relationship between microstructure and mechanical
TRANSCRIPT
MINOS Workshop, Materials Innovation for Nuclear Optimized SystemsDecember 5-7, 2012, CEA – INSTN Saclay, France
RELATIONSHIP BETWEEN MICROSTRUCTURE
AND MECHANICAL PROPERTIES IN ODS
MATERIALS FOR NUCLEAR APPLICATION
Yann de Carlan et al., CEA , DEN, SRMA, 91191 GIF/YVETTE FRANCE
2
ODS FOR SODIUM FAST REACTORS
Rapsodie
Beginning of the
studies on the Fast
Sodium Reactors to
produce electricity
First ODS (SCK-
CEN)
Phénix
First irradiated
tubes
Superphénix
Industrial
Production
(DourMetal)
ODS tubes in
Phenix reactor
Forum Gen IV : reactors
1967 1973 1985 1987 20001960
Materials
Optimization
of the
austenitic
steels
New reinforced
ferritic alloys :
ODS alloys
PHENIXPHENIX
SPXSFR
L. Toualbi
Need of
optimized
materials is still
relevant !
3
Why ODS materials for Nuclear Applications ?
ODS materials
Limited swelling under irradiation Low thermal creep
Nano dispersion
(Oxide Dispersion Strengthened)
0
1
2
3
4
5
6
7
8
9
10
60 70 80 90 100 110 120 130 140 150 160 170 180 190
dose (dpa)
Average 316 Ti
Ferritic-martensitic (F/M) steels ODS included
Average 15/15TiBest lot of 15/15Ti
Use limit for Phenix reactor
Sw
ellin
g(%
)
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
0,0001 0,001 0,01 0,1 1 10 100 1000 10000
Temps (h)
Allo
ngem
ent
(%)
180 MPa – 650°C
Conventional steel
ODS
SFRDose > 150 dpaStress ~ 100 MPaTemperatures : 400°C – 670°C
4
METALLURGY OF ODS MATERIALS
nano-phases (~2-4nm)
Complex manufacturing� ODS steels present low ductility and limited consolidation at room temperature
� Low deformability
� Intermediate heat treatments needed for stress relief purpose
5
METALLURGY OF ODS MATERIALS
Ex:ODS steel18 Cr-1W Ti 0,5 Y2O3
Uniform distribution ofnano oxides
0
0,2
0,4
0,6
0,8
1
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1D in mm
Wt (
%).
0.46 Y
0.3 Ti
0.85 W
Microprobe
Homogeneous microstructureFine ferritic grains
elongatedin extrusion direction
Longitudinal direction Transverse direction
TEM
nano-oxides
50 nm
TEM
SANS
TAP
Optical
DSM – LLBOrphée
0
0,2
0,4
0,6
0 1 2 3 4 5 6 7 8 9 10
Rayon moyen (nm)
H(r
) *
fp
90×14×14 nm3
Y,YO and O
Clusters
Ti, TiO
8 1023 m-3
1,8 nm
Texture
8 1022 m-3 φ 3 nm
1, 2 µm - 300nm 400 nm - 200 nm
fp 1,1%
GPM RouenO. Kalokhtina, B. Radiguet, Ph. Pareige
Plate
EFTEMHRTEM
6
METALLURGY OF ODS MATERIALS
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6 7
ODS metallurgyConventional metallurgy
Temperature /°C
Time / h
7
� Ferritic grades
Fe -12/20Cr
� Martensitic grades
Fe - 9 Cr
Large differences between both type of alloys as a function of their finalmicrostructure but generic creep behavior is noticed.
Fe-9Cr Fe-12/20Cr
METALLURGY OF ODS MATERIALS
8
METALLURGY OF ODS MATERIALS
Ferritic Fe-14Cr ODS :Extruded at 1100°C + 1h at 1050°C (very difficult to recrystallize)
Typical microstructures
10µm
Martensitic Fe-9Cr ODS :Tempered martensite(very high critical cooling rates)
L. Toualbi, Phd Thesis
9
austenite + ferrite
austenite + martensite
� Martensitic grade: Fe-9Cr-1W-0.2Ti-0.3Y2O3
� CCT diagram
- Transformation temperatures
- Critical cooling rates ~ 1°C/s
L. Toualbi, Phd Thesis
METALLURGY OF ODS MATERIALS
10
MECHANICAL PROPERTIES OF ODS
� Tensile properties
� Creep properties
� Impact properties
11
TENSILE PROPERTIES OF ODS ALLOYS
� Ferritic (Fe-14 Cr ODS)
A. Alamo et al. Journal of Nuclear Materials 329–333 (2004) 333–337
As-extruded
12
TENSILE PROPERTIES OF ODS ALLOYS
0
100
200
300
400
500
600
0 1 2 3 4 5 6 7 8 9 10Allongement rationnel (%)
Con
trai
nte
vrai
e (M
Pa)
7.10-4 s-1
10-5 s-1
Extruded and annealed ferritic ODS (Fe-18Cr), tensile test at 650°C in the transvers direction, large decrease of the ductility when the deformation rate is decreasing.
