SIST EN 623-5:2009
(Main)Advanced technical ceramics - Monolithic ceramics - General and textural properties - Part 5: Determination of phase volume fraction by evaluation of micrographs
Advanced technical ceramics - Monolithic ceramics - General and textural properties - Part 5: Determination of phase volume fraction by evaluation of micrographs
This part of EN 623 specifies a manual method of making measurements for the determination of volume fraction of major phases in advanced technical ceramics using micrographs of polished and etched sections, overlaying a square grid of lines, and counting the number of intersections lying over each phase.
NOTE 1 This method assumes that the true phase volume fractions are equivalent to area fractions on a randomly cut cross-section according to stereological principles.
NOTE 2 Guidelines for polishing and etching of advanced technical ceramics can be found in Annexes A and B.
The method applies to ceramics with one or more distinct secondary phases, such as found in Al2O3/ZrO2, Si/SiC,or Al2O3/SiCw.
If the test material contains discrete pores, these can be treated as a secondary phase for the purpose of this method provided that there is no evidence of grain pluck-out during polishing being confused with genuine pores.
NOTE 3 If the material contains more than about 20 % porosity there is a strong risk that the microstructure will be damaged during the polishing process, and measurement of volume fraction of pores may become misleading.
Secondary phase volume fractions or porosity present at levels of less than 0,05 are subject to considerable error and potential scatter in results. A larger number of micrographs than the minimum of three is normally needed to improve the consistency and accuracy of the results.
NOTE 4 Many ceramics contain small amounts of secondary glassy phases. In order to make a reasonable estimate of glassy phase content, the glass material between crystalline grains should be readily observable, and thus should be at least 0,5 µm in width. The method in this European Standard is not considered appropriate for narrow glassy films around grains.
This method assumes that the selected regions of a prepared cross-section are statistically representative of the whole sampled section.
Hochleistungskeramik - Monolithische Keramik - Allgemeine und strukurelle Eigenschaften - Teil 5: Bestimmung des Volumenanteils von Phasen durch Auswertung von Mikrogefügeaufnahmen
Dieser Teil von EN 623 legt ein manuelles Messverfahren zur Bestimmung des Volumenanteils der Hauptphasen
in Hochleistungskeramiken fest, indem auf Mikrogefügeaufnahmen polierter und geätzter Querschnitte
ein quadratisches Liniengitter aufgelegt und die Anzahl der Schnittpunkte der Gitterlinien über jeder
Phase ausgezählt werden.
ANMERKUNG 1 Bei diesem Verfahren wird vorausgesetzt, dass die tatsächlich vorhandenen Volumenanteile einer
Phase nach stereologischen Prinzipien den Flächenanteilen entsprechen, die auf einem zufällig festgelegten Querschnitt
vorhanden sind.
ANMERKUNG 2 Anleitungen zum Polieren und Ätzen von Hochleistungskeramiken können in den Anhängen A und B
nachgelesen werden.
Das Verfahren gilt für keramische Werkstoffe mit einer oder mehreren deutlich erkennbaren
Sekundärphase(n), die z. B. in Al2O3/ZrO2, Si/SiC oder in Al2O3/SICw gefunden werden.
Falls der zu untersuchende Werkstoff diskrete Poren enthält, können sie im Rahmen dieses Verfahrens als
Sekundärphase angesehen werden, sofern es keine Hinweise darauf gibt, dass beim Polieren Körner aus
dem Gefüge herausgebrochen wurden, die mit echten Poren verwechselt werden könnten.
ANMERKUNG 3 Falls der Werkstoff eine Porosität von mehr als etwa 20 % aufweist, ist das Risiko groß, dass beim
Polieren eine Schädigung des Feingefüges aufgetreten ist und ein irreführender Porenvolumenanteil ermittelt werden
kann.
Ergebnisse der Bestimmung von Volumenanteilen einer Sekundärphase oder von Porenvolumenanteilen, die
weniger als 0,05 betragen, können merkliche Fehler und möglicherweise auch eine Streuung aufweisen.
Üblicherweise müssen, um Konsistenz und Genauigkeit der Ergebnisse zu verbessern, mehr als die
Mindestanzahl von drei Mikrogefügeaufnahmen ausgewertet werden.
ANMERKUNG 4 Viele Keramiken enthalten kleine Mengen glasartiger Sekundärphasen.
Céramiques techniques avancées - Céramiques monolithiques - Propriétés générales et textures - Partie 5: Détermination de la fraction volumique de phase par évaluation des microphotographies
La présente partie de l'EN 623 spécifie une méthode manuelle de mesurage permettant de déterminer la fraction
volumique des principales phases dans les céramiques techniques avancées à l'aide de microphotographies de
parties polies et décapées, en recouvrant une grille carrée de lignes, et en comptant le nombre d'intersections se
trouvant sur chaque phase.
NOTE 1 Cette méthode suppose que les fractions volumiques de phase véritables sont équivalentes aux fractions de
surface sur une section transversale coupée de façon aléatoire selon les principes stéréologiques.
NOTE 2 Les directives de polissage et de décapage des céramiques techniques avancées sont mentionnées en
Annexes A et B.
La méthode s'applique aux céramiques avec une ou plusieurs phases secondaires distinctes, telles que dans
Al2O3/ZrO2, Si/SiC, ou dans Al2O3/SiCw.
Si le matériau d'essai contient des pores discrets, ceux-ci peuvent être traités en tant que phase secondaire pour
les besoins de la présente méthode sous réserve qu'il n'y ait pas de preuve d'arrachage de grain au cours du
polissage pouvant être confondu avec les pores réels.
