ASTM E1382-97(2004)

Standard Test Methods for Determining Average Grain Size Using Semiautomatic and Automatic Image Analysis

SIGNIFICANCE AND USE
These test methods cover procedures for determining the mean grain size, and the distribution of grain intercept lengths or grain areas, for polycrystalline metals and nonmetallic materials with equiaxed or deformed grain shapes, with uniform or duplex grain size distributions, and for single phase or multiphase grain structures.
The measurements are performed using semiautomatic digitizing tablet image analyzers or automatic image analyzers. These devices relieve much of the tedium associated with manual measurements, thus permitting collection of a larger amount of data and more extensive sampling which will produce better statistical definition of the grain size than by manual methods.  
The precision and relative accuracy of the test results depend on the representativeness of the specimen or specimens, quality of specimen preparation, clarity of the grain boundaries (etch technique and etchant used), the number of grains measured or the measurement area, errors in detecting grain boundaries or grain interiors, errors due to detecting other features (carbides, inclusions, twin boundaries, and so forth), the representativeness of the fields measured, and programming errors.
Results from these test methods may be used to qualify material for shipment in accordance with guidelines agreed upon between purchaser and manufacturer, to compare different manufacturing processes or process variations, or to provide data for structure-property-behavior studies.
SCOPE
1.1 These test methods are used to determine grain size from measurements of grain intercept lengths, intercept counts, intersection counts, grain boundary length, and grain areas.
1.2 These measurements are made with a semiautomatic digitizing tablet or by automatic image analysis using an image of the grain structure produced by a microscope.
1.3 These test methods are applicable to any type of grain structure or grain size distribution as long as the grain boundaries can be clearly delineated by etching and subsequent image processing, if necessary.
1.4 These test methods are applicable to measurement of other grain-like microstructures, such as cell structures.
1.5 This standard deals only with the recommended test methods and nothing in it should be construed as defining or establishing limits of acceptability or fitness for purpose of the materials tested.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.6 The sections appear in the following order:

General Information

• Status: Historical
• Publication Date: 31-Oct-2004
• Technical Committee: E04 - Metallography
• Drafting Committee: E04.14 - Quantitative Metallography

Relations

• Replaces: ASTM E1382-97 - Standard Test Methods for Determining Average Grain Size Using Semiautomatic and Automatic Image Analysis
• Effective Date: 01-Nov-2004
• Referred By: ASTM E112-13(2021) - Standard Test Methods for Determining Average Grain Size
• Effective Date: 01-Nov-2004
• Referred By: ASTM C1557-20 - Standard Test Method for Tensile Strength and Young's Modulus of Fibers
• Effective Date: 01-Nov-2004
• Referred By: ASTM F3160-21 - Standard Guide for Metallurgical Characterization of Absorbable Metallic Materials for Medical Implants
• Effective Date: 01-Nov-2004
• Referred By: ASTM F1376-92(2020) - Standard Guide for Metallurgical Analysis for Gas Distribution System Components (Withdrawn 2023)
• Effective Date: 01-Nov-2004
• Referred By: ASTM E2627-13(2019) - Standard Practice for Determining Average Grain Size Using Electron Backscatter Diffraction (EBSD) in Fully Recrystallized Polycrystalline Materials
• Effective Date: 01-Nov-2004

