Microbeam analysis — Guidelines for misorientation analysis to assess mechanical damage of austenitic stainless steel by electron backscatter diffraction (EBSD)

This document describes the guidelines for misorientation analysis to assess mechanical damage such as fatigue and creep induced by plastic and/or creep deformation for metallic materials by using electron backscatter diffraction (EBSD) technique. This international standard defines misorientation parameters and specifies measurement conditions for such mechanical damage assessment. This document is recommended to evaluate mechanical damage of austenitic stainless steel, which is widely used for various components of power plants and other facilities. In this document, the mechanical damage refers to the damage which causes the fracture of structural materials due to external overload, fatigue and creep; excepting the chemical and thermal damages themselves.

Analyse par microfaisceaux — Lignes directrices relatives à l'analyse des défauts d'orientation pour l'évaluation des dommages mécaniques de l'acier inoxydable austénitique par diffraction d'électrons rétrodiffusés (EBSD)

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INTERNATIONAL ISO
STANDARD 23703
First edition
2022-01
Microbeam analysis — Guidelines
for misorientation analysis to assess
mechanical damage of austenitic
stainless steel by electron backscatter
diffraction (EBSD)
Analyse par microfaisceaux — Lignes directrices relatives à
l'analyse des défauts d'orientation pour l'évaluation des dommages
mécaniques de l'acier inoxydable austénitique par diffraction
d'électrons rétrodiffusés (EBSD)
Reference number
ISO 23703:2022(E)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO 23703:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 23703:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Abbreviated terms ............................................................................................................................................................................................. 4

5 Equipment for EBSD measurement .................................................................................................................................................. 4

6 Preparation ............................................................................................................................................................................................................... 4

6.1 Calibration .................................................................................................................................................................................................. 4

6.2 Specimen preparation ...................................................................................................................................................................... 5

7 Measurement procedures ..........................................................................................................................................................................6

7.1 Setting SEM operating conditions ......................................................................................................................................... 6

7.1.1 Accelerating voltage ........................................................................................................................................................ 6

7.1.2 Probe current ........................................................................................................................................................................ 6

7.1.3 Magnification observation ........................................................................................................................................ 6

7.1.4 Working distance ............................................................................................................................................................... 6

7.1.5 Focus ............................................................................................................................................................................................. 6

7.2 Setting the EBSD measurement conditions .................................................................................................................. 6

7.2.1 Background correction ................................................................................................................................................. 6

7.2.2 Binning ........................................................................................................................................................................................ 7

7.2.3 Pattern averaging .............................................................................................................................................................. 7

7.2.4 Hough transform ................................................................................................................................................................ 7

7.2.5 Measurement area ............................................................................................................................................................ 7

7.2.6 Step size ...................................................................................................................................................................................... 7

7.2.7 Scanning grid ......................................................................................................................................................................... 8

8 Calculation of misorientation ................................................................................................................................................................8

8.1 Defining grains ....................................................................................................................................................................................... 8

8.1.1 General ........................................................................................................................................................................................ 8

8.1.2 Setting the misorientation to define grains ............................................................................................... 8

8.1.3 Setting of minimum grain size ............................................................................................................................... 8

8.1.4 Caution ........................................................................................................................................................................................ 8

8.2 Data screening ........................................................................................................................................................................................ 8

8.2.1 Evaluation of reliability of measured data .................................................................................................. 8

8.2.2 Treatment of blank pixels ........................................................................................................................................... 9

8.3 Calculation of misorientation parameters ..................................................................................................................... 9

9 Material damage assessment ..............................................................................................................................................................11

9.1 General ........................................................................................................................................................................................................ 11

9.2 Misorientation parameter for qualitative assessments ..................................................................................12

9.3 Misorientation parameter for quantitative assessments ..............................................................................12

10 Report ...........................................................................................................................................................................................................................12

Annex A (informative) Round robin crystal orientation measurement for damage

assessment ..............................................................................................................................................................................................................15

Bibliography .............................................................................................................................................................................................................................25

iii
© ISO 2022 – All rights reserved
---------------------- Page: 3 ----------------------
ISO 23703:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 202, Microbeam analysis.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO 2022 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 23703:2022(E)
Introduction

