Microstructure Characterization of Hot Deformed Fe-32%Ni Alloy

2011 ◽  
Vol 230-232 ◽  
pp. 154-158 ◽  
Author(s):  
Bao Jun Han
Keyword(s):  
Dislocation Density ◽  
Dynamic Equilibrium ◽  
Optical Microscope ◽  
Electron Back Scatter Diffraction ◽  
High Dislocation Density ◽  
Hot Deformation Behavior ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Ni Alloy

Hot deformation behavior and microstructure evolution of Fe-32%Ni alloy were investigated when compressed at the temperature of 1000°C and a strain rate of 2×10-3s-1. The microstructures were analyzed using optical microscope (OM), electron back scatter diffraction (EBSD) and transmission electron microscope (TEM). The results show that the generation and development of dynamic recrystallization (DRX) can obviously refine the grains of Fe-32Ni% alloy and the DRX reached dynamic equilibrium when the strain was high. According to the TEM observations, the DRX microstructure can be categorized into three kinds: grains with low dislocation density, which are DRX nucleations; grains with low dislocation density around the grain boundary and high dislocation density in its interior which means that grains with dislocation density gradient and which are DRX grains in growth; grains with high dislocation density, which are fully work-hardened DRX grains.

Grain Refinement of Fe-32%Ni Alloy by Multi-Axial Forging

2011 ◽  
Vol 80-81 ◽  
pp. 18-21
Author(s):  
Xiao Juan Wang ◽  
Bao Jun Han
Keyword(s):  
Electron Microscopy ◽  
Microstructure Evolution ◽  
Large Angle ◽  
Optical Microscope ◽  
Electron Back Scatter Diffraction ◽  
Deformation Bands ◽  
Transmission Electron ◽  
Ni Alloy ◽  
Cumulative Strain ◽  
Austenite Grains

The effect of strain on the microstructure evolution of Fe-32%Ni alloy during multi-axial forging at the temperature of 500°C and a strain rate of 210-2 s-1 was investigated by optical microscope (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back scatter diffraction (EBSD) observations. The results show that the austenite grains were greatly refined with increasing cumulative strain, and the microstructure evolution during multi-axial forging can be summarized as such a process that deformation bands crossing each other subdivide the original austenite grain into several sub-grains and then these sub-grains are subdivided into more small ones and gradually angled to new independent grains with their boundaries transformed into large angle boundaries in subsequent compression.

Heteroepitaxy and Characterization of Low-Dislocation-Density GaN on Periodically Grooved Substrates

2000 ◽  
Vol 639 ◽  
Author(s):  
T. Detchprohm ◽  
M. Yano ◽  
R. Nakamura ◽  
S. Sano ◽  
S. Mochiduki ◽  
...  
Keyword(s):  
Dislocation Density ◽  
New Method ◽  
Growth Technique ◽  
New Approach ◽  
Density Area ◽  
Low Dislocation Density ◽  
Dislocation Densities ◽  
Movpe Growth

ABSTRACTWe have developed a new method to prepare low-dislocation-density GaN by using periodically grooved substrates in a conventional MOVPE growth technique. This new approach was demonstrated for GaN grown on periodically grooved α-Al2O3(0001), 6H-SiC(0001)Si and Si(111) substrates. Dislocation densities were 2×107 cm−2 in low-dislocation-density area.

Misfit dislocations in heteroepitaxial systems with low dislocation density

1978 ◽  
Vol 36 (1) ◽  
pp. 132-133
Author(s):  
W. Hagen ◽  
H. Strunk
Keyword(s):  
Electron Microscopy ◽  
Dislocation Density ◽  
Misfit Dislocations ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Heteroepitaxial Layers ◽  
Transparent Area ◽  
Electron Transparent Area

The growth of heteroepitaxial layers causes stress across the interface which in a certain range of layer thickness may he relaxed by the formation of misfit dislocations at the interface. Systematic investigations of such misfit structures by transmission electron microscopy (TEM) have previously heen conducted only on systems with a relatively large misfit parameter f, i.e. with a high dislocation density. However, this case presents difficulties in the analysis because of the complexity of the dense structures.Interfaces containing a low density of misfit dislocations, e.g. heteroepitaxial systems with low misfit, should consequently be investigated. High voltage electron microscopy (HVEM) enables us to study specimens of several μm in thickness and offers decisive advantages over 100 kV TEM: i) generally, specimens can he prepared by thinning the substrate only, ii) thick foils are mechanically stable, which allows the preparation of specimens with an electron transparent area of several mm2.We report here new results on the initial formation of misfit dislocation structures in the heteroepitaxial system Ge on GaAs (f = 0.074%).

Characterization of Dislocations in GaN Thin Film and GaN/AlN Multilayer

2012 ◽  
Vol 725 ◽  
pp. 75-78
Author(s):  
Noriko Ohmori ◽  
Tomonori Uchimaru ◽  
Hiroyuki Fujimori ◽  
Jun Komiyama ◽  
Yoshihisa Abe ◽  
...  
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Density ◽  
Buffer Layer ◽  
Direction Parallel ◽  
Density Of Dislocations ◽  
Transmission Electron ◽  
Sudden Decrease

The dislocations in GaN thin film with GaN/AlN multilayer (ML) as the buffer layer were evaluated using transmission electron microscopy. A high density of dislocations parallel to the GaN/ML interface and a sudden decrease in the dislocation density at the GaN/ML interface were found. Dislocation propagation in the direction parallel to the GaN/ML interface by turning horizontally on the GaN/ML interface is considered to be effective in decreasing the dislocation density at the top layer of GaN.