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E1382 – 97 (Reapproved 2004)
Standard Test Methods for
Determining Average Grain Size Using Semiautomatic and
Automatic Image Analysis
This standard is issued under the fixed designation E1382; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
These test methods may be used to determine the mean grain size, or the distribution of grain
interceptlengthsorareas,inmetallicandnonmetallicpolycrystallinematerials.Thetestmethodsmay
be applied to specimens with equiaxed or elongated grain structures with either uniform or duplex
grain size distributions. Either semiautomatic or automatic image analysis devices may be utilized to
perform the measurements.
1. Scope
Section Sec-
tion
1.1 These test methods are used to determine grain size
Scope 1
frommeasurementsofgraininterceptlengths,interceptcounts,
Referenced Documents 2
Terminology 3
intersection counts, grain boundary length, and grain areas.
Definitions 3.1
1.2 These measurements are made with a semiautomatic
Definitions of Terms Specific to This Standard 3.2
digitizingtabletorbyautomaticimageanalysisusinganimage
Symbols 3.3
Summary of Test Method 4
of the grain structure produced by a microscope.
Significance and Use 5
1.3 These test methods are applicable to any type of grain
Interferences 6
structure or grain size distribution as long as the grain Apparatus 7
Sampling 8
boundariescanbeclearlydelineatedbyetchingandsubsequent
Test Specimens 9
image processing, if necessary.
Specimen Preparation 10
1.4 These test methods are applicable to measurement of Calibration 11
Procedure:
other grain-like microstructures, such as cell structures.
Semiautomatic Digitizing Tablet 12
1.5 This standard deals only with the recommended test
Intercept Lengths 12.3
methods and nothing in it should be construed as defining or Intercept and Intersection Counts 12.4
Grain Counts 12.5
establishing limits of acceptability or fitness for purpose of the
Grain Areas 12.6
materials tested.
ALA Grain Size 12.6.1
1.6 This standard does not purport to address all of the Two-Phase Grain Structures 12.7
Procedure:
safety concerns, if any, associated with its use. It is the
Automatic Image Analysis 13
responsibility of the user of this standard to establish appro-
Grain Boundary Length 13.5
Intersection Counts 13.6
priate safety and health practices and determine the applica-
Mean Chord (Intercept) Length/Field 13.7.2
bility of regulatory limitations prior to use.
Individual Chord (Intercept) Lengths 13.7.4
1.7 The sections appear in the following order:
Grain Counts 13.8
Mean Grain Area/Field 13.9
Individual Grain Areas 13.9.4
ALA Grain Size 13.9.8
Two-Phase Grain Structures 13.10
These test methods are under the jurisdiction of ASTM Committee E04 on
Calculation of Results 14
Metallography and are the direct responsibility of Subcommittee E04.14 on
Test Report 15
Quantitative Metallography.
Precision and Bias 16
Current edition approved Nov. 1, 2004. Published November 2004. Originally
Grain Size of Non-Equiaxed Grain Structure Speci- Annex
approved in 1991. Last previous edition approved in 1997 as E1382–97. DOI:
mens A1
10.1520/E1382-97R09.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1382 – 97 (2004)
rebuild the grain structure with a very thin line (grain bound-
Section Sec-
tion
aries) separating each grain.
Examples of Proper and Improper Grain Boundary De- Annex
3.3 Symbols:
lineation A2
a=the phase of interest for grain size measurement in a
two-phase (constituent) microstructure.
2. Referenced Documents
¯
A =average area of a grains in a two-phase (constituent)
a
2.1 ASTM Standards:
microstructure.
E3 Guide for Preparation of Metallographic Specimens
¯
A =area fraction of a grains in a two-phase microstruc-
Aa
E7 Terminology Relating to Metallography
ture.
E112 Test Methods for Determining Average Grain Size
th
A =total area of grains in the i field.
gi
E407 Practice for Microetching Metals and Alloys
th th
A =true area of the i grain; or, the test area of the i field.
E562 Test Method for Determining Volume Fraction by i
th
¯
A =mean grain area for the i field.
i
Systematic Manual Point Count
A =area of the largest observed grain.
E883 Guide for Reflected−Light Photomicrography max
th
A =true test area for the i field.
E930 Test Methods for Estimating the Largest Grain Ob- ti
d=diameter of test circle.
served in a Metallographic Section (ALA Grain Size)
G=ASTM grain size number.
E1181 Test Methods for Characterizing Duplex Grain Sizes
¯
l =mean lineal intercept length.
E1245 Practice for Determining the Inclusion or Second-
¯
Phase Constituent Content of Metals by Automatic Image l =mean lineal intercept length of the a phase in a
a
Analysis two-phase microstructure for n fields measured.
¯
l =mean lineal intercept length of the a phase in a
