SIST EN 623-3:2002

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Advanced technical ceramics - Monolithic ceramics - General and textural properties - Part 3: Determination of grain size and size distribution (characterized by the Linear Intercept Method)Hochleistungskeramik - Monolithische Keramik - Allgemeine undstrukturelle Eigenschaften - Teil 3: Bestimmung der Korngrößeund der Korngrößenverteilung (Linienschnittverfahren)Céramiques techniques avancées - Céramiques monolithiques - Propriétés générales et texturales - Partie 3: Détermination de la taille des grains et de la distribution granulométrique (selon la méthode de l'intersection linéaire)Advanced technical ceramics - Monolithic ceramics - General and textural properties - Part 3: Determination of grain size and size distribution (characterized by the Linear Intercept Method)81.060.30Sodobna keramikaAdvanced ceramicsICS:Ta slovenski standard je istoveten z:EN 623-3:2001SIST EN 623-3:2002en01-januar-2002SIST EN 623-3:2002SLOVENSKI
STANDARDSIST ENV 623-3:20001DGRPHãþD



SIST EN 623-3:2002



EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 623-3May 2001ICS 81.060.30Supersedes ENV 623-3:1993English versionAdvanced technical ceramics - Monolithic ceramics - Generaland textural properties - Part 3: Determination of grain size andsize distribution (characterized by the Linear Intercept Method)Céramiques techniques avancées - Méthodes d'essai pourcéramiques monolithiques - Propriétés générales ettexturales - Partie 3: Détermination de la taille des grainsHochleistungskeramik - Monolithische Keramik -Allgemeine und strukturelle Eigenschaften - Teil 3:Bestimmung der KorngrößeThis European Standard was approved by CEN on 19 April 2001.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2001 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 623-3:2001 ESIST EN 623-3:2002



Page 2EN 623-3:2001ContentsPage1 Scope.32 Normative references.33 Terms and definitions.44 Significance and use.45 Apparatus.56 Test piece preparation.67 Photomicrography.78 Measurement of micrographs.89 Calculation of results.1010 Interferences and uncertainties.1011
Test Report.11Annex A (informative) Bibliography on stereology and grain size measurement.13Annex B (informative)
Grinding and polishing procedures.14Annex C (informative) Etching procedures.16Annex D (informative) Setting Köhler illumination in an optical microscope.18Annex E (informative) Round-robin verification of the procedure in this standard.19Annex F (informative) Grain size distribution measurement.20Annex G (informative)
Results sheet - Grain size in accordance with EN 623-3.21SIST EN 623-3:2002



Page 3EN 623-3:2001ForewordThis European Standard has been prepared by Technical Committee CEN/TC 184 "Advancedtechnical ceramics ", the secretariat of which is held by BSI.This European Standard shall be given the status of a national standard, either by publicationof an identical text or by endorsement, at the latest by November 2001, and conflictingnational standards shall be withdrawn at the latest by November 2001.This European Standard supersedes ENV 623-3:1993.Annexes A, B, C, D, E, F and G are informative.According to the CEN/CENELEC Internal Regulations, the national standards organizationsof the following countries are bound to implement this European Standard: Austria, Belgium,Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the UnitedKingdom.1ScopeThis Part of EN 623 describes manual methods of making measurements for the determinationof mean linear intercept grain size of advanced technical ceramics using photomicrographs ofpolished and etched test pieces. This is not the true mean grain diameter, but a somewhatsmaller parameter representing the average path length of a line drawn across a two-dimensionalsection. The relationship to true grain dimensions depends on grain shape and degree ofmicrostructural anisotropy. This standard contains two methods, A and B.Method A applies to single-phase ceramics, and to ceramics with a principal crystalline phaseand a glassy grain-boundary phase of less than about 5% by volume for which interceptcounting suffices. Method B applies to ceramics with more than about 5% by volume of poresor secondary phases, or ceramics with more than one major crystalline phase where individualintercept lengths are measured, which can optionally be used to create a size distribution. Thislatter method allows the pores or phases to be distinguished and the mean linear intercept sizefor each to be calculated separately.NOTE A method of determining volume fraction(s) of secondary phase(s) is under development as ENV 623-5; thiswill provide a means of determining whether Method A or Method B should be applied in borderline cases.Some users of this standard may wish to apply automatic or semiautomatic image analysis tomicrographs or directly captured microstructural images This is permitted by this standardprovided that the technique employed simulates the manual method (see clause 4 and 8.4).2Normative referencesThis European Standard incorporates, by dated or undated reference, provisions from otherpublications. These normative references are cited at the appropriate places in the text and thepublications are listed hereafter. For dated references, subsequent amendments to or revisions ofany of these publications apply to this European Standard only when incorporated in it bySIST EN 623-3:2002



