ASTM E112-13(2021)
(Test Method)Standard Test Methods for Determining Average Grain Size
Standard Test Methods for Determining Average Grain Size
SIGNIFICANCE AND USE
4.1 These test methods cover procedures for estimating and rules for expressing the average grain size of all metals consisting entirely, or principally, of a single phase. The grain size of specimens with two phases, or a phase and a constituent, can be measured using a combination of two methods, a measurement of the volume fraction of the phase and an intercept or planimetric count (see Section 17). The test methods may also be used for any structures having appearances similar to those of the metallic structures shown in the comparison charts. The three basic procedures for grain size estimation are:
4.1.1 Comparison Procedure—The comparison procedure does not require counting of either grains, intercepts, or intersections but, as the name suggests, involves comparison of the grain structure to a series of graded images, either in the form of a wall chart, clear plastic overlays, or an eyepiece reticle. There appears to be a general bias in that comparison grain size ratings claim that the grain size is somewhat coarser (1/2 to 1 G number lower) than it actually is (see X1.3.5). Repeatability and reproducibility of comparison chart ratings are generally ±1 grain size number.
4.1.2 Planimetric Procedure—The planimetric method involves an actual count of the number of grains within a known area. The number of grains per unit area, NA , is used to determine the ASTM grain size number, G. The precision of the method is a function of the number of grains counted. A precision of ±0.25 grain size units can be attained with a reasonable amount of effort. Results are free of bias and repeatability and reproducibility are less than ±0.5 grain size units. An accurate count does require marking off of the grains as they are counted.
4.1.3 Intercept Procedure—The intercept method involves an actual count of the number of grains intercepted by a test line or the number of grain boundary intersections with a test line, per unit length of test line, used to calculate t...
SCOPE
1.1 These test methods cover the measurement of average grain size and include the comparison procedure, the planimetric (or Jeffries) procedure, and the intercept procedures. These test methods may also be applied to nonmetallic materials with structures having appearances similar to those of the metallic structures shown in the comparison charts. These test methods apply chiefly to single phase grain structures but they can be applied to determine the average size of a particular type of grain structure in a multiphase or multiconstituent specimen.
1.2 These test methods are used to determine the average grain size of specimens with a unimodal distribution of grain areas, diameters, or intercept lengths. These distributions are approximately log normal. These test methods do not cover methods to characterize the nature of these distributions. Characterization of grain size in specimens with duplex grain size distributions is described in Test Methods E1181. Measurement of individual, very coarse grains in a fine grained matrix is described in Test Methods E930.
1.3 These test methods deal only with determination of planar grain size, that is, characterization of the two-dimensional grain sections revealed by the sectioning plane. Determination of spatial grain size, that is, measurement of the size of the three-dimensional grains in the specimen volume, is beyond the scope of these test methods.
1.4 These test methods describe techniques performed manually using either a standard series of graded chart images for the comparison method or simple templates for the manual counting methods. Utilization of semi-automatic digitizing tablets or automatic image analyzers to measure grain size is described in Test Methods E1382.
1.5 These test methods deal only with the recommended test methods and nothing in them should be construed as defining or establishing limits of acceptability or fitness of purpose of the ma...
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E112 − 13 (Reapproved 2021)
Standard Test Methods for
Determining Average Grain Size
This standard is issued under the fixed designation E112; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
INTRODUCTION
These test methods of determination of average grain size in metallic materials are primarily
measuring procedures and, because of their purely geometric basis, are independent of the metal or
alloy concerned. In fact, the basic procedures may also be used for the estimation of average grain,
crystal, or cell size in nonmetallic materials. The comparison method may be used if the structure of
the material approaches the appearance of one of the standard comparison charts. The intercept and
planimetric methods are always applicable for determining average grain size. However, the
comparison charts cannot be used for measurement of individual grains.
