ASTM_E_2627_-_13.pdf

Designation:E262713Standard Practice forDetermining Average Grain Size Using Electron BackscatterDiffraction(EBSD)in Fully Recrystallized PolycrystallineMaterials1This standard is issued under the fixed designation E2627;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 reapproval.1.Scope1.1 This practice is used to determine grain size frommeasurements of grain areas from automated electron back-scatter diffraction(EBSD)scans of polycrystalline materials.1.2 The intent of this practice is to standardize operation ofan automated EBSD instrument to measure ASTM G directlyfrom crystal orientation.The guidelines and caveats of E112apply here,but the focus of this standard is on EBSD practice.1.3 This practice is only applicable to fully recrystallizedmaterials.1.4 This practice is applicable to any crystalline materialwhich produces EBSD patterns of sufficient quality that a highpercentage of the patterns can be reliably indexed usingautomated indexing software.1.5 The practice is applicable to any type of grain structureor grain size distribution.1.6 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.7 This 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 use.2.Referenced Documents2.1 ASTM Standards:2E7 Terminology Relating to MetallographyE112 Test Methods for Determining Average Grain SizeE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE766 Practice for Calibrating the Magnification of a Scan-ning Electron MicroscopeE1181 Test Methods for Characterizing Duplex Grain SizesE1382 Test Methods for Determining Average Grain SizeUsing Semiautomatic and Automatic Image Analysis3.Terminology3.1 Definitions:3.1.1 cleanupPost processing applied to EBSD scan datato reassign extraneous points in the scan grid to neighboringpoints.The extraneous points are assumed to arise fromnon-indexed or misindexed EBSD patterns.3.1.2(crystallographic)orientationThe rotation requiredto bring the principle axes of a crystal into coincidence with theprinciple axes assigned to a specimen.For example,in a rolledmaterial with cubic crystal symmetry,it is the set of rotationsrequired to bring the 100,010 and 001 axes of the crystalinto coincidence with the rolling,transverse and normaldirections of the specimen.Orientations may be described interms of various sets of angles,a matrix of direction cosines ora rotation vector.3.1.3 electron backscatter diffraction(EBSD).A crystal-line specimen is placed in a scanning electron microscope(SEM)at a high tilt angle(70).When a stationary electronbeam is positioned on a grain,the electrons are scattered in asmall volume(typically 30nm in the tilt direction,10nm in thetransverse direction and 20 nm in depth for a field emission gunSEM and approximately an order of magnitude larger in thelateral directions for a tungsten filament SEM).Electrons thatsatisfy Braggs law are diffracted back out of the specimen.Thediffracted electrons strike a phosphor screen(or alternatively aYAG crystal)placed in the chamber.The colliding electronsfluoresce the phosphor and produce a pattern.The pattern iscomposed of a set of intersecting bands(Kikuchi lines).Thesebands are indicative of the arrangement of crystal lattice planesin the diffracting crystal volume.Assuming the material is of1This practice is under the jurisdiction of ASTM Committee E04 on Metallog-raphy and is the direct responsibility of Subcommittee E04.11 on X-Ray andElectron Metallography.Current edition approved Nov.1,2013.Published December 2013.Originallyapproved in 2010.Last previous edition approved in 2010 as E262710.DOI:10.1520/E262713.2For referenced ASTM standards,visit the ASTM website,www.astm.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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 known crystal structure,the orientation of the crystal within thediffracting volume can be determined.3.1.4 EBSD patternAn EBSD pattern is composed of a setof intersecting bands.The geometrical arrangement of thesebands is indicative of the crystallographic orientation of thecrystal lattice within the diffraction volume.3.1.5 EBSD scanUnder computer control,the beam of theSEM is moved to a point on the specimen,an EBSD patterncaptured and indexe