ASTM E112-96(2004)
(Test Method)Standard Test Methods for Determining Average Grain Size
Standard Test Methods for Determining Average Grain Size
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 materials tested.
1.6 The measured values are stated in SI units, which are regarded as standard. Equivalent inch-pound values, when listed, are in parentheses and may be approximate.
1.7 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.
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Designation: E 112 – 96 (Reapproved 2004)
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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the 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 for the comparison method or simple templates for the manual
counting methods. Utilization of semi-automatic digitizing
1.1 These test methods cover the measurement of average
tablets or automatic image analyzers to measure grain size is
grainsizeandincludethecomparisonprocedure,theplanimet-
described in Test Methods E1382.
ric (or Jeffries) procedure, and the intercept procedures. These
1.5 Thesetestmethodsdealonlywiththerecommendedtest
testmethodsmayalsobeappliedtononmetallicmaterialswith
methods and nothing in them should be construed as defining
structures having appearances similar to those of the metallic
or establishing limits of acceptability or fitness of purpose of
structures shown in the comparison charts. These test methods
the materials tested.
apply chiefly to single phase grain structures but they can be
1.6 The measured values are stated in SI units, which are
applied to determine the average size of a particular type of
regarded as standard. Equivalent inch-pound values, when
grain structure in a multiphase or multiconstituent specimen.
listed, are in parentheses and may be approximate.
1.2 These test methods are used to determine the average
1.7 This standard does not purport to address all of the
grain size of specimens with a unimodal distribution of grain
safety concerns, if any, associated with its use. It is the
areas, diameters, or intercept lengths. These distributions are
responsibility of the user of this standard to establish appro-
approximately log normal. These test methods do not cover
priate safety and health practices and determine the applica-
methods to characterize the nature of these distributions.
bility of regulatory limitations prior to use.
Characterization of grain size in specimens with duplex grain
1.8 The paragraphs appear in the following order:
size distributions is described in Test Methods E1181. Mea-
Section Number
surement of individual, very coarse grains in a fine grained
Scope 1
matrix is described in Test Methods E930.
Referenced Documents 2
1.3 These test methods deal only with determination of
Terminology 3
Significance and Use 4
planar grain size, that is, characterization of the two-
Generalities of Application 5
dimensional grain sections revealed by the sectioning plane.
Sampling 6
Determinationofspatialgrainsize,thatis,measurementofthe
Test Specimens 7
Calibration 8
sizeofthethree-dimensionalgrainsinthespecimenvolume,is
Preparation of Photomicrographs 9
beyond the scope of these test methods.
Comparison Procedure 10
1.4 These test methods describe techniques performed Planimetric (Jeffries) Procedure 11
General Intercept Procedures 12
manually using either a standard series of graded chart images
Heyn Linear Intercept Procedure 13
Circular Intercept Procedures 14
Hilliard Single-Circle Procedure 14.2
These test methods are under the jurisdiction of ASTM Committee E04 on
Abrams Three-Circle Procedure 14.3
Metallography and are the direct responsibility of Subcommittee E04.08 on Grain
Statistical Analysis 15
Size.
Specimens with Non-equiaxed Grain Shapes 16
Current edition approved Nov. 1, 2004. Published November 2004. Originally
Specimens Containing Two or More Phases or Constituents 17
e3
approved in 1955. Last previous edition approved 1996 as E112–96 .
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 112 – 96 (2004)
3.2.3 grain boundary intersection count—determination of
Report 18
Precision and Bias 19
the number of times a test line cuts across, or is tangent to,
Keywords 20
grain boundaries (triple point intersections are considered as
Annexes:
Basis of ASTM Grain Size Numbers Annex 1- ⁄2 intersections).
A1
3.2.4 graininterceptcount—determinationofthenumberof
Equations for Conversions Among Various Grain Size Measurements Annex
A2
times a test line cuts through individual grains on the plane of
Austenite Grain Size, Ferritic and Austenitic Steels Annex
polish (tangent hits are considered as one half an interception;
A3
test lines that end within a grain are considered as one half an
Fracture Grain Size Method Annex
A4
interception).