NOTE 3 Si le matériau contient plus de 20 % de porosité environ il existe un risque majeur d'endommagement de la
microstructure au cours du processus de polissage, et le mesurage de fraction volumique des pores peut être faussé.
Les fractions volumiques de phase secondaire ou la porosité, présentes à des niveaux inférieurs à 0,05
constituent une source d'erreur considérable et de dispersion potentielle des résultats. Un nombre de
microphotographies supérieur au nombre minimum de trois microphotographies est normalement requis afin
d'améliorer l'uniformité et la précision des résultats.
NOTE 4 De nombreuses céramiques renferment de petites quantités de phases vitreuses secondaires.
Sodobna tehnična keramika - Monolitna keramika - Splošne in strukturne lastnosti - 5. del: Določanje volumenskega deleža faz z vrednotenjem mikrostrukture
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 623-5:2009
01-november-2009
1DGRPHãþD
SIST ENV 623-5:2007
6RGREQDWHKQLþQDNHUDPLND0RQROLWQDNHUDPLND6SORãQHLQVWUXNWXUQHODVWQRVWL
GHO 'RORþDQMHYROXPHQVNHJDGHOHåDID]]YUHGQRWHQMHPPLNURVWUXNWXUH
Advanced technical ceramics - Monolithic ceramics - General and textural properties -
Part 5: Determination of phase volume fraction by evaluation of micrographs
Hochleistungskeramik - Monolithische Keramik - Allgemeine und strukurelle
Eigenschaften - Teil 5: Bestimmung des Volumenanteils von Phasen durch Auswertung
von Mikrogefügeaufnahmen
Céramiques techniques avancées - Céramiques monolithiques - Propriétés générales et
textures - Partie 5: Détermination de la fraction volumique de phase par évaluation des
microphotographies
Ta slovenski standard je istoveten z: EN 623-5:2009
ICS:
81.060.30 Sodobna keramika Advanced ceramics
SIST EN 623-5:2009 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 623-5:2009
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SIST EN 623-5:2009
EUROPEAN STANDARD
EN 623-5
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2009
ICS 81.060.30 Supersedes ENV 623-5:2002
English Version
Advanced technical ceramics - Monolithic ceramics - General
and textural properties - Part 5: Determination of phase volume
fraction by evaluation of micrographs
Céramiques techniques avancées - Céramiques Hochleistungskeramik - Monolithische Keramik -
monolithiques - Propriétés générales et textures - Partie 5: Allgemeine und strukurelle Eigenschaften - Teil 5:
Détermination de la fraction volumique de phase par Bestimmung des Volumenanteils von Phasen durch
évaluation des microphotographies Auswertung von Mikrogefügeaufnahmen
This European Standard was approved by CEN on 19 June 2009.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN 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 translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 623-5:2009: E
worldwide for CEN national Members.
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SIST EN 623-5:2009
EN 623-5:2009 (E)
Contents
page
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 5
4 Apparatus . 5
4.1 Sectioning equipment . 5
4.2 Mounting equipment. 5
4.3 Grinding and polishing equipment . 5
4.4 Microscope . 5
4.5 Transparent grid . 5
5 Test piece preparation . 6
5.1 Sampling . 6
5.2 Cutting . 6
5.3 Mounting . 6
5.4 Grinding and polishing . 6
5.5 Etching . 6
6 Photomicrography . 7
6.1 General aspects . 7
6.2 Inspection . 7
6.3 Number of micrographs . 7
6.4 Optical microscopy. 7
6.5 Scanning electron microscopy (SEM) . 7
7 Measurement of micrographs . 8
8 Calculation of results . 8
9 Interferences and uncertainties . 9
10 Test report . 9
Annex A (informative) Grinding and polishing procedures . 11
Annex B (informative) Etching procedures . 13
Annex C (informative) Use of automatic image analysis (AIA) . 14
C.1 Background . 14
C.2 Analysis techniques . 14
C.3 Micrograph requirements . 14
C.4 Calibration . 14
Annex D (informative) Setting Köhler illumination in an optical microscope . 15
D.1 Purpose . 15
D.2 Definition . 15
D.3 Setting up for Köhler illumination . 15
Annex E (informative) Round robin verification of this procedure . 16
Annex F (informative) Results sheet . 17
Bibliography . 18
2
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SIST EN 623-5:2009
EN 623-5:2009 (E)
Foreword
This document (EN 623-5:2009) has been prepared by Technical Committee CEN/TC 184 “Advanced technical
ceramics”, the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an identical text or
by endorsement, at the latest by January 2010, and conflicting national standards shall be withdrawn at the latest
by January 2010.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights.
CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes ENV 623-5:2002.
EN 623 consists of five parts, under the general title "Advanced technical ceramics - Monolithic ceramics - General and
textural properties":
Part 1: Determination of the presence of defects by dye penetration
Part 2: Determination of density and porosity
Part 3: Determination of grain size and size distribution (characterized by the Linear Intercept Method)
Part 4: Determination of surface roughness
Part 5: Determination of phase volume fraction by evaluation of micrographs
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden,
Switzerland and the United Kingdom.
3
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SIST EN 623-5:2009
EN 623-5:2009 (E)
1 Scope
This part of EN 623 specifies a manual method of making measurements for the determination of volume fraction of
major phases in advanced technical ceramics using micrographs of polished and etched sections, overlaying a square
grid of lines, and counting the number of intersections lying over each phase.
NOTE 1 This method assumes that the true phase volume fractions are equivalent to area fractions on a randomly cut cross-
section according to stereological principles.
