Anomalous Growth of Dislocation Density in Titanium During Recovery

2021 ◽  
Author(s):  
Ivan Ivanov ◽  
Kemal Emurlaev ◽  
Daria Lazurenko ◽  
Ivan Bataev
Keyword(s):  
Dislocation Density ◽  
Anomalous Growth

Observations of dislocation interactions with recrystallized grain boundaries

1988 ◽  
Vol 46 ◽  
pp. 628-629
Author(s):  
C. W. Price
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Dislocation Structure ◽  
Hot Deformation ◽  
Static Recrystallization ◽  
High Dislocation Density ◽  
High Angle ◽  
Dislocation Interactions

Little evidence exists on the interaction of individual dislocations with recrystallized grain boundaries, primarily because of the severely overlapping contrast of the high dislocation density usually present during recrystallization. Interesting evidence of such interaction, Fig. 1, was discovered during examination of some old work on the hot deformation of Al-4.64 Cu. The specimen was deformed in a programmable thermomechanical instrument at 527 C and a strain rate of 25 cm/cm/s to a strain of 0.7. Static recrystallization occurred during a post anneal of 23 s also at 527 C. The figure shows evidence of dissociation of a subboundary at an intersection with a recrystallized high-angle grain boundary. At least one set of dislocations appears to be out of contrast in Fig. 1, and a grainboundary precipitate also is visible. Unfortunately, only subgrain sizes were of interest at the time the micrograph was recorded, and no attempt was made to analyze the dislocation structure.

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

Model-based correlation between change of electrical resistance and change of dislocation density of fatigued-loaded ICE R7 wheel steel specimens

2018 ◽  
Vol 60 (7-8) ◽  
pp. 669-677 ◽  
Author(s):  
Peter Starke ◽  
Frank Walther ◽  
Dietmar Eifler
Keyword(s):  
Dislocation Density ◽  
Electrical Resistance ◽  
Wheel Steel ◽  
Model Based

DIFFRACTION ANALYSIS OF DEFORMED METALS: Theory, Methods, Programs

2019 ◽  
Author(s):  
Faina Satdarova
Keyword(s):  
Experimental Design ◽  
Dislocation Density ◽  
Mathematical Models ◽  
Diffraction Analysis ◽  
Experimental Research ◽  
Russian Federation ◽  
Statistical Estimation ◽  
X Rays ◽  
National University ◽  
The Russian Federation

General analysis of the distribution of crystals orientation and dislocation density in the polycrystalline system is presented. Recovered information in diffraction of X-rays adopting is new to structure states of polycrystal. Shear phase transformations in metals — at the macroscopic and microscopic levels — become a clear process. Visualizing the advances is produced by program included in package delivered. Mathematical models developing, experimental design, optimal statistical estimation, simulation the system under study and evolution process on loading serves as instrumentation. To reduce advanced methods to research and studies problem-oriented software will promote when installed. Automation programs passed a testing in the National University of Science and Technology “MISIS” (The Russian Federation, Moscow). You score an advantage in theoretical and experimental research in the field of physics of metals.

Low dislocation density AlN on sapphire prepared by double sputtering and annealing

2020 ◽  
Vol 13 (9) ◽  
pp. 095501
Author(s):  
Ding Wang ◽  
Kenjiro Uesugi ◽  
Shiyu Xiao ◽  
Kenji Norimatsu ◽  
Hideto Miyake
Keyword(s):  
Dislocation Density ◽  
Low Dislocation Density

ВЛИЯНИЕ ТВЕРДОФАЗНОЙ РЕКРИСТАЛЛИЗАЦИИ С ДВОЙНОЙ ИМПЛАНТАЦИЕЙ НА ПЛОТНОСТЬ СТРУКТУРНЫХ ДЕФЕКТОВ В УЛЬТРАТОНКИХ СЛОЯХ КРЕМНИЯ НА САПФИРЕ

2020 ◽  
Vol 96 (3s) ◽  
pp. 154-159
Author(s):  
Н.Н. Егоров ◽  
С.А. Голубков ◽  
С.Д. Федотов ◽  
В.Н. Стаценко ◽  
А.А. Романов ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Solid Phase ◽  
Modern Method ◽  
Structural Defects ◽  
Structural Quality ◽  
Mos Transistors ◽  
Ultrathin Layers ◽  
Heteroepitaxial Layers ◽  
Xrd And Tem

