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Fundamental understanding of Nb
effect on corrosion mechanisms of
Zr-Nb alloys in and out of reactor
Zefeng Yu1, Michael Moorehead2, Leo Borrel2,
Mukesh Bachhav3, Lingfeng He3, Jing Hu4 and Adrien Couet1,2
1University of Wisconsin, Madison – Material Science and Engineering Department2University of Wisconsin, Madison – Engineering Physics Department
3Idaho National Laboratory – Materials and Fuels Complex4Argonne National Laboratory – Intermediate Voltage Electron Microscopy-Tandem Facility
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
2
RESEARCH BACKGROUND AND MOTIVATION
• Irradiation effect on microstructure of ZrNb alloy:
• In-reactor irradiation induces “βNb” platelets [2].
• Proton irradiation also induces the precipitation of those platelets [3].
• Hypothesis: Irradiation reduces Nb concentration in α-Zr matrix by
precipitating Nb-rich irradiation-induced platelets resulting in lower
corrosion kinetics
[2] Doriot, S, et al. ASTM Special Technical Publication, vol. 1543, 2015, pp. 759–799.
1 dpa proton irradiated M5 neutron irradiated M5
[3] Verlet, Romain. Influence of Irradiation and Radiolysis on the Corrosion Rate and Mechanisms of Zirconium Alloys, 2015.
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
14 dpa
3
720 Cͦ
580 Cͦ
ZrNb Microchemistry Effect on Corrosion Kinetics:
• Understand how Nb distribution affect corrosion kinetics of Zr alloys.
Samples:
• 720 Cͦ Zr-1.0Nb: αZr + βZr (Fe = 750 ppm)
• 580 Cͦ Zr-1.0Nb: αZr + βNb + Laves phases (Fe = 600 ppm)
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
720 ͦC 580 ͦC
Expected microstructures:
UNIRRADIATED ZR-1.0NB MODEL ALLOY
1. Nb distribution and electronic structure in the oxide
4UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
CORROSION KINETICS OF ZR-1.0NB
1. Nb distribution and electronic structure in the oxide
1. Exponent of oxidation kinetics
varies from:
0.5 (720°C) → 0.36 (580°C)
2. Parabolic kinetics are
typically associated with
electroneutrality (and other
things…)
3. Sub-parabolic kinetics can
be caused by space charges
(and other things…)
5
UNIRRADIATED ZR-1.0NB CHARACTERIZATION• 720 Cͦ Zr-1.0Nb:
αZr + βZr (highlighted in yellow)
βZr
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19th International Symposium on Zirconium in the Nuclear Industry
• 580 Cͦ Zr-1.0Nb:
aZr + βNb (highlighted in red)
BF HAADF
1. Nb distribution and electronic structure in the oxide
[5] M. Moorehead, Z. Yu, L. Borrel, Z. Couet, J. Hu, Z. Cai, Comprehensive Investigation of the
Role of Nb on the Oxidation Kinetics of Zr-Nb Alloys, Corrosion Science (2019).
After corrosion
360 °C, 18 MPa
Nb in βZr
dissolves in oxide
βNb remains in
oxide, limited Nb
dissolution
7 daysThickness:
0.86 μm
45 daysThickness:
1.8 μm
6
UNIRRADIATED ZR-1.0NB CHARACTERIZATION
• Microchemistry of βZr at oxide and metal interface :
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
1. Nb distribution and electronic structure in the oxide
[5] M. Moorehead, Z. Yu, L. Borrel, Z. Couet, J. Hu, Z. Cai, Comprehensive Investigation of the
Role of Nb on the Oxidation Kinetics of Zr-Nb Alloys, Corrosion Science (2019).
oxi
de
metal
• Nb is seen to leech out from the β-Zr precipitate upon oxidation.
• Doping the oxide with additional Nb in solid solution
• WHAT IS THE Nb OXIDATION STATE?