M. Ratti, PhD thesis
13
TENSILE PROPERTIES OF ODS ALLOYS
� Martensitic (Fe-9Cr ODS)
L. Toualbi, Phd Thesis
Tensile properties in different metallurgical state :- J95-M3, tempered martensite- J95- M5, Softened ferrite
Tempered martensite
Softened ferrite
14
CREEP PROPERTIES OF ODS ALLOYS
� Ferritic (Fe-18 Cr ODS)
Extrusion direction
ODS plateExtruded and annealed
Extrusion direction
SL ST S45
200 nm
Bamboo like microstructure
M. Ratti, Phd Thesis
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CREEP PROPERTIES OF ODS ALLOYS
� Ferritic Fe-18 Cr ODS at 650°C 250 MPa
M. Ratti, Phd Thesis
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
2
0 1000 2000 3000 4000 5000 6000 7000
Temps (heures)
Allo
ngem
ent
(%)
Very low deformation rates (Long-250 MPa : 7.10-8 h-1).
almost no tertiary domain .
Different order of magnitude on the rupture time as a function of the orientation of the sample / texture of the microstructure
Transvers
45°°°°
Long (in progress)
16
Inoué et al.
17
CREEP PROPERTIES OF ODS ALLOYS
� Ferritic ODS
A. Alamo et al. Journal of Nuclear Materials 329–333 (2004) 333–337
0
100
200
300
400
500
10-1 100 101 102 103 104 105
Str
ess
(MP
a)
Rupture Time (h)
MA957 - Fine grains 650°C
9Cr2MoVNb (EM12) 650°C
MA957 - Recryst. 700°C
MA957 - Recryst. 650°C
15/15Ti 700°C
Aust.15/15Ti 650°C
0
100
200
300
400
500
10-1 100 101 102 103 104 105
Str
ess
(MP
a)
Rupture Time (h)
MA957 - Fine grains 650°C
9Cr2MoVNb (EM12) 650°C
MA957 - Recryst. 700°C
MA957 - Recryst. 650°C
15/15Ti 700°C
Aust.15/15Ti 650°C
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CREEP PROPERTIES OF ODS ALLOYS
M. Praud, J.Malaplate et al., creep 2012
Higher performances of Fe-14Cr ODS alloys (fine grains) in the longitudinal direction compared to Fe-9Cr ODS (softened ferrite)
19
� Martensitic Fe-9 Cr ODS
17104.1 −−⋅= sIIε&
110101.1 −−⋅= sIIε&
CREEP PROPERTIES OF ODS ALLOYS
M. Praud, J.Malaplate et al., creep 2012
20
CREEP PROPERTIES OF ODS ALLOYS
• Creation of cavities • Decohesion along the grain boundaries
INTERGRANULAR mechanismConsistent with the macroscopic observations
ODS 9%Cr
ODS 14%Cr
In situ relaxation tests at 550°C
• Dislocation still pinned on oxides
• Viscous motion
• Activation of sources of dislocations at the grain boundaryM. Praud, J.Malaplate et al., creep 2012
21
IMPACT PROPERTIES OF ODS ALLOYS
Fine grain
A. Alamo et al. Journal of Nuclear Materials 329–333 (2004) 333–337
� Ferritic Fe-14 Cr ODS alloys
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IMPACT PROPERTIES OF ODS ALLOYS
DBTT (°C) USE (J)LT TL LT TL
rod Ø36 -29 108 7.6 3.8
� anisotropic impact behaviourfor the rod : higher USE and lower DBTT under LT loading
extrusion direction
TL
LT
diameter: 36mm
Fe-14Cr 1W ODS“Fine grain microstructure”
� Ferritic Fe-14 Cr ODS alloys
AL Rouffié et al. http://dx.doi.org/10.1016/j.jnucmat.2012.08.050 22
23
IMPACT PROPERTIES OF ODS ALLOYS
AL Rouffié et al. http://dx.doi.org/10.1016/j.jnucmat.2012.08.050
DBTT (°C) USE (J)LT TL LT TL
rod Ø36 -29 108 7.6 3.8
� anisotropic impact behaviourfor the rod : higher USE and lower DBTT under LT loading
ED
notch
expected propagation
plane
effective propagation plane
For different samples, tendency to delamination
� Ferritic Fe-14 Cr ODS alloys
24
IMPACT PROPERTIES OF ODS ALLOYS
AL Rouffié et al. http://dx.doi.org/10.1016/j.jnucmat.2012.08.050
� Ferritic Fe-9Cr ODS alloys (thick plate)
Quasi-isotropicbehaviour
25
CONCLUSIONS
The mechanical properties of nuclear F/M alloys depend stro ngly on the chemical compositionand the microstructure of the product
�Tensile properties- Large dependence on the grain size / morphology / dislocation density / nano-precipitation
- Collapse of the strength from 400°C
- Strain rate effect on the ductility
� Creep properties- No tertiary creep but high performances
- Reduced fracture strain
- Damage more severe at high temperature low strain rate / low stress => Intergranularmechanism of failure
� Impact properties- Low toughness and in general “low” Upper Shelf Energy and sometimes tendency to
delamination
- Very important impact of the microstructure (morphological texture) on the impact properties
The fabrication route of ODS materials with the appropriatemicrostructure is a key issue for the nuclear applications