ai
th
3. Terminology
two-phase microstructure for the i field.
3.1 Definitions—For definitions of terms used in these test L=test line or scan line length.
¯
L =mean grain boundary length per unit test area.
methods, (feature-specific measurement, field measurement,
A
th
flicker method, grain size, gray level, and threshold setting), L =grainboundarylengthperunittestareaforthei field.
Ai
th
l =intercept length for the i grain.
see Terminology E7.
i
th
¯
3.2 Definitions of Terms Specific to This Standard:
l =mean intercept length for the i field.
i
th
3.2.1 chord (intercept) length—the distance between two
L =length of grain boundaries in the i field.
i
th
opposed, adjacent grain boundary intersection points on a
L =true test line or scan line length for the i field.
ti
straight test line segment that crosses the grain at any location
L =length of grain edges per unit volume.
v
due to random placement of the test line.
M=magnification.
3.2.2 graininterceptcount—determinationofthenumberof
n=number of fields measured or the number of grid
times a test line cuts through individual grains on the plane of
placements (or the number of any measurements).
polish (tangent hits are considered as one half an interception).
N=number of grains measured or the number of grain
3.2.3 grain boundary intersection count—determination of
intercepts counted.
the number of times a test line cuts across, or is tangent to,
¯
N =mean number of grains per unit test area for nfields
A
grain boundaries (triple point intersections are considered as
measured.
th
1 ⁄2 intersections).
N =number of grains per unit area for the i field.
Ai
3.2.4 image processing—a generic term covering a variety
¯
N =mean number of a grains in a two-phase microstruc-
a
of video techniques that are used to enhance or modify
ture intercepted by the test lines or scan lines.
contrast, find and enhance edges, clean images, and so forth,
N =number of a grains in a two-phase microstructure
ai
th
prior to measurement.
intercepted by the test lines or scan lines for the i field.
3.2.5 skeletonization—an iterative image amendment pro-
N =number of grains intercepted by the test lines or scan
i
th th
cedure in which pixels are removed from the periphery of the
linesforthei field;or,thenumberofgrainscountedinthei
grain boundaries (88thinning”), or other features, unless re-
field.
moval would produce a loss of connectivity, until each pixel
¯
N =meannumberofgraininterceptsperunitlengthoftest
L
has no more than two nearest neighbors (except at a junction);
lines or scan lines for n fields measured.
this is followed by extension of line ends until they meet other
N =number of grains intercepted per unit length of test
Li
th
line ends, to connect missing or poorly delineated grain
lines or scan lines for the i field.
boundaries.
P =numberofgrainboundariesintersectedbythetestlines
i
3.2.6 watershed segmentation—an iterative image amend- th
or scan lines for the i field.
ment procedure in which each grain, or other features, is
¯
P =mean number of grain boundary intersections per unit
L
eroded to a single pixel, without loosing that pixel (88ultimate
length of test lines or scan lines for nfields measured.
erosion”); this is followed by dilation without touching to
P =numberofgrainboundaryintersectionsperunitlength
Li
th
of test lines or scan lines for the i field.
¯
P =point fraction of the a grains in a two-phase micro-
Pa
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
structure.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
s =grain boundary surface area per unit volume.
Standards volume information, refer to the standard’s Document Summary page on v
2 ½
¯
the ASTM website. s=standard deviation=[(1/(n−1) ( (X −X) ] .
i
E1382 – 97 (2004)
¯
X=any mean value= ( X /n. 6.2 Etching techniques or etchants that produce only partial
i
X =any individual measurement. delineation of the grain boundaries will bias test results and
i
95% CI=95% confidence interval. must be avoided.
% RA=percent relative accuracy. 6.3 Etching techniques or etchants that reveal annealing
twins in certain face-centered cubic metals and alloys usually
4. Summary of Test Methods
should be avoided if the grain size is to be measured by
4.1 Determination of the mean grain size is based on
automatic image analyzers. The presence of twin boundaries
measurement of the number of grains per unit area, the length
can be tolerated when semiautomatic digitizing tablets are
of grain boundaries in unit area, grain areas, the number of
utilized but measurement errors are more likely to occur.
graininterceptsorgrainboundaryintersectionsperunitlength,
Etching techniques and etchants that do not delineate twin
or grain intercept lengths. These measurements are made for a
boundaries are preferred for these specimens. Discrimination