Mechanical damage such as creep or fatigue, in engineering materials can be assessed by misorientation

analysis using electron backscatter diffraction (EBSD) technique. The EBSD technique measures

crystal orientation of sample surface by indexing EBSD patterns which are acquired by scanning its

surface with electron beam in a scanning electron microscope (SEM). It can give orientation maps and

misorientation maps. To determine the degree of damage induced in the materials, the misorientations

calculated from the mapping data are qualified by various parameters such as the local misorientation,

which is an averaged misorientation between neighbouring measurement points, and intra-grain

misorientations, which is an averaged misorientation between the reference orientation assigned to

each crystal grain and measurement points inside the grain. These misorientation parameters correlate

well with the degree of mechanical damage caused by deformation, fatigue and/or creep. Therefore, the

magnitude of the material damage can be estimated using the correlation curve which represents the

relationship between the misorientation parameters and the degree of the damage (hereafter called

correlation curve).

In the EBSD measurement, the crystal orientation is identified through electron beam illumination to

the material surface, acquisition of the EBSD pattern by an image detector, and then crystal orientation

identification by indexing of the EBSD patterns. It was shown that the point to point accuracy of the

crystal orientation measurement is about 0,05° to 0,5°. The misorientation parameters vary depending

on SEM conditions, observation conditions, EBSD pattern acquisition conditions and crystal orientation

identification conditions. Several measurement parameters are determined for calculating the

misorientation parameters. In particular, the local misorientation greatly depends on the distance

between the measurement points (step size). Furthermore, the accuracy of the crystal orientation

measurement and the definition of the misorientation parameters may depend on the hardware and

software used for the measurement and analysis. There are several venders of commercial EBSD

measurement and analysis systems. The correlation curve obtained for a certain condition using a

certain measurement system is not always comparable with other master curve obtained with different

conditions or systems. Therefore, it is necessary to have a standard to measure comparable master

curves to show the degree of mechanical damage by using any EBSD systems.

This document describes measurement procedures and conditions and definitions of misorientation

parameters independent on the measurement system in order to assess damage of austenitic stainless

steel precisely.
© ISO 2022 – All rights reserved
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 23703:2022(E)
Microbeam analysis — Guidelines for misorientation
analysis to assess mechanical damage of austenitic
stainless steel by electron backscatter diffraction (EBSD)
1 Scope

This document describes the guidelines for misorientation analysis to assess mechanical damage

such as fatigue and creep induced by plastic and/or creep deformation for metallic materials by using

electron backscatter diffraction (EBSD) technique. This international standard defines misorientation

parameters and specifies measurement conditions for such mechanical damage assessment. This

document is recommended to evaluate mechanical damage of austenitic stainless steel, which is widely

used for various components of power plants and other facilities.

In this document, the mechanical damage refers to the damage which causes the fracture of structural

materials due to external overload, fatigue and creep; excepting the chemical and thermal damages

themselves.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 24173:2009, Microbeam analysis — Guidelines for orientation measurement using electron backscatter

diffraction
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
area averaged intra-grain misorientation
average of intra grain misorientation of all pixels in the measurement area
3.2
area averaged local misorientation
average of local misorientation of all pixels in the measurement area
3.3
blank point
non-indexed point (pixel) due to insufficient quality of the EBSD pattern

Note 1 to entry: This can occur for a variety of reasons, such as insufficient specimen surface condition, dust or

contamination on the specimen surface, overlapping patterns at the grain boundary, a poor-quality pattern due

to the effects of strain, or if the pattern is from an unanticipated phase.
Note 2 to entry: See ISO 13067:2020, 3.4.2 for definition of non-indexing.
© ISO 2022 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 23703:2022(E)
3.4
electron backscatter diffraction
EBSD

diffraction process that arises between the backscattered electrons and the crystal planes in a highly

tilted crystalline specimen when illuminated by a stationary incident electron beam

[SOURCE: ISO 24173:2009, 3.7]
3.5
electron backscatter diffraction pattern
EBSD pattern

Kikuchi pattern like electron diffraction pattern which is generated on a phosphor screen or

photographic film by backscatter diffracted electrons in a SEM

Note 1 to entry: A specimen is generally tilted to 70 degrees to get better quality of the diffraction pattern.

[SOURCE: ISO 24173:2009, 3.8, modified — The definition has been modified.]
3.6
grain averaged intra-grain misorientation
one value for each grain by averaging intra grain misorientations
3.7
grain averaged local misorientation
average of local misorientation of all pixels in a grain
3.8
grain boundary
lines between grains in an EBSD orientation map

Note 1 to entry: Grains are defined by grouping connected neighbour pixels which misorientation is less than the

specified tolerance angle.
[SOURCE: ISO 13067:2020, 3.2.1, modified — The definition has been modified.]
3.9
Hough transform

mathematical transformation of image processing techniques, which converts a line in an image to a

point
Note 1 to entry: This allows automated detection of bands in an EBSD pattern.

