ASTM E1181-2002 Standard Test Methods for Characterizing Duplex Grain Sizes《描述双颗粒尺寸特征的标准试验方法》.pdf

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1、Designation: E 1181 02Standard Test Methods forCharacterizing Duplex Grain Sizes1This standard is issued under the fixed designation E 1181; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in par

2、entheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONTest methods are well established for the determination of average grain size, and estimation oflargest grain size, in products assumed to contain

3、a single log-normal distribution of grain sizes. Thetest methods in this standard are set forth to characterize grain size in products with any otherdistributions of grain size.The term “duplex grain size” is chosen to describe any of these other distributions of grain size,because of its common usa

4、ge and familiarity. However, the use of that term does not imply that onlytwo grain size distributions exist.These test methods are equally aimed at describing the nature of the deviation from a singlelog-normal distribution of grain sizes, and at describing with reasonable accuracy the distribution

5、s ofsizes that actually exist.1. Scope1.1 These test methods provide simple guidelines for decid-ing whether a duplex grain size exists. The test methodsseparate duplex grain sizes into one of two distinct classes,then into specific types within those classes, and providesystems for grain size chara

6、cterization of each type.1.2 This standard may involve hazardous materials, opera-tions, and equipment. This standard does not purport toaddress all of the safety concerns associated with its use. It isthe responsibility of the user of this standard to consultappropriate safety and health practices

7、and determine theapplicability of regulatory limitations prior to its use.2. Referenced Documents2.1 ASTM Standards:E3 Methods of Preparation of Metallographic Specimens2E7 Terminology Relating to Metallography2E112 Test Methods for Determining the Average GrainSize2E 407 Practice for Microetching M

8、etals and Alloys2E 562 Practice for Determining Volume Fraction by Sys-tematic Manual Point Count2E 883 Guide for Metallographic Photomicrography2E 930 Test Methods for Estimating the Largest Grain Ob-served in a Metallographic Section (ALA Grain Size)22.2 ASTM Adjuncts:Comparison Chart for Estimati

9、on of Area Fractions33. Terminology3.1 Definitions:3.1.1 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 bands or bandingin grain size, alternating areas ofsignificantly different grain sizes.

10、These areas are usuallyelongated in a direction parallel to the direction of working.3.2.2 grain sizeequivalent in meaning to the average of adistribution of grain sizes.3.2.3 necklace or necklace structureindividual coarsegrains surrounded by rings of significantly finer grains.3.2.4 topologically

11、varyingvarying nonrandomly, in somedefinable pattern; that pattern may be related to the shape of thespecimen or product being examined.4. Summary of Test Method4.1 These test methods provide means for recognizing thepresence of duplex grain size. The test methods separate duplexgrain sizes into two

12、 classes (randomly varying, and topologi-cally varying), and define specific types of duplex grain sizeswithin these classes. The test methods provide means forestimating area fractions occupied by distinct grain sizes, andoffer existing standard methods (Methods E112, MethodsE 930) for determining

13、grain size in specific identified areas.1These test methods are under the jurisdiction of ASTM Committee E04 onMetallography and are the direct responsibility of Subcommittee E04.08 on GrainSize.Current edition approved April 10, 2002. Published June 2002. Originallypublished as E 118194. Last previ

14、ous edition E 118194(1998).2Annual Book of ASTM Standards, Vol 03.01.3This comparison chart shows different area percentages of light grains amongdark grains. Available from ASTM Headquarters. Order Adjunct: ADJE1181.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke

15、n, PA 19428-2959, United States.The test methods provide for reporting of specific, distinctiveinformation for each type of duplex grain size. And, as analternative, the test methods offer a procedure for statisticallydetermining the distribution of all the grain sizes present in aduplex grain size

16、specimen.5. Significance and Use5.1 Duplex grain size may occur in some metals and alloysas a result of their thermomechanical processing history. Forcomparison of mechanical properties with metallurgical fea-tures, or for specification purposes, it may be important to beable to characterize grain s

17、ize in such materials. Assigning anaverage grain size value to a duplex grain size specimen doesnot adequately characterize the appearance of that specimen,and may even misrepresent its appearance. For example,averaging two distinctly different grain sizes may result inreporting a size that does not

18、 actually exist anywhere in thespecimen.5.2 These test methods may be applied to specimens orproducts containing randomly intermingled grains of two ormore significantly different sizes (henceforth referred to asrandom duplex grain size). Examples of random duplex grainsizes include: isolated coarse

