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Atom Probe Tomography of Ion-Irradiated Model ODS Alloys
Andrew London* 4th Year DPhilC.R.M Grovenor, S Lozano-Perez*
B. K. Panigrahi**
* Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK** Indira Gandhi Centre for Atomic Research, Kalpakkam - 603 102, TN, India
Y, YO blueTi, TiO greenO, FeO red
Purpose of my research
What questions are we trying to answer?• Oxide dispersion strengthened steel:
– What are the dispersed oxides, structure/chemistry? So we can control them and therefore the materials’ properties.
– What is the influence of alloy chemistry on oxide particles, specifically chromium?
– What is the influence of ion-irradiation?
Purpose of my research
What questions are we trying to answer?• Oxide dispersion strengthened steel:
– What are the dispersed oxides, structure/chemistry? So we can control them and therefore the materials’ properties.
– What is the influence of alloy chemistry on oxide particles, specifically chromium?
– What is the influence of ion-irradiation?
London, A. J., et al. "Comparison of atom probe tomography and transmission electron microscopy analysis of oxide dispersion strengthened steels." Journal of Physics: Conference Series. Vol. 522. No. 1. IOP Publishing, 2014.
Purpose of my research
What questions are we trying to answer?• Oxide dispersion strengthened steel:
– What are the dispersed oxides, structure/chemistry? So we can control them and therefore the materials’ properties.
– What is the influence of alloy chemistry on oxide particles, specifically chromium?
– What is the influence of ion-irradiation?
Expectation: High temperatureAs-received
500 C 75 dpa
500 C 150 dpa
Lescoat, M-L., et al. Acta Materialia 78 (2014): 328-340.
Allen, Todd R., et al. Journal of Nuclear Materials 375.1 (2008): 26-37.
He, Jianchao, et al. Journal of Nuclear Materials 455.1 (2014): 41-45.
Expectation: Low temperatureRoom temperature
Lescoat, M-L., et al. Acta Materialia 78 (2014): 328-340.
“the 100 dpa, −75 °C samples data set showed no significant clustering … Y, Ti, and O were randomly distributed in solid solution.”
Certain, A., et al. Journal of Nuclear Materials 434.1 (2013): 311-321.
(own work) Irrd. at 120K (a), and as-received (b)
Indian Programme on ODS Materials• Currently working on a ODS cladding tube alloy.• Fe-9Cr-2W-0.1C-0.2Ti-0.35Y2O3
Clad-tubes with 6.6 mm O.D., 0.45 mm thick and 4.2 m length have been successfully produced
Pre-alloyed powder
Nanocrystalline yttria
My Collaboration with Indira Gandhi Centre for Atomic Research (IGCAR)
Three model alloys produced by extrusion to study the influence of alloy content.
Nominal Compositions: (wt %)• Fe–14Cr–0.2Ti–0.3Y2O3
• Fe–0.2Ti–0.3Y2O3
• Fe–0.3Y2O3
Methods:Example TEM and APT of the same sample
100 nm
Large Yttrium & Oxygen particle Carbon on grain boundary
Atom Probe data
Y & YO
Ti & TiO
Oxygen
Low-temperature irradiation
As-receivedFe-14Cr-0.2Ti-0.3Y2O3
50 nm
>50 dpa @ 120K
Y/YO TiO/Ti
surface
Low-temperature irradiation
20 n
m
100 nm
50 nm
Cr-oxide contamination particle
150K Ion Irradiation of Fe-Ti-Y2O3 ODS alloysto 100 dpa
CarbideMatrix
diffuse Y-Ti clusters
0 20 40 60 800
5
10
15
Distance nm
Ca
rbo
n %
CarbonErf fit
50 nm
High-temperature irradiationAs-receivedFe-14Cr-0.2Ti-0.3Y2O3
>50 dpa @ 900KIncreased Ti content of the clusters, but no significant change to number density or size distribution
High-temperature irradiation
The high-yttrium content clusters are lost, more Ti-rich oxides are observed and the average Ti-fraction of the clusters increases.
Fe14Cr-0.2Ti-0.3Y2O3 ~50 dpa, APT data
High-temperature irradiation
No significant change in radius, but reduction in average number density with irradiation at 500 to 600 C.
Fe14Cr-0.2Ti-0.3Y2O3 ~50 dpa, APT data
After cryo-irradiation:
50 nm
Annealed @ 900K
Irradiated @ 900K100 dpa0 dpa
50 nm
Irradiated @ 900K(after 120K irradiation)
50 nm
grain boundaries
High number density of small “flat” clusters
Monnet et al. JNM 335.3 (2004): 311-321.800K, 78.8 dpa, 25 days
10 nm
Preliminary conclusions• Irradiation at low temperature does not homogenise the
solute distribution as reported by others [1,2], but does partially dissolve the particles.
• Subsequent annealing results in similar particles to the original, even at “low” temperatures (900K).
• Subsequent ion-irradiation at high temperature forms a high number density of very small clusters, with a high solute concentration on the grain boundaries.
• It is possible to use ion irradiation as an analogue for neutron damage but care is required to design appropriate experiments.
[1] Certain, A., et al. Journal of Nuclear Materials 434.1 (2013): 311-321.[2] Parish, CM., et al. Journal of Nuclear Materials 445.1 (2014): 251-260.
Any Questions?