ASTM E1181-87(1998)e1
(Test Method)Standard Test Methods for Characterizing Duplex Grain Sizes
Standard Test Methods for Characterizing Duplex Grain Sizes
SCOPE
1.1 These test methods provide simple guidelines for deciding whether a duplex grain size exists. The test methods separate duplex grain sizes into one of two distinct classes, then into specific types within those classes, and provide systems for grain size characterization of each type.
1.2 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 consult appropriate safety and health practices and determine the applicability of regulatory limitations prior to its use.
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e1
Designation: E 1181 – 87 (Reapproved 1998)
Standard Test Methods for
Characterizing Duplex Grain Sizes
This standard is issued under the fixed designation E 1181; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Paragraph 8.3.1.3 was corrected editorially in April 1998.
INTRODUCTION
Test methods are well established for the determination of average grain size, and estimation of
largest grain size, in products assumed to contain a single log-normal distribution of grain sizes. The
test methods in this standard are set forth to characterize grain size in products with any other
distributions of grain size.
The term “duplex grain size” is chosen to describe any of these other distributions of grain size,
because of its common usage and familiarity. However, the use of that term does not imply that only
two grain size distributions exist.
These test methods are equally aimed at describing the nature of the deviation from a single
log-normal distribution of grain sizes, and at describing with reasonable accuracy the distributions of
sizes that actually exist.
1. Scope 2.2 ASTM Adjuncts:
Comparison Chart for Estimation of Area Fractions
1.1 These test methods provide simple guidelines for decid-
ing whether a duplex grain size exists. The test methods
3. Terminology
separate duplex grain sizes into one of two distinct classes,
3.1 Definitions:
then into specific types within those classes, and provide
3.1.1 All terms used in these test methods are either defined
systems for grain size characterization of each type.
in Terminology E 7, or are discussed in 3.2.
1.2 This standard may involve hazardous materials, opera-
3.2 Definitions of Terms Specific to This Standard:
tions, and equipment. This standard does not purport to
3.2.1 grain size—equivalent in meaning to the average of a
address all of the safety concerns associated with its use. It is
distribution of grain sizes.
the responsibility of the user of this standard to consult
3.2.2 topologically varying—varying nonrandomly, in some
appropriate safety and health practices and determine the
definable pattern; that pattern may be related to the shape of the
applicability of regulatory limitations prior to its use.
specimen or product being examined.
2. Referenced Documents 3.2.3 bands or banding— in grain size, alternating areas of
significantly different grain sizes. These areas are usually
2.1 ASTM Standards:
2 elongated in a direction parallel to the direction of working.
E 3 Methods of Preparation of Metallographic Specimens
3.2.4 necklace or necklace structure—individual coarse
E 7 Terminology Relating to Metallography
grains surrounded by rings of significantly finer grains.
E 112 Test Methods for Determining the Average Grain
Size
4. Summary of Test Method
E 407 Practice for Microetching Metals and Alloys
4.1 These test methods provide means for recognizing the
E 562 Practice for Determining Volume Fraction by Sys-
presence of duplex grain size. The test methods separate duplex
tematic Manual Point Count
2 grain sizes into two classes (randomly varying, and topologi-
E 883 Guide for Metallographic Photomicrography
cally varying), and define specific types of duplex grain sizes
E 930 Test Methods for Estimating the Largest Grain Ob-
2 within these classes. The test methods provide means for
served in a Metallographic Section (ALA Grain Size)
estimating area fractions occupied by distinct grain sizes, and
offer existing standard methods (Methods E 112, Methods
E 930) for determining grain size in specific identified areas.
These test methods are under the jurisdiction of ASTM Committee E-4 on
Metallography and are the direct responsibility of Subcommittee E04.08 on Grain
Size.
Current edition approved Aug. 28, 1987. Published October 1987. This comparison chart shows different area percentages of light grains among
Annual Book of ASTM Standards, Vol 03.01. dark grains. Available from ASTM Headquarters. Order Adjunct: ADJE1181.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 1181
The test methods provide for reporting of specific, distinctive 6. Apparatus
information for each type of duplex grain size. And, as an
6.1 Certain items may be helpful or necessary in applying
alternative, the test methods offer a procedure for statistically
the various procedures of these test methods. These items are
determining the distribution of all the grain sizes present in a
briefly described below, under the headings of the specific
duplex grain size specimen.
procedures to which they apply.
