ASTM E1382-97

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

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.
1.6 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.  
1.7 The sections appear in the following order:  Section Section Scope 1 Referenced Documents 2 Terminology 3 Definitions 3.1 Descriptions of Terms Specific to This Standard 3.2 Symbols 3.3 Summary of Test Method 4 Significance and Use 5 Interferences 6 Apparatus 7 Sampling 8 Test Specimens 9 Specimen Preparation 10 Calibration 11 Procedure: Semiautomatic Digitizing Tablet 12 Intercept Lengths 12.3 Intercept and Intersection Counts 12.4 Grain Counts 12.5 Grain Areas 12.6 ALA Grain Size 12.6.1 Two-Phase Grain Structures 12.7 Procedure: Automatic Image Analysis 13 Grain Boundary Length 13.5 Intersection Counts 13.6 Mean Chord (Intercept) Length/Field 13.7 Individual Chord (Intercept) Lengths 13.7.4 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 Calculation of Results 14 Test Report 15 Precision and Bias 16 Grain Size of Non-Equiaxed Grain Structure Specimens A1 Examples of Proper and Improper Grain Boundary Delineation A2

General Information

• Status: Historical
• Publication Date: 09-Apr-1997
• ICS: 19.120 - Particle size analysis. Sieving
• Technical Committee: E04 - Metallography
• Drafting Committee: E04.14 - Quantitative Metallography

Relations

• Replaced By: ASTM E1382-97(2004) - Standard Test Methods for Determining Average Grain Size Using Semiautomatic and Automatic Image Analysis
• 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: 10-Apr-1997
• Referred By: ASTM E112-13(2021) - Standard Test Methods for Determining Average Grain Size
• Effective Date: 10-Apr-1997
• Referred By: ASTM F3160-21 - Standard Guide for Metallurgical Characterization of Absorbable Metallic Materials for Medical Implants
• Effective Date: 10-Apr-1997
• Referred By: ASTM F1376-92(2020) - Standard Guide for Metallurgical Analysis for Gas Distribution System Components (Withdrawn 2023)
• Effective Date: 10-Apr-1997
• Referred By: ASTM C1557-20 - Standard Test Method for Tensile Strength and Young's Modulus of Fibers
• Effective Date: 10-Apr-1997

