ASTM E930-99(2007)
(Test Method)Standard Test Methods for Estimating the Largest Grain Observed in a Metallographic Section (ALA Grain Size)
Standard Test Methods for Estimating the Largest Grain Observed in a Metallographic Section (ALA Grain Size)
SIGNIFICANCE AND USE
The presence of large grains has been correlated with anomalous mechanical behavior in, for example, crack initiation, crack propagation, and fatigue. Thus there is engineering justification for reporting the ALA grain size.
These methods shall only be used with the presence of outlier coarse grains, 3 or more ASTM grain size numbers larger than the rest of the microstructure and comprising 5 % or less of the specimen area. A typical example is shown in Annex A1 as Fig. A1.1.
These methods shall not be used for the determination of average grain size, which is treated in Test Methods E 112. Examples of microstructures that do not qualify for ALA treatment are shown in Annex A1 as Fig. A1.2, Fig. A1.3, and Fig. A1.4.
These methods may be applied in the characterization of duplex grain sizes, as instructed in the procedures for Test Methods E 1181.
SCOPE
1.1 These test methods describe simple manual procedures for measuring the size of the largest grain cross-section observed on a metallographically prepared plane section.
1.2 These test methods shall only be valid for microstructures containing outlier coarse grains, where their population is too sparse for grain size determination by Test Methods E 112.
1.3 This standard does not purport to address all of the safety problems, 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: E930 − 99(Reapproved 2007)
Standard Test Methods for
Estimating the Largest Grain Observed in a Metallographic
Section (ALA Grain Size)
This standard is issued under the fixed designation E930; 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 (´) 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
Commercial material specifications sometimes include, in size limits for grain structures, the need
for identification of the largest grain observed in a sample, often expressed asALA(as large as) grain
size. The methods presented here are for use when the number of large grains is too few for
measurement by Test Methods E112. It shall be understood that larger (but unobserved) grains may
exist in the local volume sampled.
1. Scope 2.2 ASTM Adjuncts:
ALAGrain SizeVisualAid for Comparison Procedure (One
1.1 These test methods describe simple manual procedures
Opaque Print and One Transparency)
for measuring the size of the largest grain cross-section
observed on a metallographically prepared plane section.
3. Terminology
1.2 These test methods shall only be valid for microstruc-
3.1 Definitions:
tures containing outlier coarse grains, where their population is
3.1.1 All terms used in these test methods are either defined
too sparse for grain size determination by Test Methods E112.
in Terminology E7, or are discussed in 3.2.
3.2 Definitions of Terms Specific to This Standard:
1.3 This standard does not purport to address all of the
3.2.1 ALA grain, n—the largest grain observed in a random
safety problems, if any, associated with its use. It is the
scatterofindividualcoarsegrainscomprising5 %orlessofthe
responsibility of the user of this standard to establish appro-
specimen area, where the apparent grain size of these coarse
priate safety and health practices and determine the applica-
grains differs by 3 or moreASTM grain size numbers from the
bility of regulatory limitations prior to use.
balance of the microstructure.
2. Referenced Documents
3.2.2 outlier grain, n—a grain substantially different in size
2.1 ASTM Standards: from the predominant grain size in a microstructure; for
example, an ALA grain.
E3 Guide for Preparation of Metallographic Specimens
E7 Terminology Relating to Metallography
4. Significance and Use
E112 Test Methods for Determining Average Grain Size
4.1 The presence of large grains has been correlated with
E407 Practice for Microetching Metals and Alloys
anomalous mechanical behavior in, for example, crack
E1181 Test Methods for Characterizing Duplex Grain Sizes
initiation, crack propagation, and fatigue. Thus there is engi-
neering justification for reporting the ALA grain size.
This test method is under the jurisdiction of ASTM Committee E04 on
4.2 These methods shall only be used with the presence of
Metallographyand is the direct responsibility of Subcommittee E04.08 on Grain
outlier coarse grains, 3 or more ASTM grain size numbers
Size.
largerthantherestofthemicrostructureandcomprising5 %or
Current edition approved Oct. 1, 2007. Published October 2007. Originally
approved in 1983. Last previous edition approved in 1999 as E930 – 99. DOI:
lessofthespecimenarea.AtypicalexampleisshowninAnnex
10.1520/E0930-99R07.
A1 as Fig. A1.1.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
Available from ASTM International Headquarters. Order Adjunct No.
the ASTM website.
ADJE0930.
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E930 − 99 (2007)
TABLE 1 Relationship of ALA Grain Area to ALA Micro-Grain Size
4.3 Thesemethodsshallnotbeusedforthedeterminationof
A
Number
average grain size, which is treated in Test Methods E112.
Area, mm Size
Examples of microstructures that do not qualify for ALA
2.06 00000 or − 4.0
treatment are shown in Annex A1 as Fig. A1.2, Fig. A1.3, and
1.46 −3.5
Fig. A1.4.
1.03 0000 or − 3.0
0.703 −2.5
4.4 These methods may be applied in the characterization of
0.516 000 or − 2.0
duplex grain sizes, as instructed in the procedures for Test
0.365 −1.5
0.258 00 or − 1.0
Methods E1181.
0.182 −0.5
0.129 0
5. Sampling
0.0912 0.5
0.0645 1.0
5.1 Sampling shall have been performed according to sam-
0.0456 1.5
pling procedures in Test Method E112.
0.0323 2.0
0.0228 2.5
5.2 Thegenerallyintendedplaneofpolishisaplanepassing
0.0161 3.0
through the center of the thickness and exhibiting maximum 0.0114 3.5
0.00807 4.0
grain aspect ratio.
0.00570 4.5
0.00403 5.0
5.3 Other polishing planes which may be more useful or
0.00285 5.5
predictive in specific products or applications are allowed.
0.00202 6.0
0.00143 6.5
5.4 An unambiguous description of the plane of polish or a
0.00101 7.0
reference to a description or drawing of the plane of polish
A
Adapted from Test Methods E112, Table 2.
shall be a part of the test report.
5.5 Specimens shall be prepared in accordance with Meth-
ods E3 and Practice E407.
6.3.4 Divide this area by the square of the magnification
6. Procedures
used, to obtain the true grain area at 1X.
6.3.5 Compare this area with the grain areas in Table 1. Use
6.1 In 6.2 a comparison procedure is presented with accu-
the nearest area in the table to obtain the ALA grain size
racy near to 61ASTM grain size number, for the apparent size
number,unlessthenextsmallerorthenextlargerareaisagreed
of the largest grain. For greater accuracy, a measuring proce-
upon between the interested parties.
dureisdescribedin6.3.Amanualquantitativemethod,toserve
as referee procedure, is described in 6.4. (The measuring
NOTE 2—Any automatic or semiautom
...
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