NOTE 2 Guidelines for polishing and etching of advanced technical ceramics can be found in Annexes A and B.
The method applies to ceramics with one or more distinct secondary phases, such as found in Al O /ZrO , Si/SiC,or
2 3 2
Al O /SiC .
2 3 w
If the test material contains discrete pores, these can be treated as a secondary phase for the purpose of this method
provided that there is no evidence of grain pluck-out during polishing being confused with genuine pores.
NOTE 3 If the material contains more than about 20 % porosity there is a strong risk that the microstructure will be damaged
during the polishing process, and measurement of volume fraction of pores may become misleading.
Secondary phase volume fractions or porosity present at levels of less than 0,05 are subject to considerable error and
potential scatter in results. A larger number of micrographs than the minimum of three is normally needed to improve
the consistency and accuracy of the results.
NOTE 4 Many ceramics contain small amounts of secondary glassy phases. In order to make a reasonable estimate of
glassy phase content, the glass material between crystalline grains should be readily observable, and thus should be at least
0,5 µm in width. The method in this European Standard is not considered appropriate for narrow glassy films around grains.
This method assumes that the selected regions of a prepared cross-section are statistically representative of the whole
sampled section.
NOTE 5 Microstructures are seldom homogeneous, and the phase contents can vary from micrograph to micrograph. It is
essential to survey a sufficiently wide area of the prepared section to ensure that those areas selected for evaluation are
representative, and do not contain eye-catching irregularities.
Some users of this European Standard can wish to apply automatic or semiautomatic image analysis to micrographs or
directly captured microstructural images. This is currently outside the scope of this European Standard, but some
guidelines are given in Annex C.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references,
only the edition cited applies. For undated references, the latest edition of the referenced document (including any
amendments) applies.
EN 1006, Advanced technical ceramics - Monolithic ceramics - Guidance on the selection of test pieces for the
evaluation of properties
EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories (ISO/IEC
17025:2005)
4
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SIST EN 623-5:2009
EN 623-5:2009 (E)
3 Terms and definitions
For the purposes of this part of EN 623, the following terms and definitions apply.
3.1
phase volume fraction
volume occupied by a distinct, identifiable phase present in a material expressed as a fraction of the whole
3.2
secondary phase
one or more distinct identifiable phases other than a primary crystalline phase in a material
NOTE A secondary phase can be in the form of discrete grains, or as a continuous phase surrounding some or all the
major phase grains. For the purposes of this European Standard, porosity may be treated as a secondary phase.
4 Apparatus
4.1 Sectioning equipment
A suitable diamond-bladed cut-off saw to prepare the initial section for investigation. The saw shall be metal bonded
with a diamond grit size of 125 µm to 150 µm and shall be cooled.
NOTE This grit size is designated D151 according to ISO 6106, see [1].
4.2 Mounting equipment
Suitable metallurgical mounting equipment and media for providing firm gripping of the test piece for polishing.
4.3 Grinding and polishing equipment
Suitable grinding and polishing equipment, employing diamond abrasive media.
NOTE A sequence of abrasives and techniques recommended for polishing are given in Annex A.
4.4 Microscope
An optical or scanning electron microscope with photomicrographic facilities.
NOTE Although the true magnification of the image is unimportant for making the measurement of volume fraction, it is
advised that a reference graticule may be used to determine magnification in an optical microscope, or a reference grid or latex
spheres may be used for calibration of magnification in a scanning electron microscope, and as a check on the homogeneity of
magnification across the field of view.
An optical microscope is additionally required for assessing polishing (see 5.4).
4.5 Transparent grid
Transparent square grid on, e.g. acetate film, and with line thickness not exceeding 0,1 mm.
NOTE 1 The grid spacing selected is not critical, but may conveniently be between 3 mm and 15 mm to minimise eyestrain.
However, it is necessary that consideration of the requirements of 6.3 is taken into account.
NOTE 2 A suitable grid may be prepared as a computer plot with sufficient accuracy of line spacing for the purposes of this
European Standard.
5
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SIST EN 623-5:2009
EN 623-5:2009 (E)
5 Test piece preparation
5.1 Sampling
The test pieces shall be sampled in accordance with the guidelines given in EN 1006, and subject to agreement
between parties.
NOTE Depending on the objectives of performing the measurement, it is desirable to maintain knowledge of the positions
within components or test pieces from which sections are prepared.
5.2 Cutting
The required section of test-piece shall be cut using the diamond saw (see 4.1).
NOTE For routine inspection of materials, a small area of side no more than 10 mm is normally adequate as the section to
be polished.
5.3 Mounting
Mount the test piece using an appropriate mounting medium. If the ceramic is suspected to have significant open
porosity in some regions (see Clause 1) it is advisable to vacuum impregnate the test piece with liquid mounting resin
before encapsulating as this will provide some support during grinding and 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 shaped test pieces
and of weak friable test pieces. The method of mounting selected should take into account the etching procedure to be used;
see Annex B.
5.4 Grinding and polishing
Grind and polish the surface of the test piece. Care should be taken to ensure that grinding produces a planar surface
with a minimum of damage. Employ successively smaller grit sizes, at each stage removing the damage from the
previous stage until there is no change in appearance when examined by an optical microscope (see 4.4) at high
magnification. At least 90 % of the test piece area shall be free from optically visible scratches, or other damage
introduced by polishing, which will interfere with the determination. In particular, discrete secondary phases may be
plucked out from the surface giving the appearance of pores. This shall be avoided.
NOTE Care should be taken in choosing the sequence of grits and lap types. It is impossible within the scope of this part of
EN 623 to make specific recommendations for all types of material. The general principle to be adopted is the minimisation of
subsurface damage, and its removal by progressively finer grits whilst retaining a flat surface. Some guidelines on polishing are
given in Annex A.
