ASTM E930-18

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Designation: E930 − 99 (Reapproved 2015) E930 − 18
Standard Test Methods for
Estimating the Largest Grain Observed in a Metallographic
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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 as ALA (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
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 E112.
1.3 This standard does not purport to address all of the safety problems,concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and
determine the applicability of regulatory limitations prior to use.
1.4 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.
2. Referenced Documents
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2.1 ASTM Standards:
E3 Guide for Preparation of Metallographic Specimens
E7 Terminology Relating to Metallography
E112 Test Methods for Determining Average Grain Size
E407 Practice for Microetching Metals and Alloys
E1181 Test Methods for Characterizing Duplex Grain Sizes
2.2 ASTM Adjuncts:
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ALA Grain Size Visual Aid for Comparison Procedure (One Opaque Print and One Transparency)
3. Terminology
3.1 Definitions:
3.1.1 All For definitions of terms used in these test methods are either defined in methods, see Terminology E7, or are discussed
in 3.2.
3.2 Definitions of Terms Specific to This Standard:Definitions:
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This test method is under the jurisdiction of ASTM Committee E04 on Metallographyand is the direct responsibility of Subcommittee E04.08 on Grain Size.
Current edition approved Oct. 1, 2015Dec. 1, 2018. Published November 2015February 2019. Originally approved in 1983. Last previous edition approved in 20072015
as E930 – 99(2007).(2015). DOI: 10.1520/E0930-99R15.10.1520/E0930-18.
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volume information, refer to the standard’s Document Summary page on the ASTM website.
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E930 − 18
3.2.1 ALA grain, n—the largest grain observed in a random scatter of individual coarse grains comprising 5 % or less of the
specimen area, where the apparent grain size of thesethe coarse grainsgrain(s) differs by 3 or more ASTM grain size numbers from
the balance of the microstructure.
3.2.2 outlier grain, n—a grain substantially different in size from the predominant grain size in a microstructure; for example,
an ALA grain.
4. Significance and Use
4.1 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.
4.2 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.
4.3 These methods sh
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