large number of grains, or all of the grains in a given area,
of grain boundaries but not twin boundaries using image
within a microscopical field and then repeated on additional
amendment techniques may be possible with some automatic
fields to obtain an adequate number of measurements to
image analyzers. Such techniques may be employed if the
achieve the desired degree of statistical precision.
operator can demonstrate their reliability. Each field evaluated
4.2 The distribution of grain intercept lengths or areas is
using these methods should be carefully examined before (or
accomplished by measuring intercept lengths or areas for a
after) measurements are made and manually edited, if neces-
large number of grains and grouping the results in histogram
sary.
fashion; i.e., frequency of occurrence vs. class limit ranges.A
6.4 Image processing techniques employed to complete
large number of measurements over several fields are required
missing or incompletely developed grain boundaries, or to
to obtain an adequate description of the distribution.
create grain boundaries in grain-contrast/color etched speci-
mens, must be used with caution as false boundaries may be
5. Significance and Use
created in the former case, and grain boundaries may not be
5.1 These test methods cover procedures for determining
producedbetweenadjacentgrainswithsimilarcontrastorcolor
the mean grain size, and the distribution of grain intercept
in the latter case.
lengths or grain areas, for polycrystalline metals and nonme-
6.5 Inclusions,carbides,nitrides,andothersimilarconstitu-
tallic materials with equiaxed or deformed grain shapes, with
ents within grains may be detected as grain boundaries when
uniformorduplexgrainsizedistributions,andforsinglephase
automatic image analyzers are utilized. These features should
or multiphase grain structures.
be removed from the field before measurements are made.
5.2 The measurements are performed using semiautomatic
6.6 Orientation-sensitive etchants should be avoided as
digitizingtabletimageanalyzersorautomaticimageanalyzers.
someboundariesaredeeplyetched,othersareproperlyetched,
These devices relieve much of the tedium associated with
while some are barely revealed or not revealed at all. Exces-
manual measurements, thus permitting collection of a larger
sively deep etching with such etchants to bring out the fainter
amount of data and more extensive sampling which will
boundaries should not be done because deep etching creates
produce better statistical definition of the grain size than by
excessive relief (deviation from planar conditions) and will
manual methods.
bias certain measurements, particularly grain intercept lengths
5.3 The precision and relative accuracy of the test results
and grain areas, performed by automatic image analysis and
depend on the representativeness of the specimen or speci-
also measurements made with a digitizing tablet.
mens, quality of specimen preparation, clarity of the grain
6.7 Detection of proeutectoid a grains in steels containing
boundaries (etch technique and etchant used), the number of
ferrite and pearlite (and other alloys with similar structures) by
grains measured or the measurement area, errors in detecting
automatic image analyzers can result in detection of ferrite
grainboundariesorgraininteriors,errorsduetodetectingother
within the pearlitic constituent when the interlamellar spacing
features (carbides, inclusions, twin boundaries, and so forth),
iscoarse.Useofhighmagnificationsaccentuatesthisproblem.
the representativeness of the fields measured, and program-
For such structures, use the lowest possible magnification, or
ming errors.
use semiautomatic devices.
5.4 Results from these test methods may be used to qualify
6.8 Dust, pieces of tissue paper, oil or water stains, or other
material for shipment in accordance with guidelines agreed
foreign debris on the surface to be examined will bias the
upon between purchaser and manufacturer, to compare differ-
measurement results.
ent manufacturing processes or process variations, or to pro-
6.9 If photographic images are measured using a digitizing
vide data for structure-property-behavior studies.
tablet, uncertainties in the magnification (particularly when
6. Interferences
enlargements are used) will bias the test results.
6.10 Vibrations, if present, can blur the image and bias test
6.1 Improper polishing techniques that leave excessively
results and must be minimized or eliminated when using
large scratches on the surface, or produce excessive deforma-
automatic image analysis.
tion or smearing of the microstructure, or produce pull-outs
and other defects, will lead to measurement errors, particularly 6.11 Dust in the microscope or camera system may produce
when automatic image analyzers
...