sampling, preparation and area selection

28.05.2018

SAMPLING, PREPARATION AND AREA SELECTION Gert Nolze, BAM Berlin

Outline

1. Sampling 2. Area selection 3. Sample preparation

The basic problem for a metallographer preparing a specimen is that the preparation process itself modifies the specimen surface and, theoretically, a “true structure” completely without artifacts can never be obtained. Geels, K.; Fowler, D. B.; Kopp, W.-U. & Rückert, M. Metallographic and Materialographic Specimen Preparation, Light Microscopy, Image Analysis and Hardness Testing. ASTM International, 2007 28.05.2018

Sampling, preparation & area selectione

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Sampling

You will get what you collect!  Complex components versus simplified specimen geometry (it is not the analyst’s fault when a specimen is not well selected or improperly manufactured; cf. sample and microstructure symmetry)

 If you are part of a service unit, you are not responsible for the collection / selection of the investigated sample.

 Nevertheless, try to get as many information as possible about the specimen and the investigation issue before you start any sample sectioning or preparation.  Ask for the amount of specimen to be compared since this decides whether you can use manual or you have to use automated preparation procedures.

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Sampling  Sampling describes the extraction of a subset in mass, volume, or amount of specimens using defined guidelines.  For water, soil, air, blood and many other materials very accurate guidelines for sampling are formulated in order to keep results comparable and reproducible.  In contrast to e.g. XRD, for EBSD a standard procedure (DIN or ISO) for sampling does not (yet) exist, i.e. everybody uses his own procedure. Therefore, sampling, sample prep and area selection need to be described as accurate as possible. 28.05.2018


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What is the purpose of a sample?

 A sample is selected to enable reliable findings and conclusions in a representative way about quality, condition, composition etc.  The aim of a sample but also of a scanned area by EBSD is a statistically verified description of a specific material condition (phase distribution, orientation, misorientation etc.) under ideal imaging conditions (drift, distortions).  Any possible variation/change/modification of the sample properties during sampling or caused by a subsequent treatment like preparation or selected investigation conditions diminishes the key role of a sample and has to be prevented.  Possible interferences have to be discussed critically, e.g. any potential change during sample preparation (sampling, cutting, embedding, grinding, polishing, coating), or reduced phase stability in SEM due to electron or ion interaction (surface cleaning), vacuum etc. 28.05.2018


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Area selection

The selected map is used to represent the entire material. Therefore, make sure:  The required area might not be identical with the location on the sample where the best hit rates can be reached. There might be a serious reason, why a mapping is possible or not!  Define position and size of the orientation map with respect to the aim of the investigation (statistical relevance, reliability, high confidence).  If the area of interest is contaminated (e.g. by dust) or shows damage remove the sample and clean or reprepare the sample again, and do not move to a less relevant place.  For publication or representation do not use the nicest but the most informative orientation map. 28.05.2018


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Area selection

You will get what you select!  For area selection this is the ordinary truth in particular for EBSD because of the

‒ very short information depth ( sample preparation), ‒ often low statistical relevance ( multiple areas) ‒ (common) focusing on maximum hit rate in order to get stunning orientation maps ( select areas you need) ‒ possibly existing microstructure gradients ‒ …  We might not be responsible for a suitable sample selection, but for area selection, preparation and measuring performance we are!  Please note: Data acquisition at high tilt angles can be tricky! 28.05.2018


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Area selection Imaging and mapping at high tilt  Tilt correction appears to be simple but practically it is extremely challenging because of possible misinterpretations.  Slight topography will be exaggerated artificially. non-tilted

70° tilted

tilt corrected

 Small (unknown) deviations from ideally flat surfaces distort the corrected image in an unpredictable way.  In case of topography high tilt prevents the scanning of hidden surface areas. 28.05.2018


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Sample preparation

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Significance of sample preparation

 Practically, sample preparation is the most essential factor for a meaningful microstructure description…not only for EBSD. During preparation a sample surface can be disastrously modified.

 Please note: You can have the best equipment and operators. If your sample is improperly prepared, any measurement is meaningless and conclusions are highly questionable.  You can measure very accurate and precise, e.g. with EBSD, but if the prepared sample surface does not reflect the characteristic microstructure anymore, any experiment is insignificant.  The opposite, an imperfect SEM, however, can be compensated until a certain degree. You possibly need to measure with a lower resolution, but still the object you really want analyse.  The key question is:

How is it possible to recognize the true microstructure? 28.05.2018


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True microstructure

1. No additionally implemented deformation

Plastically deformed layer caused by preparation should be removed.