Page 4EN 623-3:2001amendment or revision. For undated references the latest edition of the publication referred toapplies (including amendments).ENV 1006Advanced technical ceramics - Methods of testing monolithic ceramics -Guidance on the sampling and selection of test piecesEN ISO/IEC 17025General requirements for the competence of testing and calibrationlaboratories (ISO/IEC 17025:1999)3Terms and definitionsFor the purposes of this European standard, the following terms and definitions apply.3.1grain sizesize of the distinct crystals in a material, and for the purposes of this method of test, that of theprimary or major phase.3.2mean linear intercept grain sizethe average value of the distance between grain boundaries as shown by randomly positionedlines drawn across a micrograph or other image of the microstructure.4Significance and useThe mean grain size and the distribution of grain sizes of a ceramic material play an importantrole in determining many properties, and thus grain size characterization is an important tool forensuring consistency of manufacture. There are many measures of grain size and/or shape, butthe linear intercept method provides the simplest possible method from a two dimensionalsection through the material. However, it must be recognised that the numerical value obtainedfor the mean linear intercept size is somewhat smaller than most other measures of grain sizebecause intercepts can cross grains at any position, and not necessarily along the largest axis.The relationship between mean linear intercept size and a true three-dimensional grain size isnot simple, and depends on the grain shape and the average number of facets. NOTE Annex A contains a bibliography of sources dealing with stereology and methods of sizing three-dimensionalobjects.This Standard provides a simple method of measuring intercept distances in single-phasematerials based on counting the number of intersections along given lengths of randomlyorientated and positioned lines or randomly positioned circles drawn onto a micrograph of asuitably sectioned, polished and etched test-piece. The length of lines crossing large poresresiding at grain boundaries can be ignored, thus eliminating any bias that porosity mayintroduce, but small pores within grains should be ignored. In materials which contain morethan one phase, the phases may be continuous or as isolated grains. It may be necessary tocharacterize the different phases separately. The principal purpose of this standard is to permitcharacterization of the major phases. The same intercept principle as for single-phase materialsSIST EN 623-3:2002



Page 5EN 623-3:2001can be used, but the individual intercept lengths across each phase must be measured, ratherthan just counted. The characterization of minor phases may require different treatment, whichis outside the scope of this Standard.If the material possesses a microstructure which has a preferred orientation of the primary orsecondary phases, the results of this measurement may not be representative of the truecharacter of the material. Rather than using randomly orientated lines, it may be necessary tomake measurements restricted to specific orientations. If undertaken, this must be reported inthe report.This Standard does not cover methods of measuring mean grain size by counting usingcalibrated microscope stage movement or projection onto screens, accompanied by visualobservation. While this latter method may produce an equivalent result to the analysis ofmicrographs, it does not provide a means of verification of the results of the measurement, sinceno permanent record is obtained.If automatic or semiautomatic image analysis (AIA) is to be used it must be recognised thatdifferent AIA systems approach the measurement in different ways, and may use differentparameters to linear intercept distance, such as those based on grain area by pixel counting. Inorder to obtain results equivalent to those of the manual method described in this standard, theAIA system needs to be programmed to operate in a similar way to the manual method. Byagreement between parties, such a near-equivalent AIA method may be used as an alternative tothe manual method, and if undertaken must be reported in the report.5Apparatus5.1Sectioning equipmentA suitable diamond-bladed cut-off saw to prepare the initial section for investigation. The sawshall be metal bonded with a diamond grit size of 125 mm to 150 mm and shall be cooled.NOTE The grit size is designated D151 in
ISO 6106, see annex A.5.2Mounting equipmentSuitable metallurgical mounting equipment and media for providing firm gripping of the testpieces for polishing.5.3Grinding and polishing equipmentSuitable grinding and polishing equipment, employing diamond abrasive media.NOTE Annex
B recommends techniques and abrasives.5.4MicroscopeAn optical or scanning electron microscope with photomicrographic facilities.
A referencegraticule is required for determination of magnification in an optical microscope, and areference square grid or latex spheres are required for calibration of magnification in a scanningelectron microscope. In all cases, the calibration of dimensions of the references shall beSIST EN 623-3:2002



