Performance of Dynamically Simulated Reference Patterns for Cross-Correlation Electron Backscatter Diffraction

2016 ◽  
Vol 22 (4) ◽  
pp. 789-802 ◽  
Author(s):  
Brian E. Jackson ◽  
Jordan J. Christensen ◽  
Saransh Singh ◽  
Marc De Graef ◽  
David T. Fullwood ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Lattice Distortion ◽  
Electron Backscatter Diffraction ◽  
Noise Levels ◽  
Reference Pattern ◽  
Electron Backscatter ◽  
Correlation Techniques ◽  
Low Levels ◽  
Backscatter Diffraction ◽  
Dynamical Patterns

AbstractHigh-resolution (or “cross-correlation”) electron backscatter diffraction analysis (HR-EBSD) utilizes cross-correlation techniques to determine relative orientation and distortion of an experimental electron backscatter diffraction pattern with respect to a reference pattern. The integrity of absolute strain and tetragonality measurements of a standard Si/SiGe material have previously been analyzed using reference patterns produced by kinematical simulation. Although the results were promising, the noise levels were significantly higher for kinematically produced patterns, compared with real patterns taken from the Si region of the sample. This paper applies HR-EBSD techniques to analyze lattice distortion in an Si/SiGe sample, using recently developed dynamically simulated patterns. The results are compared with those from experimental and kinematically simulated patterns. Dynamical patterns provide significantly more precision than kinematical patterns. Dynamical patterns also provide better estimates of tetragonality at low levels of distortion relative to the reference pattern; kinematical patterns can perform better at large values of relative tetragonality due to the ability to rapidly generate patterns relating to a distorted lattice. A library of dynamically generated patterns with different lattice parameters might be used to achieve a similar advantage. The convergence of the cross-correlation approach is also assessed for the different reference pattern types.

Crystallographic correlation between 5M and 7M martensite in an Ni–Mn–Ga alloy

2016 ◽  
Vol 49 (2) ◽  
pp. 507-512
Author(s):  
Zongbin Li ◽  
Zhenzhuang Li ◽  
Bo Yang ◽  
Yudong Zhang ◽  
Claude Esling ◽  
...  
Keyword(s):  
Lattice Distortion ◽  
Electron Backscatter Diffraction ◽  
Deep Insight ◽  
Ferromagnetic Shape Memory Alloys ◽  
Electron Backscatter ◽  
Ferromagnetic Shape Memory ◽  
Backscatter Diffraction ◽  
Orientation Determination ◽  
Specific Orientation ◽  
Insight Into

In Ni–Mn–Ga ferromagnetic shape memory alloys, a structural transformation from one type of martensite to another is frequently observed upon cooling or heating. In this work, the microstructural features associated with the transformation from 5M to 7M martensite in an Ni50Mn26Ga22Cu2 alloy were studied. On the basis of the crystallographic orientation determination and an examination of the microstructure by means of the electron backscatter diffraction technique, the 5M to 7M transformation was found to be accompanied by the thickening of martensite plates. The two kinds of martensite (5M and 7M) possess a specific orientation relationship with (001)5M//(001)7M and [100]5M//[100]7M. Through further lattice distortion, four types of 5M variant can evolve into four 7M martensite variants in one variant colony. The present study is expected to provide a deep insight into the crystallographic correlation between 5M and 7M martensite in Ni–Mn–Ga alloys.

Resolving pseudosymmetry in γ-TiAl using cross-correlation electron backscatter diffraction with dynamically simulated reference patterns

2018 ◽  
Vol 51 (3) ◽  
pp. 655-669 ◽  
Author(s):  
Brian Jackson ◽  
David Fullwood ◽  
Jordan Christensen ◽  
Stuart Wright
Keyword(s):  
Cross Correlation ◽  
Electron Backscatter Diffraction ◽  
Experimental Sample ◽  
Correct Orientation ◽  
Pattern Noise ◽  
Electron Backscatter ◽  
Diffraction Patterns ◽  
Backscatter Diffraction ◽  
Pattern Resolution ◽  
Pattern Center