1. Scope 1.4 These test methods describe techniques performed
manually using either a standard series of graded chart images
1.1 These test methods cover the measurement of average
for the comparison method or simple templates for the manual
grain size and include the comparison procedure, the planim-
counting methods. Utilization of semi-automatic digitizing
etric (or Jeffries) procedure, and the intercept procedures.
tablets or automatic image analyzers to measure grain size is
These test methods may also be applied to nonmetallic
described in Test Methods E1382.
materialswithstructureshavingappearancessimilartothoseof
the metallic structures shown in the comparison charts. These
1.5 Thesetestmethodsdealonlywiththerecommendedtest
test methods apply chiefly to single phase grain structures but
methods and nothing in them should be construed as defining
theycanbeappliedtodeterminetheaveragesizeofaparticular
or establishing limits of acceptability or fitness of purpose of
type of grain structure in a multiphase or multiconstituent
the materials tested.
specimen.
1.6 The measured values are stated in SI units, which are
1.2 These test methods are used to determine the average
regarded as standard. Equivalent inch-pound values, when
grain size of specimens with a unimodal distribution of grain
listed, are in parentheses and may be approximate.
areas, diameters, or intercept lengths. These distributions are
1.7 This standard does not purport to address all of the
approximately log normal. These test methods do not cover
safety concerns, if any, associated with its use. It is the
methods to characterize the nature of these distributions.
responsibility of the user of this standard to establish appro-
Characterization of grain size in specimens with duplex grain
priate safety, health, and environmental practices and deter-
size distributions is described in Test Methods E1181. Mea-
mine the applicability of regulatory limitations prior to use.
surement of individual, very coarse grains in a fine grained
1.8 The paragraphs appear in the following order:
matrix is described in Test Methods E930.
Section Number
1.3 These test methods deal only with determination of
Scope 1
planar grain size, that is, characterization of the two-
Referenced Documents 2
Terminology 3
dimensional grain sections revealed by the sectioning plane.
Significance and Use 4
Determinationofspatialgrainsize,thatis,measurementofthe
Generalities of Application 5
sizeofthethree-dimensionalgrainsinthespecimenvolume,is
Sampling 6
Test Specimens 7
beyond the scope of these test methods.
Calibration 8
Preparation of Photomicrographs 9
Comparison Procedure 10
These test methods are under the jurisdiction of ASTM Committee E04 on
Planimetric (Jeffries) Procedure 11
Metallography and are the direct responsibility of Subcommittee E04.08 on Grain
General Intercept Procedures 12
Size.
Heyn Linear Intercept Procedure 13
Current edition approved Sept. 1, 2021. Published November 2021. Originally
Circular Intercept Procedures 14
approved in 1955. Last previous edition approved 2013 as E112–13. DOI:
Hilliard Single-Circle Procedure 14.2
10.1520/E0112-13R21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E112 − 13 (2021)
100X magnification. To obtain the number per square milli-
Abrams Three-Circle Procedure 14.3
Statistical Analysis 15
metre at 1X, multiply by 15.50.
Specimens with Non-equiaxed Grain Shapes 16
3.2.2 grain—an individual crystal with the same atomic
Specimens Containing Two or More Phases or Constituents 17
Report 18
configuration throughout in a polycrystalline material; the
Precision and Bias 19
grain may or may not contain twinned regions within it or
Keywords 20
Annexes: sub-grains.
Basis of ASTM Grain Size Numbers Annex
3.2.3 grain boundary—a very narrow region in a polycrys-
A1
talline material corresponding to the transition from one
Equations for Conversions Among Various Grain Size Measurements Annex
A2
crystallographic orientation to another, thus separating one
Austenite Grain Size, Ferritic and Austenitic Steels Annex
adjacent grain from another; on a two-dimensional plane
A3
Fracture Grain Size Method Annex through three-dimensional polycrystalline materials, the grain
A4
edgesbetweenadjacentgrainssurroundingasinglegrainmake
Requirements for Wrought Copper and Copper-Base Alloys Annex
up the outline of the two-dimensional grains that are observed
A5
Application to Special Situations Annex in the light microscope and are measured or counted by the
A6
procedures in this test method.
