Atom Probe Tomography of IonIrradiated Model ODS Alloys
Andrew London* 4th Year DPhil
C.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 blue
Ti, TiO green
O, 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 temperature
As-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 temperature
Room temperature
“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)
Lescoat, M-L., et al. Acta
Materialia 78 (2014): 328-340.
Indian Programme on ODS Materials
• Currently working on a ODS cladding tube alloy.
• Fe-9Cr-2W-0.1C-0.2Ti-0.35Y2O3
Pre-alloyed powder
Nanocrystalline yttria
Clad-tubes with 6.6 mm O.D., 0.45 mm thick and 4.2 m length have been successfully produced
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
Carbon on grain boundary
Large Yttrium & Oxygen particle
Oxygen
Atom Probe data
Y & YO
Ti & TiO
100 nm
Low-temperature irradiation
As-received
Fe-14Cr-0.2Ti-0.3Y2O3
50 nm
>50 dpa @ 120K
Low-temperature irradiation
20 nm
surface
Y/YO
TiO/Ti
150K Ion Irradiation of Fe-Ti-Y2O3 ODS alloys
to 100 dpa
Carbide
Matrix
100 nm
diffuse Y-Ti clusters
15
Carbon
Erf fit
Carbon %
50 nm
10
5
0
0
Cr-oxide contamination particle
20
40
Distance nm
60
80
High-temperature irradiation
As-received
Fe-14Cr-0.2Ti-0.3Y2O3
Increased Ti content of the
clusters, but no significant
change to number density
or size distribution
>50 dpa @ 900K
50 nm
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 @ 900K
0 dpa
100 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?