Note 2 to entry: In EBSD, a linear Hough transform is used to identify the position and orientation of the Kikuchi

bands in each EBSD pattern, which enables the EBSD pattern to be indexed. Each Kikuchi band is identified as a

bright spot in Hough space. The Hough transform is essentially a special case of the Radon transform. Generally,

the Hough transform is for binary images, and the Radon transform is for grey-level images.

[SOURCE: ISO 24173:2009, 3.12, modified — The definition has been modified.]
3.10
indexing reliability

numerical value that indicates the confidence/reliability of indexing result which indexing software

place in automatic analysis procedure

Note 1 to entry: This parameter varies between EBSD manufacturers, but can include:

a) the average difference between the experimentally determined angles between diffracting planes and those

angles calculated for the orientation determined by EBSD software;

b) the difference between the number of triplets (intersections of three Kikuchi bands) in the EBSD pattern

matched by the chosen orientation and the next best possible solution, divided by the total number of

triplets.
© ISO 2022 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 23703:2022(E)
3.11
intra-grain misorientation
misorientation of each pixel with the average orientation of the grain
Note 1 to entry: See Figure 3.

Note 2 to entry: A map that displays the deviation of a pixel to a reference orientation

3.12
local misorientation
average misorientation between the measured pixel (P ) and neighbouring pixels
Note 1 to entry: See Figure 2.

Note 2 to entry: When the misorientation between the measured pixel (P ) and neighbour pixel exceeds the

threshold angle like the measured pixels at the grain boundary as shown in Figure 2, these pixels are excluded

from the misorientation calculation.
3.13
master curve

correlation curve obtained experimentally between misorientation parameter and mechanical damage

degree
Note 1 to entry: It is used to estimate damage degree quantitatively.
3.14
minimum grain size
number of pixels required to constitute a grain

Note 1 to entry: If the sum number of measurements constituting a grain are less than this value then the grain

is excluded.
3.15
misorientation

angle/axis pair, required to rotate one set of crystal axes into coincidence with the other set of crystal

axes for the given two crystal orientations
Note 1 to entry: The smallest angle used here.
3.16
misorientation parameter

parameter calculated from misorientation such as “local misorientation”, “intra-grain misorientation”

Note 1 to entry: It is classified as 3 groups; parameter for each pixel, grain or area.

3.17
pattern quality

measure of the sharpness of the diffraction bands or the range of contrast within a diffraction pattern

Note 1 to entry: Different terms are used in different commercial software packages, including, for example,

band contrast, band slope and image quality.
3.18
pixel

smallest area of an EBSD map, with the dimensions of the step size, to which is assigned the result of a

single orientation measurement made by stopping the beam at a point at the centre of that area

[SOURCE: ISO 13067:2020, 3.1.2]
Note 1 to entry: This is different from "camera pixels".
© ISO 2022 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 23703:2022(E)
3.19
scanning grid
pattern of spacing of measurement points

Note 1 to entry: A regular hexagonal grid or a regular square grid is adopted generally. A hexagonal (square) grid

means that the individual points making up the scan area are situated on a hexagonal (or square) array.

3.20
step size

distance between adjacent points from which individual EBSD patterns are acquired during collection

of data for an EBSD map
[SOURCE: ISO 13067:2020, 3.1.1]
4 Abbreviated terms
CCD charge coupled device
CMOS complementary metal-oxide semiconductor
EBSD electron backscatter diffraction
EBSP electron backscatter diffraction pattern
SEM scanning electron microscope/microscopy
WD working distance
5 Equipment for EBSD measurement
See ISO 24173:2009, Clause 4.

5.1 SEM, EPMA or FIB instrument, fitted with an electron column and including controls for beam

position, stage, focus and magnification.

5.2 Accessories, for detecting and indexing electron backscatter diffraction patterns, including:

5.2.1 Phosphorescent (“phosphor”) screen, which is fluoresced by electrons from the specimen to

form the diffraction pattern.

5.2.3 Image acquisition device, with low light sensitivity, for viewing the diffraction pattern

produced on the screen.