Appendixes:
Results of Interlaboratory Grain Size Determinations Appendix 3.2.4 grain boundary intersection count, P—determination
X1
of the number of times a test line cuts across, or is tangent to
Referenced Adjuncts Appendix
(tangent hits are counted as one (1) intersection) grain bound-
X2
aries (triple point intersections are considered as 1- ⁄2 intersec-
1.9 This international standard was developed in accor-
tions).
dance with internationally recognized principles on standard-
3.2.5 grain intercept count, N—determinationofthenumber
ization established in the Decision on Principles for the
of times a test line cuts through individual grains on the plane
Development of International Standards, Guides and Recom-
of polish (tangent hits are considered as one half an intercep-
mendations issued by the World Trade Organization Technical
tion;testlinesthatendwithinagrainareconsideredasonehalf
Barriers to Trade (TBT) Committee.
an interception).
2. Referenced Documents
3.2.6 intercept length—the distance between two opposed,
2.1 ASTM Standards: adjacent grain boundary intersection points on a test line
E3Guide for Preparation of Metallographic Specimens segment that crosses the grain at any location due to random
E7Terminology Relating to Metallography placement of the test line.
E407Practice for Microetching Metals and Alloys
3.3 Symbols:
E562Test Method for Determining Volume Fraction by
Systematic Manual Point Count
α = matrix grains in a two phase (constituent)
E691Practice for Conducting an Interlaboratory Study to microstructure.
Determine the Precision of a Test Method A = test area.
¯
A = mean grain cross sectional area.
E883Guide for Reflected–Light Photomicrography
AI = grainelongationratiooranisotropyindexfora
E930Test Methods for Estimating the Largest Grain Ob- ℓ
longitudinally oriented plane.
served in a Metallographic Section (ALA Grain Size)
¯
d = mean planar grain diameter (Plate III).
E1181Test Methods for Characterizing Duplex Grain Sizes
¯
D = mean spatial (volumetric) grain diameter.
E1382Test Methods for Determining Average Grain Size
f = Jeffries multiplier for planimetric method.
Using Semiautomatic and Automatic Image Analysis
G = ASTM grain size number.
2.2 ASTM Adjuncts:
¯
ℓ = mean lineal intercept length.
2.2.1 For a complete adjunct list, see Appendix X2
¯
ℓ = mean lineal intercept length of the α matrix
α
phase in a two phase (constituent) microstruc-
3. Terminology
ture.
¯
3.1 Definitions—For definitions of terms used in these test
ℓ = mean lineal intercept length on a longitudi-
ℓ
methods, see Terminology E7. nally oriented surface for a non-equiaxed
grain structure.
3.2 Definitions of Terms Specific to This Standard:
¯
ℓ = mean lineal intercept length on a transversely
t
3.2.1 ASTM grain size number—the ASTM grain size
oriented surface for a non-equiaxed grain
number, G, was originally defined as:
structure.
G21
N 52 (1)
¯
AE
ℓ = mean lineal intercept length on a planar ori-
p
ented surface for a non-equiaxed grain struc-
where N is the number of grains per square inch at
AE
ture.
ℓ = baseinterceptlengthof32.00mmfordefining
the relationship between G and ℓ (and N ) for
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
L
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
macroscopically or microscopically deter-
Standards volume information, refer to the standard’s Document Summary page on
mined grain size by the intercept method.
the ASTM website.
E112 − 13 (2021)
size of specimens with two phases, or a phase and a
L = length of a test line.
constituent, can be measured using a combination of two
M = magnification used.
M = magnification used by a chart picture series. methods, a measurement of the volume fraction of the phase
b
n = number of fields measured. andaninterceptorplanimetriccount(seeSection17).Thetest
N = number of α grains intercepted by the test line
α methods may also be used for any structures having appear-
in a two phase (constituent) microstructure.
ances similar to those of the metallic structures shown in the
N = number of grains per mm at 1X.
A comparison charts. The three basic procedures for grain size
N = number of α grains per mm at 1X in a two
Aα
estimation are:
phase (constituent) microstructure.
2 4.1.1 Comparison Procedure—The comparison procedure
N = number of grains per inch at 100X.
