Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Thermal annealing influence
on ions implanted Fe-Cr model alloys
S. Sojaka, , V. Slugeňa, V. Kršjakb, W. Eggerc, L. Ravellic, M. Petriskaa, S. Stančeka, M. Skarbad, P. Priputend, K. Vitázeka, M. Stachoa, J. Veterníkováa, V.
Sabelováa
aInstitute of Nuclear and Physical Engineering, Slovak University of Technology, Ilkovičova 3, 812 19 Bratislava, Slovakia
bJRC Petten, European Commission, Postbus 3, 1755 PG PettencLRT2, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D-
85577 Neubiberg, GermanydInstitute of Materials Science, Slovak University of Technology, Bottova 25,
917 24 Trnava, Slovakia
email: [email protected]
Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Outline
Motivation
Positron annihilation spectroscopy
Experimental Fe-Cr results Binary Fe-Cr alloys treatments
Results of annealed Fe-11.62%Cr alloys
Summary
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Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Motivation
Investigation of Reduced Activation Ferritic/Martensitic (RAFM) steels as a candidate structural materials for new fission/fusion reactors.
Radiation damage simulation by ion implantation.
Different temperatures annealing of the steels in order to study changes in microstructure
Positron lifetime measurements before and after treatment and evaluation of measured results.
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Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Pulsed low energy positron system (PLEPS)
remoderated positrons
[1] P. Sperr, W. Egger, G. Kögel, G. Dollinger, Ch. Hugenschmidt, R. Repper, C. Piochacz, Applied Surface Science 255 (2008) 35–38 [2] Hugenschmidt C., Dollinger G., Egger W., Kögel G.,Löwe B., Mayer J., Pikart P., Piochacz C., Repper R., Schreckenbach K., Sperr P., Stadlbauer M., Applied Surface Science, Volume 255, Issue 1, p. 29-32
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Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Spectra evaluation Measured spectra evaluation by PosWin software. Output – positron lifetimes (3 components):
τ1: positron lifetime in bulk
τ2: positron lifetime in defects
τ3: positron lifetime in large
defects Intensity of each component
(I1, I2, I3) Mean lifetime (MLT)
332211 ... IIIMLT
1 iI
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Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Experiment & Results
Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Binary Fe-Cr alloys treatmentSpecimen Cr
[wt%]
P[wt%]
Si[wt%]
Al[wt%]
Ti[wt%]
Mn [wt%]
Ni[wt%]
Cu[wt%]
C[wt%]
N[wt%]
V[wt%]
L251 2.36 0.013 0.002 0.003 0.004 0.009 0.044 0.005 0.008 0.0173 0.001
L259 4.62 0.011 0.006 0.0033 0.0028 0.02 0.06 0.01 0.02 0.0344 0.001
L252 8.39 0.012 0.00066 0.0069 0.0034 0.03 0.07 0.01 0.02 0.0353 0.002
L253 11.62 0.05 0.006 0.003 0.0037 0.03 0.09 0.01 0.03 0.0397 0.002
Specimens preparation:
Dimensions 10x10x0,4 mm,
One side mirror-like polished
Manufactured at Dept. of Metallurgy at Ghent University, Belgium
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Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Radiation damage simulation Simulation of radiation damage of binary Fe-
Cr alloys by ion implantation Implantation of He ions with energy of 250 &
100 keV Dose of implanted ions: 0.1 – 0.5 C/cm2
(6.24x1017 – 3.12x1018 ions/cm2)
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Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Influence of thermal annealing of structural changes.
Annealed: Fe-11.62%Cr: 0; 0.1; 0.3; 0.5 C/cm2.
Annealing temperatures 400, 475, 525, 600 ºC for 2 hours
Argon atmosphere, pressure 10 kPa
Thermal annealing
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Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
[3] KRŠJAK, V.: Positron annihilation study of advanced nuclear reactor materials, Doctoral thesis, Slovak
University of Technology, Slovakia, 2008.
Scanning electron microscopy (SEM) results of not annealed Fe-Cr alloy
10
xZ
1m
SEM results show the PLEPS prediction of large voids in the depth >500nm, which correspond to the helium implantation profile maximum.
Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
SRIM simulations
Dose [ions/cm2] 6.24x1017 1.24x1018 1.87x1018 2.5x1018 3.12x1018
DPA 18.51 37.02 55.53 74.05 92.56
Depth profile of binary Fe-Cr alloy after 250 & 100 keV He2
+ ion implantation.
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Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
PLEPS results of Fe-11.62%Cr
No peaks from 100 and 250 keV Helium ions were observed.
Therefore other technique support was needed.
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0 2 4 6 8 10 12 14 16 18 20
160
180
200
220
240
260
280
300
320
340
360
380
400
420
not annealed 400 C 475 C 525 C
523433273 35020490 14347
Fe-11.62%Cr: irr. 0.3 C/cm2
Mean p
ositron life
time [p
s]
Positron energy [keV]
16
Depth [nm]
Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Diagonal cut under the 12º angle of the Fe-11.62%Cr specimen, 1 μm annealed at 475 ºC.
Major damage in two regions, considering the SRIM simulation => damaged areas from 100 and 250 keV Helium
13
~1 μm
~0.3 μm
~0.55 μm
Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
MLT after 600 °C
At 600 ºC was observed significant decrease of mean positron lifetime. It should mean annealing out of defects size/amount.
How the structure looks like under SEM at this temperature?
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0 2 4 6 8 10 12 14 16 18 20
160
180
200
220
240
260
280
300
320
340
360
380
400
420
not annealed 400 C 475 C 525 C 600 C
523433273 35020490 14347
Fe-11.62%Cr: irr. 0.3 C/cm2
Mean p
ositron life
time [p
s]
Positron energy [keV]
16
Depth [nm]
[4] RONALD, K.L. – HARRIES, D.R.: High-Chromium Ferritic and Martensitic steels for Nuclear Applications, ASTM USA (2001).
Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Positron lifetimes in defects and bulks (τ2, τ1)
>200 nm oxide layer is influencing defects and bulk lifetimes. Defects lifetime of specimens annealed at 600 °C decreased also in
comparison to not annealed specimen. Intensity stays increasing with depth.
Positron lifetime in bulk reached level of 140 ps, which corresponds to bulk with dislocations [3].
0 2 4 6 8 10 12 14 16 18 20220
240
260
280
300
320
340
360
380
400
420
440
460
480
500
not annelaed 400 C 475 C 525 C 600 C
523433273 35020490 14347
Fe-11.62%Cr: irr. 0.3 C/cm2
Positron life
time in
defe
cts
[ps]
Positron energy [keV]
16
Depth [nm]
0 2 4 6 8 10 12 14 16 18 200
20
40
60
80
100
120 not annealed 400 C 475 C 525 C 600 C
523433273 35020490 14347
Fe-11.62%Cr: irr. 0.3 C/cm2
Inte
nsity
I 2 [%
]
Positron energy [keV]
16
Depth [nm]
0 2 4 6 8 10 12 14 16 18 20
020406080
100120140160180200220240260280300320340360380400
not annealed 400 C 475 C 525 C 600 C
523433273 35020490 14347
Fe-11.62%Cr: irr. 0.3 C/cm2
Pos
itron
life
time
1 [p
s]
Positron energy [keV]
16
Depth [nm]
0 2 4 6 8 10 12 14 16 18 20
0
20
40
60
80
100
120
not annealed 400 C 475 C 525 C 600 C
523433273 35020490 14347
Fe-11.62%Cr: irr. 0.3 C/cm2
Inte
nsity
I 1 [%
]Positron energy [keV]
16
Depth [nm]
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Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Summary Significant damage areas were observed by SEM technique
in Fe-11.62%Cr alloy annealed at 475 ºC but no peaks from PLEPS technique were registered.
Extensive decrease of positron lifetimes in case of 600 ºC annealed specimens was observed. The bulk was well recognized with high intensity level.
Questions about the structure changes at temperature of 600 ºC is still going to front rank and more experiments with SEM has to be done.
Ion implantation damage with connection to the thermal annealing at lower temperatures and oxide layer on the surface introduced many variables and created complicated system for the final evaluation of measured data. Because of such significantly damaged structure, we will use for next experiments lower implantation energies to maximum level of 0.3 C/cm2.
Positron and Positronium Chemistry PPC10, 2. -5. September, Smolenice Castle, Slovakia
Thank you for your attention!
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