EBSD specimen preparation techniques
Yongjun Chen
The Norwegian University of Science and Technology (NTNU),
Department of Materials Technology,
Email: kgcyj_123@163.com
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Trondheim
May 16, 2011
• Mechanical polishing sequence suggested by EDAX TSL
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Steps
Methods
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Section and mount the sample
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Grind until planar using 240 grit SiC paper
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400 grit SiC paper
15-20 seconds
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600 grit SiC paper
15-20 seconds
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800 grit SiC paper
15-20 seconds
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1200 grit SiC paper
15-20 seconds, this step
may be repeated 2-3 times
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9 micron diamond solution
5-10 min
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3 micron diamond solution
5-10 min
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1 micron alpha alumina solution
5-20 min
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0.3 micron alpha alumina solution
5-15 min
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0.05 micron colloidal silica solution Above 1 min
Trondheim
Time
May 16, 2011
Outline of final preparation techniques
1. Silica polishing
2. Electropolishing
3. Chemical etching
4. FIB
5. Ion Milling
6. Hitachi polisher
Note: Many samples have their own requirements for
preparation.
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Trondheim
May 16, 2011
1. Silica polishing
Silica solution consists of negatively charged
particles of silicon dioxide (SiO2) with a pH
value between 8 and 11. The solution polishes
and slightly etches the specimen, removing
most of the surface deformation layer.
This solution works well with nearly all materials,
with particular effectiveness on ceramic and
geological samples that are otherwise difficult to
prepare.
Comment: Not the first choice method. Not good
for Al, Ti and Mg samples.
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Trondheim
May 16, 2011
Series of BSE images (a-d) and corresponding
EBSPs (e-l) after various polishing stages on the
duplex steel.
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Series of BSE (a-c) FSD (d-f) and corresponding
EBSPs (g-i) from the alumina sample after various
mechanical polishing stages.
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2. Electropolishing
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Removes material from the surface of the sample by electrolytic
action
Works very well on many metals.
Find an ideal solution for your sample on http://www.struers.com or
from a literature.
electrolytes that are used to produce TEM thin foils can be used on
bulk specimens
Comments,
1.No universal electrolyte that works with all materials
2. Many solutions have a short shelf life.
3. The most popular and effective method for EBSD so far.
4. Quick, 10s to 1 min.
Common Problems with electropolishing and how to do?
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You should be able to do like these with
electropolishing (Raw data, without clean up)
Titanium (alloys)
Mg alloys
Pure Ti, Mean CI: 0.7, Details in
Y.J. Chen et al, Scripta Mater. 64 (2011) 904
Mg alloys, Mean CI: 0.58, Details in
Y.J. Chen et al, Scripta mater. 58 (2008) 311
Al alloys
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Al alloys, Mean CI: 0.68
3. Chemical etching
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Advantages:
Fast
Can be reproducible
No mechanical deformation
Can be automated
Can produce excellent surfaces for EBSD
A good first choice for many materials is Nital (5% Nitric
Acid, 95% Ethanol).
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Disadvantages:
Conductive specimens only
Not all alloys can be polished
Preferential attack or pitting can occur
Hazardous Electrolytes
4. 3D-EBSD assisted with FIB milling
Mechanical polising
Electropolishing
Chemical etching
Special methods
.e.g. FIB
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Trondheim
Easy and convenient, Damages surface
and exists of residual stress
Quick and convenient, But different
material needs different electrolyte.
Toxic chemicals. Lone time to
optimize the parameters.
Qestion, Can we find a
universal method to polish all
sample?
May 16, 2011
3D-EBSD assisted with FIB milling
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Trondheim
May 16, 2011
Summarized parameters used in FIB with
3D-EBSD
Materials
Ni-based
superalloy
Si
Iron and
Ni-0.3% Si
ECAPed
Cu alloys
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Voltage
(Kv)
30
Current (
nA)
3
30, 5 and 2
-
30
20 for
milling
3 for clean
30
500pA
Trondheim
Incidence
angle
1
Area
(μm3)
Instrument
50×50×0.
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FEI Nova
600
Nanolab
dual-beam
-
FEI helios
dual
platform
35×35×22
FEI
Novolab
200
DualBeam
20×20×10
Zeiss
XB1560
crossbeam
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7
small
May 16, 2011
Milling strategies
Edge milling
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Surface
milling
Results comparison
SEM: 20 KV
SEM: 10 KV
SEM: 5 KV
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Trondheim
May 16, 2011
Comments on FIB for 3D-EBSD
1. Advantages,
1.expose surfaces that are directly suitable for EBSD, make in-situ 3D
EBSD become reality.
2. preparing materials that are too soft for conventional preparation.
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2. Changlenges,
• FIB milling of high atomic numbers (Ni, Fe, Cu, Ag and Au) generates
better quality of free surface than the low atomic numbers (Mg and Al).
The reason to this issue is the higher degrees of surface penetration of
Ga+ ions with low atomic numbers during FIB milling, and the
considerate surface damage generated by the interacting of Ga+ ions
and the low efficiency of backscattering electrons.
1. Time consuming and expensive. Serial sectioning of a 20×20×20
μm3 of materials using a 0.1 μm slice thickness with a moderate to
high milling rate and EBSD mapping using a 0.1μm step size with a
frame rate of 50 patterns/s requires at least 100 h of microscope time.
5. Ion beam milling/ etching
• Routinely used for the preparation of samples for TEM analysis,
• Works on almost all types of material.
• Can very accurately remove a given thickness of material from the
surface.
• It is important that the ion beam energy is low (low voltages/currents),
otherwise this can introduce damage to the crystal lattice – this often
happens with focused ion beam (FIB) instrument
• High tilts (45° - 70°)
• Better to etch slowly for a long time, than quickly for a short time
• Can also be used to remove layers on the surface, such as oxides or
contamination
Comments,
• Usually limited to relatively small areas (< 1cm2), making it unsuitable for
preparing coarse grained geological samples
• Long time
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2.5 kV Etch with No Tilt on Polished Ni
As Polished
IQ=156
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20 min etching
IQ=80
5 min etching
IQ=78
30 min etching
IQ=83
10 min etching
IQ=77
2.5 kV Tilt Etch on Passivated Cu
No Etch
IQ=20
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Etch 120 min.
IQ=48
Etch 30 min.
IQ=30
Etch 240 min.
IQ=156
Etch 60 min.
IQ=30 Votes=35
Etch 480 min.
IQ=238
The effect of different ion milling times on
pattern quality acquired on a copper sample.
The effect of different ion milling times on pattern quality acquired on a copper sample.
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6. Commercial polisher, Ion beam cross section polisher
(Hitachi E-3500)
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1. SEM imaging, X-ray analysis, and
EBSD
2. uses a wide argon ion beam to cut
through nearly any material and gives
a clear mirror-like finish with a large
viewing area.
3. The polisher eliminates flaws or
distortions resulting from mechanical
grinding or cutting .
4. reduces milling induced artifacts by
slightly swinging the specimen stage
during milling.
Thank you for your attention
(Acknowledge the documents searched from internet! )
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Yongjun Chen, NTNU