AE
does not require counting of either grains, intercepts, or
N = N on a longitudinally oriented surface for a
Aℓ A
intersectionsbut,asthenamesuggests,involvescomparisonof
non-equiaxed grain structure.
the grain structure to a series of graded images, either in the
N = N on a transversely oriented surface for a
At A
form of a wall chart, clear plastic overlays, or an eyepiece
non-equiaxed grain structure.
reticle. There appears to be a general bias in that comparison
N = N on a planar oriented surface for a non-
Ap A
grain size ratings claim that the grain size is somewhat coarser
equiaxed grain structure.
( ⁄2 to 1 G number lower) than it actually is (see X1.3.5).
N = number of intercepts with a test line.
I
N = number of grains completely within a test
Repeatability and reproducibility of comparison chart ratings
Inside
circle.
are generally 61 grain size number.
N = numberofgrainsinterceptedbythetestcircle.
Intercepted
4.1.2 Planimetric Procedure—The planimetric method in-
N = number of intercepts per unit length of test
L
volves an actual count of the number of grains within a known
line.
area. The number of grains per unit area, N , is used to
A
N = N on a longitudinally oriented surface for a
Lℓ L
determine the ASTM grain size number, G. The precision of
non-equiaxed grain structure.
the method is a function of the number of grains counted. A
N = N on a transversely oriented surface for a
Lt L
precision of 60.25 grain size units can be attained with a
non-equiaxed grain structure.
reasonable amount of effort. Results are free of bias and
N = N on a planar oriented surface for a non-
Lp L
repeatability and reproducibility are less than 60.5 grain size
equiaxed grain structure.
units.An accurate count does require marking off of the grains
P = numberofgrainboundaryintersectionswitha
I
as they are counted.
test line.
P = number of grain boundary intersections per
4.1.3 Intercept Procedure—The intercept method involves
L
unit length of test line.
an actual count of the number of grains intercepted by a test
P = P on a longitudinally oriented surface for a
line or the number of grain boundary intersections with a test
Lℓ L
non-equiaxed grain structure.
line, per unit length of test line, used to calculate the mean
P = P on a transversely oriented surface for a
¯ ¯
Lt L
lineal intercept length, ℓ. ℓ is used to determine the ASTM
non-equiaxed grain structure.
grainsizenumber, G.Theprecisionofthemethodisafunction
P = P on a planar oriented surface for a non-
Lp L
of the number of intercepts or intersections counted. A preci-
equiaxed grain structure.
sion of better than 60.25 grain size units can be attained with
Q = correction factor for comparison chart ratings
a reasonable amount of effort. Results are free of bias;
using a non-standard magnification for micro-
repeatability and reproducibility are less than 60.5 grain size
scopically determined grain sizes.
units. Because an accurate count can be made without need of
Q = correction factor for comparison chart ratings
m
marking off intercepts or intersections, the intercept method is
using a non-standard magnification for mac-
faster than the planimetric method for the same level of
roscopically determined grain sizes.
precision.
s = standard deviation.
S = grain boundary surface area to volume ratio
V
4.2 For specimens consisting of equiaxed grains, the
for a single phase structure.
method of comparing the specimen with a standard chart is
S = grain boundary surface area to volume ratio
Vα
most convenient and is sufficiently accurate for most commer-
for a two phase (constituent) structure.
cial purposes. For higher degrees of accuracy in determining
t = students’ t multiplier for determination of the
averagegrainsize,theinterceptorplanimetricproceduresmay
confidence interval.
be used. The intercept procedure is particularly useful for
V = volume fraction of the α phase in a two phase
Vα
structures consisting of elongated grains (see Section 16).
(constituent) microstructure.
95 %CI = 95% confidence interval.
4.3 Incaseofdispute,theplanimetricprocedureshallbethe
%RA = percent relative accuracy.
referee procedure in all cases.
4.4 Noattemptshouldbemadetoestimatetheaveragegrain
4. Significance and Use
size of heavily cold-worked material. Partially recrystallized
4.1 These test methods cover procedures for estimating and
wroughtalloysandlig
...
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