Analysing crystal distortions to deduce dislocation slip systems

2021 ◽  
Author(s):  
John Wheeler ◽  
Sandra Piazolo ◽  
David Prior ◽  
Jake Tielke ◽  
Pat Trimby
Keyword(s):  
Electron Backscatter Diffraction ◽  
Direct Method ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Dislocation Slip ◽  
Slip Systems ◽  
Crystalline Materials ◽  
Burgers Vector ◽  
Growth Defects ◽  
Backscatter Diffraction

<p>In many parts of the Earth rocks deform by dislocation creep. There is therefore a need to understand which slip systems operated in nature and in experimental products. Knowing the conditions of experiments may then allow natural conditions and strain rates to be characterised. Dislocation creep typically gives lattice preferred orientations (LPOs), since activity on particular slip systems leads to lattice rotations and alignment. For decades LPOs, measured first optically and since the 1990s by EBSD, have been used to infer slip systems. This is a valuable technique but the link between slip sytem activity and LPO is complicated, especially if recrystallisation and/or grain boundary sliding have been involved.</p><p>Here we present a more direct method to deduce “geometrically necessary” dislocations (GNDs) from the distortions within crystals. Distortions may be optically visible (e.g. undulose extinction in quartz) but EBSD has revealed how common distortions are, and allowed them to be quantified. The method does not give the complete picture of GNDs but allows hypotheses to be tested about possible slip systems. We illustrate this “Weighted Burgers Vector” method with a number of examples. In olivine the method distinguishes slip parallel to a and c, and in plastically deformed plagioclase it reveals a variety of slip systems which would be difficuilt to deduce from LPOs alone. GNDs may not necessarily reflect the full slip system activity, since many dislocations will have passed through crystals and merged with grain boundaries leaving no signature. Neverthless the method highlights what dislocations are present “stranded” in the microstructure. In many case these will have been produced by deformation although the method can also characterise growth defects.</p><p>Wheeler et al. 2009. The weighted Burgers vector: a new quantity for constraining dislocation densities and types using electron backscatter diffraction on 2D sections through crystalline materials. <span>DOI:</span> 10.1111/j.1365-2818.2009.03136.x</p>

Orientation relationships of carlsbergite in schreibersite and kamacite in the north Chile iron meteorite

2006 ◽  
Vol 70 (4) ◽  
pp. 373-382 ◽  
Author(s):  
G. Nolze ◽  
G. Wagner ◽  
R. Saliwan Neumann ◽  
R. Skála ◽  
V. Geist
Keyword(s):  
Electron Backscatter Diffraction ◽  
Metallic Matrix ◽  
Iron Meteorite ◽  
Orientation Relationships ◽  
Orientation Relation ◽  
Crystalline Materials ◽  
The North ◽  
Transmission Electron ◽  
Backscatter Diffraction ◽  
General Connection

AbstractThe crystallographic orientation of carlsbergite (CrN) in the north Chile meteorite (hexahedrite) was investigated using electron backscatter diffraction and transmission electron microscopy. These studies examined the CrN crystals in the rhabdites (idiomorphic schreibersite) and in kamacite. It was found that the CrN crystals embedded in rhabdite show a number of different orientation relationships with the host crystals. These orientations can be explained based on the lattice dimensions of both coexisting crystalline materials. It was also found that both carlsbergite and kamacite are characterized by a high dislocation density (≥ l09 cm-2) while rhabdite is free of dislocations. It is supposed that in spite of the deformed metallic matrix, a general connection between the orientation relation of all the phases involved exists.

scholarly journals Novel −75°C SEM cooling stage: application for martensitic transformation in steel

Microscopy ◽  
2020 ◽  
Author(s):  
Kaneaki Tsuzazki ◽  
Motomichi Koyama ◽  
Ryosuke Sasaki ◽  
Keiichiro Nakafuji ◽  
Kazushi Oie ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Electron Backscatter Diffraction ◽  
Dislocation Slip ◽  
In Situ Observation ◽  
Contrast Imaging ◽  
Cooling Stage ◽  
Electron Channelling ◽  
Electron Backscatter ◽  
Backscatter Diffraction

Abstract Microstructural changes during the martensitic transformation from face-centred cubic (FCC) to body-centred cubic (BCC) in an Fe-31Ni alloy were observed by scanning electron microscopy (SEM) with a newly developed Peltier stage available at temperatures to  −75°C. Electron channelling contrast imaging (ECCI) was utilized for the in situ observation during cooling. Electron backscatter diffraction analysis at ambient temperature (20°C) after the transformation was performed for the crystallographic characterization. A uniform dislocation slip in the FCC matrix associated with the transformation was detected at −57°C. Gradual growth of a BCC martensite was recognized upon cooling from −57°C to −63°C.

scholarly journals Decoupling the Impacts of Strain Rate and Temperature on TRIP in a Q&P Steel

JOM ◽  
2022 ◽  
Author(s):  
Christopher B. Finfrock ◽  
Diptak Bhattacharya ◽  
Brady N. L. McBride ◽  
Trevor J. Ballard ◽  
Amy J. Clarke ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Strain Rate ◽  
Strain Hardening ◽  
Electron Backscatter Diffraction ◽  
Dislocation Slip ◽  
Transformation Induced Plasticity ◽  
High Strain Rate Deformation ◽  
The Individual ◽  
Backscatter Diffraction ◽  
Strain Hardening Rate