5.5 Etching
When a good quality polished surface has been achieved, the test piece shall be etched if necessary to reveal the
individual phases. Any suitable technique shall be used, subject to agreement between parties.
NOTE 1 Some general guidelines recommending etching procedures for various commonly available advanced technical
ceramics are given in Annex B.
NOTE 2 For optical evaluation, it is usually necessary to etch oxide materials in such a way that the individual phases are
distinguished by having different contrast levels. For evaluation by scanning electron microscopy (SEM), it may not be
necessary to etch if a backscattered electron detector is used which has adequate resolution of net atomic number difference
between the phases such that contrast is generated. If a secondary electron detector is used, it will usually be necessary to etch
to produce topographic contrast unless the atomic number difference between the phases is large.
6
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SIST EN 623-5:2009
EN 623-5:2009 (E)
6 Photomicrography
6.1 General aspects
If it suspected that the average grain size of each phase or the widths of continuous glassy phases between grains is
less than 2 µm, it will be necessary to prepare the test piece for SEM. Between 2 µm and 4 µm either SEM or optical
microscopy may be used. Otherwise, optical microscopy will normally be adequate.
It is important to achieve sufficient contrast between phases in order to identify individual grains clearly and
unambiguously.
6.2 Inspection
Inspect the sampled cross-section in the microscope. If the microstructure appears homogeneous, prepare
micrographs from randomly selected areas. If inhomogeneity of microstructure is suspected, select representative
areas of relevance for measurement.
6.3 Number of micrographs
At least three micrographs shall be prepared at a magnification sufficient to identify clearly all the phases to be counted.
In addition, at least 100 features in total of any given type shall be present to be counted in the set of micrographs.
NOTE For a nominally homogeneous material, it may be sufficient to use a small number of micrographs analysed with a
small grid spacing, but for an inhomogeneous material, results representative of the average for the sampled section can be
prepared reliably only by selecting a large number of micrographs of different areas, with less intensive counting from a larger
grid.
6.4 Optical microscopy
Set up Köhler illumination in the microscope.
NOTE Guidance on setting Köhler illumination conditions is given in Annex D.
Examine the test piece at a magnification sufficient to resolve the individual grains clearly. If the contrast obtained is
insufficient, e.g. in white or translucent materials, apply a suitable thin metallic coating by evaporation or sputtering.
Prepare micrographs of at least three different randomly selected areas of the test-piece surface, taking into account
the apparent homogeneity of the microstructure (see 6.2). As a guideline, the average size of discrete phase area to be
counted should appear typically at least 3 mm across. If the total number of individual grains of any one phase to be
counted in any one set of micrographs is less than one hundred, prepare more micrographs. Micrographs should be
typically of a size (100 x 75) mm, but may with advantage be enlarged later to aid evaluation.
6.5 Scanning electron microscopy (SEM)
Mount the test piece on the test piece holder of the microscope. If the test piece is not electrically conducting, apply a
thin evaporated or sputtered conductive coating. Insert the test-piece in the microscope, ensuring that the surface to be
characterised is normal to the electron beam to within 5°.
NOTE 1 This ensures that the image does not suffer from excessive distortion or loss of focus due to the angle of viewing.
Prepare micrographs at a suitable magnification (see 6.4) from at least three different randomly selected areas of the
test piece, using either secondary electron imaging or backscattered electron imaging.
NOTE 2 Although the contrast between phases can be enhanced using backscattered electron imaging, a noisier image than
in secondary electron imaging may result and may render the boundaries between contrasting phases indistinct. It can be
helpful to use secondary electron images for counting the phase proportions, but backscattered images to aid identification of
each phase.
7
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SIST EN 623-5:2009
EN 623-5:2009 (E)
If the number of grains of the phase to be counted is less than 100 in total over all the micrographs, increase the
number of areas photographed. Micrographs should typically be of a size (100 x 75) mm, but may with advantage be
enlarged later to aid evaluation.
NOTE 3 It is possible that the photographic screen in the microscope will not have constant magnification at all points. A
square grid makes a suitable reference for ascertaining the degree of distortion in the screen, since it is easy to detect
distortions of the grid. For the purposes of this test method, distortions of typically up to 5 % may be acceptable provided that
the phases being counted are distributed homogeneously across the entire area of the micrograph.
7 Measurement of micrographs
If desirable, enlarge the photomicrograph to a size suitable for easier observation of the features. Examine the
dimensions of the smallest features to be counted. Select a suitable grid spacing and prepare a square grid (see 4.5,
6.3 and comments in Clause 9) such that the grid area covers the entire micrograph.
Tape the micrograph to a smooth surface. Overlay the grid such that the entire area of the micrograph is covered by
the grid, with no grid intersections immediately over the edges of the micrograph. Count the number of grid
intersections n of the grid that lie over each phase j. If the grid intersection lies exactly over the boundary between two
j
phases, count this as one half of a grid intersection for each phase. If porosity is to be estimated, use the same rule for
when a grid intersection lies exactly on the edge of a pore. Count the total number of grid intersections over the area of
the micrograph. If pores are not being counted, count the number of grid intersections lying over the crystalline or
glassy phases in the material.
NOTE It can be helpful in counting to screen with pieces of paper those lines of intersections above and below the one
being counted; this reduces eye strain and the risk of miscounting.
8 Calculation of results
For the case where porosity is to be counted as one of the phases, calculate the volume fraction of each phase using
Equation (1):
n
j
= (1)
V
f j
N
where
n is the total number of grid intersections over phase j;
j
N is the total number of grid intersections lying over the micrograph.
