Positron Annihilation Spectroscopy

34 Pages·2015·4.81 MB·English

by  Scepanovic ., Masa

Effects of ion irradiation on
ODS steels for fusion
Maša Šćepanović
Universidad Carlos III de Madrid
Fe-14Cr-0.3Y O
2 3
Fe-14Cr-2W-0.3Ti-0.3Y O
2 3
Outline
Introduction – samples
●
General microstructure of samples before
●
irradiation
Irradiation conditions
●
General microstructure of samples after
●
irradiation
Positron annihilation spectroscopy
●
Future work
●
Introduction
The operating temperature for steels for structural
●
applications in nuclear fusion reactors can be
significantly raised by reinforcing these steels with a
homogeneous dispersion of hard particles.
Particles of yttria are used most commonly, being one
●
of the most thermodynamically stable oxides.
These particles act as sinks for irradiation induced
●
point defects and He, thus inhibiting the growth of
bubbles and migration of He to grain boundaries.
Damage profiles are being characterized using
●
Positron Annihilation Spectroscopy and
Transmission Electron Microscopy.
Samples
Samples were produced at UC3M by mechanical alloying and
●
consolidated by hot isostatic pressing at 1100°C and 200MPa,
forged at 1100°C and subsequently treated at 850°C.
Mirror polished with 50nm particle size alumina.
●
Electropolished or FIBed for TEM.
●
Fe-14Cr-0.3Y O
2 3
Fe-14Cr-2W-0.3Ti-0.3Y O
2 3
General microstructure
OODDSS FFee--1144CCrr
Quite homogeneous ferritic grain structure (< 3 µm).
OODDSS FFee--1144CCrr--22WW--00..33TTii
Bimodal ferritic grain structure: Larger recovered (up to 15 µm) and
smaller unrecovered (400 - 800 nm) grains.
ODS Fe-14Cr ODS Fe-14Cr-2W-0.3Ti
General microstructure
OODDSS FFee--1144CCrr
Cr
Cr rich particles with sizes up to 1μm indexed as either Cr O or M C
2 3 23 6
General microstructure
OODDSS FFee--1144CCrr--22WW--00..33TTii
Type 1 - Less numerous, undefined shapes,
larger sizes (up to 1.5 µm).
Cr, W – rich. Indexed as M23C6 (M=Cr, W, Fe)
Two types of Cr-rich precipitates
Type 2 - More numerous, round shapes, sizes
from 50 to 500 nm.
Cr, Ti – rich. Indexed as M2O3 (M=Cr, Ti).
General microstructure
Homogeneous nanoparticle distribution in both samples
Y
OODDSS FFee--1144CCrr OODDSS FFee--1144CCrr--22WW--00..33TTii
STEM-DF
Fe-K Cr Y
STEM-BF
nanoparticle
Y-(K+L)
Cr-K W-L Ti-K
500 nm
Irradiation conditions
simultaneous triple
Samples were simultaneously triple ion irradiated at the JANNUS-
Saclay Facility in France at 600°C to simulate fusion relevant
conditions (DEMO damage per year)
Irradiation conditions
simultaneous triple with beam degrader
Flat profile
~800nm