2. No scratches

Scratches normally indicate a surface that is not yet sufficiently prepared.

3. No pull-outs

Especially in brittle materials.

4. No introduction of foreign elements

Abrasive grains can be embedded in the surface.

5. No smearing

The matrix or one of the phases might smear (flow).

6. No relief or rounding of edges

Relief can develop between different constituents of the surface, caused by different hardness or other condition.

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True microstructure Requirements for reliable EBSD results  The small information depth of EBSD (a few 10nm only) requires an exceptional quality of surface preparation. (10nm are maximal 30 unit cells)  Nobody knows, which preparation technique is suitable to deliver a defectpoor surface! All mechanically prepared surfaces will have defects!  Earlier used statements like: “If Kikuchi patterns are visible” …or…”When we reach a high hit rate”…are definitely misleading!  “Fortunately”: Remaining preparation artefact are hidden by the limited accuracy and precision of the indexing procedures used in EBSD software.  This means: The better the orientation precision, the higher the requests on the surface preparation.  For an orientation approximation, e.g. a texture interpretation, this error is typically irrelevant.  In contrast, for interpretation of misorientations it is essential to be sure that the derived small misorientation is not the result of sample preparation. 28.05.2018


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Surface preparation for EBSD

Standard materialographic

Sampling

Ni plating

Sectioning

hot

Mounting

cold

Parallel grinding Grinding Polishing Ion polishing

(Vibration) polishing

Typical workflow for the surface preparation required for EBSD. In simple terms: A common standard materialographic surface preparation is followed by an EBSD specific surface finishing in order to remove all remaining damages from former steps.

Electrolytic polishing

(Coating)

EBSD specific 28.05.2018


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Some general preparation rules

1) Cutting: Use the gentlest possible cutting technique (cooling!). Sectioning is a violent process and it can introduce massive damage if done improperly.

2) Grinding: a) First, make all of the specimens in the holder co-planar. b) Gently remove the damages caused during sectioning. c) Grind with fresh abrasive paper changing grit and direction. 3) Polishing: a) Utilize flat, low-resilience woven cloths or pads that minimize relief problems. b) Keep the polishing surface uniformly coated with abrasive and lubricant during polishing. 4) Cleaning: Clean and dry carefully without touching the surface.

With a bit experience you will see:

There is absolutely no mystery! 28.05.2018


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Machining and cutting

Transverse taper section of a surface of annealed 30% Zn brass orthogonally machined by a planning tool with a -35° rake angle, the depth of cut being 25µm. SBL: shear-band layer, DL: deformed layer

 Typically samples are machined or cut from some materials using destructive techniques like sawing or cutting.  Alternative techniques like spark erosion or ion etching (FIB) change the material at the surface by carburization (surface roughness!) or ion implementation (ion channeling!).

Samuels, L. E. Metallographic Polishing by Mechanical Methods. ASM International, 2003 28.05.2018

 Non-destructive techniques like wire etching or water jet cutting are best suited since they are assumed to damage the surface only marginally.


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Cutting Some general rules • Preparation faults introduced during sectioning a sample are very difficult to remove. • A gentle cutting lasts longer, does not modify the microstructure and finally saves time during subsequent polishing. • Common tools are precision saw (very thin blade), or wire saw (takes longer time). • In all cases ensure adequate cooling!

• Please note: The damage depth also depends on the material, i.e. depends on chemical composition and crystal structure.

Depth of damage after band-saw cutting of fcc, hcp and bcc materials. fcc (Cu)

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hcp (Ti)


P.T. Pinard et al. Microsc. Microanal. 15 (2009)

bcc (Fe) Suppl 2, 778-779

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Cutting Laboratory abrasive saw • For abrasive cutting the damaged zone is clearly thinner. The displayed profiles simply use the band contrast measured along the cross section of cut surfaces.

abrasive saw

band-saw fcc (Cu)

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hcp (Ti)


P.T. Pinard et al. Microsc. Microanal. 15 (2009)

bcc (Fe) Suppl 2, 778-779

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Embedding Electrically conductive resin (hot mounting) Advantages  fast (for a single mount)  reduces charging  higher abrasion resistance (reduces rounding effects along the interface) Struers

 reduced fissure formation  Hot mounting provides parallel top and bottom surfaces (no out-of-plane distortions).  Most hot mounting materials are stable in vacuum.  No out-gassing or vapor which may cause contaminations.

