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Page 1
© Oxford Instruments 2012 CONFIDENTIAL
The Business of Science®
Phase diagrams application
in EBSD/EDS phase identification
P. Nowakowski, H. S. Ubhi
Oxford Instruments
Acknowledgements:
K. Larsen (Oxford Instruments), A. Guesnier (Struers), C. Seguineau (Nowa Mems), P. Nguyen (CNES),
V. Chazal (Thales), J-M Desmarres (CNES)
Page 2
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1) Materials study of common use instrument
2) Analyze of space technology alloy
Two unknown samples were considered in this work
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SEM observation of reservoir
BSE image
We can distinguish at least two phases
light and
grey
contrast
grains with twins
grains without
twins
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EDS analyses of reservoir
Element Cu Zn Pb Total
EDS quant
results wt. %
59.26 38.37 2.37 100.00
Area of
analysis Chemical composition
What phase can be predicted from the
composition?
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Cu-Zn phase diagram
For the composition of
60 wt. % Cu
40 wt. % Zu
The expected phase
composition is:
- α-brass, fcc structure
- β-brass, bcc structure
Page 7
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Phase ID: Reservoir
At % Cu Zn Total
α 65.33 34.67 100.00
β 57.98 42.02 100.00
β-brass, bcc
α-brass, fcc
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EBSD / EDS Maps: Reservoir
EDS layered map EBSD phase distribution map
EDS IPF colored map
β-brass (Zn rich), bcc
α-brass (Cu rich), (fcc) -
8 kV
Step size : 50 nm
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SEM observation of ball
BSE image
We can distinguish at least two phases
matrix
grey particles
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EDS: Ball
Element Si Cr Mn
Fe Total
EDS quant
results wt. %
0.40
12.9
1.0
85.7
100.00
It could be a high chromium rich steel
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EDS: Ball
Wt %
Si Cr Mn Fe Total
ball 0.4 12.9 1.0 85.7
100.00
wt % C Si Mn Cr
X65 Cr13
0.6-0.8 <0.35 0.6-0.7
12.5
-
13.5
Possible steel composition
ED Quant of ball
The expected phase composition is:
- α-Fe, structure bcc
- M23C6, structure fcc
Calculated isopleth section of Fe-C
system at 14% wt. Cr
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EDS/EBSD combined Phase ID
M23C6 - Carbides
αFe - matrix
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Carbide particle size 0.3 µm
EBSD / EDS Maps: Ball
Cr Kα EDS map EBSD phase distribution map
EDS IPF colored map
M23C6, (fcc) -
α-Fe, (bcc) -
8 kV
Step size : 50 nm
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Space technology material
CNES (French National Center for Space Research)
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SEM observation
We can distinguish at least three phases
- irregular grey particles
- matrix
- regular small bright particles
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It could be an aluminum 2024 or V65 type alloy used for riveting applications in space technology (1)
(1) Abhay K. Jha et al, J Fail. Anal. and Preven. (2011)
EDS analyses
Element
Mg
Al
Si
Mn
Fe
Cu
Total
EDS quant
results wt. %
0.5
93.0
1.0
0.8
0.7
4.0
100.00
Page 17
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EDS analyses
Element
Mg
Al
Si
Mn
Fe
Cu
Total
EDS quant
results wt. %
0.5
93.0
1.0
0.8
0.7
4.0
100.00
For that chemical the composition of Al based alloys we can find in literature
three thermodynamically equilibrated systems (2):
1) binary Al-Cu
2) quaternary Al-Mn-Fe-Si
3) ternary Al-Mg-Si (2)Z. Zhu, PhD Thesis (2006)
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For the composition of
4 wt. % Cu
93 wt. % Al
The expected phase composition is:
- Al matrix, fcc structure
- θ-phase (Al2Cu), tetragonal
structure
Al-Cu phase diagram
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For the composition
The expected phase composition is:
- Al matrix, fcc structure
- α-Al(Fe,Mn)Si phases, cubic structure
(4, 5)
- Si, fcc structure
Calculated isopleth section of Al-Fe-Mn-Si
system at 1% wt. Mn and 3% wt. Si (3)
(3) J. LACAZE et al., Metallurgical and materials transaction A (2010)
(4) N.V. Kazennov et al, Moscow University Chemistry Bulletin (2010)
(5)J. E. Tibballs et al. Journal of materials science (2001)
Element
Al
Si
Mn
Fe
EDS
quant
results
wt. %
93.0
1.0
0.8
0.7
Al-Mn-Fe-Si phase diagram
Page 20
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For the composition:
The expected phase composition is:
- Al matrix, fcc structure
- Mg2Si, fcc structure
Calculated isopleth section of Al-Mg-Si
system at 2% wt. Si (6) (6)V. Raghavan, Journal of Phase Equilibria and Diffusion (2007)
Element
Mg
Al
Si
EDS
quant
results
wt. %
0.5
93.0
1.0
Al-Mg-Si phase diagram
Page 21
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From the EDS analyses and thermodynamic data we can predict a phase list:
Element
Mg
Al
Si
Mn
Fe
Cu
Total
EDS quant
results wt. %
0.5
93.0
1.0
0.8
0.7
4.0
100.00
Al-Mg-Si
Al-Cu Al-Mn-Fe-Si
Al matrix (fcc), Al2Cu (tetragonal), α-Al(Fe,Mn)Si (cubic) and Mg2Si (fcc)
Thermodynamic phase diagrams analyses
Page 22
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Al - matrix
-Al2Cu
EDS/EBSD
PhaseID
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α-Al(Mn,Fe)Si
Mg2Si
EDS/EBSD
PhaseID
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Al (fcc) -
Al2Cu (tetragonal) -
Al(Mn,Fe)Si (cubic) -
Mg2Si (fcc) -
20 kV
Step size : 0.3 µm
Hit rate: 92 %
EDS layered map EBSD phase distribution map
EDS IPF colored map
EBSD / EDS Maps
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Conclusions
Material composition from EDS can be used to predict phases present from
phase diagrams, even in complex cases ;
Perspective
The Phases Search Engine could be optimized by including the Thermodynamic Data Bases
Using composition with phase diagrams makes easy phases identification
Page 26
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Thanks for your attention