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.

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.

In situ TEM studies of deformation and fracture

1989 ◽  
Vol 47 ◽  
pp. 622-623
Author(s):  
I.M. Robertson ◽  
T.C. Lee ◽  
D.K. Dewald ◽  
H.K. Birnbaum
Keyword(s):  
Grain Boundary ◽  
Video Camera ◽  
In Situ Tem ◽  
Video Tape ◽  
Slip Systems ◽  
Camera System ◽  
Dynamic Events ◽  
Transmission Electron ◽  
Deformation And Fracture

The in-situ TEM straining technique has been used to investigate the micromechanisms of deformation and fracture in several ductile and semi-brittle systems. Attention has been focussed on the dislocation structures ahead of advancing cracks and on the interaction between lattice dislocations and grain boundaries.The deformation experiments were performed in-situ in a transmission electron microscope equipped with a video camera system. The dynamic events were recorded on video tape with a time resolution of l/30th of a second. Static interactions were recorded using the regular microscope plate system. The straining stage deforms the samples in Mode I and can operate at a displacement rate of 4 in sec-1.An example of one of the possible interactions between lattice dislocations and a ∑- 3 ([ll)/60°) grain boundary in 310 stainless steel is shown in the micrograph in Figure 1. The dislocations on slip systems A (a/2[110)1 (ll) 1 ) and B (a/2[101] (11) 1 ) impinge on the grain boundary, generating slip systems C (a/2[l0) 2/(111) 2) and D (a/2[l0) 2/(111) 2). To understand this effect three conditions were considered:

Grain boundary dislocation networks in YBa2Cu3O7-δ

1988 ◽  
Vol 46 ◽  
pp. 622-623
Author(s):  
S.E. Babcock
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Plane ◽  
Boundary Dislocation ◽  
Contrast Imaging ◽  
Plane Normal ◽  
Transmission Electron ◽  
Key Characteristics ◽  
Regular Networks ◽  
Beam Diffraction

The crystallography, morphology, and structure of typical grain boundaries in sintered samples of the high temperature superconducting oxide YBa2Cu3O7-δ (123) have been investigated by transmission electron microscopy using two-beam diffraction contrast imaging and selected area diffraction techniques.Since most of the grains present in sintered samples of 123 are plate shaped with the plate normal parallel to the c-axis of the crystal, the grain boundaries can be divided into two classes: (a) those for which the boundary plane normal is nearly parallel to the c-axis of one of the abutting grains (basal-plane-faced boundaries), and (b) those which are not basal-planefaced. Regular networks of grain boundary dislocations have been observed in high-angle grain boundaries of both types. These networks extend the length of the imagable portion (i.e., sufficiently thin) of the boundary without changing their basic geometry. The line contrast produced by the networks shows several of the key characteristics of dislocation images.

Interaction of Slip Bands with Grain Boundary - in situ TEM Observation

2000 ◽  
Vol 652 ◽  
Author(s):  
Juliana Gemperlová ◽  
Alain Jacques ◽  
Antonín Gemperle ◽  
Niva Zárubová
Keyword(s):  
Grain Boundary ◽  
Slip System ◽  
The Other ◽  
In Situ Tem ◽  
Post Mortem ◽  
Secondary Slip ◽  
Slip Bands ◽  
Transmission Electron ◽  
Primary Slip System

ABSTRACTMechanism of the slip transmission across the grain boundaries was studied on Σ3 bicrystals of Fe-4at%Si by transmission electron microscopy. In situ straining experiments as well as post mortem observations were performed. Three distinct events were observed in dependence on the angle α between the slip and grain boundary planes, namely transformation of the tertiary slip system in one grain into the secondary slip system in the other grain for α ≍ 90°, cross slip of dislocations of the primary slip system into the {112} plane parallel to the grain boundary for α ≍21°, and an abrupt formation of a sub-grain boundary in one grain for α ≍49°. Reasons for these diverse phenomena will be discussed in terms of interactions between the slip dislocations and the grain boundary dislocations.

Dislocation - Grain Boundary Interaction in Nickel Bicrystals Evolution of the Resulting Defects under Thermal Treatment

2000 ◽  
Vol 652 ◽  
Author(s):  
Louisette Priester ◽  
Sophie Poulat ◽  
Brigitte Décamps ◽  
Jany Thibault
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Thermal Treatment ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Dislocation Network ◽  
Boundary Interaction ◽  
Transmission Electron

ABSTRACTThe interactions between lattice dislocations and grain boundaries were studied in nickel bicrystals. Three types of grain boundaries, according to their energy, were investigated : singular σ3 {111}, vicinal near σ11 {311} and general near σ11 {332} grain boundaries. The experiments were performed by transmission electron microscopy using a set of techniques : conventional, weak beam, in situ and high resolution transmission electron microscopy. Dislocation transmission from one crystal to the other was only observed for σ3 {111} GB. It consists in a decomposition within the grain boundary of the trapped lattice dislocation followed by the emission of one partial in the neighbouring crystal. A high resolved shear stress is required to promote the emission process. Most often, the absorbed lattice dislocations or extrinsic grain boundary dislocations react with the intrinsic dislocation network giving rise to complex configurations. The evolutions with time and upon thermal treatment of these configurations were followed by in situ transmission electron microscopy. The evolution processes, which differ with the type of grain boundaries, were analyzed by comparison with the existing models for extrinsic grain boundary dislocation accommodation. They were tentatively interpretated on the basis of the grain boundary atomic structures and defects obtained by high resolution transmission electron microscopy studies.

Direct Observations of Grain Boundary Phenomena during Indentation of Al and Al-Mg Thin Films

2003 ◽  
Vol 795 ◽  
Author(s):  
W. A. Soer ◽  
J. Th. M. De Hosson ◽  
A. M. Minor ◽  
E. A. Stach ◽  
J. W. Morris
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Dislocation Dynamics ◽  
Direct Observations ◽  
Transmission Electron ◽  
The Matrix ◽  
Grain Boundary Motion

ABSTRACTThe deformation behavior of Al and Al-Mg thin films has been studied with the unique experimental approach of in-situ nanoindentation in a transmission electron microscope. This paper concentrates on the role of solute Mg additions in the transfer of plasticity across grain boundaries. The investigated Al alloys were deposited onto a Si substrate as thin films with a thickness of 200–300 nm and Mg concentrations of 0, 1.1, 1.8, 2.6 and 5.0 wt% Mg. The results show that in the Al-Mg alloys, the solutes effectively pin high-angle grain boundaries, while in pure Al considerable grain boundary motion is observed at room temperature. The mobility of low-angle grain boundaries is however not affected by the presence of Mg. In addition, Mg was observed to affect dislocation dynamics in the matrix.

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.

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