scholarly journals Electron backscatter diffraction study of orientation gradients at the grain boundaries of a polycrystalline steel sheet deformed along different loading paths

2017 ◽  
Vol 50 (4) ◽  
pp. 1179-1191 ◽  
Author(s):  
J. W. Signorelli ◽  
A. Roatta ◽  
N. De Vincentis ◽  
C. Schwindt ◽  
M. Avalos ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Steel Sheet ◽  
Electron Backscatter Diffraction ◽  
Effective Thickness ◽  
Local Orientation ◽  
Orientation Gradient ◽  
Loading Paths ◽  
Electron Backscatter ◽  
Backscatter Diffraction ◽  
Local Misorientation

In a polycrystal, the heterogeneity of plastic deformation in a particular grain is greatly enhanced by adjacent grains that constrain the grain's local behavior, often imposing orientation gradients. This work aims to characterize and quantify the local orientation gradients near grain boundaries (GBs). Electron backscatter diffraction (EBSD) measurements were made on a 0.67 mm thick aluminium-killed drawing quality (AKDQ) steel sheet subjected to different loading paths that are typical of forming operations. A statistical analysis shows that a considerable fraction of the analyzed GB profiles can be described by an orientation profile with a constant slope near the GB. In order to quantify this behavior, as well as the degree of localization, two new parameters, based on the local orientation gradient assessed by EBSD, are proposed: BET (boundary effective thickness) and GAS (gradient average severity). These parameters should be considered together, the BET as an effective thickness of the GB zone where the orientation gradient takes place and the GAS as a measure of the magnitude or severity of the orientation gradient. Additionally, the GAS parameter shows a strong correlation with the accumulated macroscopic strain for the investigated deformation levels and loading paths, while the BET profile clearly reveals the influence of the GB on the misorientation profiles. Tension and biaxial stretching results lead to a BET value between 1.5 and 2 µm. Finally, it is shown that the local misorientation in the GB zone, on both sides of the GB line, is disperse and it does not correlate simply with misorientation or even the slip-transfer geometry across the GB. Moreover, the observed average local misorientation dispersions in GB zones are different for each loading condition.

Orientation Precision of Electron Backscatter Diffraction Measurements Near Grain Boundaries

2014 ◽  
Vol 20 (3) ◽  
pp. 852-863 ◽  
Author(s):  
Stuart I. Wright ◽  
Matthew M. Nowell ◽  
René de Kloe ◽  
Lisa Chan
Keyword(s):  
Grain Boundaries ◽  
Electron Backscatter Diffraction ◽  
Crystal Lattices ◽  
Pile Up ◽  
Electron Backscatter ◽  
Common Technique ◽  
Ebsd Pattern ◽  
Backscatter Diffraction ◽  
Physical Phenomena ◽  
Local Misorientation

AbstractElectron backscatter diffraction (EBSD) has become a common technique for measuring crystallographic orientations at spatial resolutions on the order of tens of nanometers and at angular resolutions <0.1°. In a recent search of EBSD papers using Google Scholar™, 60% were found to address some aspect of deformation. Generally, deformation manifests itself in EBSD measurements by small local misorientations. An increase in the local misorientation is often observed near grain boundaries in deformed microstructures. This may be indicative of dislocation pile-up at the boundaries but could also be due to a loss of orientation precision in the EBSD measurements. When the electron beam is positioned at or near a grain boundary, the diffraction volume contains the crystal lattices from the two grains separated by the boundary. Thus, the resulting pattern will contain contributions from both lattices. Such mixed patterns can pose some challenge to the EBSD pattern band detection and indexing algorithms. Through analysis of experimental local misorientation data and simulated pattern mixing, this work shows that some of the rise in local misorientation is an artifact due to the mixed patterns at the boundary but that the rise due to physical phenomena is also observed.

scholarly journals Pop-in behavior and elastic-to-plastic transition of polycrystalline pure iron during sharp nanoindentation

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Fabian Pöhl
Keyword(s):  
Grain Boundaries ◽  
Strong Influence ◽  
Electron Backscatter Diffraction ◽  
Dislocation Nucleation ◽  
Stress Fields ◽  
Shear Stresses ◽  
Statistical Process ◽  
Iron Crystal ◽  
Electron Backscatter ◽  
Backscatter Diffraction