5.2.4 Computer, with image processing, computer-aided pattern indexing, data storage and data

processing, and SEM beam (or stage) control to allow mapping.

NOTE Modern systems generally use charge-coupled devices (CCDs) or complementary metal-oxide

semiconductor (CMOS).
6 Preparation
6.1 Calibration
The procedures described in ISO 24173 shall be followed.
© ISO 2022 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 23703:2022(E)
6.2 Specimen preparation

The areas chosen for examination shall be representative of location of interest, and, if there is variation

with position in the specimen, the positions examined shall be recorded in relation to the specimen

geometry.
The procedures set out in ISO 24173:2009, Annex B shall be followed.

For specimen preparation for EBSD analysis, the following equipment can be required (depending on

the types of specimen to be prepared, ISO 24173:2009, Annex B):
— cutting and mounting equipment;
— mechanical grinding and polishing equipment;
— electrolytic polisher;
— ultrasonic cleaner;
— ion-sputtering equipment; and
— coating equipment.

It should also be considered to avoid any phase transformation during specimen preparation.

Undesired damage on the specimen surface shall be removed carefully. In order to obtain the desired

damage-free surface for misorientation analysis, final polishing using colloidal silica or electro-

polishing is effective. If scratches remain on the surface, they cause larger misorientation as shown in

Figure 1
a) Pattern quality map b) Local misorientation map
Key
1 scratches
Figure 1 — Example of remaining scratches
© ISO 2022 – All rights reserved
---------------------- Page: 10 ----------------------
ISO 23703:2022(E)
7 Measurement procedures
7.1 Setting SEM operating conditions
7.1.1 Accelerating voltage

Accelerating voltage ranging between 10 kV and 20 kV is recommended to get reasonable EBSD

patterns. Increasing the accelerating voltage may result in increasing beam spread in the specimen,

and hence make the spatial resolution worse. It depends on the specimen Z number, but in most cases,

there is no merit to use higher accelerating voltage more than 20 kV with recent high sensitivity image

detectors.
See ISO 24173:2009, 5.3.1.
7.1.2 Probe current

Increasing the probe current increases the number of electrons contributing to the diffraction pattern

and it will give brighter EBSD patterns. This improves the signal/noise ration of the EBSD patterns

resulting in better band detection and better orientation determination. Therefore, it allows shorter

camera exposure time, namely faster mapping.
See ISO 24173:2009, 5.3.1.
7.1.3 Magnification observation

Depending on the observation’s purpose, it is recommended that the measurement area is nearly equal

to the observation area because of that the effective probe diameter depends on SEM’s magnification.

The measurement area should be set to include more than about 100 grains to avoid effects of individual

grains becoming too large. Therefore, the magnification should be set between 300 and 500 times in

case of that the grain size (diameter) is about couple of 10 µm.
7.1.4 Working distance

The ideal working distance for EBSD is the working distance at which the brightest region of the raw

EBSD pattern (i.e. without background correction) becomes nearly at the centre of the phosphor screen.

It is set at around 15 mm in general case, but it can be changed depending on each SEM/EBSD system

configuration. Short working distances generally improve the spatial resolution of EBSD measurements,

although additional care shall be paid to avoid collisions between the specimen and the pole-piece or

the backscatter detector (if present).
See ISO 24173:2009, 5.3.2.
7.1.5 Focus

EBSD measurement will be done with a highly tilted specimen in a SEM. Therefore, the focus can vary

depending on the beam position on the specimen (see ISO 24173). The dynamic focus is recommended

to be used to avoid the out of focus condition at upper and lower of measurement area.

See also ISO 24173:2009, 5.3.
7.2 Setting the EBSD measurement conditions
7.2.1 Background correction

EBSD patterns generally have a bright centre and become much darker near the corners. The brightness

of raw EBSD pattern images decrease seriously in the surrounding area. Background correction should

© ISO 2022 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 23703:2022(E)

be used to make the “raw” EBSD pattern image into ones with more uniform brightness across its whole

area with better local contrast.
See ISO 24173:2009, 5.3.6.
7.2.2 Binning

The number of camera pixels, which form EBSD pattern image acquired through an image detector can

be adjusted by binning setting. If the image size becomes smaller, it means binning is set larger. Then

the time required for measurement becomes shorter, though the accuracy of orientation measurement

can 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 data

transfer speed. The accuracy of orientation measurement for distinguishing about 0,5˚ orientation

difference, can be acquired by setting the binning to the image size between 100 × 100 and 200 × 200

camera 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 frame

at the same measurement point. However, the pattern averaging makes the measurement speed slower

a lot. For this reason, it is recommended to increase the probe current to acquire the same quality of

