On In-Situ Study of Dislocation/Grain Boundary Interactions Using X-ray Topography and Tem

1993 ◽  
Vol 319 ◽  
Author(s):  
Ian Baker ◽  
Fuping Liu
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stress Concentrations ◽  
X Ray ◽  
Advantages And Disadvantages ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Dislocation Behavior ◽  
Generation Mechanisms

AbstractThe advantages and disadvantages of in-situ straining using both synchrotron x-ray topography and transmission electron microscopy for examining dislocation/grain boundary interactions are compared and examples given of the use of each technique. For x-ray topography, studies on ice polycrystals are discussed. Ice is well-suited for x-ray topographic studies since it has both low absorption and can be produced with a low dislocation density. Stress concentrations have been observed at grain boundaries in ice which are partially relieved by generation of 1/3<1120> dislocations. Interestingly, grain boundary generation of dislocations completely overwhelms lattice generation mechanisms. Examples of transmission electron microscope in-situ straining studies include dislocation/grain boundary interactions in L12-structured and B2-structured intermetallics. Slip transmission across grain boundaries by dislocations gliding ahead of an advancing crack is a principal feature of these studies. A significant advantage of the such studies is their inherently high resolution. However, the dislocation behavior is dominated by the inherent thinness of the specimens.

X-Ray Reflectivity Study of Single- and Bicrystals of Gold

1990 ◽  
Vol 208 ◽  
Author(s):  
M. R. Fitzsimmons ◽  
E. Burkel ◽  
J. Peisl
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Diffuse Scattering ◽  
Direct Evidence ◽  
X Ray ◽  
Specular Reflectivity ◽  
Boundary Measurements

ABSTRACTX-ray reflectivity techniques have been used to characterize the surfaces of 0.4µm thick Au films epitaxially grown on single-crystals of NaCl. Measurements of both the specular and non-specular reflectivity suggest that the Au surface is very rough. The nonspecular reflectivity provides valuable information about the correlation of the heights at different points on the surface. The first in situ reflectivity study of the formation and destruction of a grain boundary shows direct evidence for the existence of diffuse scattering from the grain boundary. Measurements of several [0011 twist grain boundaries suggest that the roughness and texture of an interface depends upon the geometrical orientation of the surrounding substrates.

The Effect of Grain Boundaries on Surface Diffusion Mediated-Planarization of Polycrystalline Cu Films

1995 ◽  
Vol 389 ◽  
Author(s):  
R.A. Brain ◽  
D.S. Gardner ◽  
D.B. Fraser ◽  
H.A. Atwater
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Surface Diffusion ◽  
Cross Sections ◽  
Boundary Surface ◽  
Surface Profile ◽  
Transmission Electron Micrograph ◽  
Cu Films ◽  
Transmission Electron

ABSTRACTIn situ, ultrahigh vacuum anneals were performed to induce Cu reflow at 500°C following deposition of Cu films and a Ta barrier layer on 1 μm wide by 1 μm deep trenches. Transmission electron micrograph cross-sections show profiles which suggest that grain boundaries and surface energy anisotropy significantly affect reflow. The extent of reflow is dependent on the structure of grain boundary-surface intersections, and the surface profile consists of regions of low curvature within grains and with sharp discontinuities in curvature at grain boundaries, a structure that inhibits surface diffusion. We present results showing how the surface diffusion mediated reflow varies with grain boundary groove angle and position, and compare these results with finite-element simulations that model surface diffusion-driven reflow.

Effect of boron on the mechanism of strain transfer across grain boundaries in Ni3Al

1987 ◽  
Vol 2 (4) ◽  
pp. 436-440 ◽  
Author(s):  
G. M. Bond ◽  
I. M. Robertson ◽  
H. K. Birnbaum
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Dislocation Motion ◽  
Strain Transfer ◽  
Undoped Material ◽  
Sudden Failure ◽  
Transmission Electron ◽  
Large Numbers ◽  
Dislocation Sources

The effect of boron on the mechanism of strain transfer across grain boundaries in Ni3Al has been investigated by dynamic recording of events occurring during in-situ straining in the transmission electron microscope. Boundaries in both doped and undoped material can act as effective barriers to dislocation motion, large numbers of dislocations being incorporated into the boundary without any plastic strain occurring in the adjacent grain. In the undoped material, the grain-boundary strain is relieved by the sudden failure of the grain boundary. In the doped material the strain is relieved by the sudden generation and emission of large numbers of dislocations from the grain boundary. This effect may be understood by boron either increasing the grain-boundary cohesion or reducing the stress required to operate grain-boundary dislocation sources, rather than easing the passage of slip dislocations through the grain boundary.

