitigating brittle fracture. Consequently, analysis of the Al-Co-Cu-Mn B2-strengthened IMMEAs suggest that the new alloy design methodology results in a good combination of strength and ductility.

scholarly journals A Study on the Damping Capacities of Mg–Zn–Y-Based Alloys with Lamellar Long Period Stacking Ordered Phases by Preparation Process

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 79
Author(s):  
Ruopeng Lu ◽  
Kai Jiao ◽  
Yuhong Zhao ◽  
Kun Li ◽  
Keyu Yao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Damping Capacity ◽  
Second Phase ◽  
Preparation Process ◽  
Obvious Effect ◽  
Lpso Phase ◽  
Long Period ◽  
Lamellar Phases ◽  
Ordered Phases

Mg alloys with fine mechanical properties and high damping capacities are essential in engineering applications. In this work, Mg–Zn–Y based alloys with lamellar long period stacking ordered (LPSO) phases were obtained by different processes. The results show that a more lamellar second phase can be obtained in the samples with more solid solution atoms. The density of the lamellar LPSO phase has an obvious effect on the damping of the magnesium alloy. The compact LPSO phase is not conducive to dislocation damping, but sparse lamellar phases can improve the damping capacity without significantly reducing the mechanical properties. The Mg95.3Zn2Y2.7 alloy with lamellar LPSO phases and ~100 μm grain size exhibited a fine damping property of 0.110 at ε = 10–3.

Effect of Small Iron, Chromium and Boron Additions as Alloying Elements on Microstructure and Mechanical Properties of Ni3Al

2007 ◽  
Vol 23 ◽  
pp. 123-126
Author(s):  
Radu L. Orban ◽  
Mariana Lucaci
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Room Temperature ◽  
Alloying Elements ◽  
Alloyed Powder ◽  
Mechanically Alloyed ◽  
Powder Mixtures ◽  
B Additions ◽  
Strength And Ductility ◽  
Iron Chromium

This paper investigates the effect of Fe, Cr and B additions, in small proportions, as alloying elements in Ni3Al with the purpose to reduce its intrinsic fragility and extrinsic embrittlement and to enhance, in the same time, its mechanical properties. It represents a development of some previous research works of the authors, proving that Ni3Al-Fe-Cr-B alloys obtained by reactive synthesis (SHS) starting from Mechanically Alloyed powder mixtures have superior both room temperature tensile strength and ductility, and compression ones at temperatures up to 800 °C, than pure Ni3Al. These create premises for their using as superalloys substitutes.

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