Plasticity and Interfacial Dislocation Structures in Ti-Al

1996 ◽  
Vol 460 ◽  
Author(s):  
L. Parrini ◽  
H. Heinrich ◽  
G. Kostorz
Keyword(s):  
Heat Treatment ◽  
Lamellar Structure ◽  
Room Temperature ◽  
Compression Tests ◽  
Interfacial Dislocation ◽  
Brittle To Ductile Transition ◽  
Transmission Electron ◽  
Interfacial Dislocations ◽  
Very High ◽  
Lamellar Interfaces

ABSTRACTThe alloy Ti-48.6Al-l.9Cr-l.9Nb-IB with an equiaxed γ microstructure, obtained by heat treatment at 1200°C for 4 h, and with a lamellar mi ero structure, obtained by heat treatment at 1380°C for 1 h, is characterized by compression tests and transmission electron microscopy. A lower activity of superdislocations and a more frequent pinning of ordinary dislocations are detected in the lamellar Ti-Al specimens in comparison with the non-lamellar ones during deformation at room temperature. The activity of superdislocations and the pinning of ordinary dislocations are responsible for the differences in yield stress and brittleness between lamellar and non-lamellar Ti-Al. A very high density of ordinary interfacial dislocations is found in the lamellar structure. These influence the activity of superdislocations and the pinning of ordinary dislocations. At high temperature a change in the deformation mechanism occurs. Above the brittle-to-ductile transition, the material is remarkably softer and the mechanical properties are insensitive to the presence of the lamellar interfaces.

ION CHANNELING AND PIXE STUDIES OF S IMPLANTATION IN GaAs

1992 ◽  
Vol 02 (02) ◽  
pp. 151-159
Author(s):  
LIU SHIJIE ◽  
WANG JIANG ◽  
HU ZAOHUEI ◽  
XIA ZHONGHUONG ◽  
GAO ZHIGIANG ◽  
...  
Keyword(s):  
Room Temperature ◽  
Dislocation Loops ◽  
Good Recovery ◽  
Electrical Measurements ◽  
X Ray ◽  
Defect Complexes ◽  
Ion Channeling ◽  
Transmission Electron ◽  
Activation Efficiency ◽  
Very High

GaAs (100) crystals were implanted with 100 keV S+ to a dose of 3×1015 cm−2 in a nonchanneling direction at room temperature, and treated with rapid thermal annealing (RTA). He+ Rutherford backscattering and particle-induced X-ray emission in channeling mode in combination with transmission electron microscopy (TEM) were used to study the damage and the lattice location of S atoms. It is revealed that the RTA at 950 °C for 10 sec has resulted in a very good recovery of crystallinity with a few residual defects in the form of dislocation loops, and a very high substitutionality (~90%). The activation efficiency and the Hall mobility of the implanted samples are found to be low after the electrical measurements. Based on these results an extended dopant diffusion effect for the residual defects and a correlation between the electrical properties and defect complexes are suggested.

scholarly journals Achieving room-temperature brittle-to-ductile transition in ultrafine layered Fe-Al alloys

2020 ◽  
Vol 6 (39) ◽  
pp. eabb6658
Author(s):  
Lu-Lu Li ◽  
Yanqing Su ◽  
Irene J. Beyerlein ◽  
Wei-Zhong Han
Keyword(s):  
Room Temperature ◽  
Extreme Environments ◽  
High Strength ◽  
Layered Composite ◽  
Al Alloys ◽  
Brittle To Ductile Transition ◽  
Transmission Electron ◽  
Structural Applications ◽  
Wear And Corrosion Resistance ◽  
New Applications

Fe-Al compounds are of interest due to their combination of light weight, high strength, and wear and corrosion resistance, but new forms that are also ductile are needed for their widespread use. The challenge in developing Fe-Al compositions that are both lightweight and ductile lies in the intrinsic tradeoff between Al concentration and brittle-to-ductile transition temperature. Here, we show that a room-temperature, ductile-like response can be attained in a FeAl/FeAl2 layered composite. Transmission electron microscopy, nanomechanical testing, and ab initio calculations find a critical layer thickness on the order of 1 μm, below which the FeAl2 layer homogeneously codeforms with the FeAl layer. The FeAl2 layer undergoes a fundamental change from multimodal, contained slip to unimodal slip that is aligned and fully transmitting across the FeAl/FeAl2 interface. Lightweight Fe-Al alloys with room-temperature, ductile-like responses can inspire new applications in reactor systems and other structural applications for extreme environments.