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: E 1382 – 97
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 (e) 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
Summary of Test Method 4
frommeasurementsofgraininterceptlengths,interceptcounts, Significance and Use 5
Interferences 6
intersection counts, grain boundary length, and grain areas.
Apparatus 7
1.2 These measurements are made with a semiautomatic
Sampling 8
digitizingtabletorbyautomaticimageanalysisusinganimage
Test Specimens 9
Specimen Preparation 10
of the grain structure produced by a microscope.
Calibration 11
1.3 These test methods are applicable to any type of grain
Procedure:
structure or grain size distribution as long as the grain Semiautomatic Digitizing Tablet 12
Intercept Lengths 12.3
boundariescanbeclearlydelineatedbyetchingandsubsequent
Intercept and Intersection Counts 12.4
image processing, if necessary.
Grain Counts 12.5
1.4 These test methods are applicable to measurement of Grain Areas 12.6
ALA Grain Size 12.6.1
other grain-like microstructures, such as cell structures.
Two-Phase Grain Structures 12.7
1.5 This standard deals only with the recommended test
Procedure:
methods and nothing in it should be construed as defining or Automatic Image Analysis 13
Grain Boundary Length 13.5
establishing limits of acceptability or fitness for purpose of the
Intersection Counts 13.6
materials tested.
Mean Chord (Intercept) Length/Field 13.7.2
1.6 This standard does not purport to address all of the Individual Chord (Intercept) Lengths 13.7.4
Grain Counts 13.8
safety concerns, if any, associated with its use. It is the
Mean Grain Area/Field 13.9
responsibility of the user of this standard to establish appro-
Individual Grain Areas 13.9.4
priate safety and health practices and determine the applica- ALA Grain Size 13.9.8
Two-Phase Grain Structures 13.10
bility of regulatory limitations prior to use.
Calculation of Results 14
1.7 The sections appear in the following order:
Test Report 15
Precision and Bias 16
Section Sec-
Grain Size of Non-Equiaxed Grain Structure Speci- Annex
tion
mens A1
Scope 1
Examples of Proper and Improper Grain Boundary De- Annex
Referenced Documents 2
lineation A2
Terminology 3
Definitions 3.1
2. Referenced Documents
Definitions of Terms Specific to This Standard 3.2
Symbols 3.3
2.1 ASTM Standards:
E3 Practice for Preparation of Metallographic Specimens
E7 Terminology Relating to Metallography
These test methods are under the jurisdiction of ASTM Committee E-4 on
E112 Test Methods for Determining Average Grain Size
Metallography and are the direct responsibility of Subcommittee E04.14 on
Quantitative Metallography.
Current edition approved Apr. 10, 1997. Published June 1997. Originally
published as E1382–91. Last previous edition E1382–91.
Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1382
E407 Practice for Microetching Metals and Alloys d 5diameter of test circle.
E562 Practice for Determining Volume Fraction by Sys- G 5ASTM grain size number.
¯
tematic Manual Point Count
l 5mean lineal intercept length.
¯
E883 Guide for Reflected Light Photomicrography
l 5mean lineal intercept length of the a phase in a
a
E930 Test Methods for Estimating the Largest Grain Ob-
two-phase microstructure for n fields measured.
served in a Metallographic Section (ALA Grain Size) ¯
l 5mean lineal intercept length of the a phase in a
ai
th
E 1181 Test Methods for Characterizing Duplex Grain
two-phase microstructure for the i field.
Sizes
L 5test line or scan line length.
E1245 Practice for Determining the Inclusion or Second-
¯
L 5mean grain boundary length per unit test area.
A
th
phase Constituent Content of Metals by Automatic Image
L 5grain boundary length per unit test area for the i
Ai
Analysis
field.
th
l 5intercept length for the i grain.
i
3. Terminology
th
¯
l 5mean intercept length for the i field.
i
3.1 Definitions—For definitions of terms used in these test
th
L 5length of grain boundaries in the i field.
i
methods, (feature-specific measurement, field measurement,
th
L 5true test line or scan line length for the i field.
ti
flicker method, grain size, gray level, and threshold setting),
L 5length of grain edges per unit volume.
v
see Terminology E7.
M 5magnification.
3.2 Definitions of Terms Specific to This Standard:
n 5number of fields measured or the number of grid
3.2.1 chord (intercept) length—the distance between two
placements (or the number of any measurements).
opposed, adjacent grain boundary intersection points on a
N 5number of grains measured or the number of grain
straight test line segment that crosses the grain at any location
intercepts counted.
due to random placement of the test line.
¯
N 5mean number of grains per unit test area for nfields
A
3.2.2 graininterceptcount—determinationofthenumberof
measured.
times a test line cuts through individual grains on the plane of
th
N 5number of grains per unit area for the i field.
Ai
polish (tangent hits are considered as one half an interception).
¯
N 5mean number of a grains in a two-phase microstruc-
a
3.2.3 grain boundary intersection count—determination of
ture intercepted by the test lines or scan lines.
the number of times a test line cuts across, or is tangent to,
N 5number of a grains in a two-phase microstructure
ai
grain boundaries (triple point intersections are considered as
th
intercepted by the test lines or scan lines for the i field.
1 ⁄2 intersections).
N 5number of grains intercepted by the test lines or scan
i
3.2.4 image processing—a generic term covering a variety
th th
linesforthei field;or,thenumberofgrainscountedinthei
of video techniques that are used to enhance or modify
field.
contrast, find and enhance edges, clean images, and so forth,
¯
N 5meannumberofgraininterceptsperunitlengthoftest
L
prior to measurement.
lines or scan lines for n fields measured.
3.2.5 skeletonization—an iterative image amendment pro-
N 5number of grains intercepted per unit length of test
Li
cedure in which pixels are removed from the periphery of the
th
lines or scan lines for the i field.
grain boundaries (88thinning”), or other features, unless re-
P 5numberofgrainboundariesintersectedbythetestlines
i
moval would produce a loss of connectivity, until each pixel
th
or scan lines for the i field.
has no more than two nearest neighbors (except at a junction);
¯
P 5mean number of grain boundary intersections per unit
L
this is followed by extension of line ends until they meet other
length of test lines or scan lines for nfields measured.
line ends, to connect missing or poorly delineated grain
P 5number of grain boundary intersections per unit
Li
boundaries.
th
length of test lines or scan lines for the i field.
3.2.6 watershed segmentation—an iterative image amend-
¯
P 5point fraction of the a grains in a two-phase
Pa
ment procedure in which each grain, or other features, is
microstructure.