6.1.1 Comparison Procedure for Estimation of Area
5. Significance and Use
Fractions—This procedure requires the use of a comparison
chart to improve the accuracy of visual estimates of area
5.1 Duplex grain size may occur in some metals and alloys
fractions occupied by distinct grain sizes. This comparison
as a result of their thermomechanical processing history. For
chart is shown in Fig. 1 . The chart shows different area
comparison of mechanical properties with metallurgical fea-
percentages of light grains among dark grains.
tures, or for specification purposes, it may be important to be
6.1.2 Point Count Procedure for Estimation of Area
able to characterize grain size in such materials. Assigning an
Fractions—This procedure requires the use of a test grid on a
average grain size value to a duplex grain size specimen does
transparent overlay, or in a reticle, that can be superimposed on
not adequately characterize the appearance of that specimen,
the specimen image. The grid should consist of equally spaced
and may even misrepresent its appearance. For example,
points formed by the intersection of fine lines. Practice E 562
averaging two distinctly different grain sizes may result in
reporting a size that does not actually exist anywhere in the
specimen.
Leidheiser, H., Jr. and Kim, D. K., “A Chemical Test for Identifying the
5.2 These test methods may be applied to specimens or
Fraction of Grains in the Surface of Galvanized Steel Sheet That Have Orientations
products containing randomly intermingled grains of two or Approximating (0001)—Importance to Paint Adherence,” Metallurgical Transac-
tions “B,” American Society for Metals, Metals Park, OH 44073, December, 1978,
more significantly different sizes (henceforth referred to as
p. 590.
random duplex grain size). Examples of random duplex grain
sizes include: isolated coarse grains in a matrix of much finer
grains, extremely wide distributions of grain sizes, and bimodal
distributions of grain size.
5.3 These test methods may also be applied to specimens or
products containing grains of two or more significantly differ-
ent sizes, but distributed in topologically varying patterns
(henceforth referred to as topological duplex grain sizes).
Examples of topological duplex grain sizes include: systematic
variation of grain size across the section of a product, necklace
structures, banded structures, and germinative grain growth in
selected areas of critical strain.
5.4 These test methods may be applied to specimens or
products regardless of their state of recrystallization.
5.5 Because these test methods describe deviations from a
single, log-normal distribution of grain sizes, and characterize
patterns of variation in grain size, the total specimen cross-
section must be evaluated.
5.6 These test methods are limited to duplex grain sizes as
identifiable within a single polished and etched metallurgical
specimen. If duplex grain size is suspected in a product too
large to be polished and etched as a single specimen, macro-
etching should be considered as a first step in evaluation. The
entire macroetched cross-section should be used as a basis for
estimating area fractions occupied by distinct grain sizes, if
possible. If microscopic examination is subsequently neces-
sary, individual specimens must be taken to allow estimation of
area fractions for the entire product cross-section, and to allow
determination of grain sizes representing the entire cross-
section as well.
5.7 These test methods are intended to be applied to duplex
grain sizes. Duplex grain structures (for example, multiphase
alloys) are not necessarily duplex in grain size, and as such are
not the subject of these methods. However, the test methods
FIG. 1 Comparison Chart for Estimation of Area Fractions
described here for area fraction estimation may be of use in
(Showing area percentages of light grains among dark grains)
describing duplex grain structures.
E 1181
gives examples of such grids, as well as details on recom- through the use of a semi-automated image analysis system
mended grid spacing, and use of the grid. with a digitizing tablet and electronic pencil or cursor. The use
6.1.3 Planimetric Procedure for Estimation of Area of this equipment is also described in 8.7.
Fractions—This procedure requires the use of a planimeter, a
7. Sampling and Test Specimens
device for measuring the areas of irregular polygons. The
regions occupied by a distinct grain size are manually outlined 7.1 Sampling:
on a photomicrograph or transparent overlay. The area of each
7.1.1 These test methods are intended to characterize pat-
of those regions is then measured by tracing its outline with the terns of variation in grain size, when they occur in a given
planimeter.
specimen or product. To characterize these patterns accurately,
6.1.4 Methods E 930, Comparison Procedure for Estimation the entire cross-section of the specimen or product must be
of Largest Grain Size Observed.
evaluated.