AbstractThe individual effects of strain rate and temperature on the strain hardening rate of a quenched and partitioned steel have been examined. During quasistatic tests, resistive heating was used to simulate the deformation-induced heating that occurs during high-strain-rate deformation, while the deformation-induced martensitic transformation was tracked by a combination of x-ray and electron backscatter diffraction. Unique work hardening rates under various thermal–mechanical conditions are discussed, based on the balance between the concurrent dislocation slip and transformation-induced plasticity deformation mechanisms. The diffraction and strain hardening data suggest that the imposed strain rate and temperature exhibited dissonant influences on the martensitic phase transformation. Increasing the strain rate appeared to enhance the martensitic transformation, while increasing the temperature suppressed the martensitic transformation.

scholarly journals Dislocation Creep of Olivine and Amphibole in Amphibole Peridotites from Åheim, Norway

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1018
Author(s):  
Sejin Jung ◽  
Takafumi Yamamoto ◽  
Jun-ichi Ando ◽  
Haemyeong Jung
Keyword(s):  
Electron Microscopy ◽  
Slip System ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Dislocation Creep ◽  
Transmission Electron ◽  
Electron Backscatter ◽  
Different Types ◽  
Localized Shear Deformation ◽  
Backscatter Diffraction

Amphibole peridotite samples from Åheim, Norway, were analyzed to understand the deformation mechanism and microstructural evolution of olivine and amphibole through the Scandian Orogeny and subsequent exhumation process. Three Åheim amphibole peridotite samples were selected for detailed microstructural analysis. The Åheim amphibole peridotites exhibit porphyroclastic texture, abundant subgrain boundaries in olivine, and the evidence of localized shear deformation in the tremolite-rich layer. Two different types of olivine lattice preferred orientations (LPOs) were observed: B- and A-type LPOs. Electron backscatter diffraction (EBSD) mapping and transmission electron microscopy (TEM) observations revealed that most subgrain boundaries in olivine consist of dislocations with a (001)[100] slip system. The subgrain boundaries in olivine may have resulted from the deformation of olivine with moderate water content. In addition, TEM observations using a thickness-fringe method showed that the free dislocations of olivine with the (010)[100] slip system were dominant in the peridotites. Our data suggest that the subgrain boundaries and free dislocations in olivine represent a product of later-stage deformation associated with the exhumation process. EBSD mapping of the tremolite-rich layer revealed intracrystalline plasticity in amphibole, which can be interpreted as the activation of the (100)[001] slip system.

Determining Grain Boundary Position and Geometry from EBSD Data: Limits of Accuracy

2021 ◽  
pp. 1-13
Author(s):  
David T. Fullwood ◽  
Sarah Sanderson ◽  
Sterling Baird ◽  
Jordan Christensen ◽  
Eric R. Homer ◽  
...  
Keyword(s):  
Electron Backscatter Diffraction ◽  
Finite Size ◽  
Sample Surface ◽  
Accurate Method ◽  
Crystalline Materials ◽  
Backscattered Electrons ◽  
Ebsd Data ◽  
Subsurface Geometry ◽  
Backscatter Diffraction ◽  
Transition Curves

As the feature size of crystalline materials gets smaller, the ability to correctly interpret geometrical sample information from electron backscatter diffraction (EBSD) data becomes more important. This paper uses the notion of transition curves, associated with line scans across grain boundaries (GBs), to correctly account for the finite size of the excitation volume (EV) in the determination of the geometry of the boundary. Various metrics arising from the EBSD data are compared to determine the best experimental proxy for actual numbers of backscattered electrons that are tracked in a Monte Carlo simulation. Consideration of the resultant curves provides an accurate method of determining GB position (at the sample surface) and indicates a significant potential for error in determining GB position using standard EBSD software. Subsequently, simple criteria for comparing experimental and simulated transition curves are derived. Finally, it is shown that the EV is too shallow for the curves to reveal subsurface geometry of the GB (i.e., GB inclination angle) for most values of GB inclination.

scholarly journals Introduction to a Special Issue on Electron Backscatter Diffraction

2011 ◽  
Vol 17 (3) ◽  
pp. 315-315
Author(s):  
Andrew Deal
Keyword(s):  
Materials Science ◽  
Electron Backscatter Diffraction ◽  
Crystalline Materials ◽  
Grain Boundary Character ◽  
Electron Backscatter ◽  
Dynamical Simulations ◽  
Scientists And Engineers ◽  
Microscopy Techniques ◽  
Backscatter Diffraction ◽  
Insight Into

Arguably one of the most significant microscopy techniques of the past decade, electron backscatter diffraction (EBSD) has provided scientists and engineers with tremendous insight into the structure of crystalline materials. What started with basic observations of electron diffraction in the middle of the 20th century has grown into a mature technology that bridges the gap between the macro and micro length scales. EBSD has found a home in both the materials science and geological communities characterizing crystallographic texture and preferred orientations, residual strain, grain boundary character and networks, and identifying constituent phases. Advancements in computational power, camera technology, indexing algorithms, sample preparation, and dynamical simulations have made this possible.

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