EBSD patterns, instead of using pattern averaging. The quality of EBSD pattern is also controlled by

adjusting the binning size and the gain of the image detector.
See ISO 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 of

a Hough transform. Hough transformation technique is used to extract bands from an EBSD pattern

acquired by an image detector. A suitable set of Hough transformation parameters should be set

depending on the features of EBSD patterns. These parameters may affect to the speed and the accuracy

of Hough transformation calculation.
See ISO 24173:2009, 5.3.7.
7.2.5 Measurement area
It is recomme
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 23703
ISO/TC 202
Microbeam analysis — Guideline for
Secretariat: SAC
misorientation analysis to assess
Voting begins on:
2021-10-27 mechanical damage of austenitic
stainless steel by electron backscatter
Voting terminates on:
2021-12-22
diffraction (EBSD)
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 23703:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2021
---------------------- Page: 1 ----------------------
ISO/FDIS 23703:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 23703:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Abbreviated terms ............................................................................................................................................................................................. 4

5 Equipment for EBSD measurement .................................................................................................................................................. 4

6 Preparation ............................................................................................................................................................................................................... 4

6.1 Calibration .................................................................................................................................................................................................. 4

6.2 Specimen preparation ...................................................................................................................................................................... 5

7 Measurement procedures ..........................................................................................................................................................................6

7.1 Setting SEM operating conditions ......................................................................................................................................... 6

7.1.1 Accelerating voltage ........................................................................................................................................................ 6

7.1.2 Probe current ........................................................................................................................................................................ 6

7.1.3 Magnification observation ........................................................................................................................................ 6

7.1.4 Working distance ............................................................................................................................................................... 6

7.1.5 Focus ............................................................................................................................................................................................. 6

7.2 Setting the EBSD measurement conditions .................................................................................................................. 6

7.2.1 Background correction ................................................................................................................................................. 6

7.2.2 Binning ........................................................................................................................................................................................ 7

7.2.3 Pattern averaging .............................................................................................................................................................. 7

7.2.4 Hough transform ................................................................................................................................................................ 7

7.2.5 Measurement area ............................................................................................................................................................ 7

7.2.6 Step size ...................................................................................................................................................................................... 7

7.2.7 Scanning grid ......................................................................................................................................................................... 8

8 Calculation of misorientation ................................................................................................................................................................8

8.1 Defining grains ....................................................................................................................................................................................... 8

8.1.1 General ........................................................................................................................................................................................ 8

8.1.2 Setting the misorientation to define grains ............................................................................................... 8

8.1.3 Setting of minimum grain size ............................................................................................................................... 8

8.1.4 Caution ........................................................................................................................................................................................ 8

8.2 Data screening ........................................................................................................................................................................................ 8

8.2.1 Evaluation of reliability of measured data .................................................................................................. 8

8.2.2 Treatment of blank pixels ........................................................................................................................................... 9

8.3 Calculation of misorientation parameters ..................................................................................................................... 9

9 Material damage assessment ..............................................................................................................................................................11

9.1 General ........................................................................................................................................................................................................ 11

9.2 Misorientation parameter for qualitative assessments ..................................................................................12

9.3 Misorientation parameter for quantitative assessments ..............................................................................12

10 Report ...........................................................................................................................................................................................................................12

Annex A (informative) Round robin crystal orientation measurement for damage

assessment ..............................................................................................................................................................................................................15

Bibliography .............................................................................................................................................................................................................................25

iii
© ISO 2021 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/FDIS 23703:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 202, Microbeam analysis.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 23703:2021(E)
Introduction

Mechanical damage such as creep or fatigue, in engineering materials can be assessed by misorientation

analysis using electron backscatter diffraction (EBSD) technique. The EBSD technique measures

crystal orientation of sample surface by indexing EBSD patterns which are acquired by scanning its

surface with electron beam in a scanning electron microscope (SEM). It can give orientation maps and

misorientation maps. To determine the degree of damage induced in the materials, the misorientations

calculated from the mapping data are qualified by various parameters such as the local misorientation,

which is an averaged misorientation between neighbouring measurement points, and intra-grain

misorientations, which is an averaged misorientation between the reference orientation assigned to

each crystal grain and measurement points inside the grain. These misorientation parameters correlate

well with the degree of mechanical damage caused by deformation, fatigue and/or creep. Therefore, the

magnitude of the material damage can be estimated using the correlation curve which represents the

relationship between the misorientation parameters and the degree of the damage (hereafter called

correlation curve).