Incident X-Ray Energy
Monochromatic
X-Ray Beam
X-Ray Detector
Nb Kα X-Ray
• Monochromatic incident X-ray beam is
increased in energy
• Shape of the Nb Kα X-ray emission
curve can be fit to known standards
using Athena
• Metallic/Oxidized fractions can then
be determined 0
0.2
0.4
0.6
0.8
1
1.2
1.4
18950 19000 19050 19100
No
rmal
ize
d C
ou
nts
Incident X-Ray Energy (eV)
XANES Sample FittingRaw Data Data Fit
NbO Powder, 2+ Nb Alloy, Metallic
Nb Powder, Metallic
XANES SETU P A T TH E
SY N C H R OTR O N APS
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1. Nb distribution and electronic structure in the oxide
8UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
2 um
• Nb experiences delayed oxidation in comparison
to the Zr matrix.
0.0%
0.2%
0.4%
0.6%
0.8%
1.0%
1.2%
-4 -2 0 2 4
Am
ou
nt
of
Nb
oxi
diz
ed
(w
t%)
Distance from interface
Oxidation Profile Zr-1.0Nb (720C)
M/O O/W
XANES DATA ANALYSIS
1. Nb distribution and electronic structure in the oxide
9UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
• More Nb remains metallic, locked in SPPs, in 580°C Zr1.0Nb oxide
than in 720°C Zr1.0Nb oxide.
• This confirms the TEM/EDS data
• WHY DO WE CARE?
XANES RESU LTS
1. Nb distribution and electronic structure in the oxide
Zr-1.0Nb (720°C)
10UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
2 um
• Rationalization using the Coupled Current Charge Compensation model:
• 1D conservation law for VO.. and 𝑒− :
𝜕𝐽𝑠 𝑥,𝑡
𝜕𝑥+
𝜕𝐶𝑠 𝑥,𝑡
𝜕𝑡= 0
• The interface reactions are at equilibrium.
• The diffusion of oxygen into the metal or suboxide formation ahead of the oxide are
neglected
• The oxide-water and oxide-metal interfaces are planar and the oxide microstructure
homogeneous.
• The coupled-current condition of net zero charge transport through the film at all times.
𝑠
diffusingspecies
𝑍𝑠𝑒𝐽𝑠 = 0, 𝐽𝑠 = 2𝑎𝜈𝑠e−
𝑒𝜁𝑠𝑘𝐵𝑇 𝐶𝑠
𝑘−1e𝑍𝑠𝑒𝑎𝐸𝑘𝑘𝐵𝑇 − 𝐶𝑠
𝑘e−
𝑍𝑠𝑒𝑎𝐸𝑘𝑘𝐵𝑇
• Local space charge at monolayer 𝑘 (hydrogen not modeled, see poster session):
𝜌𝑘 =
𝑠
Allspecies
𝑍𝑠𝐶𝑠𝑘 = 2𝐶VO
..𝑘 − 𝐶e−
𝑘 +
𝑖
Aliovalentions
𝑍𝑖𝐶𝑖𝑘
1. Nb distribution and electronic structure in the oxide
MO D ELIN G O F NB EFFEC T O N
CO R R O S IO N
11UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
2 um
• Space charge 𝝆 𝒙 → local electric field, 𝐸𝑘 :
𝐸𝑘 = 𝐸0 +8𝜋𝑎𝑒
𝜀𝜀0Γ𝑘
𝑙=1
𝑘
2𝐶VO..𝑙 − 𝐶e−
𝑙
with Γ𝑘 = 1 −
𝑙=1
𝑘 σ𝑚=05 4 −𝑚 𝐶
Nb 4−m ′𝑙
2𝐶VO..𝑙 − 𝐶e−
𝑙
• Γ𝑘 is defined as the space charge compensation factor evaluated at the 𝑘th
layer.