Novel Methods for Preparation and Surface Treatment of Nano-CaCO3

2013 ◽  
Vol 750-752 ◽  
pp. 336-339
Author(s):  
Fa Chao Wu ◽  
Teng Fei Shen
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Particle Size ◽  
Fourier Transform ◽  
Room Temperature ◽  
Transmission Electron ◽  
Reduce Energy Consumption ◽  
Scanning Electron

In this work, CaCO3 nanoparticles have been synthesized via heat-treatment of a new precursor. Effect of calcinations temperature on particle size has been investigated. The products were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). nanoCaCO3 was modified using chloroform as solvent and fatty acid as modifier atroom temperature. The advantage of this modification is that it can be proceed at room temperature and it can reduce energy consumption.

Microstructure Evolution of Hydrogenated Ti6Al4V Alloy during Compression

2012 ◽  
Vol 190-191 ◽  
pp. 517-521
Author(s):  
Bao Guo Yuan ◽  
Qiang Chen ◽  
Hai Ping Yu ◽  
Ping Li ◽  
Ke Min Xue ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Density ◽  
Microstructure Evolution ◽  
Room Temperature ◽  
True Strain ◽  
True Stress ◽  
Compression Tests ◽  
Transmission Electron ◽  
Good Repeatability

Compression tests of the hydrogenated Ti6Al4V0.2H alloy were carried out using an Instron 5569 machine at room temperature. True stress-strain curves of the hydrogenated Ti6Al4V0.2H alloy under different compressive strains were obtained. Microstructure evolution of the hydrogenated Ti6Al4V0.2H alloy during the process of compression was investigated by optical microscopy and transmission electron microscopy. Results show that true stress-true strain curves of Ti6Al4V0.2H alloy have good repeatability. The deformation of grains, the dislocation density and slipping evolution during the process of compression are discussed.

HEAT-TREATMENT INFLUENCE ON THE MAGNETIC AND ELECTRIC PROPERTIES OF HIGH-TcYBa2Cu3O7−δ SUPERCONDUCTOR

1996 ◽  
Vol 10 (20) ◽  
pp. 955-961
Author(s):  
LAUREAN HOMORODEAN ◽  
IULIU POP ◽  
ION BURDOI
Keyword(s):  
Heat Treatment ◽  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Room Temperature ◽  
Liquid Nitrogen Temperature ◽  
Superconducting Phase ◽  
Superconducting Transition ◽  
Temperature Dependences ◽  
Magnetic And Electric Properties ◽  
Very High

The changes in the temperature dependences of the magnetic susceptibility and the electrical resistivity of a very-high-T c superconducting YBa 2 Cu 3 O 7−δ sample during the thermal cycling between the liquid-nitrogen temperature and the room temperature are studied. Some singularities corresponding to the superconducting transition, the possible existence of a super-high-temperature superconducting phase and the migration of the oxygen atoms in the Cu-O chains are emphasized on these dependencies.

In situ transmission electron microscope study of interface sliding and migration in an ultrafine lamellar structure

2006 ◽  
Vol 21 (10) ◽  
pp. 2453-2459 ◽  
Author(s):  
L.M. Hsiung ◽  
J. Zhou ◽  
T.G. Nieh
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Lamellar Structure ◽  
Cooperative Movement ◽  
Transmission Electron ◽  
Transmission Electron Microscope Study ◽  
Interfacial Dislocations ◽  
And Migration ◽  
Interface Sliding

The instability of interfaces in an ultrafine TiAl-(γ)/Ti3Al-(α2) lamellar structure by straining at room temperature has been investigated using in situ straining techniques performed in a transmission electron microscope. The purpose of this study was to obtain experimental evidence to support the creep mechanisms based upon the interface sliding in association with a cooperative movement of interfacial dislocations, which was proposed previously to rationalize a nearly linear creep behavior of ultrafine lamellar TiAl alloys. The results reveal that the sliding and migration of lamellar interfaces can take place simultaneously as a result of the cooperative movement of interfacial dislocations, which can lead to an adverse effect in the performance of ultrafine lamellar TiAl alloy.