Requirements for Wrought Copper and Copper-Base Alloys Annex
A5 3.2.5 intercept length—the distance between two opposed,
Application to Special Situations Annex
adjacent grain boundary intersection points on a test line
A6
segment that crosses the grain at any location due to random
Appendixes:
Results of Interlaboratory Grain Size Determinations Appen-
placement of the test line.
dix X1
3.3 Symbols:Symbols:
Referenced Adjuncts Appen-
dix X2
a = matrix grains in a two phase (constituent)
2. Referenced Documents
2 microstructure.
2.1 ASTM Standards:
A = test area.
E3 Practice for Preparation of Metallographic Specimens
—
= mean grain cross sectional area.
A
E7 Terminology Relating to Metallography
AI = grain elongation ratio or anisotropy index
,
E407 Practice for Microetching Metals and Alloys
for a longitudinally oriented plane.
E562 Practice for Determining Volume Fraction by Sys-
—
= mean planar grain diameter (Plate III).
d
tematic Manual Point Count
—
= mean spatial (volumetric) grain diameter.
E691 Practice for Conducting an Interlaboratory Study to
D
Determine the Precision of a Test Method
f = Jeffriesmultiplierforplanimetricmethod.
E883 Guide for Reflected-Light Photomicrography
G = ASTM grain size number.
E930 Test Methods for Estimating the Largest Grain Ob- = mean lineal intercept length.
,
served in a Metallographic Section (ALA Grain Size)
—
= mean lineal intercept length of the a
,
a
E1181 TestMethodsforCharacterizingDuplexGrainSizes
matrix phase in a two phase (constituent)
E1382 Test Methods for Determining Average Grain Size
microstructure.
Using Semiautomatic and Automatic Image Analysis
—
= mean lineal intercept length on a longitu-
,
,
2.2 ASTM Adjuncts:
dinally oriented surface for a non-
2.2.1 For a complete adjunct list, see Appendix X2
equiaxed grain structure.
—
= mean lineal intercept length on a trans-
,
t
3. Terminology
versely oriented surface for a non-
equiaxed grain structure.
3.1 Definitions—For definitions of terms used in these test
—
= mean lineal intercept length on a planar
methods, see TerminologyE7.
,
p
oriented surface for a non-equiaxed grain
3.2 Definitions of Terms Specific to This Standard:
structure.
3.2.1 ASTM grain size number—the ASTM grain size
, = base intercept length of 32.00 mm for
number, G, was originally defined as:
defining the relationship between G and ,
G21
N 52 (1)
AE
(and N ) for macroscopically or micro-
L
where N is the number of grains per square inch at 100X scopically determined grain size by the
AE
magnification. To obtain the number per square millimetre at intercept method.
L = length of a test line.
1X, multiply by 15.50.
M = magnification used.
3.2.2 grain—that area within the confines of the original
M = magnification used by a chart picture
(primary) boundary observed on the two-dimensional plane-
b
series.
of-polish or that volume enclosed by the original (primary)
n = number of fields measured.
boundaryinthethree-dimensionalobject.Inmaterialscontain-
N = numberof agrainsinterceptedbythetest
a
ing twin boundaries, the twin boundaries are ignored, that is,
line in a two phase (constituent) micro-
the structure on either side of a twin boundary belongs to the
structure.
grain.
N = number of grains per mm at 1X.
A
N = number of a grains per mm at 1X in a
Aa
two phase (constituent) microstructure.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or N = number of grains per inch at 100X.
AE
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
N = N onalongitudinallyorientedsurfacefor
A, A
Standards volume information, refer to the standard’s Document Summary page on
a non-equiaxed grain structure.
the ASTM website.
E 112 – 96 (2004)
4.1.1 Comparison Procedure—The comparison procedure
N = N onatransverselyorientedsurfacefora
At A
does not require counting of either grains, intercepts, or
non-equiaxed grain structure.
intersectionsbut,asthenamesuggests,involvescomparisonof
N = N on a planar oriented surface for a
Ap A
the grain structure to a series of graded images, either in the
non-equiaxed grain structure.
form of a wall chart, clear plastic overlays, or an eyepiece
N = number of intercepts with a test line.
i
N = number of grains completely within a test
reticle. There appears to be a general bias in that comparison
Inside
circle. grain size ratings claim that the grain size is somewhat coarser
N = number of grains intercepted by the test
( ⁄2 to 1 G number lower) than it actually is (see X1.3.5).