• If Γ𝑘 = 0 ⟺ σ𝑚=05 4 −𝑚 𝐶
Nb 4−m ′𝑙 = 2𝐶VO
..𝑙 − 𝐶e−
𝑙 , then local
electroneutrality is achieved thanks to the solute Nb in the oxide
• If Γ𝑘 = 0 ⟹ parabolic kinetics
• Solved using a robust Newton-Raphson method.
1. Nb distribution and electronic structure in the oxide
MO D ELIN G O F NB EFFEC T O N
CO R R O S IO N
12UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
2 um
• C4 model result:
1. Nb distribution and electronic structure in the oxide
MODELING OF NB EFFECT ON CORROSION
As expected, the ZrNb alloy corrosion
kinetics decreases (and becomes sub-
parabolic) IF LESS Nb IS IN SOLID
SOLUTION to compensate the space charge
13
XANES VS C4
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Ok… solute Nb matters for corrosion rate… Do that apply to irradiation?
M. Moorehead, Z. Yu, L. Borrel, Z. Couet, J. Hu, Z. Cai, Comprehensive Investigation of
the Role of Nb on the Oxidation Kinetics of Zr-Nb Alloys, Corrosion Science (2019).
1. Nb distribution and electronic structure in the oxide
C4 model:For Nb2+:
Γ𝑘 = 0
⟺ 2𝐶Nb2
′𝑙 = 2𝐶VO
..𝑙 − 𝐶e−
𝑙
For Nb3+:
Γ𝑘 = 0 ⟺ 𝐶Nb′𝑙 = 2𝐶VO
..𝑙 − 𝐶e−
𝑙
XANES:
𝑚=0
5
𝐶Nb𝑚
′𝑙
However, XANES is not sensitive enough for:
𝑚=0
5
4 − 𝑚 𝐶Nb 4−m ′𝑙
Zr1.0Nb (720 °C)
135 days
7 days
Nb2′
Nb3′
Nb2′
Nb3′
Nb2′
Nb3′
Nb2′
Nb3′
Zr1.0Nb (580 °C)
7 days
135 days
14
IR R A D IAT IO N EX P ER IM EN TA L SETU P
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19th International Symposium on Zirconium in the Nuclear Industry
2MeV Proton Irradiation at University of Wisconsin-Madison
Ion Beam Laboratory
Parameters:
8-10 μA , 1.3x1019 ions/cm2/s, 1.0 dpa, 123 hrs, 350°C
Temperature history
[4] Yu, et al. “Irradiation-Induced Nb Redistribution of ZrNb Alloy: An APT Study.” Journal of Nuclear Materials, vol. 516, 2019, pp. 100–110.
2. Proton irradiation induced Nb redistribution
• 2MeV Proton Irradiation• 20 μA , 6.94E13 ions/cm2s, 1 dpa, 350°C• Indium cooling stage • Temperature control with IR camera (Calibrated)
UW-Madison Ion Beam Laboratory
15
(S)TEM/EDS ON UNIRRADIATED ZR-XNB• Total element composition:
• 570 Cͦ Zr-0.5Nb : αZr + β Nb + Laves phases
• 570 Cͦ Zr-1.0Nb: α Zr + βNb + Laves phases
UW Environmental Degradation of Nuclear Materials Laboratory
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ppm Nb Fe Al Cr Ni Si
Zr0.5Nb 5270 430 50 30 20 20
Zr1.0Nb 11270 470 40 40 20 10
2. Proton irradiation induced Nb redistribution
16
(S)TEM/EDS ON IRRADIATED ZR-XNB
• Irradiated samples were prepared by FIB
• Irradiation induced platelets were found in 1 dpa Zr0.5Nb
UW Environmental Degradation of Nuclear Materials Laboratory
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FeZr
Nb Cr
STEM BF platelets + native
2. Proton irradiation induced Nb redistribution
17
• Irradiation induced platelets were also found in 1 dpa Zr1.0Nb
• There are lots of Nb-rich platelets (max. 40 at.%) for 1 dpa Zr1.0Nb
135 ± 69 nm long 27 ± 12 nm wide
•
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
BF
30 nm
(S)TEM/EDS ON IRRADIATED ZR-XNB
2. Proton irradiation induced Nb redistribution
18
APT CHARACTERIZATION
• APT study on Zr1.0Nb and Zr0.5Nb shows Nb-rich nanoclusters in the
irradiated samples.