Abstract This study analyzes the elastic-to-plastic transition during nanoindentation of polycrystalline iron. We conduct nanoindentation (Berkovich indenter) experiments and electron backscatter diffraction analysis to investigate the initiation of plasticity by the appearance of the pop-in phenomenon in the loading curves. Numerous load–displacement curves are statistically analyzed to identify the occurrence of pop-ins. A first pop-in can result from plasticity initiation caused by homogeneous dislocation nucleation and requires shear stresses in the range of the theoretical strength of a defect-free iron crystal. The results also show that plasticity initiation in volumes with preexisting dislocations is significantly affected by small amounts of interstitially dissolved atoms (such as carbon) that are segregated into the stress fields of dislocations, impeding their mobility. Another strong influence on the pop-in behavior is grain boundaries, which can lead to large pop-ins at relatively high indentation loads. The pop-in behavior appears to be a statistical process affected by interstitial atoms, dislocation density, grain boundaries, and surface roughness. No effect of the crystallographic orientation on the pop-in behavior can be observed.

scholarly journals Coupling Automated Electron Backscatter Diffraction with Transmission Electron and Atomic Force Microscopies

2000 ◽  
Vol 6 (S2) ◽  
pp. 940-941
Author(s):  
A.J. Schwartz ◽  
M. Kumar ◽  
P.J. Bedrossian ◽  
W.E. King
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Thermomechanical Processing ◽  
Electron Backscatter Diffraction ◽  
Grain Boundary Character Distribution ◽  
Atomic Force ◽  
Transmission Electron ◽  
Electron Backscatter ◽  
Network Engineering ◽  
Backscatter Diffraction

Grain boundary network engineering is an emerging field that encompasses the concept that modifications to conventional thermomechanical processing can result in improved properties through the disruption of the random grain boundary network. Various researchers have reported a correlation between the grain boundary character distribution (defined as the fractions of “special” and “random” grain boundaries) and dramatic improvements in properties such as corrosion and stress corrosion cracking, creep, etc. While much early work in the field emphasized property improvements, the opportunity now exists to elucidate the underlying materials science of grain boundary network engineering. Recent investigations at LLNL have coupled automated electron backscatter diffraction (EBSD) with transmission electron microscopy (TEM)5 and atomic force microscopy (AFM) to elucidate these fundamental mechanisms.An example of the coupling of TEM and EBSD is given in Figures 1-3. The EBSD image in Figure 1 reveals “segmentation” of boundaries from special to random and random to special and low angle grain boundaries in some grains, but not others, resulting from the 15% compression of an Inconel 600 polycrystal.

Electron backscatter diffraction investigation of local misorientations and orientation gradients in connection with evolution of grain boundary structures in deformed and annealed zirconium. A new approach in grain boundary analysis

2013 ◽  
Vol 46 (2) ◽  
pp. 483-492 ◽  
Author(s):  
Mariusz Jedrychowski ◽  
Jacek Tarasiuk ◽  
Brigitte Bacroix ◽  
Sebastian Wronski
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Orientation ◽  
Electron Backscatter Diffraction ◽  
Lattice Defect ◽  
Line Segments ◽  
Compression Direction ◽  
Electron Backscatter ◽  
Grain Orientation Spread ◽  
Backscatter Diffraction

The main aim of the present work is to study the relation between microstructural features – such as local misorientations, grain orientation gradients and grain boundary structures – and thermomechanical treatment of hexagonal zirconium (Zr702α). Electron backscatter diffraction (EBSD) topological maps are used to analyze the aforementioned material parameters at the early stages of plastic deformation imposed by channel-die compression, as well as at a partial recrystallization state achieved by brief annealing. The evolution of local misorientations and orientation gradients is investigated using the so-called kernel average misorientation (KAM) and grain orientation spread (GOS) statistics implemented in the TSLOIMdata analysis software [TexSEM Laboratories (2004), Draper, UT, USA]. In the case of grain boundaries (GBs) a new method of analysis is presented. As an addition to the classical line segments method, where the grain boundary is represented by line segments that separate particular pairs of neighboring points, an approach that focuses on grain boundary areas is proposed. These areas are represented by sets of EBSD points, which are specially selected from a modified calculation procedure for the KAM. Different evolution mechanisms of intragranular boundaries, low-angle grain boundaries and high-angle grain boundaries are observed depending on the compression direction. The observed differences are consistent with the results obtained from KAM and GOS analysis. It is also concluded that the proposed method of grain boundary characterization seems to be promising, as it provides new and interesting analysis tools such as textures, absolute fractions and other EBSD statistics of the GB areas. This description may be more compatible with a real deformed microstructure, especially for grain boundaries with very small misorientation, which are indeed clustered areas of lattice defect accumulation.