Grain Boundary Responses to Local and Applied Stress: An In Situ TEM Deformation Study

2006 ◽  
Vol 976 ◽  
Author(s):  
Bryan Miller ◽  
Jamey Fenske ◽  
Dong Su ◽  
Chung-Ming Li ◽  
Lisa Dougherty ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Transmission Electron Microscope ◽  
In Situ Tem ◽  
Deformation Twins ◽  
Transmission Electron ◽  
Dislocation Interactions

AbstractDeformation experiments at temperatures between 300 and 750 K have been performed in situ in the transmission electron microscope to investigate dislocation interactions and reactions with grain boundaries and other obstacles. Dislocations, both partial and perfect, as well as deformation twins have been observed being emitted from grain boundaries and, in some cases, even the same grain boundary. The ejection of dislocations from the grain boundary can result in its partial or total annihilation. In the latter case, the disintegration of the grain boundary was accompanied by grain growth and a change in misorientation.

The Slip Transfer Process Through Grain Boundaries in HCP Ti

1993 ◽  
Vol 319 ◽  
Author(s):  
J. Shirokoff ◽  
I.M. Robertson ◽  
H.K. Birnbaum
Keyword(s):  
Grain Boundary ◽  
Slip System ◽  
Grain Boundaries ◽  
Slip Systems ◽  
Boundary Dislocation ◽  
Burgers Vector ◽  
Slip Transfer ◽  
Transmission Electron ◽  
Fcc Materials

AbstractInformation on the mechanisms of slip transfer across grain boundaries in an HCP α-Ti alloy has been obtained from deformation experiments performed In situ in the transmission electron microscope. Initially, lattice dislocations are accommodated within the grain boundary until a critical local dislocation density is reached. The boundary then responds by activating slip in the adjoining grain on the slip system experiencing the highest local resolved shear stress and producing the residual grain-boundary dislocation with the smallest Burgers vector. Slip on secondary slip systems may be initiated provided they reduce the magnitude of the Burgers vector of, or eliminate, the residual grainboundary dislocation. The selection rules used to predict the slip system activated by the grain boundary are the same as apply in ordered and disordered FCC materials.

Investigation of Grain Boundary Migration in Situ by Synchrotron X-Ray Topography

1988 ◽  
Vol 143 ◽  
Author(s):  
C. L. Bauer ◽  
J. Gastaldi ◽  
C. Jourdan ◽  
G. Grange
Keyword(s):  
Grain Boundary ◽  
Boundary Migration ◽  
Boundary Structure ◽  
Grain Boundary Migration ◽  
X Ray ◽  
Grain Boundary Mobility ◽  
Advantages And Disadvantages ◽  
Grain Boundary Character ◽  
Crystallographic Facets

AbstractGrain boundary migration has been investigated in prestrained monocrystalline specimens of aluminum in situ, continuously and at temperatures ranging from 415 to 610°C by synchrotron (polychromatic) x-ray topography (SXRT). In general, new (recrystallized) grains nucleate at prepositioned surface indentations and expand into the prestrained matrix, revealing complex evolution of crystallographic facets and occasional generation of (screw) dislocations in the wake of the moving boundaries. Analysis of corresponding migration rates for several faceted grain boundaries yields activation energies ranging from 56 to 125 kCal/mole, depending on grain boundary character. it is concluded that grain boundary mobility is a sensitive function of grain boundary inclination, resulting in ultimate survival of low-mobility (faceted) inclinations as a natural consequence of growth selection. Advantages and disadvantages associated with measurement of grain boundary migration by SXRT are enumerated and corresponding results are interpreted in terms of fundamental relationships between grain boundary structure and corresponding migration kinetics.

scholarly journals Direct observation of individual dislocation interaction processes with grain boundaries

2016 ◽  
Vol 2 (11) ◽  
pp. e1501926 ◽  
Author(s):  
Shun Kondo ◽  
Tasuku Mitsuma ◽  
Naoya Shibata ◽  
Yuichi Ikuhara
Keyword(s):  
Grain Boundaries ◽  
Polycrystalline Materials ◽  
High Angle ◽  
Dislocation Interaction ◽  
Structural Stabilization ◽  
Dislocation Glide ◽  
Transmission Electron ◽  
Dislocation Behavior ◽  
Geometric Effects

In deformation processes, the presence of grain boundaries has a crucial influence on dislocation behavior; these boundaries drastically change the mechanical properties of polycrystalline materials. It has been considered that grain boundaries act as effective barriers for dislocation glide, but the origin of this barrier-like behavior has been a matter of conjecture for many years. We directly observe how the motion of individual dislocations is impeded at well-defined high-angle and low-angle grain boundaries in SrTiO3, via in situ nanoindentation experiments inside a transmission electron microscope. Our in situ observations show that both the high-angle and low-angle grain boundaries impede dislocation glide across them and that the impediment of dislocation glide does not simply originate from the geometric effects; it arises as a result of the local structural stabilization effects at grain boundary cores as well, especially for low-angle grain boundaries. The present findings indicate that simultaneous consideration of both the geometric effects and the stabilization effects is necessary to quantitatively understand the dislocation impediment processes at grain boundaries.