• Observation of nanoclusters are consistent with literatures.
• Proton irradiation on Low-Tin ZirloTM by E. Francis [6].
• 4MeV Ni3+ at 573K on J-AlloyTM [7] .
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
1dpa Zr0.5NbZr1.0Nb
[4] Zefeng Y., Couet A. (2019). JNM
[6] Francis, E., Babu, R., Harte, A., Martin, T., Frankel, R., Jadernas, D., . . . Preuss, M. (2019). Effect of Nb and Fe on damage evolution in a Zr-alloy
during proton and neutron irradiation. Acta Materialia, 165, 603-614.
[7] Matsukawa, Y., Yang, H.L., Saito, K., Murakami, Y., Maruyama, T., Iwai, T., . . . Abe, H. (2016). The effect of crystallographic mismatch on the obstacle
strength of second phase precipitate particles in dispersion strengthening: Bcc Nb particles and nanometric Nb clusters embedded in hcp Zr. ActaMaterialia, 102, 323-332.
2. Proton irradiation induced Nb redistribution
19
APT CHARACTERIZATION
• Nb concentration of irradiated Zr-xNb after cluster analysis
Iso-density method is used (but did max. separation as well…, same
results)
• Nb concentration in the solid solution is reduced as irradiation dose
increases. UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
2. Proton irradiation induced Nb redistribution
20UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
2 um
• C4 model result:
2. Proton irradiation induced Nb redistribution
MO D ELIN G O F NB EFFEC T O N
CO R R O S IO N
As expected, the irradiated ZrNb alloy
corrosion kinetics slowly decreases (and
becomes more and more sub-parabolic)
as less and less Nb is available to
compensate the oxide space charges.
21
DEFECT AT PLATELET/MATRIX INTERFACE
• HRSTEM shows edge dislocations (pointed white arrows) nearby the
two ends of irradiation induced platelets.
• Orientation relationship: 𝟐ഥ𝟏ഥ𝟏𝟎 𝒁𝒓// 𝟏ഥ𝟏𝟏 𝑵𝒃 ; (000ഥ𝟐)Zr // (011)Nb
UW Environmental Degradation of Nuclear Materials Laboratory
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b
3. Nb redistribution under irradiation mechanism
22
4D-STEM STRAIN MAPPING
• 4D-STEM plots the strain relative to the irradiated Zr matrix.
• Relatively large strain field (yellow regions) were found nearby the two
ends of platelets.
UW Environmental Degradation of Nuclear Materials Laboratory
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റ𝑔1: റ𝑔2:
B) C)
റ𝑔1: matrix [000ത2] / platelet [011]റ𝑔2: matrix [0ത11ത1] / platelet [ത101]
d-s
pac
ing
(A)
d-s
pac
ing
(A)
റ𝑔1 റ𝑔2
A)
20 nm
3. Nb redistribution under irradiation mechanism
23
SCHEMATIC OF PRECIPITATE GROWTH
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
Native β-Nb
Strain field
Growth
RecoilDissolution
Matrix
Proton irradiation
+
+
+
+
Enhanced Nb Diffusion
Zr
SoluteResolution
Irradiation induced point defects.
Nucleation of Nb-rich platelet
24
CO N C LU S IO N
• ZrNb Microchemistry analysis :
• Nb is locked into βNb in the oxide, while Nb dissolves from βZr in the oxide.