Pseudosymmetry is a phenomenon that occurs when grains with different lattice parameters produce nearly identical diffraction patterns such that conventional electron backscatter diffraction (EBSD) techniques are unable to unambiguously differentiate the lattice orientations. This commonly occurs in materials with near-unity tetragonality, such as γ-TiAl. The current study uses cross-correlation EBSD to resolve pseudosymmetry in γ-TiAl. Three dynamically simulated reference patterns are generated for each point in the scan, one for each of the three potential pseudosymmetric orientations, which are subsequently correlated with the original pattern using six different methods in order to identify the correct orientation. The methods are first applied to a scan of dynamically simulated patterns, which is used to evaluate the sensitivity of the method to pattern resolution, pattern noise and pattern center error. It was determined that all six methods were 100% successful up to about 13 µm of pattern center error and pattern resolutions of about 80 × 80 pixels, and hence the methods were applied to an experimental sample of lamellar γ-TiAl. A hybrid combination of two of the methods was shown to successfully select the correct pseudosymmetry for about 96% of the points in the scan, improving upon the 70% accuracy of the Hough-based methods for the current study and 90% accuracy for previous studies resolving pseudosymmetry in lamellar γ-TiAl.

Influence of Noise-Generating Factors on Cross-Correlation Electron Backscatter Diffraction (EBSD) Measurement of Geometrically Necessary Dislocations (GNDs)

2017 ◽  
Vol 23 (3) ◽  
pp. 460-471 ◽  
Author(s):  
Landon T. Hansen ◽  
Brian E. Jackson ◽  
David T. Fullwood ◽  
Stuart I. Wright ◽  
Marc De Graef ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Electron Backscatter Diffraction ◽  
Low Cost ◽  
Electron Backscatter ◽  
Deformation Mechanics ◽  
Ebsd Technique ◽  
Backscatter Diffraction ◽  
The Impact ◽  
Influence Of Noise ◽  
Shed Light

AbstractStudies of dislocation density evolution are fundamental to improved understanding in various areas of deformation mechanics. Recent advances in cross-correlation techniques, applied to electron backscatter diffraction (EBSD) data have particularly shed light on geometrically necessary dislocation (GND) behavior. However, the framework is relatively computationally expensive—patterns are typically saved from the EBSD scan and analyzed offline. A better understanding of the impact of EBSD pattern degradation, such as binning, compression, and various forms of noise, is vital to enable optimization of rapid and low-cost GND analysis. This paper tackles the problem by setting up a set of simulated patterns that mimic real patterns corresponding to a known GND field. The patterns are subsequently degraded in terms of resolution and noise, and the GND densities calculated from the degraded patterns using cross-correlation ESBD are compared with the known values. Some confirmation of validity of the computational degradation of patterns by considering real pattern degradation is also undertaken. The results demonstrate that the EBSD technique is not particularly sensitive to lower levels of binning and image compression, but the precision is sensitive to Poisson-type noise. Some insight is also gained concerning effects of mixed patterns at a grain boundary on measured GND content.

Electron backscatter diffraction study of variant selection during ordering phase transformation in L10-type red gold alloy

2019 ◽  
Vol 52 (5) ◽  
pp. 1202-1213 ◽  
Author(s):  
Margaux N. D. Larcher ◽  
Cyril Cayron ◽  
Andreas Blatter ◽  
Raphaëlle Soulignac ◽  
Roland E. Logé
Keyword(s):  
Lattice Distortion ◽  
Gold Alloy ◽  
Electron Backscatter Diffraction ◽  
Martensitic Transformations ◽  
Careful Analysis ◽  
Mechanical Work ◽  
Variant Selection ◽  
Ebsd Data ◽  
Electron Backscatter ◽  
Backscatter Diffraction

A shape-memory effect is known to appear in red gold alloys with compositions close to Au–Cu. The aim of this paper is to study by electron backscatter diffraction (EBSD) the variant selection in the A1 → L10 transformation occurring under stress, in bending conditions. The L10 domains are successfully identified by this technique despite the c/a ratio being close to unity. The orientation relationship between the cubic and tetragonal phases is determined by a careful analysis of the EBSD data. The distortion of the lattice for each variant is then modelled and calculated from the experimental orientations. The mechanical work associated with the transformation is computed from the lattice distortion by neglecting the obliquity. Finally, the distribution of this mechanical work is compared with the case of a uniform distribution of all variants, in order to evaluate the extent of variant selection. The maximal work criterion, often used for martensitic transformations, enabled quantification of the variant selection phenomenon.

Sign in / Sign up

Export Citation Format

Share Document