Nano-probe microanalysis of grain boundary chemistry in YBa2Cu4O8 and its relationship to weak-link behavior

1993 ◽  
Vol 51 ◽  
pp. 598-599
Author(s):  
Z.L. Wang ◽  
J. Brynestad ◽  
D.M. Kroeger ◽  
Y.R. Sun ◽  
J.R. Thompson ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Weak Link ◽  
Oxygen Deficiency ◽  
High Temperature Superconductors ◽  
Cation Composition ◽  
X Ray ◽  
Transmission Electron ◽  
Boundary Chemistry ◽  
Electron Energy Loss

Weak-link behavior in high temperature superconductors limits bulk applications of polycrystalline high Tc compounds. Possible sources of the effect include grain boundary (GB) disorder, microcracks and nonstoichiometric material at grain boundaries. Recently, electron energy-loss spectroscopy (EELS) studies of YBa2Cu3O7-x (Y123) have shown that grain boundary oxygen deficiency is correlated with the crystallographic misorientations of between the Y123 grains. Studies of grain boundary chemistry in YBa2Cu4O8 (Y124) by nano-probe energy dispersive X-ray spectroscopy (EDS) and EELS are reported in this paper. Transmission electron microscopy (TEM) studies were performed at 100 kV in a Philips EM400 TEM/STEM equipped with a field emission gun (FEG), which generates an electron probe smaller than 2 nm in diameter. The cation composition was determined by EDS and the O:Ba composition was determined using EELS. Kikuchi patterns were recorded from both sides of the grain boundaries to determine the misorientation of the two adjacent grains.The observation of a pre-edge peak (Fig. 1) near the oxygen K ionization edge (O K) is related to the hole states produced by the O 2p state and Cu 3d states.

In-Plane Grain Boundary Effects on the Transport Properties of La0.7Sr0.3MnO3-δ Thin Films

1997 ◽  
Vol 494 ◽  
Author(s):  
J. Y. Gu ◽  
S. B. Ogale ◽  
K. Ghosh ◽  
T. Venkatesan ◽  
R. Ramesh ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Effects ◽  
Epitaxial Relationship ◽  
X Ray ◽  
Low Field ◽  
Grain Structures ◽  
Transmission Electron

ABSTRACTC-axis oriented La0.7Sr0.3MnO3.δ (LSMO) films were fabricated on the top of SrTiO3/YBa2Cu3O7 grown on MgO(001) substrates. From x-ray φ-scan and planar transmission electron microscopy measurements, the LSMO layer in the LSMO/SrTiO3/YBa2Cu3O7/MgO heterostructure is found to have coherent in-plane grain boundaries with a predominance of 45° rotations (between [100] and [110] grains) in addition to the cube-on-cube epitaxial relationship. Also, epitaxial LSMO/Bi4Ti3O12/LaAl03 (001) and c-axis textured LSMO/Bi4Ti3O12/SiO2/Si(001) with random in-plane grain boundaries are introduced as the counterparts for comparison. The resistivity and magnetoresistance (MR) of LSMO layer were measured and compared in these three different heterostructures. The low field MR at low temperature shows a dramatic dependence on the nature of the grain boundary. An attempt is made to interpret these results on the basis of correlation between the magnetic properties and grain structures.

X-Ray Diffraction Analysis and Modeling of Strain Induced Thermal Cycling in a Thin Aluminum (011) Bicrystal Film

2001 ◽  
Vol 695 ◽  
Author(s):  
D. E. Nowak ◽  
O. Thomas ◽  
S. P. Baker ◽  
E. A. Stach ◽  
K. Balzuweit ◽  
...  
Keyword(s):  
Thermal Cycling ◽  
Dislocation Motion ◽  
X Ray Diffraction ◽  
Metal Thin Films ◽  
X Ray ◽  
Transmission Electron ◽  
Threshold Temperatures ◽  
Slip Planes ◽  
Dislocation Behavior

ABSTRACTHeteroepitaxial films of aluminum bicrystals grown on silicon provide a model system in which to study plasticity in polycrystalline metal thin films. For the bicrystal films, dislocations are confined to move on two different slip plane orientations because of the orientation of the crystals on the substrate. In-situ transmission electron microscopy (TEM) observations during thermal cycling have shown two threshold temperatures for dislocation motion on cooling. A simple model uses the resolved shear stress on the possible slip planes to explain the TEM observations. Mechanisms responsible for the dislocation behavior are studied in-situ during thermal cycling between room temperature and 450°C with x-ray diffraction. The strains are determined using a sin2(Ψ) analysis at each temperature. Direct comparisons are made between the TEM observations, the model and x-ray diffraction results.

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