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Embedding Electrically conductive resin (hot mounting) Disadvantages  Not transparent!  Only limited specimen size.  Possible contamination from the filler.  Fragile and brittle materials cannot be hot mounted.

Struers

 For soft materials the abrasion rate is possibly higher so that the sample will not polished properly.  In case of high temperature embedding 180°C are required (cold embedding: during polymerization shortly 110°C are reached)

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Grinding

• Grinding particles are at least 100-times bigger than the information depth of EBSD. How big is the deformation zone? • Band contrast analysis demonstrates: The damage depth is approximately one tenth of the particle size. Depth of damage after grinding of Cu. P80 ≈200µm

P220 ≈70µm

• In contrast, respective FIB images suggest a misleading smaller depth, i.e., instead of 15…20µm only ≈5µm.

P.T. Pinard et al. Microsc. Microanal. 15 (2009) P1000≈18µm Suppl 2, 778-779

P80 ≈200µm

5µm

P.T. Pinard et al. Microsc. Microanal. 16 (2010) Suppl 2, 700-701 28.05.2018


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Mechanical polishing

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Deformation during preparation

 The depth of a deformation zone of a material is in general unknown! Only a cleaved surface is perfect!

 Each preparation step removes material but also implements new surface damages.

Sketch of an ideal preparation procedure removing step by step the (unknown) inherent deformation, but mainly the newly implemented damaging during polishing. Piotrowski, T. & Accinno, D. J. Metallography of the precious metals. Metallography 10 (1977), 243-289

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 For standard metallography this is often not essential because of a subsequent etching which removes this layer, or because of the lower image resolution used in light microscopy.

 For EBSD any unrepresentative damaging is significant, anyway if still remaining or just implemented. 23

Polishing Induced deformations

Samuels, L. E. Metallographic Polishing by Mechanical Methods ASM International, 2003

During preparation different surface damaging can happen: A. a loose, tumbling particle, B. a fixed particle plowing a groove, C. a fixed particle cutting a chip All of them generate deformations around and below them which are usually invisible in the surface image since smeared up by removed material.  After standard polishing always deformations exist. 28.05.2018


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Silica polishing

 As surface finishing a polishing with colloidal silica is preferred.  Colloidal silica is a chemo-mechanical polish which combines mechanical and chemical attacking. (topography!)  Typical abrasive size is 0.05 micron.  Please note: Not all silica is the same! Different pH-levels and lubricants cause various etching behavior. Warning:  Colloidal silica crystallizes readily and will ruin polishing cloths if left to dry. Clean them carefully!  More problematic, a film can be formed on the polished surface.  To prevent this, flush the polishing cloth with (hot) water during the last few seconds of polishing.  Remove and dry the sample using a solvent with low water content. Alcohol is ideal. Do not use acetone! 28.05.2018


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Vibration polishing

 Designed to prepare high quality surfaces on a wide variety of materials by an automated polishing with colloidal silica.  As pressure the own sample mass or small additional weights are used.  A horizontal vibratory motion of typically 7200 cycles per minute produces a very effective polishing action.

 Often long-time polishing (several hours) is reported.  The vibratory action generates less deformation, flatter surfaces and lower edge rounding.  It also yields a stress-”free” surface without the use of dangerous electrolytes associated with electropolishing. 28.05.2018


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Vibration polishing

An improvement of the band contrast of only ≈10…20% after 20 min vibration polishing may not look that much. However, it tells us that the applied standard polishing was definitely imperfect, and the EBSD maps suboptimal. 28.05.2018


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Some references Standard metallographic preparation Bauer, O. & Deiß, E.: Probenahme und Analyse von Eisen und Stahl, Verlag Julius Springer, 1922 Berglund, T. & Meyer, A.: Handbuch der metallographischen Schleif-, Polier und Ätzverfahren, Verlag Julius Springer, 1940 Miley, D. V.; Calabra, A. E.; McCall, J. L. & Mueller, W. M. (Eds.): Metallographic Specimen Preparation: Optical and Electron Microscopy. Springer US, 1974 Elssner, G.; Hoven, H.; Kiessler, G. & Wellner, P.: Ceramics and Ceramic Composites: Materialographic Preparation, Elsevier Science, 1999 Chinn, R. E.: Ceramography: Preparation and Analysis of Ceramic Microstructures, ASM International, 2002, 35-44

