Analysis Of EBSD Data Research Articles

Machine learning enhanced analysis of EBSD data for texture representation

Generating reduced-order, synthetic grain structure datasets that accurately represent the measured grain structure of a material is important for reducing the cost and increasing the accuracy of computational crystal plasticity efforts. This study introduces a machine-learning-based approach, termed texture adaptive clustering and sampling (TACS), for generating representative Euler angle datasets that accurately mimic the crystallographic texture. The TACS approach employs K-means clustering and density-based sampling in a closed-loop iteration to create representative Euler angle datasets. Proof-of-principle experiments were performed on rolled and recrystallized low-carbon steel. Validation of the TACS approach was extended to twenty-two datasets, varying lattice structures, and complex crystallographic textures, thereby encompassing a broad range of materials and crystal structures. Kolmogorov-Smirnov (K-S) test comparisons underscore the performance of the TACS approach over traditional electron backscatter diffraction EBSD dataset reduction techniques, with average K-S test scores nearing 0.9, indicating a high-fidelity representation of the original datasets. In contrast, conventional methods display scores below 0.3, indicating less reliability of the structure representation. The independence of the TACS approach from material texture and its capability to autonomously generate datasets with predetermined data points demonstrates its unbiased potential in streamlining dataset preparation for crystallographic analysis.

EBSD-data analysis of an additive manufactured maraging 300 steel submitted to different tempering and aging treatments

Maraging is a high alloy steel sensitive to the precipitation of intermetallics from a supersaturated solid solution during aging heat treatments. The precipitation phenomenon is well described in the literature, which gave rise to the alloy name regarding a martensite matrix with precipitates formed by aging treatment. Many studies have been performed to characterize this material, usually subjected to many sample preparations for transmission microscopy, which is very laborious, and few EBSD analyses. Therefore, in this work, a large study was conducted using electron backscatter diffraction (EBSD) to analyze maraging microstructures through band-contrast, kernel average misorientation (KAM), grain orientation spread (GOS), and misorientation distribution. Our results show that solubilization of the additive manufactured maraging steel resulted in a more homogeneous microstructure with new angle grain boundaries. Furthermore, tempering heat treatments relieve martensite strain, increasing band contrast values. Posterior aging presented a low impact on the results of EBSD analysis.

In-situ evidence for rotation of Si particles with respect to grains in tensile-deformed Al−Si alloys

To clarify whether the Si particles rotate with respect to the matrix grains during tensile deformation of Al−Si alloys, in-situ tensile SEM and ex-situ EBSD were coupled to investigate the relationship between Si particles' rotation and grain rotation. By comparing the on-plane projection of 3D orientations of grains revealed by EBSD and in-situ SEM observations of Si particles during deformation, noticeable relative rotation of Si particles on the sample surface plane with respect to the matrix grains was found. Besides, greater relative rotation of the Si particle was found to introduce a higher density of geometrically necessary dislocations (GNDs) which can cause work-hardening effects in the matrix nearby the Si particles, according to kernel average misorientation (KAM) analysis of EBSD data. In summary, the larger relative rotation of Si particles can cause higher work-hardening effects.

Cover Picture: Materials and Corrosion. 6/2023

Cover: Corrosion of stainless steel ropes from a nominally austenitic alloy in seawater may result in hollow wires. This phenomenon was replicated by electrochemical tests and analysis of EBSD data indicates the susceptibility to such preferential axial corrosion being much more related to crystal orientation than to the amount of α'-martensite induced by cold drawing of the wires. Different production technologies may result in significantly diff erent corrosion behaviour. More detailed information can be found in: Paul Linhardt, Maria V. Biezma, Roland Haubner, Roman Schuster, Tomasz Wojcik, Hollow wire corrosion of stainless steel ropes in a marine mooring system and its relation to microstructure, Materials and Corrosion 2023, 74, 818.

Role of Grain Size and Recrystallization Texture in the Corrosion Behavior of Pure Iron in Acidic Medium

This work investigates the role of grain size and recrystallization texture in the corrosion behavior of pure iron in 0.1 M sulfuric acid solution. Annealing heat treatment was applied to obtain samples with different average grain sizes (26, 53 and 87 µm). Optical microscopy, X-ray diffraction and electron backscatter diffraction techniques were used to characterize the microstructure. The EBSD data analysis showed ferrite phase with no inclusions and very low geometrically necessary dislocation density, indicating strain-free grains constituting all samples. The crystallographic texture analysis of the samples revealed that the 26 µm grain size sample had a high volume fraction of {111} oriented grains parallel to the sample surface, while other samples exhibited nearly random crystallographic texture. The electrochemical results from potentiodynamic polarization and electrochemical impedance spectroscopy showed a decrease in corrosion resistance from 87 µm to 53 µm grain size sample and then an increase for the 26 µm grain size sample. This increase was attributed to the dominant effect of recrystallization texture on the corrosion behavior of the sample. The cathodic hydrogen evolution reaction kinetics was found to play a decisive role in the corrosion behavior of iron.