In the EBSD measurement, the crystal orientation is identified through electron beam illumination to

the material surface, acquisition of the EBSD pattern by an image detector, and then crystal orientation

identification by indexing of the EBSD patterns. It was shown that the point to point accuracy of the

crystal orientation measurement is about 0,05° to 0,5°. The misorientation parameters vary depending

on SEM conditions, observation conditions, EBSD pattern acquisition conditions and crystal orientation

identification conditions. Several measurement parameters are determined for calculating the

misorientation parameters. In particular, the local misorientation greatly depends on the distance

between the measurement points (step size). Furthermore, the accuracy of the crystal orientation

measurement and the definition of the misorientation parameters may depend on the hardware and

software used for the measurement and analysis. There are several venders of commercial EBSD

measurement and analysis systems. The correlation curve obtained for a certain condition using a

certain measurement system is not always comparable with other master curve obtained with different

conditions or systems. Therefore, it is necessary to have a standard to measure comparable master

curves to show the degree of mechanical damage by using any EBSD systems.

This document describes measurement procedures and conditions and definitions of misorientation

parameters independent on the measurement system in order to assess damage of austenitic stainless

steel precisely.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 23703:2021(E)
Microbeam analysis — Guideline for misorientation
analysis to assess mechanical damage of austenitic
stainless steel by electron backscatter diffraction (EBSD)
1 Scope

This document describes the guidelines for misorientation analysis to assess mechanical damage

such as fatigue and creep induced by plastic and/or creep deformation for metallic materials by using

electron backscatter diffraction (EBSD) technique. This international standard defines misorientation

parameters and specifies measurement conditions for such mechanical damage assessment. This

document is recommended to evaluate mechanical damage of austenitic stainless steel, which is widely

used for various components of power plants and other facilities.

In this document, the mechanical damage refers to the damage which causes the fracture of structural

materials due to external overload, fatigue and creep; excepting the chemical and thermal damages

themselves.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 24173:2009, Microbeam analysis — Guidelines for orientation measurement using electron backscatter

diffraction
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
area averaged intra-grain misorientation
average of intra grain misorientation of all pixels in the measurement area
3.2
area averaged local misorientation
average of local misorientation of all pixels in the measurement area
3.3
blank point
non-indexed point (pixel) due to insufficient quality of the EBSD pattern

Note 1 to entry: This can occur for a variety of reasons, such as insufficient specimen surface condition, dust or

contamination on the specimen surface, overlapping patterns at the grain boundary, a poor-quality pattern due

to the effects of strain, or if the pattern is from an unanticipated phase.
Note 2 to entry: See ISO 13067:2020, 3.4.2 for definition of non-indexing.
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ISO/FDIS 23703:2021(E)
3.4
electron backscatter diffraction
EBSD

diffraction process that arises between the backscattered electrons and the crystal planes in a highly

tilted crystalline specimen when illuminated by a stationary incident electron beam

[SOURCE: ISO 24173:2009, 3.7]
3.5
electron backscatter diffraction pattern
EBSD pattern

Kikuchi pattern like electron diffraction pattern which is generated on a phosphor screen or

photographic film by backscatter diffracted electrons in a SEM

Note 1 to entry: A specimen is generally tilted to 70 degrees to get better quality of the diffraction pattern.

[SOURCE: ISO 24173:2009, 3.8, modified — The definition has been modified.]
3.6
grain averaged intra-grain misorientation
one value for each grain by averaging intra grain misorientations
3.7
grain averaged local misorientation
average of local misorientation of all pixels in a grain
3.8
grain boundary
lines between grains in an EBSD orientation map

Note 1 to entry: Grains are defined by grouping connected neighbour pixels which misorientation is less than the

specified tolerance angle.
[SOURCE: ISO 13067:2020, 3.2.1, modified — The definition has been modified.]
3.9
Hough transform

mathematical transformation of image processing techniques, which converts a line in an image to a

point
Note 1 to entry: This allows automated detection of bands in an EBSD pattern.