• More Nb doping in the oxide in βZr containing alloy
• XANES shows that the main oxidation of Nb in the oxide is below 4+
• Effect on corrosion of ZrNb alloys:
• The C4 model reveals that the Nb doping can compensate the space charges:
• Space charge compensation induces faster, parabolic kinetics.
• Effect of irradiation on ZrNb microchemistry and microstructure:
• 2MeV, 350C, 1dpa, proton irradiation induces β Nb-rich platelets
• 2MeV, 350C, 1dpa, proton irradiation induces a reduction of solute Nb
• CONCLUSION: Irradiation of ZrNb results in a decrease of oxidation rate because ofradiation induced/enhanced precipitation, decreasing Nb in solid solution, providing lesscompensation of oxide space charges.
• Need to develop a radiation induced/enhanced precipitation mechanism to predict the Nbsolute depletion rate and evolution of space charge compensation factor.
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
UW Environmental Degradation of Nuclear Materials Laboratory19th International Symposium on Zirconium in the Nuclear Industry
THANK YOU
26
RESEARCH BACKGROUND AND MOTIVATION
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
thic
kne
ss
time
[1] Motta, Arthur T., et al. “Corrosion of Zirconium Alloys Used for Nuclear Fuel Cladding.” Annual Review of Materials Research, vol. 45, no. 1, 2015, pp. 311–343.
27
ATO M IC PR O B E TO M O G R A P H Y O N
ZRNB• Nb concentration in the entire needles.
• Nb concentrations are acquired from full 31 Da peak and
deconvoluted 46.5 Da peak by IVAS .
• From ZrNb phase diagram, the maximum solubility limit of Nb is
0.6 at%
• Unirradiated
needles contains
0.3-0.4 at% Nb.
• Despite dose level,
all alloys exhibit Nb
concentration
lower than the bulk
Nb concentration.
III. APT characterization
UW Environmental Degradation of Nuclear Materials Laboratory
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28
ATOMIC PROBE TOMOGRAPHY ON ZRNB• Fe concentration in the entire needles.
• A) is using the front portion of 28 Da peak, ranging from 27.95 Da to 28.02 Da, to the avoid CO+ contribution.
• B) is using natural isotope of Fe at 27 Da (54Fe2+) with abundance of 5.845 %.
III. APT characterization
• There is an increase of Fe in
irradiated samples, and rise above
commonly accepted 0.02 at% Fe
in Zr solid solution.
• Fe content is unexpectedly high.
• No obvious trend
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
29
ATO M IC PR O B E TO M O G R A P H Y O N
ZRNB• Nb concentration of irradiated Zr-xNb after cluster analysis
• Max separation, proximity histogram, iso-density.
• The Nb concentration in the solid solution of irradiated samples
are reduced, comparing to unirradiated condition.
• Note: • Bar plots are after
iso-density method. • Ref means “assumed
values”, either based on literature review or thermodynamics prediction.
Ref
Ref
III. APT characterization
UW Environmental Degradation of Nuclear Materials Laboratory
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30UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
• Corrosion of 1 dpa Zr1.0Nb and 1 dpa Zr0.5Nb
• Oxide thickness is measured from SEM and TEM images.
• Unexpectedly, the irradiated area has slightly higher oxide thickness than
unirradiated area.
VIII. Post-irradiation corrosion
CO R R O S IO N O F P R O TO N
IRRADIATED ZRNB
Zr1.0Nb/Zr0.5Nb7/6 days
Zr1.0Nb/Zr0.5Nb38/37 days
31
• Native precipitates (blue arrow) were survived in 1 dpa Zr1.0Nb
UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
➢ Minimum reduction of Nb concentration in native precipitates to about 60
at.%. Some of native βNb have reduced to 40 at.% or even less.
30 nm
➢ Total particle density is decreasing as dpa
increases.
➢ Native precipitates were suspected to
dissolve upon proton irradiation.
