1、Designation: E 930 99 (Reapproved 2007)Standard Test Methods forEstimating the Largest Grain Observed in a MetallographicSection (ALA Grain Size)1This standard is issued under the fixed designation E 930; the number immediately following the designation indicates the year oforiginal adoption or, in
2、the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript 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.INTRODUCTIONCo
3、mmercial material specifications sometimes include, in size limits for grain structures, the needfor identification of the largest grain observed in a sample, often expressed as ALA (as large as) grainsize. The methods presented here are for use when the number of large grains is too few formeasurem
4、ent by Test Methods E112. It shall be understood that larger (but unobserved) grains mayexist in the local volume sampled.1. Scope1.1 These test methods describe simple manual proceduresfor measuring the size of the largest grain cross-sectionobserved on a metallographically prepared plane section.1
5、.2 These test methods shall only be valid for microstruc-tures containing outlier coarse grains, where their population istoo sparse for grain size determination by Test Methods E112.1.3 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is there
6、sponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic SpecimensE7 Terminology Relating to Metallogra
7、phyE112 Test Methods for Determining Average Grain SizeE 407 Practice for Microetching Metals and AlloysE 1181 Test Methods for Characterizing Duplex Grain Sizes2.2 ASTM Adjuncts:ALA Grain Size Visual Aid for Comparison Procedure (OneOpaque Print and One Transparency)33. Terminology3.1 Definitions:3
8、.1.1 All terms used in these test methods are either definedin Terminology E7, or are discussed in 3.2.3.2 Definitions of Terms Specific to This Standard:3.2.1 ALA grain, nthe largest grain observed in a randomscatter of individual coarse grains comprising 5 % or less of thespecimen area, where the
9、apparent grain size of these coarsegrains differs by 3 or more ASTM grain size numbers from thebalance of the microstructure.3.2.2 outlier grain, na grain substantially different in sizefrom the predominant grain size in a microstructure; forexample, an ALA grain.4. Significance and Use4.1 The prese
10、nce of large grains has been correlated withanomalous mechanical behavior in, for example, crack initia-tion, crack propagation, and fatigue. Thus there is engineeringjustification for reporting the ALA grain size.4.2 These methods shall only be used with the presence ofoutlier coarse grains, 3 or m
11、ore ASTM grain size numberslarger than the rest of the microstructure and comprising 5 % orless of the specimen area.Atypical example is shown inAnnexA1 as Fig. A1.1.4.3 These methods shall not be used for the determination ofaverage grain size, which is treated in Test Methods E112.Examples of micr
12、ostructures that do not qualify for ALAtreatment are shown in Annex A1 as Fig. A1.2, Fig. A1.3, andFig. A1.4.4.4 These methods may be applied in the characterization ofduplex grain sizes, as instructed in the procedures for TestMethods E 1181.1This test method is under the jurisdiction of ASTM Commi
13、ttee E04 onMetallography and is the direct responsibility of Subcommittee E04.08 on GrainSize.Current edition approved Oct. 1, 2007. Published October 2007. Originallyapproved in 1983. Last previous edition approved in 1999 as E 930 99.2For referenced ASTM standards, visit the ASTM website, www.astm
14、.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from ASTM International Headquarters. Order Adjunct No.ADJE0930.1Copyright ASTM International, 100 Barr Harbor Dri
15、ve, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Sampling5.1 Sampling shall have been performed according to sam-pling procedures in Test Method E112.5.2 The generally intended plane of polish is a plane passingthrough the center of the thickness and exhibiting maximumgrain aspect
16、 ratio.5.3 Other polishing planes which may be more useful orpredictive in specific products or applications are allowed.5.4 An unambiguous description of the plane of polish or areference to a description or drawing of the plane of polishshall be a part of the test report.5.5 Specimens shall be pre
17、pared in accordance with Meth-ods E3and Practice E 407.6. Procedures6.1 In 6.2 a comparison procedure is presented with accu-racy near to 61ASTM grain size number, for the apparent sizeof the largest grain. For greater accuracy, a measuring proce-dure is described in 6.3.Amanual quantitative method,
18、 to serveas referee procedure, is described in 6.4. (The measuringprocedure is especially recommended over the comparisonprocedure when the ALA grain sections shape is substantiallydifferent from those shown in Annex A2.)6.2 Comparison Procedure:6.2.1 Scan the entire microsection at a convenient mag
19、nifi-cation to locate the larger grains.6.2.2 Position the largest grain in the middle of the micro-scope viewing screen, eyepiece, or on a photomicrograph.6.2.3 Estimate the grain size by comparing theALAgrain toa visual aid that is based on the relationship of area to grain sizeexpressed in Table