Высокая плотность структурных дефектов является основной проблемой при изготовлении электроники на гетероструктурах «кремний на сапфире» (КНС). Современный метод получения ультратонких структур КНС с помощью твердофазной эпитаксиальной рекристаллизации позволяет значительно снизить дефектность в гетероэпитаксиальном слое КНС. В данной работе ультратонкие (100 нм) слои КНС были получены путем рекристаллизации и утонения субмикронных (300 нм) слоев кремния на сапфире, обладающих различным структурным качеством. Плотность структурных дефектов в слоях КНС оценивалась с помощью рентгеноструктурного анализа и просвечивающей электронной микроскопии. Кривые качания от дифракционного отражения Si(400), полученные в ω-геометрии, продемонстрировали максимальную ширину на полувысоте пика не более 0,19-0,20° для ультратонких слоев КНС толщиной 100 нм. Формирование структурно совершенного субмикронного слоя КНС 300 нм на этапе газофазной эпитаксии обеспечивает существенное уменьшение плотности дислокаций в ультратонком кремнии на сапфире до значений ~1 • 104 см-1. Тестовые n-канальные МОП-транзисторы на ультратонких структурах КНС характеризовались подвижностью носителей в канале 725 см2 Вс-1. The high density of structural defects is the main problem on the way to the production of electronics on silicon-on-sapphire (SOS) heteroepitaxial wafers. The modern method of obtaining ultrathin SOS wafers is solid-phase epitaxial recrystallization which can significantly reduce the density of defects in the SOS heteroepitaxial layers. In the current work, ultrathin (100 nm) SOS layers were obtained by recrystallization and thinning of submicron (300 nm) SOS layers, which have various structural quality. The density of structural defects in the layers was estimated by using XRD and TEM. Full width at half maximum of rocking curves (ω-geometry) was no more than 0.19-0.20° for 100 nm ultra-thin SOS layers. The structural quality of 300 nm submicron SOS layers, which were obtained by CVD, depends on dislocation density in 100 nm ultrathin layers. The dislocation density in ultrathin SOS layers was reduced by ~1 • 104 cm-1 due to the utilization of the submicron SOS with good crystal quality. Test n-channel MOS transistors based on ultra-thin SOS wafers were characterized by electron mobility in the channel 725 cm2 V-1 s-1.

scholarly journals A dislocation density-based model for the work hardening and softening behaviors upon stress reversal

2021 ◽  
Vol 21 (2) ◽  
Author(s):  
Paulina Lisiecka-Graca ◽  
Krzysztof Bzowski ◽  
Janusz Majta ◽  
Krzysztof Muszka
Keyword(s):  
Dislocation Density ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Back Stress ◽  
Carbon Steels ◽  
Internal Variables ◽  
Low Carbon ◽  
Average Dislocation Density ◽  
Calculation Results ◽  
Mechanical Behaviours

AbstractThe mechanical behaviours of microalloyed and low-carbon steels under strain reversal were modelled based on the average dislocation density taking into account its allocation between the cell walls and cell interiors. The proposed model reflects the effects of the dislocations displacement, generation of new dislocations and their annihilation during the metal-forming processes. The back stress is assumed as one of the internal variables. The value of the initial dislocation density was calculated using two different computational methods, i.e. the first one based on the dislocation density tensor and the second one based on the strain gradient model. The proposed methods of calculating the dislocation density were subjected to a comparative analysis. For the microstructural analysis, the high-resolution electron backscatter diffraction (EBSD) microscopy was utilized. The calculation results were compared with the results of forward/reverse torsion tests. As a result, good effectiveness of the applied computational methodology was demonstrated. Finally, the analysis of dislocation distributions as an effect of the strain path change was performed.

scholarly journals Microstructure, Grain Growth and Hardness of Nanostructured Ferritic ODS Steel Powder during Annealing

2021 ◽  
Author(s):  
Krzysztof Nowik ◽  
Zbigniew Oksiuta
Keyword(s):  
Dislocation Density ◽  
Size Distribution ◽  
Hot Isostatic Pressing ◽  
Domain Size ◽  
Oxide Dispersion Strengthened ◽  
Alloy Formation ◽  
Nanocrystalline State ◽  
Ferritic Alloy ◽  
Ods Steel ◽  
Double Phase

AbstractNanocrystalline oxide-dispersion strengthened ferritic alloy formation and its annealing behavior were examined through modern X-ray diffraction pattern analysis and supplemented by microhardness and microscopic measurements. The basic microstructure features, with particular emphasis on evolution of domain size distribution and defect content during mechanical and thermal treatment, were quantified via the whole powder pattern modeling approach. The microstructure of the powdered alloy, formed during mechanical alloying, evolved toward nanocrystalline state consisting of narrow dispersion of very fine crystallites with substantial dislocation density, which exhibited relatively high stability against elevated temperature. It was shown that crystallite size is seriously sustained by the grain-boundary strain, therefore coarsening of grains begins only after the density of dislocations drops below certain level. Obtaining correct results for the annealing-related data at specific temperature range required the incorporation of the “double-phase” model, indicating possible bimodal domain size distribution. The dislocation density and grain size were found not to be remarkably affected after consolidation by hot isostatic pressing.

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