Page 6EN 623-3:2001traceable to national or international standards of length measurement.An optical microscope is additionally required for assessing quality of polishing (see 6.4).5.5Calibrated rule or scaleA calibrated rule or scale reading to better than 0.5 mm and accurate to better than 0,5%.6Test piece preparation6.1 SamplingThe test pieces shall be sampled in accordance with the guidelines given in ENV 1006, andsubject to agreement between parties.NOTE Depending on the objectives of the measurement, it is desirable to maintain full knowledge of the positionswithin components or test pieces from which sections are prepared.6.2CuttingThe required section of the test piece shall be cut using the diamond saw (see 5.1).NOTE For routine inspection of materials, a small area of not more than 10 mm side is normally adequate as thesection to be polished.6.3MountingMount the test piece using an appropriate mounting medium. If the ceramic is suspected to havesignificant open porosity in some regions (see clause 1) it is advisable to vacuum impregnate thetest piece with liquid mounting resin before encapsulating as this will provide some supportduring polishing.NOTE It is not essential to encapsulate the test piece. For example, it could be affixed to a metal holder. However,encapsulation in a polymer-based medium allows easy gripping and handling, especially of small irregularly shapedtest pieces and of weak, friable materials. The method of mounting selected should take into account the etchingprocedure to be used; see annex C.6.4Grinding and polishingGrind and polish the surface of the test piece. Care should be taken to ensure that grindingproduces a planar surface with a minimum of damage. Employ successively smaller grit sizes, ateach stage removing the damage from the previous stage until there is no change in appearancewhen examined by an optical microscope (see 5.4) at high magnification. The final surface shallbe free from optically visible scratches, or other damage introduced by polishing, which wouldinterfere with the determination.NOTE Care should be taken in choosing the sequence of grits and lap types. It is impossible within the scope of thisStandard to
make specific recommendations for all types of material. The general principle to be adopted is theminimization of subsurface damage, and its removal by
progressively finer grits whilst retaining a flat surface.Some guidelines on grinding and polishing are given in annex B.SIST EN 623-3:2002



Page 7EN 623-3:20016.5EtchingWhen a good quality surface has been achieved, the test piece shall be etched if necessary toreveal grain boundaries. Any suitable technique shall be used, subject to agreement betweenparties.NOTE Some general guidelines recommending etching procedures for various commonly available advancedtechnical ceramics are given in annex C.7Photomicrography7.1General aspectsIf the grain structure of the test material is too small for optical microscopy adequately toresolve and count grain boundary intersections (Method A) or measure the individual grains(Method B), scanning electron microscopy is to be used.NOTE Typically, if the mean linear intercept size of the principal phase is less than 2 m for Method A, or 4 µm forMethod B, then scanning electron microscopy should be used.7.2Optical microscopySet up Köhler illumination in the microscope.NOTE Guidance on setting Köhler illumination is given in annex D.Examine the test piece at a magnification sufficient to resolve the individual grains clearly. Ifthe contrast obtained is insufficient, e.g. in white or translucent materials, apply a suitablemetallic coating by evaporation or sputtering. Prepare micrographs of at least three differentareas of the test piece surface. As a guideline for Method A the average size of each distinctgrain should appear typically at least 3 mm across. For Method B, the typical size of discretephase areas or pores should appear at least 5 mm across. If the grains or phase areas appearsmaller than these levels, increase the magnification and prepare fresh micrographs.Micrographs should be typically of a size 100 mm x 75 mm, but may with advantage beenlarged later to aid evaluation.7.3Scanning electron microscopyMount the test piece on the test piece holder of the microscope. If the test piece is notelectrically conducting, apply a thin evaporated or sputtered conductive coating. Insert the testpiece into the microscope, ensuring that the surface to be characterized is normal to the electronbeam to within 5o.NOTE This ensures that the image does not suffer from excessive distortion due to the angle of viewing.Prepare micrographs at a suitable magnification (see 7.2) from at least three different areas ofthe test piece.SIST EN 623-3:2002