For the case where porosity is to be ignored, see Equation (2):
n n
j j
= = (2)
V
f j
S (N - )
n
p
where
n is the number of grid intersections lying over solid phase j;
j
n is the number of grid intersections lying over pores;
p
8
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SIST EN 623-5:2009
EN 623-5:2009 (E)
S is the sum of all grid intersections lying over all solid phases.
9 Interferences and uncertainties
The nature of the microstructure of the material can affect the result determined in this test. The test is effective when a
sufficient number of grid intersections of each phase are counted. This can be achieved either by intensive analysis of
the minimum number of three micrographs, or by less intensive analysis of a larger number of micrographs. For
intensive analysis, the grid shall be small enough such that there is a good chance that a grid intersection will lie over
each grain. Failure to do this means that the results are subject to increasing possible random error depending on
exactly where the grid is positioned. The random error is minimised by adhering to the above guideline, but will always
exist because of random positioning of the grid on the micrograph. Typically, for a homogeneous material with
randomly distributed phases results from a given series of three micrographs counting at least 100 grains of each type
should give phase volume fractions consistent to ± 0,02.
If the material appears inhomogeneous, either more areas should be analysed intensively to establish the extent of the
inhomogeneity, or if an average result only is required, a larger grid spacing can be used for less intensive analysis
provided that at least 100 grains of each phase type in total are counted. The procedure adopted should be reported.
The counting process requires visual observation of the phase lying underneath each grid intersection. Clean, well-
defined phase boundaries are required. If the phase boundaries are poorly defined as a result of limited optical or SEM
resolution, it is necessary to adopt a consistent criterion for assessing which side of the true boundary the grid
intersection overlies. Failure to do this can lead to under or overestimation of phase volume fraction, and is particularly
dangerous for small volume fractions.
The micrographs should not contain features which are ambiguous. Grain pluckout during polishing could inadvertently
be treated as porosity and, vice versa, features seen within shallow pores might be counted as solid grains. Particular
caution should be taken to avoid subsurface grains giving strong signals in backscattered electron images, or edge
highlights in secondary electron images hiding individual grains.
NOTE Annex E contains information from a round robin activity associated with the development of this European
Standard which illustrates these concerns.
10 Test report
The report of the test shall be in accordance with the reporting provisions of EN ISO/IEC 17025 and shall include at
least the following information:
a) name and address of the testing establishment;
b) date of the test;
c) on each page, a unique report identification and page number;
d) customer name and address;
e) reference to this European Standard, i.e. determined in accordance with EN 623-5;
f) authorizing signature;
NOTE 1 For routine presentation of results it is useful if a standardised format is adopted. A recommended scheme is given
in Annex F.
g) any deviation from the method described, with appropriate validation, i.e.
...
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.WUXNWXUHHochleistungskeramik - Monolithische Keramik - Allgemeine und strukurelle Eigenschaften - Teil 5: Bestimmung des Volumenanteils von Phasen durch Auswertung von MikrogefügeaufnahmenCéramiques techniques avancées - Céramiques monolithiques - Propriétés générales et textures - Partie 5: Détermination de la fraction volumique de phase par évaluation des microphotographiesAdvanced technical ceramics - Monolithic ceramics - General and textural properties - Part 5: Determination of phase volume fraction by evaluation of micrographs81.060.30Sodobna keramikaAdvanced ceramicsICS:Ta slovenski standard je istoveten z:prEN 623-5kSIST prEN 623-5:2009en,fr,de01-marec-2009kSIST prEN 623-5:2009SLOVENSKI
STANDARD
kSIST prEN 623-5:2009
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMFINAL DRAFTprEN 623-5December 2008ICS 81.060.30Will supersede ENV 623-5:2002
English VersionAdvanced technical ceramics - Monolithic ceramics - Generaland textural properties - Part 5: Determination of phase volumefraction by evaluation of micrographsCéramiques techniques avancées - Céramiquesmonolithiques - Propriétés générales et textures - Partie 5:Détermination de la fraction volumique de phase parévaluation des microphotographiesHochleistungskeramik - Monolithische Keramik -Allgemeine und strukurelle Eigenschaften - Teil 5:Bestimmung des Volumenanteils von Phasen durchAuswertung von MikrogefügeaufnahmenThis draft European Standard is submitted to CEN members for unique acceptance procedure. It has been drawn up by the TechnicalCommittee CEN/TC 184.If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations whichstipulate the conditions for giving this European Standard the status of a national standard without any alteration.This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other languagemade by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has thesame status as the official versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice andshall not be referred to as a European Standard.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre:
Avenue Marnix 17,
B-1000 Brussels© 2008 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. prEN 623-5:2008: EkSIST prEN 623-5:2009
prEN 623-5:2008 (E) 2 Contents page Foreword.3 1 Scope.4 2 Normative references.4 3 Terms and definitions.5 4 Apparatus.5 4.1 Sectioning equipment.5 4.2 Mounting equipment.5 4.3 Grinding and polishing equipment.5 4.4 Microscope.5 4.5 Transparent grid.5 5 Test piece preparation.6 5.1 Sampling.6 5.2 Cutting.6 5.3 Mounting.6 5.4 Grinding and polishing.6 5.5 Etching.6 6 Photomicrography.7 6.1 General aspects.7 6.2 Inspection.7 6.3 Number of micrographs.7 6.4 Optical microscopy.7 6.5 Scanning electron microscopy (SEM).7 7 Measurement of micrographs.8 8 Calculation of results.8 9 Interferences and uncertainties.9 10 Test report.9 Annex A (informative)