6.1.4.1 This procedure requires the use of a visual aid for 7.1.2 If variations in grain size occur in a product too large
estimation of the size of the largest grain found in a given
to be polished and etched as a single specimen, individual
metallographic section. That visual aid is shown in Methods specimens must be taken to allow estimation of area fractions
E 930, and is available as an ASTM Adjunct (see Methods
for the entire product cross-section, and to allow determination
E 930 for details). of grain sizes representing the entire cross-section as well.
6.1.5 Methods E 930, Measuring Procedure for Estimation
7.2 Specimen Orientation:
of Largest Grain Size Observed. 7.2.1 All of the types of duplex grain size described in this
6.1.5.1 This procedure may require the use of a measuring
test method (see 3.2 and 8.3) can be detected in a longitudinal
microscope eyepiece or measuring microscope reticle. These
specimen orientation (that is, in a plane parallel to the direction
are available from microscope manufacturers. of maximum product deformation, during manufacture). Ac-
6.1.6 Methods E 930, Referee Procedure for Estimation of
cordingly, the longitudinal orientation is recommended, with
Largest Grain Size Observed. one exception. If the specimen being examined is the full
6.1.6.1 This procedure requires the use of a test grid on a
cross-section of a round bar, the longitudinal section should not
transparent overlay that can be superimposed on the specimen be used to estimate the area fraction occupied by different grain
image. The test grid consists of a square network of grid lines,
sizes. That estimate can be made most accurately only on a
with a recommended interline spacing of 5 mm. Use of the grid transverse section. For a tubular product, estimates of area
is described in Methods E 930.
fractions made on longitudinal sections are reasonable approxi-
6.1.7 Test Methods E 112, Comparison Procedure for De- mations of the same estimates made on transverse sections. For
termination of Average Grain Size.
all other products, area fraction estimates should be equally
6.1.7.1 This procedure requires the use of grain size com- accurate with either specimen orientation.
parison charts or overlay transparencies, or grain size compari-
7.2.2 Other specimen orientations may be used, provided
son reticles fitted into microscopes. Various comparison charts that their limitations are recognized. For instance, banding
and overlay transparencies are available as ASTM adjuncts
present in a given specimen may not be easily recognizable in
(see Methods E 112 for details). a transverse orientation.
6.1.7.2 Grain size comparison reticles are available from
7.2.3 The specimen orientation used should be reported
various manufacturers of microscopes. along with the duplex grain size characterization.
6.1.8 Methods E 112, Intercept Procedures for Determina-
8. Procedure
tion of Average Grain Size,
6.1.8.1 The Intercept Procedures of Methods E 112 require
8.1 Specimen Preparation—Prepare specimens according
the use of patterns of test lines, usually on transparent overlays.
to Methods E 3, and etch specimens in accordance with
The use of these is described in detail in Methods E 112. A
Practice E 407. Etch specimens so that all grain boundaries are
transparency of one such pattern is available as an ASTM
distinct and easily visible.
adjunct (see Methods E 112 for details).
8.2 Preparation of Photomicrographs— If photomicro-
6.1.9 Statistical Determination of Grain Size Distribution:
graphs are required for characterizing duplex grain size,
6.1.9.1 This procedure requires the use of a test grid on a
prepare them in accordance with Practice E 883.
transparent overlay that can be superimposed on the specimen
8.3 Recognizing and Classifying Duplex Grain Size:
image. The test grid consists of a series of fine, parallel lines,
8.3.1 A random duplex grain size is defined as any of the
with an interline spacing of 5 mm. Use of the grid is described
following:
in 8.7.
8.3.1.1 The presence of randomly distributed individual
6.1.9.2 This procedure may be carried out using manual
coarse grains, differing in size by three or more ASTM grain
measuring and counting techniques, but as such, will be very
size numbers from the average size of the balance of the grains
laborious and time-consuming. This procedure can be carried
(henceforth referred to as the ALA (As Large As) condition).
out much more efficiently through the use of an automated
These individual coarse grains should comprise 5 % or less of
image analysis system with an electronic pencil or cursor, or
the area of the specimen. If they comprise more than 5 % of the
A Keuffel & Esser Compensating Polar Planimeter available from drafting
equipment suppliers, or equivalent, has been found to be satisfactory for this A Zeiss Videoplan System, or its equivalent, has been found sati
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