Influence of Crystallography on Nucleation of Ferrite Precipitates at Austenite Grain Boundary Corners in a Co-15Fe Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 378-383
Author(s):  
Guo Hong Zhang ◽  
Tomoaki Takeuchi ◽  
Masato Enomoto ◽  
Yoshitaka Adachi
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Major Influence ◽  
Austenite Grain ◽  
Electron Backscatter ◽  
The Matrix ◽  
Triple Points ◽  
Individual Grains ◽  
Austenite Grain Boundary ◽  
Backscatter Diffraction

The nucleation of bcc ferrite precipitates at austenite grain corners in a Co-15Fe alloy was studied by serial sectioning coupled with electron backscatter diffraction (EBSD) analysis. Grain corners were identified by recombination of triple points and triangular annihilation, whereas quite a few precipitates were surrounded by more than four matrix grains when twins were counted as individual grains. More than 40% of corners composed all of high angle grain boundaries were vacant at an undercooling of ~60°C from the g/(a+g) phase boundary. All the precipitates had K-S or N-W orientation relationship with at least one grain and a larger proportion of them had the OR with two and three grains. For half of vacant corners a hypothetical precipitate could have the OR with more than one grain. It is likely that not only the misorientations among the matrix grains, but also the orientations of the grain boundary planes have a major influence on nucleation potency even at grain corners.

scholarly journals Characterization of Coarse-Grained Heat-Affected Zones in Al and Ti-Deoxidized Offshore Steels

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1096
Author(s):  
Henri Tervo ◽  
Antti Kaijalainen ◽  
Vahid Javaheri ◽  
Satish Kolli ◽  
Tuomas Alatarvas ◽  
...  
Keyword(s):  
Prior Austenite ◽  
Electron Backscatter Diffraction ◽  
Coarse Grained ◽  
Grain Coarsening ◽  
Austenite Grain ◽  
The Matrix ◽  
Backscatter Diffraction ◽  
Prior Austenite Grain ◽  
Deoxidation Practice

Deterioration of the toughness in heat-affected zones (HAZs) due to the thermal cycles caused by welding is a known problem in offshore steels. Acicular ferrite (AF) in the HAZ is generally considered beneficial regarding the toughness. Three experimental steels were studied in order to find optimal conditions for the AF formation in the coarse-grained heat-affected zone (CGHAZ). One of the steels was Al-deoxidized, while the other two were Ti-deoxidized. The main focus was to distinguish whether the deoxidation practice affected the AF formation in the simulated CGHAZ. First, two different peak temperatures and prolonged annealing were used to study the prior austenite grain coarsening. Then, the effect of welding heat input was studied by applying three cooling times from 800 °C to 500 °C in a Gleeble thermomechanical simulator. The materials were characterized using electron microscopy, energy-dispersive X-ray spectrometry, and electron backscatter diffraction. The Mn depletion along the matrix-particle interface was modelled and measured. It was found that AF formed in the simulated CGHAZ of one of the Ti-deoxidized steels and its fraction increased with increasing cooling time. In this steel, the inclusions consisted mainly of small (1–4 μm) TiOx-MnS, and the tendency for prior austenite grain coarsening was the highest.

Use of Electron Backscatter Diffraction Technique in Characterization of 6XXX Aluminum Alloy Extrusions

2000 ◽  
Vol 6 (S2) ◽  
pp. 954-955
Author(s):  
Steven R. Claves ◽  
Wojciech Z. Misiolek ◽  
William H. Van Geertruyden ◽  
David B. Williams
Keyword(s):  
Electron Backscatter Diffraction ◽  
Metal Flow ◽  
Extrusion Process ◽  
Cross Sectional ◽  
Electron Backscattering Diffraction ◽  
Electron Backscatter ◽  
Individual Grains ◽  
Backscatter Diffraction ◽  
6Xxx Series

Electron Backscattering Diffraction (EBSD) is an important tool for analyzing the crystal grain orientation of a microstructure and can be used to formulate conclusions about microtexture, texture determined from individual grains. This technique has been used to study a 6xxx series aluminum alloy's response to the deformation of the extrusion process. Extrusion is the process by which a billet of material is forced, under high pressure, through a die. The material undergoes a significant decrease in cross sectional area, and is formed into a shape equivalent to the geometry of the die orifice. Different bearing lands are shown in shown in Figure 1. These surfaces form the part, and are designed to control the metal flow making it uniform through the die, thus yielding good mechanical properties. This research was focused on the resultant microstructure. The shaded regions of Figure 2 show the two surface regions where EBSD measurements were taken.