20、1. Examples of visual aids are shown inAnnex A2, with their specifications in Annex A3. Figure A2.1may be used only at the magnification specified on the aid.NOTE 1The use of Test Methods E112 comparison plates is notallowed, since few of the grain sections illustrated correspond to theaverage area
21、for that grain size number.6.3 Measuring Procedure (for greater accuracy than withcomparison procedure):6.3.1 Locate and position the largest grain in a microscopeimage or in a photomicrograph, as in 6.2.1 and 6.2.2.6.3.2 Using a measuring eyepiece, internal reticle, or exter-nal scale, as appropria
22、te, measure the maximum caliper diam-eter and the caliper diameter perpendicular to the maximumcaliper diameter.6.3.3 Multiply the product of these two measurements by0.785, to obtain the area of an ellipse with axes equal to thecaliper diameters at the magnification used.6.3.4 Divide this area by t
23、he square of the magnificationused, to obtain the true grain area at 1X.6.3.5 Compare this area with the grain areas in Table 1. Usethe nearest area in the table to obtain the ALA grain sizenumber, unless the next smaller or the next larger area is agreedupon between the interested parties.NOTE 2Any
24、 automatic or semiautomatic measuring device whichprovides the area of a grain section can also be used within the frameworkof this manual method.6.4 Referee Procedure:6.4.1 Photograph the largest grain, using the largest magni-fication that shows the entire grain in the image area. (In caseof uncer
25、tainty about which of several grain sections is thelargest, photograph them all and carry out the following stepsfor all of the photographs.)6.4.2 Apply a transparent overlay containing a square net-work of grid lines to the photograph, so that the large grain iscompletely covered by the grid. An in
26、terline grid spacing of 5mm is recommended. Count the number of grid intersections(points) that fall within the large grain being estimated. Pointsfalling on the grain boundary are counted as one half.6.4.3 Reapply the overlay to the photo at least four moretimes at different angular placements, eac
27、h time tallying thegrid intersections as in 6.4.2.6.4.4 The estimated area of the grain section is determinedby the following equation:A 5P u! d2M2where:P u! = number of points falling within the grain averagedover several angles,d2= area of each small square of the grid with spacingd,M = magnificat
28、ion of the photomicrograph, andA = estimated area of the grain section.6.4.5 Compare the area determined with the area column inTable 1. Use the nearest area in the table to report the ALAgrain size number, unless the next smaller or the next largerarea is agreed upon between the interested parties.
29、6.4.6 Retain the photomicrograph, and record the following:grid points counted for each grid placement, Pi(u); total gridpoints counted, (Pi(u); average number of grid points counted,Pu!; inter-point spacing in grid, d; magnification used, M;measured area of ALA grain, A; and the ALA grain sizenumbe
30、r.TABLE 1 Relationship of ALA Grain Area to ALA Micro-GrainSize NumberAArea, mm2Size2.06 00000 or 4.01.46 3.51.03 0000 or 3.00.703 2.50.516 000 or 2.00.365 1.50.258 00 or 1.00.182 0.50.129 00.0912 0.50.0645 1.00.0456 1.50.0323 2.00.0228 2.50.0161 3.00.0114 3.50.00807 4.00.00570 4.50.00403 5.00.00285
31、 5.50.00202 6.00.00143 6.50.00101 7.0AAdapted from Test Methods E112, Table 2.E 930 99 (2007)27. Precision and Bias7.1 The precision and bias of these methods have not yetbeen determined.8. Keywords8.1 ALA grain; caliper diameter; comparison procedure;ellipse measurement; grain size; largest grain;
32、measuringprocedure; metallography; microstructure; outlier grain; point-count procedureANNEXES(Mandatory Information)A1. MICROSTRUCTURAL EXAMPLESNOTE A1.1These figures are taken from Test Methods E 1181,AnnexA1.FIG. A1.1 1253, ALA Condition Rateable to E 930E 930 99 (2007)3FIG. A1.2 503, Wide-Range
33、Condition Not Rateable to E 930FIG. A1.3 1003, Bimodal Condition Not Rateable to E 930E 930 99 (2007)4FIG. A1.4 1003, Necklace Condition Not Rateable to E 930E 930 99 (2007)5A2. ALA GRAIN SIZE VISUAL AID FOR 6.2, COMPARISON PROCEDUREA3. DIMENSIONS FOR Fig. A2.1ASTM International takes no position re
34、specting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This
35、 standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM Inter
36、national Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown b
37、elow.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-955
38、5 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).NOTE 1This reduced illustration is for information purposes only.FIG. A2.1 ALA Grain Size Visual AidLetterArea,mm2Diameters of Figures, mmACircle1:2 Ellipse 1:4 EllipseMajor Minor Major MinorA 645 28.7 40.5 20.3 57.3 14.3B 456 24.1 34.1 17.0 48.2 12.0C 323 20.3 28.7 14.3 40.6 10.1D 228 17.0 24.1 12.0 34.1 8.5E 161 14.3 20.2 10.1 28.6 7.2ARounded to nearest 0.1 mm.E 930 99 (2007)6
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