Note 2 to entry: In EBSD, a linear Hough transform is used to identify the position and orientation of the Kikuchi

bands in each EBSD pattern, which enables the EBSD pattern to be indexed. Each Kikuchi band is identified as a

bright spot in Hough space. The Hough transform is essentially a special case of the Radon transform. Generally,

the Hough transform is for binary images, and the Radon transform is for grey-level images.

[SOURCE: ISO 24173:2009, 3.12, modified — The definition has been modified.]
3.10
indexing reliability

numerical value that indicates the confidence/reliability of indexing result which indexing software

place in automatic analysis procedure

Note 1 to entry: This parameter varies between EBSD manufacturers, but can include:

a) the average difference between the experimentally determined angles between diffracting planes and those

angles calculated for the orientation determined by EBSD software;

b) the difference between the number of triplets (intersections of three Kikuchi bands) in the EBSD pattern

matched by the chosen orientation and the next best possible solution, divided by the total number of

triplets.
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ISO/FDIS 23703:2021(E)
3.11
intra-grain misorientation
misorientation of each pixel with the average orientation of the grain
Note 1 to entry: See Figure 3.

Note 2 to entry: A map that displays the deviation of a pixel to a reference orientation

3.12
local misorientation
average misorientation between the measured pixel (P1) and neighbouring pixels
Note 1 to entry: See Figure 2.

Note 2 to entry: When the misorientation between the measured pixel (P2) and neighbour pixel exceeds the

threshold angle like the measured pixels at the grain boundary as shown in Figure 2, these pixels are excluded

from the misorientation calculation.
3.13
master curve

correlation curve obtained experimentally between misorientation parameter and mechanical damage

degree
Note 1 to entry: It is used to estimate damage degree quantitatively.
3.14
minimum grain size
number of pixels required to constitute a grain

Note 1 to entry: If the sum number of measurements constituting a grain are less than this value then the grain

is excluded.
3.15
misorientation

angle/axis pair, required to rotate one set of crystal axes into coincidence with the other set of crystal

axes for the given two crystal orientations
Note 1 to entry: The smallest angle used here.
3.16
misorientation parameter

parameter calculated from misorientation such as “local misorientation”, “intra-grain misorientation”

Note 1 to entry: It is classified as 3 groups; parameter for each pixel, grain or area.

3.17
pattern quality

measure of the sharpness of the diffraction bands or the range of contrast within a diffraction pattern

Note 1 to entry: Different terms are used in different commercial software packages, including, for example,

band contrast, band slope and image quality.
3.18
pixel

smallest area of an EBSD map, with the dimensions of the step size, to which is assigned the result of a

single orientation measurement made by stopping the beam at a point at the centre of that area

[SOURCE: ISO 13067:2020, 3.1.2]
Note 1 to entry: This is different from "camera pixels".
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ISO/FDIS 23703:2021(E)
3.19
scanning grid
pattern of spacing of measurement points

Note 1 to entry: A regular hexagonal grid or a regular square grid is adopted generally. A hexagonal (square) grid

means that the individual points making up the scan area are situated on a hexagonal (or square) array.

3.20
step size

distance between adjacent points from which individual EBSD patterns are acquired during collection

of data for an EBSD map
[SOURCE: ISO 13067:2020, 3.1.1]
4 Abbreviated terms
CCD charge coupled device
CMOS complementary metal-oxide semiconductor
EBSD electron backscatter diffraction
EBSP electron backscatter diffraction pattern
SEM scanning electron microscope/microscopy
WD working distance
5 Equipment for EBSD measurement
See ISO 24173:2009, Clause 4.

5.1 SEM, EPMA or FIB instrument, fitted with an electron column and including controls for beam

position, stage, focus and magnification.

5.2 Accessories, for detecting and indexing electron backscatter diffraction patterns, including:

5.2.1 Phosphorescent (“phosphor”) screen, which is fluoresced by electrons from the specimen to

form the diffraction pattern.

5.2.3 Image acquisition device, with low light sensitivity, for viewing the diffraction pattern

produced on the screen.

5.2.4 Computer, with image processing, computer-aided pattern indexing, data storage and data

processing, and SEM beam (or stage) control to allow mapping.

NOTE Modern systems generally use charge-coupled devices (CCDs) or complementary metal-oxide

semiconductor (CMOS).
6 Preparation
6.1 Calibration
The procedures described in ISO 24173 shall be followed.
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ISO/FDIS 23703:2021(E)
6.2 Specimen preparation

The areas chosen for examination shall be representative of location of interest, and, if there is variation

with position in the specimen, the positions examined shall be recorded in relation to the specimen

geometry.
The procedures set out in ISO 24173:2009, Annex B shall be followed.