eroded to a single pixel, without loosing that pixel (88ultimate
s 5grain boundary surface area per unit volume.
v
erosion”); this is followed by dilation without touching to
2 ½
¯
s 5standard deviation 5[(1/(n−1) ( (X −X) ] .
i
rebuild the grain structure with a very thin line (grain bound-
¯
X 5any mean value5( X /n.
i
aries) separating each grain.
X 5any individual measurement.
i
3.3 Symbols:
95% CI 595% confidence interval.
a5the phase of interest for grain size measurement in a
%RA 5percent relative accuracy.
two-phase (constituent) microstructure.
¯
A 5average area of a grains in a two-phase (constituent)
a
4. Summary of Test Methods
microstructure.
¯
A 5area fraction of a grains in a two-phase microstruc- 4.1 Determination of the mean grain size is based on
Aa
ture. measurement of the number of grains per unit area, the length
th
A 5total area of grains in the i field. of grain boundaries in unit area, grain areas, the number of
gi
th th
A 5trueareaofthei grain;or,thetestareaofthei field. graininterceptsorgrainboundaryintersectionsperunitlength,
i
th
¯
A 5mean grain area for the i field. or grain intercept lengths. These measurements are made for a
i
A 5area of the largest observed grain. large number of grains, or all of the grains in a given area,
max
th
A 5true test area for the i field. within a microscopical field and then repeated on additional
ti
E 1382
fields to obtain an adequate number of measurements to using these methods should be carefully examined before (or
achieve the desired degree of statistical precision. after) measurements are made and manually edited, if neces-
4.2 The distribution of grain intercept lengths or areas is sary.
accomplished by measuring intercept lengths or areas for a 6.4 Image processing techniques employed to complete
large number of grains and grouping the results in histogram missing or incompletely developed grain boundaries, or to
fashion; i.e., frequency of occurrence vs. class limit ranges. A create grain boundaries in grain-contrast/color etched speci-
large number of measurements over several fields are required mens, must be used with caution as false boundaries may be
to obtain an adequate description of the distribution. created in the former case, and grain boundaries may not be
producedbetweenadjacentgrainswithsimilarcontrastorcolor
5. Significance and Use
in the latter case.
5.1 These test methods cover procedures for determining
6.5 Inclusions, carbides, nitrides, and other similar constitu-
the mean grain size, and the distribution of grain intercept
ents within grains may be detected as grain boundaries when
lengths or grain areas, for polycrystalline metals and nonme-
automatic image analyzers are utilized. These features should
tallic materials with equiaxed or deformed grain shapes, with
be removed from the field before measurements are made.
uniform or duplex grain size distributions, and for single phase
6.6 Orientation-sensitive etchants should be avoided as
or multiphase grain structures. some boundaries are deeply etched, others are properly etched,
5.2 The measurements are performed using semiautomatic
while some are barely revealed or not revealed at all. Exces-
digitizingtabletimageanalyzersorautomaticimageanalyzers. sively deep etching with such etchants to bring out the fainter
These devices relieve much of the tedium associated with
boundaries should not be done because deep etching creates
manual measurements, thus permitting collection of a larger excessive relief (deviation from planar conditions) and will
amount of data and more extensive sampling which will
bias certain measurements, particularly grain intercept lengths
produce better statistical definition of the grain size than by and grain areas, performed by automatic image analysis and
manual methods.
also measurements made with a digitizing tablet.
5.3 The precision and relative accuracy of the test results
6.7 Detection of proeutectoid a grains in steels containing
depend on the representativeness of the specimen or speci-
ferrite and pearlite (and other alloys with similar structures) by
mens, quality of specimen preparation, clarity of the grain
automatic image analyzers can result in detection of ferrite
boundaries (etch technique and etchant used), the number of
within the pearlitic constituent when the interlamellar spacing
grains measured or the measurement area, errors in detecting
is coarse. Use of high magnifications accentuates this problem.
grainboundariesorgraininteriors,errorsduetodetectingother
For such structures, use the lowest possible magnification, or
features (carbides, inclusions, twin boundaries, and so forth),
use semiautomatic devices.
the representativeness of the fields measured, and program-
6.8 Dust, pieces of tissue paper, oil or water stains, or other
ming errors.
foreign debris on the surface to be examined will bias the
5.4 Results from these test methods may be used to qualify
measurement results.
material for shipment in accordance with guidelines agreed
6.9 If photographic images are measured using a digitizing
upon between purchaser and manufacturer, to compare differ- tablet, uncertainties in the magnification (particularly when
ent manufacturing processes or process variations, or to pro-
enlargements are used) will bias the test results.
vide data for structure-property-behavior studies. 6.10 Vibrations, if present, can blur the image and bias test
results and must be minimized or eliminated when using
6. Interferences
automatic image analysis.
6.1 Improper polishing techniques that leave excessively
6.11 Dust in the microscope or camera system may produce
large scratches on the surface, or produce excessive deforma-
spurious detail in the image that may be detected as a grain
tion or smearing of the microstructure, or produce pull-outs
boundary, particularly on automatic image analyzers, and will
and other defects, will lead to measurement errors, particularly
biasthetestresults.Consequently,theimagingsystemmustbe
when automatic image analyzers are employed.
kept clean.
6.2 Etching techniques or etchants that produce only partial
6.12 Nonuniform illumination can influence feature detec-
delineation of the grain boundaries will bias test results and
tionandthresholdingusingautomaticimageanalyzers.Priorto
must be avoided.
analysis, center the light source (as described in the operating
6.3 Etching techniques or etchants that reveal annealing
instructions for the microscope) and adjust the field and
twins in certain face-centered cubic metals and alloys usually
aperture diaphragms for best image clarity. Digital correction
should be avoided if the grain size is to be measured by
methods for nonuniform illumination may be used subse-
automatic image analyzers. The presence of twin boundaries
quently; however, these methods should not be used in lieu of
can be tolerated when semiautomatic digitizing tablets are
proper micros
...