Nanoindentation of alumina and multiphase inclusions in 42CrMo4 steel

Cleaning filter systems for metal melt filtration combine reactive filtration by functionalized filter surfaces for chemical reaction with the steel melt and active (mechanical) filtration. In the present work, a combined cleaning filter system was applied to 42CrMo4 steel melt containing nonmetallic inclusions, which were generated artificially before filtration. The nonmetallic inclusions in the solidified steel were investigated by an automated scanning electron microscope (ASPEX), nanoindentation, atomic force microscopy (AFM), focused ion beam technique (FIB) and confocal laser scanning microscopy (CLSM). The combined filter system was found to reduce the amount of aluminum in the steel and to form novel multiphase inclusions. These multiphase inclusions consist of TiO 2-x and Al 2 O 3 in a low-melting spessartine matrix and were characterized by nanoindentation. Compared to pure Al 2 O 3 inclusions, the spessartine inclusions are softer and have a lower Young's modulus, fitting much better to the mechanical properties of the steel. The area below the indents was investigated by focused ion beam technique and transmission scanning electron microscopy revealing cracks and dislocations. Furthermore, the low-melting character of the spessartine matrix was proven by means of a confocal laser scanning microscope. Accordingly, the low-melting spessartine inclusions appear as liquid inclusions during steel melt processing and could contribute to clogging prevention in continuous steel casting. • Combined steel melt filtration system caused formation of multiphase inclusions. • Multiphase inclusions entrapped TiO2-x and Al2O3 in a matrix of soft spessartine. • During nanoindentation of Al2O3, pop-in events marked elastic-plastic transition. • Analysis of EBSD data by MTEX suggest activation of pyramidal slip system in Al2O3. • Beneath the indents, plastic zone based on dislocations was observed by t-SEM.

Influence of plastic deformation in fatigue crack behavior in bainitic steel

In the present paper, the behavior of fatigue microcracks is studied in a high-strength bainitic steel with the aim of identifying the microstructural features that influence the mode of initiation and propagation of microcracks. For this study, a gradual monitoring of surface damage during low-cycle fatigue test at different plastic strain ranges was carried out by means of light optical and electron microscopy along with EBSD data analysis. Moreover, the dislocation structure near the surface was analyzed and correlated with the crack initiation site. The results showed a change with respect to cracking mechanisms from 0.2% plastic strain.

Statistical analysis of EBSD data to predict potential abnormal grain growth in 3.0 wt% Si grain-oriented electrical steel

The role of grain topology as a predictor on abnormal grain growth (AGG) of primary recrystallized silicon steel sheet has been investigated by EBSD technique. Goss oriented grains in the primary recrystallized silicon steel sheet were observed to have larger grain sizes than average matrix grains. The average grain size of grains with the smallest deviation angle (<1°) from the Goss orientation was around 2.6 times larger than the average grain size of the matrix. Also, as the grain orientation approaches the Goss orientation, it had the higher number of neighboring grains. In this study, eight grains were identified as AGG candidates that have at least three times larger grain sizes than the average grain size, and have orientations close to the Goss orientation, i.e., with <5° deviation angle from Goss. However, it was not possible to determine which is more likely to happen for the abnormal grain growth among these grains.