Page 8EN 623-3:20017.4Calibration micrographs7.4.1Optical microscopyFor optical microscopy, unless already undertaken, prepare a micrograph of a graticule at thesame magnification as that used for preparing micrographs to provide a calibration ofmagnification. Measure the size of the spacing of the calibrated graticule as shown by amicrograph and calculate the magnification.7.4.2Scanning electron microscopyFor calibration of the lateral and vertical magnifications of the scanning electron micrographs,prepare similar images of a graticule or grid, or of calibrated spheres, at the same workingdistance of the microscope stage as that used for taking micrographs.NOTE The photographic screen in the microscope may not have constant magnification at all points. A square gridmakes a suitable reference for ascertaining the degree of distortion in the screen, since it is easy to detect distortionsof the grid. If the image distortion is uniform across the field of view, i.e. lateral (X-direction) and vertical (Y-direction) magnifications appear to be constant but different, it is possible to make corrections when measuring themicrographs. The effective magnification of each drawn line can be calculated by noting its angle relative to thehorizontal on the micrographs and applying an angular correction to the X-direction magnification. This proceduremay only be adopted by agreement between parties, and shall be reported (see clause 11).Use the same procedure as for optical micrographs (see 7.4.1) to calculate the magnificationhorizontally and vertically. If calibration spheres have been used, measure the horizontal andvertical dimensions of at least six spheres and calculate the respective mean values. If thevertical and horizontal magnifications calculated are different by more than 5% or individuallyvary by more than 5% across the screen, the distortion of the image is not acceptable for thepurposes of this standard.8Measurement of micrographs8.1GeneralInspect the micrographs. If they appear to be essentially single phase and to contain less than 5%of a secondary phase, use Method A. If they appear to contain 5% or more of a secondary phase,either continuous or as discrete grains, employ the procedure given in Method B. If therequirement is for determining additionally a grain size distribution, use Method B.8.2Method ADraw at least five thin straight lines of random position and orientation across each micrographintersecting at least 100 grains.NOTE 1 On a micrograph of typical size 100 mm x 75 mm showing grains averaging 3 mm across satisfying therequirements of 7.1, five lines of length 75 mm will provide an adequate number of grain intersections for this testmethod.Measure each line length to the nearest 0,5 mm using the calibrated rule or scale (see 5.5) andSIST EN 623-3:2002



Page 9EN 623-3:2001calculate the total line length L(t).
Count the number N(i) of intersections of the lines with grainboundaries. If the line intersects the junction of three grains, count this as 1,5 intersections. Ifthe line intersects a large pore, a wide grain boundary, or a secondary phase, either discrete orcontinuous, count this as one intersection. Measure the total length of line that crosses largepores L(p). If the line runs along a grain boundary, count this as one intersection.Alternatively, on each micrograph draw at least three circles of diameter not less than 10 timesthe expected mean grain size using a pair of compasses and randomly positioning the centres.Measure the diameters of the circles d to the nearest 0,5 mm using the calibrated rule or scale(see 5.5), and calculate the sum of their circumferences L(t). Count the number N(i) ofintersections of each circle with the grain boundaries. If the intersection coincides with thejunction of three grains, count this as 1,5 intersections. If the line intersects a large pore, a widegrain boundary, or a secondary phase, either discrete or continuous, count this as oneintersection. Measure the approximate arc length that crosses large pores L(p).NOTE 2 For the purposes of this standard, a large pore is one which resides at grain boundaries. Small poresentrained within grains should be ignored.8.3Method BDraw at least five randomly positioned and randomly orientated lines across the micrographsuch that at least 100 discrete phase regions or pores of the type to be assessed are intersected.Ignore grains which touch the edge of the micrograph. Using a visual aid as necessary,measure the distance, Li, between intersections of grain boundaries across each phase regionor pore to the nearest 0,5 mm using the calibrated rule or scale (see 5.5). Count the totalnumber of phase regions or pores, N(g), measured.8.4Use of automatic or semiautomatic image analysis for methods A and BIf it is desired to apply an automatic or semi-automatic image analyser to the measurement ofmicrographs or directly recorded images, in order that the results are comparable with themanual method described in this standard the following points are to be noted:(a)Care must be taken that the contrast change at a grain boundary is sufficient for thedetection system to identify it as such. If the captured image requires enhancement tomore clearly reveal grain boundaries, this should be performed manually rather thanusing any proprietary software until confidence is built up that the software methodproduces equivalent results.(b)The image must be line-scanned in at least five random directions, which may beachieved either through software design or by rotating the image to random orientationsand taking horizontal line scans. Scanning in only one direction on the test piece is notacceptable since it does not allow for anisotropy.(c)The analyser must be calibrated for magnification using micrographs or images of agraticule or grid, as for the manual methods.(d)The calculation routine incorporated in the software must operate in the same way asthis manual method in order that large pores are discounted.SIST EN 623-3:2002