Grinding and polishing procedures.11 Annex B (informative)
Etching procedures.13 Annex C (informative)
Use of automatic image analysis (AIA).15 C.1 Background.15 C.2 Analysis techniques.15 C.3 Micrograph requirements.15 C.4 Calibration.15 Annex D (informative)
Setting Köhler illumination in an optical microscope.16 D.1 Purpose.16 D.2 Definition.16 D.3 Setting up for Köhler illumination.16 Annex E (informative)
Round robin verification of this procedure.17 Annex F (informative)
Results sheet.18 Bibliography.19
kSIST prEN 623-5:2009
prEN 623-5:2008 (E) 3 Foreword This document (prEN 623-5:2008) has been prepared by Technical Committee CEN/TC 184 “Advanced technical ceramics”, the secretariat of which is held by BSI. This document is currently submitted to the Unique Acceptance Procedure. This document will supersede ENV 623-5:2002. EN 623 consists of five parts, under the general title "Advanced technical ceramics - Monolithic ceramics - General and textural properties": Part 1: Determination of the presence of defects by dye penetration Part 2: Determination of density and porosity Part 3: Determination of grain size and size distribution (characterized by the Linear Intercept Method) Part 4: Determination of surface roughness Part 5: Determination of phase volume fraction by evaluation of micrographs
kSIST prEN 623-5:2009
prEN 623-5:2008 (E) 4
1 Scope This part of EN 623 specifies a manual method of making measurements for the determination of volume fraction of major phases in advanced technical ceramics using micrographs of polished and etched sections, overlaying a square grid of lines, and counting the number of intersections lying over each phase. NOTE 1 This method assumes that the true phase volume fractions are equivalent to area fractions on a randomly cut cross-section according to stereological principles. NOTE 2 Guidelines for polishing and etching of advanced technical ceramics can be found in Annexes A and B. The method applies to ceramics with one or more distinct secondary phases, such as found in Al2O3/ZrO2, Si/SiC,or Al2O3/SiCw. If the test material contains discrete pores, these can be treated as a secondary phase for the purpose of this method provided that there is no evidence of grain pluck-out during polishing being confused with genuine pores. NOTE 3 If the material contains more than about 20 % porosity there is a strong risk that the microstructure will be damaged during the polishing process, and measurement of volume fraction of pores may become misleading. Secondary phase volume fractions or porosity present at levels of less than 0,05 are subject to considerable error and potential scatter in results. A larger number of micrographs than the minimum of three is normally needed to improve the consistency and accuracy of the results. NOTE 4 Many ceramics contain small amounts of secondary glassy phases. In order to make a reasonable estimate of glassy phase content, the glass material between crystalline grains should be readily observable, and thus should be at least 0,5 µm in width. The method in this European Standard is not considered appropriate for narrow glassy films around grains. This method assumes that the selected regions of a prepared cross-section are statistically representative of the whole sampled section. NOTE 5 Microstructures are seldom homogeneous, and the phase contents can vary from micrograph to micrograph. It is essential to survey a sufficiently wide area of the prepared section to ensure that those areas selected for evaluation are representative, and do not contain eye-catching irregularities. Some users of this European Standard can wish to apply automatic or semiautomatic image analysis to micrographs or directly captured microstructural images. This is currently outside the scope of this European Standard, but some guidelines are given in Annex C. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. prEN 1006, Advanced technical ceramics - Monolithic ceramics - Guidance on the selection of test pieces for the evaluation of properties EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories (ISO/IEC 17025:2005) kSIST prEN 623-5:2009
prEN 623-5:2008 (E) 5 3 Terms and definitions For the purposes of this part of EN 623, the following terms and definitions apply. 3.1 phase volume fraction volume occupied by a distinct, identifiable phase present in a material expressed as a fraction of the whole 3.2 secondary phase one or more distinct identifiable phases other than a primary crystalline phase in a material NOTE A secondary phase can be in the form of discrete grains, or as a continuous phase surrounding some or all the major phase grains. For the purposes of this European Standard, porosity may be treated as a secondary phase. 4 Apparatus 4.1 Sectioning equipment A suitable diamond-bladed cut-off saw to prepare the initial section for investigation. The saw shall be metal bonded with a diamond grit size of 125 µm to 150 µm and shall be cooled. NOTE This grit size is designated D151 according to ISO 6106, see [1]. 4.2 Mounting equipment Suitable metallurgical mounting equipment and media for providing firm gripping of the test piece for polishing. 4.3 Grinding and polishing equipment Suitable grinding and polishing equipment, employing diamond abrasive media. NOTE A sequence of abrasives and techniques recommended for polishing are given in Annex A. 4.4 Microscope An optical or scanning electron microscope with photomicrographic facilities. NOTE Although the true magnification of the image is unimportant for making the measurement of volume fraction, it is advised that a reference graticule may be used to determine magnification in an optical microscope, or a reference grid or latex spheres may be used for calibration of magnification in a scanning electron microscope, and as a check on the homogeneity of magnification across the field of view. An optical microscope is additionally required for assessing polishing (see 5.4). 4.5 Transparent grid Transparent square grid on, e.g. acetate film, and with line thickness not exceeding 0,1 mm. NOTE 1 The grid spacing selected is not critical, but may conveniently be between 3 mm and 15 mm to minimise eyestrain. However, it is necessary that consideration of the requirements of 6.3 is taken into account. NOTE 2 A suitable grid may be prepared as a computer plot with sufficient accuracy of line spacing for the purposes of this European Standard.