Transmission Electron Microscopy of Longitudinal Double Submerged Arc Weld (LDSAW) of X-120M Steel Line Pipe

2012 ◽  
Vol 585 ◽  
pp. 460-464
Author(s):  
Jai Dev Singh Chandel ◽  
Nand Lal Singh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Density ◽  
Arc Welding ◽  
Microstructural Characterization ◽  
Submerged Arc Welding ◽  
High Dislocation Density ◽  
Line Pipe ◽  
Transmission Electron ◽  
Submerged Arc

This paper deals with the development of submerged arc welding wires for longitudinal double submerged arc welded (LDSAW) line pipe weld through transmission electron microscopy (TEM). The experimental procedure in the paper describes the test coupons preparation for submerged arc welding (SAW) with various combinations of wire and flux with varying level of alloying element. Microstructural characterization by transmission electron microscopy has been carried out to establish the desired microstructure in the weld of LDSAW for manufacturing the API-5L X-120M line pipes. The TEM micrographs for shows the lath type ferrite and bainitic type ferrite with high dislocation density. The lath type ferrite and bainitic type ferrite with high dislocation density also have fine precipitates in the ferrite matrix having orientation relationship. The weld metal suitable for X-120M have the microstructure of mainly bainitic and martensitic with high dislocation density and coarse precipitates in the matrix. The bainitic and martensitic microstructure have excellent fracture toughness down to -20 °C at this strength level (X-120M).

Multiscale Approach to Texture-Microstructure Coupling

2006 ◽  
Vol 509 ◽  
pp. 1-10
Author(s):  
Richard Penelle ◽  
Thierry Baudin
Keyword(s):  
Titanium Aluminides ◽  
Processing Route ◽  
Multiscale Approach ◽  
Electron Backscattered Diffraction ◽  
Local Texture ◽  
Transmission Electron ◽  
Ni Alloy ◽  
Complementary Techniques

Materials exhibit microstructures and textures that influence their use and properties. Xray and neutron diffraction allow characterization of the bulk texture, whereas Electron Backscattered Diffraction (EBSD) permits determination of the local texture. In many cases Transmission Electron Microscopy (TEM) remains necessary to characterize the substructure and the local texture for highly deformed materials. Depending on the scale considered, all these complementary techniques permit the coupling of texture and microstructure so that it becomes possible to control microstructure and its evolution during a processing route. Some examples in titanium aluminides, (α + β) titanium alloys and an Fe-Ni alloy will illustrate this challenge.

A Fretting Damage Analysis of Railway Axle

2013 ◽  
Vol 652-654 ◽  
pp. 1393-1398 ◽  
Author(s):  
Yue Jun Zhang ◽  
Jin Fang Peng ◽  
Zhen Bing Cai ◽  
Min Hao Zhu
Keyword(s):  
Electron Microscope ◽  
Dislocation Density ◽  
Cellular Structure ◽  
Optical Microscope ◽  
Hardness Tester ◽  
Press Fit ◽  
Railway Axle ◽  
Transmission Electron ◽  
Leeb Hardness ◽  
Fretting Damage

A railway axle operated over 6×105 km has been detected by varied micro-examination methods in detail. The examination of Leeb hardness tester results showed that the hardness of the press-fit seats presented higher hardness than that of other sites. According to the micro morphological analyses by optical microscope (OM), scanning electron microscope (SEM), energy dispersive X-ray spectrum (EDX), and profilometer on the surface at different press-fit seats, the most severe damage band was occurred at the inner edge of wheel seat near the gear seat. The transmission electron microscope (TEM) results indicated that the dislocation density of subsurface, beneath the axle surface about 20 μm, was much higher with a great deal of dislocation tangles, pile-ups and cellular structure formation. However, when the examination depth increased to 100 μm, no cellular structure can be founded, the dislocation density was very low, so the damage depth was less than 100 μm.

TEM studies of dislocations in deformed Ga1-xInxAs single crystals

1988 ◽  
Vol 46 ◽  
pp. 900-901
Author(s):  
R. S. Rai ◽  
S. Guruswamy ◽  
K. T. Faber ◽  
J. P. Hirth
Keyword(s):  
High Temperature ◽  
Dislocation Density ◽  
Single Crystals ◽  
Dark Field ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
High Temperature Strength ◽  
Density Reduction ◽  
Transmission Electron

The perfection of GaAs single crystals can be controlled by doping the GaAs with In, at a level of about 5x1019-1x1020/cm3, in single crystals grown by the LEC process. It has been observed that In doping at this level reduces the grown in dislocation density from 104-l05 to ≤ 102/cm2 and results in a large increase in high temperature strength . However, the role of In in dislocation density reduction is not clearly understood. Therefore, a systematic study has been performed with the help of high temperature deformation of In-doped and undoped GaAs single crystals followed by dislocation structural characterization by transmission electron microscopy of the deformed specimens. Here, some results of dislocation studies performed by TEM are descri bed.Samples were examined in a JEOL JEM 200CX transmission electron microscope equipped with a double tilt goniometer stage. The standard g.b criterion was employed for characterization of dislocations. Dark-field weak beam pictures were taken for characterization of partial dislocations and dipoles.

Microwave performance and structural characterization of MBE-grown AlGaN/GaN HEMTs on low dislocation density GaN substrates

2007 ◽  
Vol 305 (2) ◽  
pp. 340-345 ◽  
Author(s):  
D.F. Storm ◽  
D.S. Katzer ◽  
J.A. Roussos ◽  
J.A. Mittereder ◽  
R. Bass ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Structural Characterization ◽  
Low Dislocation Density ◽  
Gan Hemts
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