Characterization of Sputtered CdTe Thin Films with Electron Backscatter Diffraction and Correlation with Device Performance

2015 ◽  
Vol 21 (4) ◽  
pp. 927-935 ◽  
Author(s):  
Matthew M. Nowell ◽  
Michael A. Scarpulla ◽  
Naba R. Paudel ◽  
Kristopher A. Wieland ◽  
Alvin D. Compaan ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Electron Backscatter Diffraction ◽  
Electrical Performance ◽  
Poor Correlation ◽  
Twin Boundaries ◽  
Electron Backscatter ◽  
Backscatter Diffraction

AbstractThe performance of polycrystalline CdTe photovoltaic thin films is expected to depend on the grain boundary density and corresponding grain size of the film microstructure. However, the electrical performance of grain boundaries within these films is not well understood, and can be beneficial, harmful, or neutral in terms of film performance. Electron backscatter diffraction has been used to characterize the grain size, grain boundary structure, and crystallographic texture of sputtered CdTe at varying deposition pressures before and after CdCl2 treatment in order to correlate performance with microstructure. Weak fiber textures were observed in the as-deposited films, with (111) textures present at lower deposition pressures and (110) textures observed at higher deposition pressures. The CdCl2-treated samples exhibited significant grain recrystallization with a high fraction of twin boundaries. Good correlation of solar cell efficiency was observed with twin-corrected grain size while poor correlation was found if the twin boundaries were considered as grain boundaries in the grain size determination. This implies that the twin boundaries are neutral with respect to recombination and carrier transport.

Morphology Evolution of Grain Boundary Carbides in Highly Twinned Inconel Alloy 600

2016 ◽  
Vol 879 ◽  
pp. 1111-1116 ◽  
Author(s):  
Hui Li ◽  
Jiao Rong Ma ◽  
Xin Rong Liu ◽  
Shuang Xia ◽  
Wen Qing Liu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Aging Time ◽  
Electron Backscatter Diffraction ◽  
Coincidence Site Lattice ◽  
Morphology Evolution ◽  
Alloy 600 ◽  
Inconel Alloy ◽  
Electron Backscatter ◽  
Backscatter Diffraction

The effects of grain boundary characters on the morphology evolution of grain boundary carbides in Inconel Alloy 600 with high proportional low Σ coincidence site lattice (CSL) boundaries aged at 715 oC for 1-100 h were investigated by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). During the aging process, the carbides precipitated at coherent twin (Σ3) boundaries are very few and finest within all the aging time. Bar like carbides precipitated near both sides of the incoherent twin (Σ3) boundaries, and bigger carbides than that of coherent Σ3 boundaries had been found on the incoherent Σ3 boundaries. Bar like carbides precipitated near only one side of Σ9 boundaries, and much bigger carbides than that of Σ3 boundaries have been found on the Σ9 boundaries. The morphology of carbides precipitated at Σ27 and random grain boundaries are similar, and is bigger than that of precipitated at other grain boundaries. The carbides precipitated at grain boundaries with all types grow bigger with the aging time prolonging, but their growth rates are different.

Effect of Phosphorus Contents on Texture and Grain Boundary Character for the Annealing High Strength Ti-IF Steels

2013 ◽  
Vol 652-654 ◽  
pp. 929-933 ◽  
Author(s):  
Xin Li Song ◽  
Kun Peng ◽  
P.P. Zhang ◽  
J.Y. Wu ◽  
J. Zhou ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Recrystallization Texture ◽  
Volume Fraction ◽  
Electron Backscatter Diffraction ◽  
Coincidence Site Lattice ◽  
High Strength ◽  
Fiber Texture ◽  
Grain Boundary Character ◽  
Electron Backscatter ◽  
Backscatter Diffraction

The effect of phosphorus contents on texture and grain boundaries character for the high strength Ti-IF annealed for 120sec at 810oC are researched by electron backscatter diffraction technique（EBSD）. The recrystallization texture is approximated by the γ-fiber texture whose components are {111} and {111} orientation texture. The highest volume fraction of //ND texture is almost 80% for the sample containing 0.056%P. A large amount of coincidence site lattice(CSL) grain boundaries ∑3，∑5, ∑7，∑9，∑11 and ∑13b are obtained.

Effect of Trench Aspect Ratio on Microstructure and Texture in Damascene Cu Interconnects

2012 ◽  
Vol 706-709 ◽  
pp. 2605-2610
Author(s):  
L. Chen ◽  
G.J. Yuan ◽  
J.G. Xu ◽  
F. Guo ◽  
N. Pang
Keyword(s):  
Aspect Ratio ◽  
Grain Boundaries ◽  
Electron Backscatter Diffraction ◽  
Coincidence Site Lattice ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cu Interconnects ◽  
Electron Backscatter ◽  
Line Spacing ◽  
Backscatter Diffraction

The effect of trench aspect ratio and line spacing on microstructure and texture in annealed damascene Cu interconnects has been investigated. The X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) analyses of Cu lines, showed a preferred {111} orientation and the trenches reduce the proportion of high-angle grain boundaries and increase the fraction of coincidence site lattice (CSL) grain boundaries, comparing with the Cu blanket film. In addition, both trench aspect ratio and line spacing can largely affect the microstructure and texture in annealed damascene Cu interconnects.

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