kSIST prEN 623-5:2009
prEN 623-5:2008 (E) 6 5 Test piece preparation 5.1 Sampling The test pieces shall be sampled in accordance with the guidelines given in prEN 1006, and subject to agreement between parties. NOTE Depending on the objectives of performing the measurement, it is desirable to maintain knowledge of the positions within components or test pieces from which sections are prepared. 5.2 Cutting The required section of test-piece shall be cut using the diamond saw (see 4.1). NOTE For routine inspection of materials, a small area of side no more than 10 mm is normally adequate as the section to be polished. 5.3 Mounting Mount the test piece using an appropriate mounting medium. If the ceramic is suspected to have significant open porosity in some regions (see Clause 1) it is advisable to vacuum impregnate the test piece with liquid mounting resin before encapsulating as this will provide some support during grinding and 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 shaped test pieces and of weak friable test pieces. The method of mounting selected should take into account the etching procedure to be used; see Annex B. 5.4 Grinding and polishing Grind and polish the surface of the test piece. Care should be taken to ensure that grinding produces a planar surface with a minimum of damage. Employ successively smaller grit sizes, at each stage removing the damage from the previous stage until there is no change in appearance when examined by an optical microscope (see 4.4) at high magnification. At least 90 % of the test piece area shall be free from optically visible scratches, or other damage introduced by polishing, which will interfere with the determination. In particular, discrete secondary phases may be plucked out from the surface giving the appearance of pores. This shall be avoided. NOTE Care should be taken in choosing the sequence of grits and lap types. It is impossible within the scope of this part of EN 623 to make specific recommendations for all types of material. The general principle to be adopted is the minimisation of subsurface damage, and its removal by progressively finer grits whilst retaining a flat surface. Some guidelines on polishing are given in Annex A. 5.5 Etching When a good quality polished surface has been achieved, the test piece shall be etched if necessary to reveal the individual phases. Any suitable technique shall be used, subject to agreement between parties. NOTE 1 Some general guidelines recommending etching procedures for various commonly available advanced technical ceramics are given in Annex B. NOTE 2 For optical evaluation, it is usually necessary to etch oxide materials in such a way that the individual phases are distinguished by having different contrast levels. For evaluation by scanning electron microscopy (SEM), it may not be necessary to etch if a backscattered electron detector is used which has adequate resolution of net atomic number difference between the phases such that contrast is generated. If a secondary electron detector is used, it will usually be necessary to etch to produce topographic contrast unless the atomic number difference between the phases is large. kSIST prEN 623-5:2009
prEN 623-5:2008 (E) 7 6 Photomicrography 6.1 General aspects If it suspected that the average grain size of each phase or the widths of continuous glassy phases between grains is less than 2 µm, it will be necessary to prepare the test piece for SEM. Between 2 µm and 4 µm either SEM or optical microscopy may be used. Otherwise, optical microscopy will normally be adequate. It is important to achieve sufficient contrast between phases in order to identify individual grains clearly and unambiguously. 6.2 Inspection Inspect the sampled cross-section in the microscope. If the microstructure appears homogeneous, prepare micrographs from randomly selected areas. If inhomogeneity of microstructure is suspected, select representative areas of relevance for measurement. 6.3 Number of micrographs At least three micrographs shall be prepared at a magnification sufficient to identify clearly all the phases to be counted. In addition, at least 100 features in total of any given type shall be present to be counted in the set of micrographs. NOTE For a nominally homogeneous material, it may be sufficient to use a small number of micrographs analysed with a small grid spacing, but for an inhomogeneous material, results representative of the average for the sampled section can be prepared reliably only by selecting a large number of micrographs of different areas, with less intensive counting from a larger grid. 6.4 Optical microscopy Set up Köhler illumination in the microscope. NOTE Guidance on setting Köhler illumination conditions is given in Annex D. Examine the test piece at a magnification sufficient to resolve the individual grains clearly. If the contrast obtained is insufficient, e.g. in white or translucent materials, apply a suitable thin metallic coating by evaporation or sputtering. Prepare micrographs of at least three different randomly selected areas of the test-piece surface, taking into account the apparent homogeneity of the microstructure (see 6.2). As a guideline, the average size of discrete phase area to be counted should appear typically at least 3 mm across. If the total number of individual grains of any one phase to be counted in any one set of micrographs is less than one hundred, prepare more micrographs. Micrographs should be typically of a size (100 x 75) mm, but may with advantage be enlarged later to aid evaluation. 6.5 Scanning electron microscopy (SEM) Mount the test piece on the test piece holder of the microscope. If the test piece is not electrically conducting, apply a thin evaporated or sputtered conductive coating. Insert the test-piece in the microscope, ensuring that the surface to be characterised is normal to the electron beam to within 5°. NOTE 1 This ensures that the image does not suffer from excessive distortion or loss of focus due to the angle of viewing. Prepare micrographs at a suitable magnification (see 6.4) from at least three different randomly selected areas of the test piece, using either secondary electron imaging or backscattered electron imaging. NOTE 2 Although the contrast between phases can be enhanced using backscattered electron imaging, a noisier image than in secondary electron imaging may result and may render the boundaries between contrasting phases indistinct. It can be helpful to use secondary electron images for counting the phase proportions, but backscattered images to aid identification of each phase. kSIST prEN 623-5:2009
prEN 623-5:2008 (E) 8 If the number of grains of the phase to be counted is less than 100 in total over all the micrographs, increase the number of areas photographed. Micrographs should typically be of a size (100 x 75) mm, but may with advantage be enlarged later to aid evaluation. NOTE 3 It is possible that the photographic screen in the microscope will not have constant magnification at all points. A square grid makes a suitable reference for ascertaining the degree of distortion in the screen, since it is easy to detect distortions of the grid. For the purposes of this test method, distortions of typically up to 5 % may be acceptable provided that the phases being counted are distributed homogeneously across the entire area of the micrograph. 7 Measurement of micrographs If desirable, enlarge the photomicrograph to a size suitable for easier observation of the features. Examine the dimensions of the smallest features to be counted. Select a suitable grid spacing and prepare a square grid (see 4.5, 6.3 and comments in Clause 9) such that the grid area covers the entire micrograph. Tape the micrograph to a smooth surface. Overlay the grid such that the entire area of the micrograph is covered by the grid, with no grid intersections immediately over the edges of the micrograph. Count the number of grid intersections nj of the grid that lie over each phase j. If the grid intersection lies exactly over the boundary between two phases, count this as one half of a grid intersection for each phase. If porosity is to be estimated, use the same rule for when a grid intersection lies exactly on the edge of a pore. Count the total number of grid intersections over the area of the micrograph. If pores are not being counted, count the number of grid intersections lying over the crystalline or glassy phases in the material. NOTE It can be helpful in counting to screen with pieces of paper those lines of intersections above and below the one being counted; this reduces eye strain and the risk of miscounting. 8 Calculation of results For the case where porosity is to be counted as one of the phases, calculate the volume fraction of each phase using Equation (1): where
n j is the total number of grid intersections over phase j;
N is the total number of grid intersections lying over the micrograph.