Page 10EN 623-3:2001(e)The report shall contain full documentation of the procedure employed.NOTE Failure to observe these points will result in results which may be substantially at variance with the manualmethod.9Calculation of results9.1Method AFor both line and circle methods, calculate the mean linear intercept distance, gmli, in micrometres, for each micrograph using the formula:[]miNpLtLg . )(10 .)( - )(( = 3mliwhere:L(t) is the total line length in millimetres; in the case of circles, the totalcircumference of the circles, in mm;L(p) is the total line length that crosses large pores, in mm;N(i) is the counted number of intersections on each micrograph;m is the calibrated magnification of the micrograph.Calculate the mean value of gmli from the values determined for each of the individualmicrographs used.9.2Method BCalculate the mean linear intercept distance gmli in micrometres of each discrete phase region orpores as follows:where:Li is the ith individual intercept length in millimetresS is the summation signN (g) is the number of discrete phase regions or pores countedm is the calibrated magnification of the micrograph10Interferences and uncertaintiesThe nature of the microstructure of the test piece can affect the result determined by this test,especially in cases where there is a wide distribution of grain sizes (e.g. a bimodal distribution),or where it is difficult to find an adequate etching method to reveal grain boundaries. Method Aassumes that the amount of continuous secondary phase is small compared with the majorcrystalline phase(s). As the widths of the layers of such secondary phase between grains of theprimary phase increase, there will be an increasing overestimate of true mean grain size, andMethod B should preferably be used. Method B also assumes that the total fine-scale porositylevel is negligible.mgNLgi . )(10 . ][
=
3mliSSIST EN 623-3:2002



Page 11EN 623-3:2001The principal causes of uncertainty in this method are considered to be the random errors ofselecting areas of the test piece from which to prepare micrographs and the positions on themicrograph in which to draw lines or circles. The former depends on the homogeneity of themicrostructure within the test piece, and the latter on any subjective element in selecting
line orcircle positions.Uncertainties arising from magnification and counting are considered to be negligible providedthat the procedure described in this standard is followed.NOTE An international round-robin has demonstrated the potential causes of scatter in undertaking measurementaccording to Method A. The findings are summarized in annex E.11 Test ReportThe report of the test shall be in accordance with EN ISO/IEC 17025 and shall contain thefollowing:a)the name of the testing laboratory;b)a unique identification of the report;c)the name and address of the client;d)details of the test piece, including material type, manufacturing code, batch number, etc.;e)the date of receipt of the test item(s) and of the test;f)a reference to this Standard, i.e. EN 623 part 3;g)a summary of the procedure for sampling, cutting, grinding, polishing and etching thetest piece;h)the observation technique employed (optical or scanning electron microscope);i)the technique employed for calibration, and the resulting magnification;j)copies of the micrographs with their magnifications used for the measurement;NOTE 1 If AIA has been used, both the original and the digitally enhanced images should be provided.k)if a manual method was employed, whether Method A or Method B was used, and ifMethod A, whether lines or circles were used for the analysis;l)if an automatic or semiautomatic method was used, full documentation of theprocedures employed, including details of image enhancement (if used), and the basisfor the calculation method employed;m)any use of the angular correction method (see 7.4);n)for Method A, the number of intercepts for each of the five lines or three circles on eachSIST EN 623-3:2002



Page 12EN 623-3:2001of the three micrographs and the total line length, corrected for large pores, employed forthe measurements, expressed in millimetres;o)for Method A, the total number of intercepts;p)for Method B, the phase types or pores measured, the individual intercept lengths,expressed in millimetres, and the total number of discrete phase regions or porescounted for each of the micrographs;q) for Method A and Method B the calculated mean linear intercept size for each of themicrographs, expressed in micrometres to two significant figures, and the overall meanvalue;r)if appropriate the intercept size distribution using Method B for each discrete phasetype;NOTE 2 Annex F contains a method by which data may be ranked for the purposes of preparing anintercept size distribution.s)any remarks on the general appearance of the microstructure, whether isotropic oranisotropic, the presence of secondary phases, whether the grain size is obviouslybimodal, or the grain shape is anisotropic;t)signatures of persons responsible for the test and authorising issue of report;NOTE 3 For routine presentation of results it is useful if a standardized format is adopted. A recommendedscheme is presented in annex G.u)comments on the test or test results, including any deviations from the procedurerequired by this standard.SIST EN 623-3:2002



Page 13EN 623-3:2001Annex A (informative)Bibliography on stereology and grain size measurementASTM E112, Standard test method for determining average grain size, ASTM Annual Book ofStandards, Vol. 3.01.ASTM E766, Practice for calibrating the magnification of a scanning electronmicroscope using NIST-SRM-484, ASTM Annual Book of Standards, Vol. 3.01.ASTM F728, Preparation of an optical microscope for dimensional measurements, standardpractice for ASTM Annual Book of Standards, Vol. 10.05.DeHoff, R.T.; Rhines, F.N.; Quantitativ
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