scholarly journals In Situ Atomic-Scale Observation of Dislocation Climb and Grain Boundary Transformation in Nanostructured Metal

2021 ◽  
Author(s):  
Shufen Chu ◽  
Pan Liu ◽  
Yin Zhang ◽  
Xiaodong Wang ◽  
Shuangxi Song ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Grain Boundary ◽  
Room Temperature ◽  
Atomic Plane ◽  
Dislocation Core ◽  
Dislocation Climb ◽  
Atomic Scale ◽  
Atomic Column ◽  
Nanostructured Metal

Abstract We report atomic-scale observations of grain boundary (GB) dislocation climb in nanostructured Au during in situ straining at room temperature. Climb of a dislocation occurs by stress-induced reconstruction of two atomic columns at the edge of an extra half atomic plane in the dislocation core. Different from the conventional belief of dislocation climb by destruction or construction of a single atomic column at the dislocation core, the new atomic route is demonstrated to be energetically favorable by Monte Carlo simulations. Our in situ observations also reveal GB transformation through dislocation climb, which suggests a means of controlling microstructures and properties of nanostructured metals.

scholarly journals In situ atomic scale mechanisms of strain-induced twin boundary shear to high angle grain boundary in nanocrystalline Pt

2018 ◽  
Vol 195 ◽  
pp. 69-73 ◽  
Author(s):  
Lihua Wang ◽  
Jiao Teng ◽  
Yu Wu ◽  
Xuechao Sha ◽  
Sisi Xiang ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Twin Boundary ◽  
Atomic Scale ◽  
High Angle ◽  
Boundary Shear

Atomic scale study of polar Lomer–Cottrell and Hirth lock dislocation cores in CdTe

2014 ◽  
Vol 70 (6) ◽  
pp. 524-531 ◽  
Author(s):  
Tadas Paulauskas ◽  
Christopher Buurma ◽  
Eric Colegrove ◽  
Brian Stafford ◽  
Zhao Guo ◽  
...  
Keyword(s):  
Elastic Energy ◽  
Semiconductor Devices ◽  
Dislocation Core ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Atomic Scale ◽  
Formation Mechanisms ◽  
Atomic Column ◽  
Dark Field Imaging ◽  
Zinc Blende

Dislocation cores have long dominated the electronic and optical behaviors of semiconductor devices and detailed atomic characterization is required to further explore their effects. Miniaturization of semiconductor devices to nanometre scale also puts emphasis on a material's mechanical properties to withstand failure due to processing or operational stresses. Sessile junctions of dislocations provide barriers to propagation of mobile dislocations and may lead to work-hardening. The sessile Lomer–Cottrell and Hirth lock dislocations, two stable lowest elastic energy stair-rods, are studied in this paper. More specifically, using atomic resolution high-angle annular dark-field imaging and atomic-column-resolved X-ray spectrum imaging in an aberration-corrected scanning transmission electron microscope, dislocation core structures are examined in zinc-blende CdTe. A procedure is outlined for atomic scale analysis of dislocation junctions which allows determination of their identity with specially tailored Burgers circuits and also formation mechanisms of the polar core structures based on Thompson's tetrahedron adapted to reactions of polar dislocations as they appear in CdTe and other zinc-blende solids. Strain fields associated with the dislocations calculatedviageometric phase analysis are found to be diffuse and free of `hot spots' that reflect compact structures and low elastic energy of the pure-edge stair-rods.

Atomic Scale Characterization of Oxygen Vacancy Segregation at SrTiO3 Grain Boundaries

2000 ◽  
Vol 654 ◽  
Author(s):  
R.F. Klie ◽  
N. D. Browning
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Oxygen Vacancies ◽  
Elevated Temperatures ◽  
Theoretical Models ◽  
Atomic Scale ◽  
Close Proximity ◽  
Scale Characterization

AbstractWe have examined the structure, composition and bonding at an un-doped 58° [001] tilt grain-boundary in SrTiO3 in order to investigate the control that the grain boundary exerts over the bulk properties. Room temperature and in-situ heating experiments show that there is a segregation of oxygen vacancies to the grain boundary that is increased at elevated temperatures and is independent of the cation arrangement. These measurements indicate that the widely observed electronic properties of grain boundaries may be due to an excess of mobile oxygen vacancies that cause a highly doped n-type region in the close proximity ( ≍ 1 unit cell) to the boundary. These results are shown to be consistent with both theoretical models and lower resolution chemical analysis.

In situ TEM observations of room temperature dislocation climb at interfaces in nanolayered Al/Nb composites

2010 ◽  
Vol 63 (4) ◽  
pp. 363-366 ◽  
Author(s):  
Nan Li ◽  
J. Wang ◽  
J.Y. Huang ◽  
A. Misra ◽  
X. Zhang
Keyword(s):  
Room Temperature ◽  
Dislocation Climb ◽  
In Situ Tem

scholarly journals Atomic Scale Manipulation of Grain Boundary Structures through Doping and In-Situ Gas Reduction

2013 ◽  
Vol 19 (S2) ◽  
pp. 1946-1947
Author(s):  
H. Yang ◽  
Y. Sato ◽  
H. Lee ◽  
Y. Ikuhara ◽  
P. Moeck ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Atomic Scale

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

In Situ Atomic-scale Observation of AuCu Alloy Nanowire with Superplasticity and High Strength at Room Temperature