For the case where porosity is to be ignored, see Equation (2): where
n j is the number of grid intersections lying over solid phase j;
Nn
=
Vj ij f (1)
)n-
(Nn
=
n n
=
Vpj ij ij ij fΣ (2) kSIST prEN 623-5:2009
prEN 623-5:2008 (E) 9
np is the number of grid intersections lying over pores;
S is the sum of all grid intersections lying over all solid phases. 9 Interferences and uncertainties The nature of the microstructure of the material can affect the result determined in this test. The test is effective when a sufficient number of grid intersections of each phase are counted. This can be achieved either by intensive analysis of the minimum number of three micrographs, or by less intensive analysis of a larger number of micrographs. For intensive analysis, the grid shall be small enough such that there is a good chance that a grid intersection will lie over each grain. Failure to do this means that the results are subject to increasing possible random error depending on exactly where the grid is positioned. The random error is minimised by adhering to the above guideline, but will always exist because of random positioning of the grid on the micrograph. Typically, for a homogeneous material with randomly distributed phases results from a given series of three micrographs counting at least 100 grains of each type should give phase volume fractions consistent to ± 0,02. If the material appears inhomogeneous, either more areas should be analysed intensively to establish the extent of the inhomogeneity, or if an average result only is required, a larger grid spacing can be used for less intensive analysis provided that at least 100 grains of each phase type in total are counted. The procedure adopted should be reported. The counting process requires visual observation of the phase lying underneath each grid intersection. Clean, well-defined phase boundaries are required. If the phase boundaries are poorly defined as a result of limited optical or SEM resolution, it is necessary to adopt a consistent criterion for assessing which side of the true boundary the grid intersection overlies. Failure to do this can lead to under or overestimation of phase volume fraction, and is particularly dangerous for small volume fractions. The micrographs should not contain features which are ambiguous. Grain pluckout during polishing could inadvertently be treated as porosity and, vice versa, features seen within shallow pores might be counted as solid grains. Particular caution should be taken to avoid subsurface grains giving strong signals in backscattered electron images, or edge highlights in secondary electron images hiding individual grains. NOTE Annex E contains information from a round robin activity associated with the development of this European Standard which illustrates these concerns. 10 Test report The report of the test shall be in accordance with the reporting provisions of EN ISO/IEC 17025 and shall include at least the following information: a) name and address of the testing establishment; b) date of the test; c) on each page, a unique report identification and page number; d) customer name and address; e) reference to this European Standard, i.e. determined in accordance with EN 623-5; f) authorizing signature; NOTE 1 For routine presentation of results it is useful if a standardised format is adopted. A recommended scheme is given in Annex F. g) any deviation from the method described, with appropriate validation, i.e. demonstrated to be acceptable to the parties involved; h) details of the test piece, including material type, manufacturing code, batch number, etc.; kSIST prEN 623-5:2009
prEN 623-5:2008 (E) 10 i) observation technique employed (optical or scanning electron microscope); j) a summary of the procedure for sampling, cutting, grinding, polishing and etching the test piece; k) copies of the micrographs used for the measurements; NOTE 2 It is good practice to provide magnifications on all micrographs, even though not a requirement of this European Standard. l) grid size employed; m) number of grid intersections lying over each of the defined phases, including pores if appropriate, on each of the micrographs; n) total number of grid intersections on each micrograph; o) calculated volume fractions of each phase in each micrograph, and the overall result from all micrographs, expressed as a decimal number to two significant figures; p) any remarks on the appearance of the microstructure, and difficulties of observing the individual phases. kSIST prEN 623-5:2009
prEN 623-5:2008 (E) 11 Annex A
(informative)
Grinding and polishing procedures Preparation of polished sections of ceramics requires different procedures from those conventionally employed for metallic materials, which typically commence with a coarse grinding stage using fixed grit silicon carbide papers of grit sizes of 30 µm or greater (see [1] for information on grit size coding). For ceramic materials, this type of procedure can produce considerable amounts of sub-surface damage in the form of extended microcracks which can then influence the microstructural appearance obtained, unless precautions are taken to minimise such damage and to
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