(S)TEM/EDS ON IRRADIATED ZR-XNB
III. Irradiation Experiment
31
2 Mev H+ irradiation, 350ºC
32
570 Cͦ
Zr-0.5Nb
Zr-1.0Nb
Autoclave corrosion at 260 ͦC and 6 MPa
Nb SOLUTE
CONCENTRATION DECREASE
1
2
3
Characterization:APT/(S)TEM/EDS/XANES
PL A N TO TEST HY P OTH ES IS
4 5
6
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33UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
PR EL IM IN A R Y CO N C LU S IO N S :1. Does Nb distribution and electronic structure in the oxide affect
corrosion kinetics? YES!• Microstructure indeed has an effect on Zr-1.0Nb corrosion kinetics.
• Since βZr dissolve upon oxidation, higher corrosion kinetics of Zr-1.0Nb with βZr is
suspected due to abundance of oxidized Nb, which compensated the space charge in
the oxide.
Hypothesis: Irradiation reduces Nb concentration in α-Zr matrix by
precipitating Nb-rich irradiation-induced platelets resulting in lower corrosion
kinetics
2. Does proton irradiation offer a good surrogate to neutron irradiation in terms of Nb
redistribution?
3. What is the mechanism of irradiation induced Nb redistribution?
4. Does the irradiation induced microstructure of the base metal survive in the oxide
formed by subsequent corrosion?
5. Is the corrosion rate of pre-irradiated ZrNb samples lower than unirradiated materials
and why?
34UW Environmental Degradation of Nuclear Materials Laboratory
19th International Symposium on Zirconium in the Nuclear Industry
2 um
• Corrosion of 1 dpa Zr1.0Nb and 1 dpa Zr0.5Nb
• Native precipitates (yellow) remains in the oxide for 6/7 days corrosion.
• Nb-rich platelets(red) were found in oxide of 37 days corroded 1 dpa
Zr1.0Nb. Also, they were found in metal.
V. Post-irradiation corrosion
CORROSION OF PROTON IRRADIATED ZRNB
Irradiated area
Unirradiated
BF
37 days corroded 1 dpa Zr1.0Nb
35
UNIRRADIATED SAMPLE CHARACTERIZATIONS
• STEM characterization of unirradiated samples
STEM showing SPPs of electropolished Zr-0.2Nb, Zr-0.4Nb, Zr-0.5Nb, Zr-1.0Nb
Examples of STEM images before and after processing to identify SPPs in Zr-0.2Nb
Effect of irradiation on ZrNb corrosion mechanism
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
36
UNIRRADIATED SAMPLE CHARACTERIZATIONS
• ChemiSTEM characterization of unirradiated samples
Effect of irradiation on ZrNb corrosion mechanism
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
• For 1000°C annealed Zr-0.5Nb, there is Nb and Fe enriched lath martensites in α-
Zr matrix.
37
PR O TO N IR R A D IA T IO N O F ZRNB
ALLO YS
• Temperature is well controlled (ASTM standard)
Effect of irradiation on ZrNb corrosion mechanism
𝐸𝑑𝑍𝑟 = 40eV
𝐸𝑑𝑁𝑏 = 60eV
g = 6.51 g/𝑐𝑚3
Fluence = 1.4E19 ions/𝑐𝑚2
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
38
• 1.0 dpa irradiated Zr-1.0Nb
• Grains remains recrystallized state. Native particles survived.
• There are multiple Nb-rich needle-like precipitates throughout the
sample at 15 μm depth from irradiation surface.
Effect of irradiation on ZrNb corrosion mechanism
CH A RA C TER IZAT IO N O F 1.0 DPA ZR 1.0NB
Histogram of length and width of irradiation
induced needle-like precipitates.