The role of kink boundaries in the deformation and recrystallisation of polycrystalline ice

Kinking is a common process in materials with a strong visco-plastic anisotropy but its impact on the plastic deformation and recrystallisation of crystal aggregates is still poorly constrained. Here, kinking is studied via constant stress experiments on polycrystalline ice under relatively low temperature (240 K) and high differential stress (13.3 MPa and 2.7 MPa, with 50 MPa confining pressure). EBSD data analysis shows that samples comprise large and small grains, interpreted as remnant and recrystallised. Boundary trace analyses and misorientation data of kinked remnant grains reveal that kink boundaries are best characterised with rotation axes within the basal plane of the ice crystal. Inferred slip directions within the basal plane are variable and include <11–20>, <10-10> and intermediate directions. Shorter grain boundaries with rotation axes outside the basal plane surround kink boundaries and indicate that non-basal dislocations or ripplocations play a role in accommodating local kink deformation. More kink boundaries per grain and a larger boundary misorientation are generally found in remnant grains in the high-stress sample. At an aggregate level, kinking as a key facilitator for the dynamic recrystallisation process is represented by many straight grain boundaries with basal rotation axes in the remnant and recrystallised grain population. The statistically preferred slip direction within the basal plane is <21–30>, consistent with coupled slip on two crystallographic a-axes with uneven contributions.

Microstructure evolution and deformation mechanisms of β phase in TiBw/Ti60 composites studied by reconstructing grain during the hot deformation

Hot compression tests were performed on the TiBw/Ti60 composite in the single β phase region to study the microstructure evolution and deformation mechanisms. The stress-strain curves exhibited obvious flow softening above the strain rate of 0.01 s−1. While the stress-strain curves exhibited dynamic balance at strain rate of 0.001 s−1. Based on the analysis of EBSD data, method have been proposed to deduce the information of microstructure of prior β grains. The pole figures of recalculated β grains matched very well with the pole figures of selected α variants according to BOR. At low strain rate the elongated β grains can be reconstructed due to DRV. The results of reconstructing grains at different strain show that the deformation mechanism of TiBw/Ti60 composite is mainly dominated by DDRX at high strain rates in β phase region. Full equiaxed prior β grains can be observed at 1120 °C/0.1 s−1 and strain of 0.4. In addition, TiBw is beneficial to DRX of β grains due to the dislocation accumulation and providing the nucleation sites. These understanding can be applied to the relationship of microstructure evolution and thermal processing parameters in TiBw/Ti60 composite.

Prediction of steel corrosion resistance based on EBSD-data analysis

We experimentally compared the samples of chromium-manganese steel prepared with various heat-treatment modes to predict the corrosion resistance of the steel relative to hydrocarbon influence. The study was done using scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscattered diffraction. The surface visualization and elemental analysis allowed to reveal the existence of inclusions and discontinuities and their elemental composition. The peculiarities of crystal structure, grain sizes and orientations were revealed by the analysis of misorientation distribution histograms, and orientation, band contrast and Schmidt factor maps. The analysis allowed to conclude which of the heat-treatment modes provides the increase of corrosion resistance relative to the hydrocarbons influence.

Grain Size and Texture Evolution During Annealing of Non-oriented Electrical Steel Deformed in Tension

The evolution of grain size and texture during annealing at 700 °C of a low C, Si-Al electrical steel strip is investigated in samples deformed between 3 and 25% in tension. After an incubation period, which decreases as the magnitude of the pre-deformation increases, the grain size-time relationship exhibits two different stages. Initially, the grain growth occurs in some especial grains until they consume the deformed microstructure. In contrast, during the second stage the rate of growth decreases rapidly and a final constant grain size is reached which depends strongly on the initial deformation. Analysis of EBSD data obtained from strained samples shows that there is a direct relationship between the magnitude of the prior tensile strain, the intergranular misorientations as estimated by the grain orientation spread (GOS) and the image quality parameters. An attempt to explain the recrystallization texture observed in terms of the Taylor factors for some orientations in the α fiber of the deformation textures was made, nevertheless this analysis was not entirely satisfactory. However, it was found that the main orientation components present in the recrystallization texture of annealed samples are those with lower internal misorientation (lower GOS) in the deformed material. These results suggest that, in the material investigated, recrystallization after tensile deformation takes place via strain-induced boundary migration during annealing. Estimation of energy losses due to magnetic hysteresis in annealed samples show that the energy losses decrease as the grain size increases and as the texture factor defined as the ratio between the volume fractions of detrimental and beneficial orientations for magnetic properties, \(f\{ 111\} + f(112)[1\overline{1}0] + f(110)[1\overline{1}0])/f\{ 001\}\), increases.