Intercepted
circle.
Repeatability and reproducibility of comparison chart ratings
N = number of intercepts per unit length of
L are generally 61 grain size number.
test line.
4.1.2 Planimetric Procedure—The planimetric method in-
N = N onalongitudinallyorientedsurfacefor
L, L
volves an actual count of the number of grains within a known
a non-equiaxed grain structure.
area. The number of grains per unit area, N , is used to
A
N = N onatransverselyorientedsurfacefora
Lt 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 planar oriented surface for a
Lp 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
P = number of grain boundary intersections
i
repeatability and reproducibility are less than 60.5 grain size
with a test line.
units.An accurate count does require marking off of the grains
P = number of grain boundary intersections
L
as they are counted.
per unit length of test line.
4.1.3 Intercept Procedure—The intercept method involves
P = P onalongitudinallyorientedsurfacefor
L, L
an actual count of the number of grains intercepted by a test
a non-equiaxed grain structure.
line or the number of grain boundary intersections with a test
P = P onatransverselyorientedsurfacefora
Lt L
line, per unit length of test line, used to calculate the mean
non-equiaxed grain structure.
— —
P = P on a planar oriented surface for a lineal intercept length, ,. , is used to determine the ASTM
Lp L
non-equiaxed grain structure. grainsizenumber, G.Theprecisionofthemethodisafunction
Q = correction factor for comparison chart of the number of intercepts or intersections counted. A preci-
ratings using a non-standard magnifica-
sion of better than 60.25 grain size units can be attained with
tion for microscopically determined grain a reasonable amount of effort. Results are free of bias;
sizes.
repeatability and reproducibility are less than 60.5 grain size
Q = correction factor for comparison chart
units. Because an accurate count can be made without need of
m
ratings using a non-standard magnifica-
marking off intercepts or intersections, the intercept method is
tionformacroscopicallydeterminedgrain
faster than the planimetric method for the same level of
sizes.
precision.
s = standard deviation.
4.2 For specimens consisting of equiaxed grains, the
S = grain boundary surface area to volume
V method of comparing the specimen with a standard chart is
ratio for a single phase structure.
most convenient and is sufficiently accurate for most commer-
S = grain boundary surface area to volume
Va
cial purposes. For higher degrees of accuracy in determining
ratio for a two phase (constituent) struc-
averagegrainsize,theinterceptorplanimetricproceduresmay
ture.
be used. The intercept procedure is particularly useful for
t = students’ t multiplier for determination of
structures consisting of elongated grains.
the confidence interval.
4.3 In case of dispute, the intercept procedure shall be the
V = volume fraction of the a phase in a two
Va
referee procedure in all cases.
phase (constituent) microstructure.
4.4 Noattemptshouldbemadetoestimatetheaveragegrain
95 % CI = 95% confidence interval.
size of heavily cold-worked material. Partially recrystallized
% RA = percent relative accuracy.
wroughtalloysandlightlytomoderatelycold-workedmaterial
may be considered as consisting of non-equiaxed grains, if a
4. Significance and Use
grain size measurement is necessary.
4.1 These test methods cover procedures for estimating and
4.5 Individual grain measurements should not be made
rules for expressing the average grain size of all metals based on the standard comparison charts. These charts were
consisting entirely, or principally, of a single phase. The test
constructed to reflect the typical log-normal distribution of
methods may also be used for any structures having appear- grain sizes that result when a plane is passed through a
ances similar to those of the metallic structures shown in the three-dimensional array of grains. Because they show a distri-
comparison charts. The three basic procedures for grain size bution of grain dimensions, ranging from very small to very
estimation are: large, depending on the relationship of the planar section and
E 112 – 96 (2004)
the three-dimensional array of grains, the charts are not should be evaluated on at least two of the three principle
applicable to measurement of individual grains. planes, transverse, longitudinal, and planar (or radial and
transverse for round bar) and averaged as described in Section
5. Generalities of Application 16 to obtain the mean grain size. If directed test lines are used,
r
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