Oxidation Behavior of Zr-Nb Alloys at 973-1273 K in Air
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1043-T09-01
Oxidation behavior of Zr-Nb alloys at 973-1273 K in air T. Arima*), K. Miyata, K. Idemitsu and Y. Inagaki
© 2008 Materials Research Society Department of Applied Quantum Physics and Nuclear Engineering, Faculty of Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan E-mail*): [email protected]
2007 MRS Fall Meeting, Nov. 26-30, 2007, Boston, MA (T. Arima)
1
Introduction
I Introduction
Background •
Zr-Nb alloy has been extensively studied from the aspect of thermal treatment, chemical composition and irradiation effects, etc.
•
For the safe management of fuels, corrosion behaviors under accident condition, e.g. LOCA, should be investigated.
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Objective
To investigate oxidation behaviors of Zr-Nb alloys under the condition of high temperatures (rapid annealing: ~1000 K/120 s, 973-1273 K) and dry air.
2
Materials
II Experimental
Element [wt%] Alloy
Sn
Fe
Cr
O
Zr
Zry-4
1.27
0.11
0.11
0.14
bal.
Nb
O
N
H
Zr
Zr-2.5Nb
2.46
0.090
0.0022
0.0034
bal.
Zr-4Nb
3.93
0.088
0.0025
0.0036
bal.
Zr-6Nb
5.89
0.087
0.0020
0.0033
bal.
Zr-10Nb
9.94
0.085
0.0023
0.0051
bal.
© 2008 Materials Research Society Zr-1Nb 0.99 0.090 0.0020 0.0032 bal.
α-Zr
α-Zr + β-Zr
3
Measurements
II Experimental
Thermo-gravimetry (TG) •
Weight gain due to oxidation was measured by Cahn-2000 micro-balance.
•
Oxidation tests were performed under flowing dry air at 973-1273 K.
X-ray diffractometry (XRD) •
X-ray diffraction patters from as-received metal and oxidized sample were
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measured by Shimadzu XD-D1. •
All measurements were done at room temperature.
Electron-prove micro-analysis (EPMA) •
Distribution of elements, Nb, Zr and O, were investigated by EPMA-1600 .
•
Cross sectional view of oxide film on metal was observed.
4
Oxidation in dry air
III Results and discussion
• Parabolic rate law dominates oxidation kinetics at high T and P(O2).
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kinetic transition (parabolic → linear)
5
Weight gain vs. Nb content
III Results and discussion
• Weight gain, δw: At low T, δw is small for low Nb content, and at high T, δw is small for Zr-2.5Nb.
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1273K, air
6
Rate constant for oxidation
III Results and discussion
• Parabolic rate constant, Kp: At low T, Kp is small for low Nb content, and at high T, Kp is small for Zr-2.5Nb. Q ~ 120 kJ/mol
• Activation energy, Q: Q is almost independent on Nb content, and at higher T, smaller Q can be observed.
© 2008 Materials Research Society Q ~ 150 kJ/mol
For samples undergoing rate transition, only pretransition data (parabolic part) was used to obtain Kp. 7
X-ray diffraction from oxide film Oxide film formed on Zr-1Nb alloy consists of m-and t-ZrO2.
III Results and discussion
On the other hand, oxide film formed on Zr-10Nb alloy consists of m-ZrO2 and Zr-Nb oxide compound.
© 2008 Materials Research Society Other peaks : monoclinic
1273K, air
Other peaks : mo
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