Quantitative Analysis of EBSD Data in Rocks and other Crystalline Materials: Investigation of Strain Induced Recrystallisation and Growth of New Phases

Misorientation can be calculated over large datasets and a theme of this paper is the usefulness of examining the results statistically. Comparing the statistics of misorientations calculated from neighbouring pixels (or grains) with those calculated from pairs of pixels (or grains) selected at random helps to indicate deformation and recrystallisation mechanisms. Taking boundary length into account provides a link to grain boundary energy, and boundary length versus misorientation data should be used to examine how boundaries with different misorientations evolve through time. Time lapse misorientation maps indicate how orientation changes through time at particular points in a microstructure during in situ experiments. The size of areas which have changed orientation by particular amounts can be linked to boundary length and boundary migration velocities. When dealing with different phases, the statistics of angular relationships, akin to intraphase misorientation analysis, can indicate orientation relationships in the absence of prior knowledge, which is advantageous in investigating the plethora of minerals that make up the Earth.

Calculating anisotropic physical properties from texture data using the MTEX open-source package

Abstract This paper presents the background for the calculation of physical properties of an aggregate from constituent crystal properties and the texture of the aggregate in a coherent manner. Emphasis is placed on the important tensor properties of 2nd and 4th rank with applications in rock deformation, structural geology, geodynamics and geophysics. We cover texture information that comes from pole figure diffraction and single orientation measurements (electron backscattered diffraction or EBSD, electron channelling pattern, Laue pattern, optical microscope universal-stage). In particular, we provide explicit formulae for the calculation of the averaged tensor from individual orientations or from an orientation distribution function (ODF). For the latter we consider numerical integration and an approach based on the expansion into spherical harmonics. This paper also serves as a reference paper for the mathematical tensor capabilities of the texture analysis software MTEX, which is a comprehensive, freely available MatLab toolbox that covers a wide range of problems in quantitative texture analysis, for example, ODF modelling, pole figure to ODF inversion, EBSD data analysis and grain detection. MTEX offers a programming interface which allows the processing of involved research problems as well as highly customizable visualization capabilities; MTEX is therefore ideal for presentations, publications and teaching demonstrations.

Accurate analysis of EBSD data for phase identification

This paper aims to investigate the reliability of software default settings in the analysis of EBSD results. To study the effect of software settings on the EBSD results, the presence of different phases in high Al steel has been investigated by EBSD. The results show the importance of appropriate automated analysis parameters for valid and reliable phase discrimination. Specifically, the importance of the minimum number of indexed bands and the maximum solution error have been investigated with values of 7–9 and 1.0–1.5° respectively, found to be needed for accurate analysis.

Electron backscatter diffraction analysis and orientation mapping of monazite

AbstractElectron backscatter diffraction (EBSD) analysis of monazite requires a comparison of empirically collected electron backscatter patterns (EBSPs) with theoretical diffraction data, or ‘match units’, derived from known crystallographic parameters. Published crystallographic data derived from compositionally varying natural and synthetic monazite are used to calculate ten different match units for monazite. These match units are used to systematically index EBSPs obtained from four natural monazite samples with different compositions. Analyses of EBSD data, derived from the indexing of five and six diffraction bands using each of the ten match units for 10,000 EBSPs from each of the four samples, indicate a large variation in the ability of the different match units to correctly index the different natural samples. However, the use of match units derived from either synthetic Gd or Eu monazite crystallographic data yield good results for three of the four analysed monazites. Comparison of sample composition with published monazite compositions indicates that these match units are likely to yield good results for the EBSD analysis of metamorphic monazite. The results provide a clear strategy for optimizing the acquisition and analysis of EBSD data from monazite but also indicate the need for the collection of new crystallographic structure data and the subsequent generation of more appropriate match units for natural monazite.

Specific analysis of EBSD data to study the texture inheritance due to the β → α phase transformation

A specific processing of EBSD data is proposed to study the β → α texture inheritance of α titanium or α zirconium alloys. A non standard misorientation map is calculated to localise the colonies inherited from the same parent β grain. The calculation of the parent orientation from its inherited variants detailed in previous works has been adapted to the data obtained from an automated EBSD analysis. Finally, a method to derive the orientation map of the parent β phase from that of the α inherited phase is proposed. The resulting α and β COMs are used to study some aspects of the variant selection occurring in the β → α transformation of a T40 sample.

Estimation of recrystallized volume fraction from EBSD data

The recrystallized volume fraction is an important parameter in the study of recrystallization processes. This paper proposes a new method to estimate this parameter, based on quantitative EBSD data analysis. The principle of the method is first presented. The method is then tested on experimental EBSD data obtained on copper and brass. Estimated recrystallized volume fractions for different annealing temperatures are compared with values estimated from micro-hardness measurements. The presented method appears to be precise and very easy to implement, provided that some conditions are met; these are discussed in the final section.