2021 ◽  
pp. 100123
Author(s):  
Libo Fu ◽  
Chengpeng Yang ◽  
Rujian Wei ◽  
Xingfei Pei ◽  
Jiao Teng ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Strength ◽  
Atomic Scale

Systematic Study of Polycrystalline Flow during In Situ Tension Test by SEM of Pb-50%Sn at Room Temperature

2014 ◽  
Vol 793 ◽  
pp. 113-118 ◽  
Author(s):  
A.J. López-Ramírez ◽  
Juan Daniel Muñoz-Andrade ◽  
E. Garfias-García ◽  
M. Aguilar-Sánchez
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Deformation Process ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Tension Test ◽  
Irreversible Deformation ◽  
Chatelier Effect ◽  
Boundary Sliding

Microstructural evolution during in situ tension test at constant crosshead velocity of 0.38 mm/min, at room temperature of polycrystalline Pb-50%Sn alloy are reported. Direct observation during four steps of deformation, with a total deformation (εT) of 0.684, allows establish that the trajectories of grains during irreversible deformation process obey a sigmoidal motion. Such behaviour is related with dynamic recrystallization phenomenology and associated with grain boundary sliding between neighbouring grains and subsequent cavitation in order to allow emerging grains from the inner volume to free surface of Pb-50%Sn, as the main mechanisms of superplastic flow. The curve of true stress versus true deformation presented several fluctuations during irreversible deformation process in a similar way of the Portevin Le Chatelier effect. Also is observed in the early steps of plastic flow, hardening deformation, up to 27 MPa associated with the maximum stress. The activation energy values for polycrystalline flow, calculated in this work are between 67.5 to 68.07 kJ/mol and there are in a closed agreement with the activation energy of 65.7 kJ/mol, for grain boundary diffusion.

scholarly journals Структурные аспекты деформационной аморфизации кристаллического сплава Ti-=SUB=-50-=/SUB=-Ni-=SUB=-25-=/SUB=-Cu-=SUB=-25-=/SUB=- при кручении под высоким давлением

2018 ◽  
Vol 60 (6) ◽  
pp. 1157
Author(s):  
Р.В. Сундеев ◽  
А.В. Шалимова ◽  
А.М. Глезер ◽  
Е.А. Печина ◽  
М.В. Горшенков
Keyword(s):  
Grain Boundary ◽  
Crystalline Phase ◽  
Crystalline State ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Amorphous State ◽  
Nanocrystalline Phase ◽  
Torsional Moment ◽  
Variation Curve

AbstractThe evolution of the structure of the Ti50Ni25Cu25 crystalline alloy during high-pressure torsion at room temperature has been studied. The torsional moment variation curve as a function of the strain value was fixed in situ, which allowed directly observing the transition of the material from the crystalline state to the amorphous state during the HPT. It was found that the amorphization of the material in the course of the HPT begins on the grain boundaries and fragments of the crystalline phase. Amorphized boundaries form a “grain-boundary carcass” in the cells of which the high-defect nanocrystalline phase is formed. Growth of deformation leads to broadening of the “grain-boundary carcass,” loss of stability of the crystalline phase, and, as a consequence, to the phase transition “crystal → amorphous” state.

Deformation Mechanisms of Aluminum at High Temperatures: in situ Straining Experiments in H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 56-57
Author(s):  
D. Caillard ◽  
P. Muchin ◽  
J. L. Martin
Keyword(s):  
High Temperature ◽  
Dislocation Density ◽  
Single Crystals ◽  
High Temperatures ◽  
Room Temperature ◽  
Dislocation Climb ◽  
Deformation Mechanisms ◽  
High Angle ◽  
The One

Aluminium single crystals have been deformed on a straining holder between room temperature and 550° C in a H.V.E.M. Observations are recorded on still photographs or movies.Evidence is shown of crosslip and dislocation climb.1) The formation of dislocation subboundaries has been observed at high temperature and low stresses. The increase with time of dislocation density of each boundary is explained and the coalescence of low angle subboundaries into high angle ones, is described on the basis of our observations by a model involving dislocation climb, different from the one proposed formerly by Dunn and Hibbard.

In situ studies on grain boundary migration in ceria-stabilized TZP

1990 ◽  
Vol 48 (4) ◽  
pp. 192-193
Author(s):  
Herbert K Schmid
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Boundary Migration ◽  
Tetragonal Zirconia ◽  
In Situ Tem ◽  
Grain Boundary Migration ◽  
Thin Foils ◽  
Prepared State

Tetragonal zirconia polycrystals (TZP) have become of interest due to their exceptionally good combination of mechanical properties. In a previous study the microstructure/microchemistry of grain boundaries (GBs) in CeO2 stabilized ZrO2 (Ce-TZP) was investigated and evidence was found on the existence of vitreous ana crystalline intergranular phases in these ceramics. Recently, the observation of wavy GBs in ceria-zirconia was reported. This phenomenon was attributed to diffusion-induced grain boundary migration (DIGM). In the present work, the in-situ TEM observation of GB migration in Ce-TZP, nominally at room temperature, is reported.Thin foils for TEM observations were prepared from a Ce-TZP ceramic nominally composed of 90 mol% ZrO2 plus 10 mol% CeO2 and were examined in a Philips EM 420 analytical STEM, operated at 120 kV. Grain boundaries were observed to migrate in specimen areas exposed to extensive electron irradiation during TEM experiments. The micrograph in Fig. 1 shows a BF image of a triple grain junction (TJ) area in the as-prepared state.

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