Samuels, L. E.: Metallographic Polishing by Mechanical Methods ASM International, 2003 Vander Voort, G. F. (Ed.): Metallography and Microstructures, ASM International, 2004, volume 9 Geels, K.; Fowler, D. B.; Kopp, W.-U. & Rückert, M.: Metallographic and Materialographic Specimen Preparation, Light Microscopy, Image Analysis and Hardness Testing, ASTM International, 2007 Echlin, P.: Handbook of Sample Preparation for Scanning Electron Microscopy and XRay Microanalysis. Springer Science+Business Media, 2009 28.05.2018


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Cleaning of samples

• Any contamination during or after sample preparation disturbs. • Frequently, ultrasound baths are used in order to remove or reduce dust particles or lose dirt on sample surfaces. They are also used by some people after each preparation step in order to prevent any contamination for the following step. • If strong contaminations appear during imaging in SEM try distilled or de-ionized water. It is said that the latter prevents carbon contamination during scanning in SEM. • In case of cracks, holes, pores etc. use a heating stage at moderate temperatures to remove hidden water. Otherwise, in SEM from each cavity the remaining water flows out and contaminates the surface again.

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Cleaning of samples

• Sometimes, a sample surface is contaminated by dirt which is not removable by a gentle air flow or ultrasound bath, e.g. crystallized silica. • A possible solution can be acetate tape (Formvar) which is commonly used for replica in TEM. • Cover your sample surface with acetone, put a thicker acetate foil on the wet surface and wait until it is dry (this lasts a few minutes only).

• Strip the tape carefully. • All loose dust and many silica particles are now fixed in the tape, and the surface can be investigated without repolishing the sample.

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Omnipresent charging A few tricks  Minimize surface topography!  Coat with gold before the final polishing step. This fills the cracks and voids with a conducting network.  Prepare a conductive tract from the sample to the stub/holder – using some silver paint or metallic tape.  Scan the surface for 30min or longer at low magnification.  If possible, leave the sample over night in the SEM.  Work in variable pressure / low vacuum mode (if you have). Often a chamber pressure of 5-20 Pa is sufficient. A higher pressure decreases resolution as well as the pattern quality.

 More efficient: Gas injection systems.

They blow gas molecules directly in the electron beam.

 Use higher acquisition speed (needs fast & sensitive detectors). The beam has a minimal dwell time.

 Work at lower probe current and/or vary the accelerating voltages. 28.05.2018


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Sample transport

• Best procedure is to go after sample preparation directly into the SEM. • If this is impossible, use Joseph paper (thin, soft and lint-free tissue paper) to protect the surface. It also helps against accidental touches. • Before mounting in the SEM, always clean the surface by a gentle air flow. • Do not use any air brushes since the used air often contains oil which contaminates your sample surface ever more!

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Demagnetisation

• EBSD measurements are based on the interaction of electrons with a sample. • The electron beam in SEMs is controlled by electric or magnetic fields. • This means: If the sample or the detector charges, the electron beam path is influenced by the respective fields. Quartz pattern • Sometimes, however, samples or only single phases can be magnetic as well. • Magnetism disturbs if patterns are impossible to index since their bands are no more straight. • Therefore, before investigating it is recommend to demagnetize the sample. • For really strong magnets this option does not exist. 28.05.2018


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How to prepare unknown samples for EBSD? Grinding and polishing vary for different materials, production and loading conditions…

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Struers: standard preparation The Metalogram displays materials according to specific physical properties: hardness and ductility. Hardness (Vickers): The easiest attribute to measure but is not sufficient information about a material to find the correct preparation method.