19、 grains in a matrix of much finergrains, extremely wide distributions of grain sizes, and bimodaldistributions of grain size.5.3 These test methods may also be applied to specimens orproducts containing grains of two or more significantly differ-ent sizes, but distributed in topologically varying pa

20、tterns(henceforth referred to as topological duplex grain sizes).Examples of topological duplex grain sizes include: systematicvariation of grain size across the section of a product, necklacestructures, banded structures, and germinative grain growth inselected areas of critical strain.5.4 These te

21、st methods may be applied to specimens orproducts regardless of their state of recrystallization.5.5 Because these test methods describe deviations from asingle, log-normal distribution of grain sizes, and characterizepatterns of variation in grain size, the total specimen cross-section must be eval

22、uated.5.6 These test methods are limited to duplex grain sizes asidentifiable within a single polished and etched metallurgicalspecimen. If duplex grain size is suspected in a product toolarge to be polished and etched as a single specimen, macro-etching should be considered as a first step in evalu

23、ation. Theentire macroetched cross-section should be used as a basis forestimating area fractions occupied by distinct grain sizes, ifpossible. If microscopic examination is subsequently neces-sary, individual specimens must be taken to allow estimation ofarea fractions for the entire product cross-

24、section, and to allowdetermination of grain sizes representing the entire cross-section as well.5.7 These test methods are intended to be applied to duplexgrain sizes. Duplex grain structures (for example, multiphasealloys) are not necessarily duplex in grain size, and as such arenot the subject of

25、these methods. However, the test methodsdescribed here for area fraction estimation may be of use indescribing duplex grain structures.6. Apparatus6.1 Certain items may be helpful or necessary in applyingthe various procedures of these test methods. These items arebriefly described below, under the

26、headings of the specificprocedures to which they apply.6.1.1 Comparison Procedure for Estimation of AreaFractionsThis procedure requires the use of a comparisonchart to improve the accuracy of visual estimates of areafractions occupied by distinct grain sizes. This comparisonchart is shown in Fig. 1

27、4. The chart shows different areapercentages of light grains among dark grains.6.1.2 Point Count Procedure for Estimation of AreaFractionsThis procedure requires the use of a test grid on atransparent overlay, or in a reticle, that can be superimposed onthe specimen image. The grid should consist of

28、 equally spacedpoints formed by the intersection of fine lines. Practice E 5624Leidheiser, H., Jr and Kim, D. K., “A Chemical Test for Identifying theFraction of Grains in the Surface of Galvanized Steel Sheet That Have OrientationsApproximating (0001)Importance to Paint Adherence,” Metallurgical Tr

29、ansac-tions “B,” American Society for Metals, Metals Park, OH 44073, December, 1978,p. 590.FIG. 1 Comparison Chart for Estimation of Area Fractions1(Showing area percentages of light grains among dark grains)E1181022gives examples of such grids, as well as details on recom-mended grid spacing, and u

30、se of the grid.6.1.3 Planimetric Procedure for Estimation of AreaFractionsThis procedure requires the use of a planimeter, adevice for measuring the areas of irregular polygons. Theregions occupied by a distinct grain size are manually outlinedon a photomicrograph or transparent overlay. The area of

31、 eachof those regions is then measured by tracing its outline with theplanimeter.56.1.4 Methods E 930, Comparison Procedure for Estimationof Largest Grain Size Observed.6.1.4.1 This procedure requires the use of a visual aid forestimation of the size of the largest grain found in a givenmetallograph

32、ic section. That visual aid is shown in MethodsE 930, and is available as an ASTM Adjunct (see MethodsE 930 for details).6.1.5 Methods E 930, Measuring Procedure for Estimationof Largest Grain Size Observed.6.1.5.1 This procedure may require the use of a measuringmicroscope eyepiece or measuring mic

33、roscope reticle. Theseare available from microscope manufacturers.6.1.6 Methods E 930, Referee Procedure for Estimation ofLargest Grain Size Observed.6.1.6.1 This procedure requires the use of a test grid on atransparent overlay that can be superimposed on the specimenimage. The test grid consists o

34、f a square network of grid lines,with a recommended interline spacing of 5 mm. Use of the gridis described in Methods E 930.6.1.7 Test Methods E112, Comparison Procedure for De-termination of Average Grain Size.6.1.7.1 This procedure requires the use of grain size com-parison charts or overlay trans

