Standard Test Methods for Determining Average Grain Size1

1 Designation: E112 13 Standard Test Methods forDetermining Average Grain Size1 This Standard is issued under the fixed designation E112; 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 parentheses indicates the year of last reapproval. Asuperscript epsilon ( ) indicates an editorial change since the last revision or Standard has been approved for use by agencies of the Department of test Methods of determination of Average Grain size in metallic materials are primarilymeasuring procedures and, because of their purely geometric basis, are independent of the metal oralloy concerned. In fact, the basic procedures may also be used for the estimation of Average Grain ,crystal, or cell size in nonmetallic materials.

2 The comparison method may be used if the structure ofthe material approaches the appearance of one of the Standard comparison charts. The intercept andplanimetric Methods are always applicable for Determining Average Grain size. However, thecomparison charts cannot be used for measurement of individual These test Methods cover the measurement of averagegrain size and include the comparison procedure, the planim-etric (or Jeffries) procedure, and the intercept test Methods may also be applied to nonmetallicmaterials with structures having appearances similar to those ofthe metallic structures shown in the comparison charts. Thesetest Methods apply chiefly to single phase Grain structures butthey can be applied to determine the Average size of a particulartype of Grain structure in a multiphase or These test Methods are used to determine the averagegrain size of specimens with a unimodal distribution of grainareas, diameters, or intercept lengths.

3 These distributions areapproximately log normal. These test Methods do not covermethods to characterize the nature of these of Grain size in specimens with duplex grainsize distributions is described in Test MethodsE1181. Mea-surementofindividual, very coarse grains in a fine grainedmatrix is described in Test Thesetest Methods deal only with determination ofplanar Grain size, that is, characterization of the two-dimensional Grain sections revealed by the sectioning of spatial Grain size, that is, measurement of thesize of the three-dimensional grains in the specimen volume, isbeyond the scope of these test These test Methods describe techniques performedmanually using either a Standard series of graded chart imagesfor the comparison method or simple templates for the manualcounting Methods .

4 Utilization of semi-automatic digitizingtablets or automatic image analyzers to measure Grain size isdescribed in Test Thesetest Methods deal only with the recommended testmethods and nothing in them should be construed as definingor establishing limits of acceptability or fitness of purpose ofthe materials The measured values are stated in SI units, which areregarded as Standard . Equivalent inch-pound values, whenlisted, are in parentheses and may be Standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this Standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to The paragraphs appear in the following order.

5 SectionNumberScope1 Referenced Documents2 Terminology3 Significance and Use4 Generalities of Application5 Sampling6 Test Specimens7 Calibration8 Preparation of Photomicrographs9 Comparison Procedure10 Planimetric (Jeffries) Procedure11 General Intercept Procedures12 Heyn Linear Intercept Procedure13 Circular Intercept Procedures14 Hilliard Single-Circle Three-Circle Analysis15 Specimens with Non-equiaxed Grain Shapes16 Specimens Containing Two or More Phases or Constituents17 Report18 Precision and Bias19 Keywords20 Annexes:Basisof ASTM Grain Size NumbersAnnexA1 Equations for Conversions Among Various Grain Size MeasurementsAnnexA2 Austenite Grain Size, Ferritic and Austenitic SteelsAnnexA3 Fracture Grain Size MethodAnnexA4 Requirements for Wrought Copper and Copper-Base AlloysAnnexA5 Application to Special SituationsAnnexA6 Appendixes:Resultsof Interlaboratory Grain Size DeterminationsAppendixX1 Referenced AdjunctsAppendixX22.

6 Referenced Standards:2E3 Guide for Preparation of Metallographic SpecimensE7 Terminology Relating to MetallographyE407 Practice for Microetching Metals and AlloysE562 Test Method for Determining Volume Fraction bySystematic Manual Point CountE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE883 Guide for Reflected Light PhotomicrographyE930 Test Methods for Estimating the Largest Grain Ob-served in a Metallographic Section (ALA Grain Size)E1181 Test Methods for Characterizing Duplex Grain SizesE1382 Test Methods for Determining Average Grain SizeUsing Semiautomatic and Automatic Image For a complete adjunct list, seeAppendix X23. For definitions of terms used in these testmethods, see of Terms Specific to This Grain size number the ASTM Grain sizenumber,G, was originally defined as:NAE52G21(1)whereNAEis the number of grains per square inch at100X magnification.

7 To obtain the number per square milli-metre at 1X, multiply by an individual crystal with the same atomicconfiguration throughout in a polycrystalline material; thegrain may or may not contain twinned regions within it boundary a very narrow region in a polycrys-talline material corresponding to the transition from onecrystallographic orientation to another, thus separating oneadjacent Grain from another; on a two-dimensional planethrough three-dimensional polycrystalline materials, the grainedges between adjacent grains surrounding a single Grain makeup the outline of the two-dimensional grains that are observedin the light microscope and are measured or counted by theprocedures in this test boundary intersection count, P determinationof the number of times a test line cuts across, or is tangent to(tangent hits are counted as one (1) intersection) Grain bound-aries (triple point intersections are considered as 1-1 2intersec-tions).

8 Intercept count, N determination of the numberof times a test line cuts through individual grains on the planeof polish (tangent hits are considered as one half an intercep-tion; test lines that end within a Grain are considered as one halfan interception). length the distance between two opposed,adjacent Grain boundary intersection points on a test linesegment that crosses the Grain at any location due to randomplacement of the test : = matrix grains in a two phase (constituent) test = mean Grain cross sectional = Grain elongation ratio or anisotropy index for alongitudinally oriented = mean planar Grain diameter (Plate III).D = mean spatial (volumetric) Grain Jeffries multiplier for planimetric ASTM Grain size number.

9 = mean lineal intercept length. = mean lineal intercept length of the matrixphase in a two phase (constituent) microstruc-ture. = mean lineal intercept length on a longitudi-nally oriented surface for a non-equiaxedgrain structure. t= mean lineal intercept length on a transverselyoriented surface for a non-equiaxed grainstructure. p= mean lineal intercept length on a planar ori-ented surface for a non-equiaxed Grain struc-ture. 0= base intercept length of mm for definingthe relationship betweenGand (andNL) formacroscopically or microscopically deter-mined Grain size by the intercept length of a test magnification magnification used by a chart picture number of fields = number of grains intercepted by the test linein a two phase (constituent) number of grains per mm2at 132NA = number of grains per mm2at 1X in a twophase (constituent)

10 Number of grains per inch2at =NAon a longitudinally oriented surface for anon-equiaxed Grain a transversely oriented surface for anon-equiaxed Grain a planar oriented surface for a non-equiaxed Grain number of intercepts with a test number of grains completely within a number of grains intercepted by the test number of intercepts per unit length of =NLon a longitudinally oriented surface for anon-equiaxed Grain a transversely oriented surface for anon-equiaxed Grain a planar oriented surface for a non-equiaxed Grain number of Grain boundary intersections with atest number of Grain boundary intersections perunit length of test =PLon a longitudinally oriented surface for anon-equiaxed Grain a transversely oriented surface for anon-equiaxed Grain a planar oriented surface for a non-equiaxed Grain correction factor for comparison chart ratingsusing a non- Standard magnification for micro-scopically determined Grain correction factor for comparison chart ratingsusing a non- Standard magnification for mac-roscopically determined Grain Standard Grain boundary surface area to volume ratiofor a single phase = Grain boundary surface area to volume ratiofor a two phase (constituent) students tmultiplier for determination of theconfidence = volume fraction of the phase in a two phase(constituent)