Ductility: The ability of a material to deform plastically is important for grinding and polishing. This property expresses how the material responds to mechanical abrasion. A B C D E F G

MgAl-alloy, cast Cu (pure) CuZn alloy, cast Grey cast iron Ball/Bearing steel 100 Cr6 WC/Co sintered carbide Ceramic Si3N4

Procedure: 1. Find the hardness on the X-axis. fast procedures X AlSi alloy Y Tool steel Z Carbides in metallic matrix

https://e-shop.struers.com/BG/EN/methods/ 28.05.2018


2. Estimate ductility according to any previous experience. Ductility is no precise number! The condition is to have an idea of how a ductile or brittle material will perform. 35

Struers: standard recipes https://www.struers.com/en/Knowledge/Grinding-and-polishing#grinding-polishing-how-to

A: MgAl alloy

B: Cu

C: medium C-steel

E: white cast Fe

F: WC/Co sintered

G: ZrO2

X: AlSi alloy

Y: tool steel

Z: carbides in metal

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D: low C-steel

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Struers: Special EBSD preparation

For EBSD, however, additional preparation step(s) are required which remove the remaining or during the last polishing step introduced deformation layer. For ferrous materials a special application note is available: https://www.struers.com/-/media/Library/ Brochures/English/Application-Note-EBSD.pdf

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Buehler: standard preparation

 About 150 pages of fundamentals and recipes (free available)

 for EBSD only some basics (p. 23-25) referring to vibration and electrolytic polishing.

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George Vander Voort Rules for Pain-Free Preparation!

http://www.georgevandervoort.com/metallography/general/ebsd/ 20001256-mechanical-specimen-preparation-for-ebsd-struers.html 28.05.2018


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Automated polishing Vander Voort, G. F. Metallographic specimen preparation for Electron Backscattered Diffraction: Part I Prakt. Metallogr., 2011, 48, 454-473

This generic mechanical preparation process is suitable for many metals and alloys. For tough materials like Ti the 3µm diamond polishing should be omitted. 41

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Manual preparation

In BAM we always start with a 4-step manual preparation. It practically works for ca. 90% of all materials (metals, minerals, ceramics…).

The rotation speed during grinding and polishing is constant. The applied force is a matter of feeling (personal experience).

42

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Special recipes

For pure Zr:

25€ /l 28.05.2018

28€ /l


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Alternatives Electrolytic polishing

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 Widely used technique because of excellent results  contact-free preparation  Works for non-planar surfaces  Factors controlling etching / polishing behavior are: ‒ Electrolyte composition ‒ Electrolyte temperature ‒ Electrolyte stirring ‒ Area to be polished/etched (current density)

Oxford Instr.

‒ Voltage

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Oxford Instr. 28.05.2018


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Advantages:

Disadvantages:

 Polishing & etching are possible

 Conductive specimens only

 Fast preparation process, i.e. easily repeatable if required  Reproducible when the process is automated  No mechanical deformation  Can produce excellent surfaces for EBSD

 Not all alloys can be polished  Preferential attack or pitting can occur (no flat surface)  No edge retention

 Limited polishing area  Limited scratch/material removal  Hazardous electrolytes  Temperature control

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Chemical etching

 Commonly easy to handle and fast.  Additionally, etching delineates the grain structure but may attack grain boundaries excessively.

 Etching may attack different phases preferentially.  Materials that are difficult to polish may benefit from repeated etching and re-polishing.  Using special acid or alkali resistant cloths, it is also possible to dilute etchants to the polishing cloth during polishing. (effective but difficult to control)  Any etchant used has to dissolve the specimen surface in an even manner without formation of any oxide or reaction product layers.

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Alternatives Ion polishing

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Broad Ion Beam (BIB) polishing (milling) Principle

HITACHI

 Non-focused ions are used to bombard and erode the surface.  Sample rotation required to generate flat surfaces.  It can also cause damages by ion implantation which can lead to an amorphous layer or phase transformation.

 Reactive gases (in vacuum) increases the milling rate.  A specimen mask enables cross sections (curtaining!) 28.05.2018


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Ion implementation BIB polishing (Ar) at Si Electron beam voltage for EBSD

Final ion polish voltage

5 kV

10 kV

15 kV

20 kV

5 kV

3 kV

2 kV courtesy of Dr. Joe Michael at Sandia National Lab, Albuquerque, USA 28.05.2018


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BIB polishing (10kV, Ar) at Cu

Also here for each material parameters have to be optimized.  For copper 10 min polishing of 10kV Ar under an angle of 8° (or 82° compared to EBSD) would give best results.  However, lower kV will likely result in higher image qualities (IQ). Dankházi, Z.; Kalácska, S.; Baris, A.; Varga, G.; Radi, Z. & Havancsák, K. EBSD Sample Preparation: High Energy Ar Ion Milling Materials Science Forum, 2015, 812, 309-314 28.05.2018


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BIB polishing (milling)

 Also ion beam milling is no solution for everything!  Very useful for all materials where any mechanical handling generates artefacts.