35、parencies, or grain size compari-son reticles fitted into microscopes. Various comparison chartsand overlay transparencies are available as ASTM adjuncts(see Methods E112for details).6.1.7.2 Grain size comparison reticles are available fromvarious manufacturers of microscopes.6.1.8 Methods E112, Int

36、ercept Procedures for Determina-tion of Average Grain Size,6.1.8.1 The Intercept Procedures of Methods E112requirethe use of patterns of test lines, usually on transparent overlays.The use of these is described in detail in Methods E112.Atransparency of one such pattern is available as an ASTMadjunc

37、t (see Methods E112for details).6.1.9 Statistical Determination of Grain Size Distribution:6.1.9.1 This procedure requires the use of a test grid on atransparent overlay that can be superimposed on the specimenimage. The test grid consists of a series of fine, parallel lines,with an interline spacin

38、g of 5 mm. Use of the grid is describedin 8.7.6.1.9.2 This procedure may be carried out using manualmeasuring and counting techniques, but as such, will be verylaborious and time-consuming. This procedure can be carriedout much more efficiently through the use of an automatedimage analysis system wi

39、th an electronic pencil or cursor, orthrough the use of a semi-automated image analysis systemwith a digitizing tablet and electronic pencil or cursor.6The useof this equipment is also described in 8.7.7. Sampling and Test Specimens7.1 Sampling:7.1.1 These test methods are intended to characterize p

40、at-terns of variation in grain size, when they occur in a givenspecimen or product. To characterize these patterns accurately,the entire cross-section of the specimen or product must beevaluated.7.1.2 If variations in grain size occur in a product too largeto be polished and etched as a single speci

41、men, individualspecimens must be taken to allow estimation of area fractionsfor the entire product cross-section, and to allow determinationof grain sizes representing the entire cross-section as well.7.2 Specimen Orientation:7.2.1 All of the types of duplex grain size described in thistest method (

42、see 3.2 and 8.3) can be detected in a longitudinalspecimen orientation (that is, in a plane parallel to the directionof maximum product deformation, during manufacture). Ac-cordingly, the longitudinal orientation is recommended, withone exception. If the specimen being examined is the fullcross-sect

43、ion of a round bar, the longitudinal section should notbe used to estimate the area fraction occupied by different grainsizes. That estimate can be made most accurately only on atransverse section. For a tubular product, estimates of areafractions made on longitudinal sections are reasonable approxi

44、-mations of the same estimates made on transverse sections. Forall other products, area fraction estimates should be equallyaccurate with either specimen orientation.7.2.2 Other specimen orientations may be used, providedthat their limitations are recognized. For instance, bandingpresent in a given

45、specimen may not be easily recognizable ina transverse orientation.7.2.3 The specimen orientation used should be reportedalong with the duplex grain size characterization.8. Procedure8.1 Specimen PreparationPrepare specimens accordingto Methods E3, and etch specimens in accordance withPractice E 407

46、. Etch specimens so that all grain boundaries aredistinct and easily visible.8.2 Preparation of PhotomicrographsIf photomicro-graphs are required for characterizing duplex grain size,prepare them in accordance with Practice E 883.8.3 Recognizing and Classifying Duplex Grain Size:8.3.1 A random duple

47、x grain size is defined as any of thefollowing:8.3.1.1 The presence of randomly distributed individualcoarse grains, differing in size by three or more ASTM grainsize numbers from the average size of the balance of the grains(henceforth referred to as the ALA (As Large As) condition).These individua

48、l coarse grains should comprise 5 % or less of5A Keuffel or, the presence of different grain sizes inspecific areas of a product cross-section (for example, coarsegrains resulting from germinative grain growth at areas ofcritical strain), such that the grain size in those specific areasdiffers from

49、the grain size in the bulk of the cross-section bythree or more ASTM grain size numbers (both conditionshenceforth referred to as the cross-section condition). Anexample photomicrograph of a cross-section condition appearsin Fig. A1.4.8.3.2.2 The presence of individual coarse grains, eachsurrounded by rings of finer grains, the coarse and fine grainsdiffering in size by three or more ASTM grain size numbers(henceforth referred to as the necklace condition). An examplephotomicrograph of the necklace condition appears in Fig.A1.5.8.3.2.3 The presence of bands of distinct grain s