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.

Angular Precision of Automated Electron Backscatter Diffraction Measurements

2011 ◽  
Vol 702-703 ◽  
pp. 548-553 ◽  
Author(s):  
Stuart I. Wright ◽  
Jay A. Basinger ◽  
Matthew M. Nowell
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Hough Transform ◽  
Angular Resolution ◽  
Electron Backscatter Diffraction ◽  
Electron Backscatter ◽  
Individual Grains ◽  
Backscatter Diffraction ◽  
Work First ◽  
Scanning Electron

Electron backscatter diffraction (EBSD) has become the preferred technique for characterizing the crystallographic orientation of individual grains in polycrystalline microstructures due to its ability to rapidly measure orientations at specific points in the microstructure at resolutions of approximately 20-50nm depending on the capabilities of the scanning electron microscope (SEM) and on the material being characterized. Various authors have studied the angular resolution of the orientations measured using automated EBSD. These studies have stated values ranging from approximately 0.1° to 2° [1-6]. Various factors influence the angular resolution achievable. The two primary factors are the accuracy of the detection of the bands in the EBSD patterns and the accuracy of the pattern center (PC) calibration. The band detection is commonly done using the Hough transform. The effect of varying the Hough transform parameters in order to optimize speed has been explored in a previous work [6]. The present work builds upon the earlier work but with the focus towards achieving the best angular resolution possible regardless of speed. This work first details the methodology used to characterize the angular precision then reports on various approaches to optimizing parameters to improve precision.

Application of Electron Backscatter Diffraction to Grain Boundaries

2010 ◽  
Vol 160 ◽  
pp. 39-46 ◽  
Author(s):  
Valerie Randle
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Experimental Methodology ◽  
Polycrystalline Materials ◽  
Grain Boundary Engineering ◽  
Network Characteristics ◽  
Grain Boundary Plane ◽  
Electron Backscatter ◽  
Measurement Strategies ◽  
Backscatter Diffraction

The technique of electron backscatter diffraction (EBSD) is ideal for the characterisation of grain boundary networks in polycrystalline materials. In recent years the experimental methodology has evolved to meet the needs of the research community. For example, the capabilities of EBSD have been instrumental in driving forward the topic of ‘grain boundary engineering’. In this paper the current capabilities of EBSD for grain boundary characterisation will be reviewed and illustrated by examples. Topics are measurement strategies based on misorientation statistics, determination of grain boundary plane distributions and grain boundary network characteristics.

Microstructural Evaluation of Alloy 800H After SCWL Exposure

2021 ◽  
Vol 7 (2) ◽  
Author(s):  
D. Marušáková ◽  
C. Aparicio ◽  
R. Fukač
Keyword(s):  
Supercritical Water ◽  
Electron Backscatter Diffraction ◽  
X Ray Diffraction ◽  
Alloy 800H ◽  
X Ray ◽  
Electron Backscatter ◽  
Microstructural Evaluation ◽  
The Matrix ◽  
Core Components ◽  
Backscatter Diffraction

Abstract Alloy 800H is a candidate material for supercritical water-cooled reactors (SCWR), specifically for in-core components in Canadian-type SCWR, that will operate at a pressure of 25 MPa and a core temperature from 350 °C to 625 °C. To evaluate this, several exposures to supercritical water took place at 395 °C and 25 MPa in a supercritical water loop (SCWL). The duration of each exposure was 500, 150, and 1000 h. Scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD), in combination with Raman spectroscopy (RS) and X-ray diffraction (XRD), was used to evaluate the microstructure of alloy 800H after the exposures to supercritical water. All these methods confirmed the presence of magnetite and trevorite/chromite crystals, with a thickness of less than 1 μm, on the surface after each exposure. No significant change occurred after the second and third exposures. The matrix crystallography did not change during the exposures and demonstrated grain twinning with a grain size of 100–400 μm.

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.

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