 Target preparation using specimen mask.  The optimization of parameters is time-consuming.

Possible drawbacks: ‒ anisotropy of milling (topography) ‒ curtaining, if sample cannot be rotated ‒ possible phase transformation ‒ point defects (ion implantation) ‒ comparatively slow 28.05.2018


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BIB polishing Sample cooling

Hitachi

During interaction with ions the sample heats up and the microstructure may change considerably: phase transformation, evaporation or sublimation. In order to prevent this, samples need to be cooled. 28.05.2018


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Focused ion beam (FIB) preparation Phase transformation

A special thermo-mechanical treatment produces causes a transformation from bcc to fcc. The lathes are nicely visible already in the SE image of the FIB cut. The EBSD scan shows nicely as well the phase boundaries and the orientation differences. Surprisingly the software identify all fcc-grain close to the surface as bcc phase! 28.05.2018


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EBSD related preparation literature Katrakova, D. & Mücklich, F.: Specimen Preparation for EBSD - Part I: Metals. Prakt. Metallogr., 2001, 38, 547-562 Katrakova, D. & Mücklich, F.: Specimen Preparation for EBSD - Part II: Ceramics. Prakt. Metallogr., 2002, 39, 644-662 Wynick, G. & Boehlert, C.: Use of electropolishing for enhanced metallic specimen preparation for electron backscatter diffraction analysis. Mater.Charact., 2005, 55, 190-202 Vander Voort, G.; van Geertruyden, W.; Dillon, S. & Manilova, E.: Specimen Preparation for Electron Backscattered Diffraction. Microsc. Microanal., 2006, 12p, 1610 Schwarzer, R.: The preparation of Mg, Cd and Zn samples for crystal orientation mapping with BKD in an SEM. Microscopy Today, 2007, 15, 40-42 Vander Voort, G. F.: Metallographic specimen preparation for Electron Backscattered Diffraction. La Metall. Ital., 2009, 11-12, 71-79 Vander Voort, G. F.: Metallographic specimen preparation for Electron Backscattered Diffraction: Part I. Prakt. Metallogr., 2011, 48, 454-473 Vander Voort, G. F.: Metallographic specimen preparation for Electron Backscattered Diffraction: Part II. Prakt. Metallogr., 2011, 48, 527-543 Koll, L.; Tsipouridis, P. & Werner, E. A.: Preparation of metallic samples for electron backscatter diffraction and its influence on measured misorientation. J. Microsc., 2011, 243, 206-219

Halfpenny, A.; Hough, R. M. & Verrall, M.: Preparation of Samples with Both Hard and Soft Phases for Electron Backscatter Diffraction: Examples from Gold Mineralization. Microsc. Microanal., 2013, 19, 1007-1018 Brodusch, N.; Demers, H. & Gauvin, R.: Field Emission Scanning Electron Microscopy: New Perspectives for Materials Characterization, Chapter 10, Springer Singapore, 2018 28.05.2018


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EBSD related preparation literature

Please note:

Literature often only describes how to get Kikuchi patterns, but not, how to get the patterns you need!

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Sample preparation Final recommendations  Conventional metallographic preparation is suitable followed by a polishing with colloidal silica (about 20min).  Different colloidal silica based polishing agents have different behaviour. You should test them!  For conductive materials electro polishing is an excellent option although for different metals different etchants are required. Often, for safety reasons, it is no more permitted.  Spend the time you really need! For texture investigations the preparation does not have to be perfect as long as no artefacts will be introduced.  For misorientation measurements – e.g. GND interpretations – preparation artefacts have to be minimized!  The standard orientation determination is not very precise. On the other hand, the best preparation is for nothing if artefacts cannot be discriminated by the used orientation determination. 28.05.2018


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Sample preparation Final recommendations  For multiphase materials, sample preparation is always a compromise since the containing phases react differently.  At multiphase materials topography can be only rarely prevented.  For “difficult” multiphase materials ion etching at low energy is an option since no new scratches will be generated. However, it also has drawbacks, like increasing topography.  For composites combining very soft and hard phases, commonly ion etching under gracing incident is the only option. Again: Any sample preparation is an intervention with unknown external interference on the microstructure.

It is not sufficient if Kikuchi patterns can be indexed with satisfying hit rate ! 28.05.2018


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sampling, preparation and area selection

sampling, preparation and area selection

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