For specimen preparation for EBSD analysis, the following equipment can be required (depending on

the types of specimen to be prepared, ISO 24173:2009, Annex B):
— cutting and mounting equipment;
— mechanical grinding and polishing equipment;
— electrolytic polisher;
— ultrasonic cleaner;
— ion-sputtering equipment; and
— coating equipment.

It should also be considered to avoid any phase transformation during specimen preparation.

Undesired damage on the specimen surface shall be removed carefully. In order to obtain the desired

damage-free surface for misorientation analysis, final polishing using colloidal silica or electro-

polishing is effective. If scratches remain on the surface, they cause larger misorientation as shown in

Figure 1
a) Pattern quality map b) Local misorientation map
Key
1 scratches
Figure 1 — Example of remaining scratches
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ISO/FDIS 23703:2021(E)
7 Measurement procedures
7.1 Setting SEM operating conditions
7.1.1 Accelerating voltage

Accelerating voltage ranging between 10 kV and 20 kV is recommended to get reasonable EBSD

patterns. Increasing the accelerating voltage may result in increasing beam spread in the specimen,

and hence make the spatial resolution worse. It depends on the specimen Z number, but in most cases,

there is no merit to use higher accelerating voltage more than 20 kV with recent high sensitivity image

detectors.
See ISO 24173:2009, 5.3.1.
7.1.2 Probe current

Increasing the probe current increases the number of electrons contributing to the diffraction pattern

and it will give brighter EBSD patterns. This improves the signal/noise ration of the EBSD patterns

resulting in better band detection and better orientation determination. Therefore, it allows shorter

camera exposure time, namely faster mapping.
See ISO 24173:2009, 5.3.1.
7.1.3 Magnification observation

Depending on the observation’s purpose, it is recommended that the measurement area is nearly equal

to the observation area because of that the effective probe diameter depends on SEM’s magnification.

The measurement area should be set to include more than about 100 grains to avoid effects of individual

grains becoming too large. Therefore, the magnification should be set between 300 and 500 times in

case of that the grain size (diameter) is about couple of 10 µm.
7.1.4 Working distance

The ideal working distance for EBSD is the working distance at which the brightest region of the raw

EBSD pattern (i.e. without background correction) becomes nearly at the centre of the phosphor screen.

It is set at around 15 mm in general case, but it can be changed depending on each SEM/EBSD system

configuration. Short working distances generally improve the spatial resolution of EBSD measurements,

although additional care shall be paid to avoid collisions between the specimen and the pole-piece or

the backscatter detector (if present).
See ISO 24173:2009, 5.3.2.
7.1.5 Focus

EBSD measurement will be done with a highly tilted specimen in a SEM. Therefore, the focus can vary

depending on the beam position on the specimen (see ISO 24173). The dynamic focus is recommended

to be used to avoid the out of focus condition at upper and lower of measurement area.

See also ISO 24173:2009, 5.3.
7.2 Setting the EBSD measurement conditions
7.2.1 Background correction

EBSD patterns generally have a bright centre and become much darker near the corners. The brightness

of raw EBSD pattern images decrease seriously in the surrounding area. Background correction should

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ISO/FDIS 23703:2021(E)

be used to make the “raw” EBSD pattern image into ones with more uniform brightness across its whole

area with better local contrast.
See ISO 24173:2009, 5.3.6.
7.2.2 Binning

The number of camera pixels, which form EBSD pattern image acquired through an image detector can

be adjusted by binning setting. If the image size becomes smaller, it means binning is set larger. Then

the time required for measurement becomes shorter, though the accuracy of orientation measurement

can 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 data

transfer speed. The accuracy of orientation measurement for distinguishing about 0,5˚ orientation

difference, can be acquired by setting the binning to the image size between 100 × 100 and 200 × 200

camera 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 frame

at the same measurement point. However, the pattern averaging makes the measurement speed slower

a lot. For this reason, it is recommended to increase the probe current to acquire the same quality of

EBSD patterns, instead of using pattern averaging. The quality of EBSD pattern is also controlled by

adjusting the binning size and the gain of the image detector.
See ISO 24173:2009, 5.3.5.
7.2.4 Hough transform

Band detection during EBSD refers to the automatic detection of Kikuchi bands in an

...

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