Academic literature on the topic 'Analysis by backscattered electron diffraction (EBSD)'

AbstractSince the automation of the electron backscatter diffraction (EBSD) technique, EBSD systems have become commonplace in microscopy facilities within materials science and geology research laboratories around the world. The acceptance of the technique is primarily due to the capability of EBSD to aid the research scientist in understanding the crystallographic aspects of microstructure. There has been considerable interest in using EBSD to quantify strain at the submicron scale. To apply EBSD to the characterization of strain, it is important to understand what is practically possible and the underlying assumptions and limitations. This work reviews the current state of technology in terms of strain analysis using EBSD. First, the effects of both elastic and plastic strain on individual EBSD patterns will be considered. Second, the use of EBSD maps for characterizing plastic strain will be explored. Both the potential of the technique and its limitations will be discussed along with the sensitivity of various calculation and mapping parameters.

Abstract Twins in micas are difficultly identified due to mica’s hexagonal pseudosymmetry. Many theoretic studies on mica twins have been reported but experimental observations are very limited. In this paper, we present an electron backscattered diffraction analysis to identify twins in the muscovite in a quartz schist occurring in the UHP-HP metamorphic rock belt in Dabie Mountain, China. A trilling twin with twin law <310>/{110} is common in the muscovite. A six-couplet twin consisting of two trilling twins related by twin laws <110>/{130} and <001>/{001}(or <100>/{100}) has been discovered. This six-couplet twin contains many cross-twin relationships among the most common mica twin laws <310>/{110}, <110>/{130} and <001>/{001}. The composition plane for twin laws <110>/{130} and <001>/{001} is {001} which is reasonable in mica structure to form a twin by rotation around twin axes, and that for twin law <310>/{110} is irregular based on EBSD resolution. A possible misindexation of a trilling twin or a 3T polytype during EBSD test is discussed, which is helpful to distinguish a twin from a polytype in micas. The occurring frequency of twin law <310>/{110} is higher than that of twin laws <110>/{130} and <001>/{001}, which is consistent to the deducing result from mica structure analysis. This research provides a convenient and effective EBSD method to identify mica twins and an experimental method to distinguish a twin from a polytype in micas, which is a problem confusing researchers for many years.

Two types of A356 alloy castings in initial and modified with nanoparticles condition produced by gravitational casting were studied. Samples, as-cut from the castings, were subjected to light optical microscopy (LM), thermal analyses, Electron Backscattered Diffraction (EBSD) and Scanning Transmission Electron Microscopy (STEM) analyses. Results, obtained by EBSD, confirmed that there is grain refinement in samples from castings with added nanoparticles compared to the initial ones. STEM analysis shows agglomerates of nanoparticles in examined foils. Nanoparticles’ position in the microstructure confirms the hypothesis that they act as nucleating sites during the alloy solidification, which is the reason for observed fine-grained microstructure.

Backscattered electron Kikuchi patterns (BEKP) were first observed by Alam et al. in 1954. J.A. Venables and C.J. Harland made the initial observation of BEKP and in the scanning electron microscope in 1973. In 1996, Goehner and Michael developed an electron backscatter diffraction (EBSD) system that uses a 1024 × 1024 pixel CCD camera coupled to a thin scintillator rather than photographic film. In their system, the quality of the raw patterns is improved by the use of “flat fielding” which normalizes the raw image to a “flat field” reference image that contains the image artifacts, including background, but not the crystallographic information. Automated pattern analysis is carried out using a Hough transform to locate bands and band edges in the pattern. The resulting crystallographic information is coupled with the elemental information from energy or wavelength dispersive x-ray spectrometry and the phase is identified is made through a link to a database such as the Powder Diffraction Files published by ICDD. An indexed pattern of the suspected phase is then synthesized for comparison to the unknown. This system is marketed commercially by Noran Instruments and offers the first practical method for rapid identification of unknown crystallographic phases in the SEM.