ISO 23703-2022 pdf free download – Microbeam analysis — Guidelines for misorientation analysis to assess mechanical damage of austenitic stainless steel by electron backscatter diffraction (EBSD).
7.2.2 Binning
The number of camera pixels, which form EBSD pattern image acquired through an image detector canbe adjusted by binning setting. lf the image size becomes smaller, it means binning is set larger. Thenthe time required for measurement becomes shorter, though the accuracy of orientation measurementcan become lower in general. Large binning does not always get the faster measurement speed either,because of that the measurement speed is sometimes limited by the image processing speed or datatransfer speed. The accuracy of orientation measurement for distinguishing about 0,5* orientationdifference, can be acquired by setting the binning to the image size between 100 x 100 and 200 × 200camera pixels.
See ISO 24173:2009,5.3.4.
NOTE The binning is applicable to CCDs cameras and not applicable to CMOs cameras.7.2.3 Pattern averaging
Quality of EBSD pattern image can be improved by averaging patterns collected more than one frameat the same measurement point.However, the pattern averaging makes the measurement speed slowera lot. For this reason, it is recommended to increase the probe current to acquire the same quality ofEBSD patterns, instead of using pattern averaging. The quality of EBSD pattern is also controlled byadjusting the binning size and the gain of the image detector.
See lSO 24173:2009,5.3.5.
7.2.4 Hough transform
Band detection during EBSD refers to the automatic detection of Kikuchi bands in an EBSP via use ofa Hough transform. Hough transformation technique is used to extract bands from an EBSD patternacquired by an image detector. A suitable set of Hough transformation parameters should be setdepending on the features of EBSD patterns.These parameters may affect to the speed and the accuracyof Hough transformation calculation.
See ISo 24173:2009,5.3.7.
7.2.5 Measurement area
lt is recommended to include reasonable number of grains,it is expected more than 100 grains as notedin 7.1.3, in the measurement area to evaluate the average status of polycrystalline materials. If themeasurement area becomes larger, then the time for measurement becomes longer. In this case, it mightbe needed to consider about the stability of SEM’s such as the beam drift or specimen drift.
7.2.6Step size
This depends on the type of specimen and the purpose of measurements.Reasonable number ofmeasurement points needs to be included in each grain.As the step size becomes smaller, more detaildistribution of misorientation can be obtained, though the time for measurement becomes longer.Also,the resolution limit of EBSD should be taken into account to decide the step size. It should not be smallerthe resolution limit. Though it depends on specification of SEMs and measurement conditions,EBSD’sresolution limit is estimated about couple of 10 nm.
To compare the local misorientation, it is necessary to set the step size same.Because the localmisorientation depends on the step size.
7.2.7 Scanning grid Either the square grid or the hexagonal grid can be chosen in some software. Both types of grid are usable for misorientation calculation, however use of the same grid type is recommended to compare the results. 8 Calculation of misorientation 8.1? Defining? grains 8.1.1 General Misorientation is calculated between two crystal orientations of measured pixels. Misorientation between two crystal orientations of measured pixels in different grains is not considered to be related to the damage discussed here. Therefore, the misorientation should be calculated among the crystal orientations of pixels within a same grain. For this reason, the grains must be defined before calculating misorientation data.ISO 23703 pdf download.