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
3 µm
3 µm 3 µm
39
Effect of irradiation on ZrNb corrosion mechanism
• HRSTEM shows Burgers orientation relationship of irradiation
induced particle/matrix: (0002) // (011), [1ത11] // [2ത1ത10]
(0002)
{110}
Precipitate
Matrix
(0002)
(0ത111)
(0ത110)
(0ത11ത1)
(0001)
Matrix
(110)
(01ത1)
[2-1-10]
(101)
SPP
OR IEN TAT IO N REL AT IO N SH IP RIP/MATRIX
C14 – Zr[2ത1ത10]
BCC – Nb[1ത11]
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
40
• 4-D STEM Introduction:
• Using fast electron camera,
imaging mode diffraction
patterns at each scanned
position are recorded at
the same speed of taking
HRSTEM imaging.
• By comparing d-spacings
from captured diffraction
patterns with reference
values, strain maps can be
generated.
Effect of irradiation on ZrNb corrosion mechanism
4D STEM ON 1.0 DPA ZRNB ALLOYS
Muller-Caspary Knut,http://www.fz-juelich.de/er-c/er-c-1/EN/Forschung/moreSTEM/_node.html
𝜀 =𝑐𝑎𝑝𝑡𝑢𝑟𝑒𝑑 − 𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒
𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
41
• How to generate strain map:
1. From 4-D STEM and HRSTEM images, diffraction patterns at each
imaging pixel size area were obtained.
Effect of irradiation on ZrNb corrosion mechanism
4D STEM O N 1.0 D PA ZRNB ALLO YS
𝜀 =𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 − 𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒
𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒
2. Choose the planes of interest that
to calculated strain. For now, we use
Ԧ𝑎(0002) and 𝑏(0ത11ത1).
3. Choose the reference values.
• Method 1:Measures the d-spacing of matrix
plane using the captured diffraction
patterns far away from SPP as
references.
• Method 2:Use ideal d-spacing of matrix plane
based on simulated values as
references.
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
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II. Effect of irradiation on ZrNb corrosion mechanism
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
43
ATO M IC PR O B E TO M O G R A P H Y O N
ZRNB• Fe concentration in the entire needles.
• Based on literature references, Fe concentrations are acquired
from selecting a portion of the peak below 28.02 Da due to CO
interference.
[5] Thuvander, & Andrén. (2011). Methods of quantitative matrix analysis of Zircaloy-2. Ultramicroscopy, 111(6), 711-714.
[6] Hudson, D., & Smith, George D. W. (2011). Zirconium Oxidation on the Atomic Scale.
III. APT characterization
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
dmax = 1.9Order = 5 Nmin = 10
L = 1.5de = L
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MA X SEPA R AT IO N METH O D• What parameters can affect calculation?
• dmax , order , Nmin , L (set L = 0.75*dmax) , de
• Example:
Zr1.0Nb
1 dpa
Fe Nb Zr
Parameter definition by IVAS manual
Identified clusters Matrix without clusters
III. APT characterization
0
100
200
300
400
0 2 4
Co
un
ts
distance (nm)
Nearest Neighbor Distribution
Data Random
dmax
0
2
4
6
8
10
6 11 16
Co
un
ts
Ions
Cluster Size Distribution
data random
Nmin
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
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ISO CO N C EN TR ATO N METH O D• What parameters can affect calculation?
• Isoconcentration or isodenstiy values
• I used isoconcentration values
• Example: 0.6 0.8
Matrixwithout clusters
Identify clusters
Values:
1dpa Zr1.0Nb
III. APT characterization
MUZIC-3 meeting EDF, 27th -29th Nov, 2018
46
PR O X IM IT Y HISTO G R A M METH O D• What parameters can affect calculation?
• Isoconcentration or isodenstiy values
• Recommended to use isodensity values
• Required manual decomposition of overlapping peaks
• Example:
Chose isodensity = 0.6Create concentration profile
III. APT characterization
Averaged to get at% in solid solution
MUZIC-3 meeting EDF, 27th -29th Nov, 2018