Two-step oxygen injection process for growing ZnO nanorods

2003 ◽  
Vol 18 (12) ◽  
pp. 2837-2844 ◽  
Author(s):  
Yung-Kuan Tseng ◽  
Hsu-Cheng Hsu ◽  
Wen-Feng Hsieh ◽  
Kuo-Shung Liu ◽  
I-Cherng Chen
Keyword(s):  
Oxygen Concentration ◽  
Room Temperature ◽  
Zno Nanorods ◽  
Oxygen Flow Rate ◽  
X Ray Diffraction ◽  
Oxygen Injection ◽  
X Ray ◽  
Injection Process ◽  
Transmission Electron ◽  
Very High

Uniform hexagonal prismatic zinc oxide rods were grown over the entire alumina substrate at 550°C using a two-step oxygen injection process, whether the substrates were coated with a catalyst or not. X-ray diffraction showed that all of the depositions exhibited a preferred orientation in the (002) plane. The influence of oxygen concentration was investigated by changing the oxygen flow rate. Oxygen concentration affected the size of ZnO nanorods, especially the diameter. The ZnO nanorods were further checked using high-resolution transmission electron microscopy, photoluminescence, Raman spectroscopy, and room-temperature ultraviolet lasing. The results showed that the rods were single crystals and had excellent optical properties. By observing the growth process, we found that the diameter increased slowly, but the longitudinal growth rate was very high. The growth of ZnO nanorods revealed that the uniform hexagonal prismatic ZnO nanorods were synthesized through vapor deposition growth and a self-catalyzed vapor–liquid–solid (VLS) process.

scholarly journals Hydrogen Detection with SAW Polymer/Quantum Dots Sensitive Films

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4481 ◽  
Author(s):  
Izabela Constantinoiu ◽  
Cristian Viespe
Keyword(s):  
Heat Treatment ◽  
Quantum Dots ◽  
Room Temperature ◽  
Limit Of Detection ◽  
Composite Films ◽  
High Specific Surface Area ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Heat Treated ◽  
Gas Molecules

Regarding the use of hydrogen as a fuel, it is necessary to measure its concentration in air at room temperature. In this paper, sensitive composite films have been developed for surface acoustic wave (SAW) sensors, using quantum dots (QDs) and polymers. Si/SiO2 QDs were used due to having a high specific surface area, which considerably improves the sensitivity of the sensors compared to those that only have a polymer. Si/SiO2 QDs were obtained by laser ablation and analyzed by X-ray diffraction and transmission electron microscopy (TEM). Two types of polymers were used: polydimethylsiloxane (PDMS) and polymethylmethacrylate (PMMA). Polymer and polymer with QDs compositions were deposited on the sensor substrate by drop casting. A heat treatment was performed on the films at 80 °C with a thermal dwell of two hours. The sensors obtained were tested at different hydrogen concentrations at room temperature. A limit of detection (LOD) of 452 ppm was obtained by the sensor with PDMS and Si/SiO2 QDs, which was heat treated. The results demonstrated the potential of using QDs to improve the sensitivity of the SAW sensors and to achieve a heat treatment that increases its adsorption capacity of the gas molecules.

An electron-microscope study of peristerite plagioclases

1965 ◽  
Vol 35 (269) ◽  
pp. 165-176 ◽  
Author(s):  
S. G. Fleet ◽  
P. H. Ribbe
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Microscope Study ◽  
Lamellar Structure ◽  
Electron Microscope Study ◽  
Transmission Electron

SummaryPlagioclase feldspars in the peristerite range An2-An17 have been investigated by transmission electron-microscopy and electron diffraction. All except the more anorthite-rich specimens were found to be unmixed into albite and oligoclase lamellae, between a few hundred and several thousand Å thick and approximately parallel to . A discussion is given of the part played by these lamellae when optical schiller is exhibited; and the effect of heat treatment on the lamellar structure and optical schiller is described.

Microstructure Control and Pseudoelasticity of Ti-Nb-Ge Alloy

2008 ◽  
Vol 47-50 ◽  
pp. 1446-1449 ◽  
Author(s):  
Won Yong Kim ◽  
Han Sol Kim
Keyword(s):  
Heat Treatment ◽  
Electron Microscope ◽  
Martensitic Transformation ◽  
Transmission Electron Microscope ◽  
Martensite Transformation ◽  
Room Temperature ◽  
Temperature Deformation ◽  
Microstructure Control ◽  
Transmission Electron ◽  
Pseudoelastic Behavior

Microstructures and pseudoelastic behavior of Ti-Nb-Ge alloys were investigated in order to correlate the pseudoelasticity and microstructure together with martensite transformation. XRD results and transmission electron microscope revealed that stress-induced martensitic transformation takes place during room temperature deformation in the present alloys. Recrystallization heat treatment of the present alloy displayed pseudoelastic behavior to be prominent. It is concluded that the pseudoelastic behavior of a metastable-β Ti-Nb-Ge alloy is correlated to the stress-induced martensite transformation.

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