Etude par Sonde Atomique Tomographique de la formation de nano ...

tel-00751814, version 1 - 14 Nov 2012
Chapter 3. Oxide Dispersion Strengthened Steels
Table 3.8. Chemical compositions of Fe-Cr rich phase measured by APT in ODS model
alloy. In total, the matrix composition is measured on three different powder grains.
LAWATAP measurements in places indicated on Figure 3.9, corresponds to 1-7 analyses.
Matrix measurements are also performed for two LATAP analyses. In one (shown on Figure
3.6), matrix composition is calculated by similar way and corresponds to 8-11 analyses. In
second one (shown on Figure 3.3), the composition is calculated for Fe-Cr rich phase and
corresponds to 12 analyse. For comparison the nominal composition is also reported. The
composition is calculated in accordance to assumption that O2 ions located at 32 amu.
Standard deviations are 2σ. The values are in at.%.
Elements Fe Cr Si Mn W C Y Ti O
Nominal (at.%) Bal. 7.45 - - - - 4.8 11.0 7.1
1 88.7 9.9 0.04 0.33 0.22 0.08 0.11 0.32 0.70
2σ 0.9 0.9 0.06 0.17 0.14 0.08 0.10 0.17 0.25
2 90.3 7.7 0.16 0.31 0.15 0.08 0.39 0.08 0.80
2σ 1.6 1.5 0.22 0.31 0.22 0.16 0.35 0.16 0.50
3 89.9 7.2 0.24 0.33 0.24 0.06 0.24 0.34 1.5
2σ 1.5 1.3 0.24 0.28 0.24 0.12 0.24 0.29 0.59
4 90.2 8.6 0.19 0.18 0.13 0.03 0.11 0.10 0.36
2σ 0.6 0.6 0.09 0.08 0.07 0.03 0.07 0.06 0.12
5 90.1 8.6 0.19 0.26 0.25 0.05 0.07 0.08 0.35
2σ 0.6 0.6 0.09 0.10 0.10 0.04 0.05 0.05 0.12
6 90.9 8.2 0.22 0.27 0.14 0.04 0.01 0.01 0.28
2σ 0.5 0.5 0.09 0.10 0.07 0.03 0.02 0.02 0.10
7 90.7 8.1 0.10 0.16 0.18 0.02 0.09 0.08 0.54
2σ 0.6 0.5 0.60 0.08 0.08 0.03 0.06 0.06 0.15
8 86.4 10.1 0.22 0.22 0.22 0.04 0.39 0.33 1.50
2σ 2.3 2.0 0.31 0.31 0.31 0.42 0.38 0.39 0.81
9 88.6 9.4 0.37 0.16 0.19 0.11 0.06 0.22 0.80
2σ 0.9 0.8 0.17 0.11 0.12 0.09 0.07 0.13 0.25
10 88.8 8.70 0.38 0.25 0.47 0.09 0.09 0.12 1.18
2σ 1.9 1.7 0.38 0.30 0.42 0.20 0.20 0.21 0.67
11 85.1 11.7 0.22 0.43 0.11 0.22 0.01 0.40 1.70
2σ 2.3 2.1 0.30 0.43 0.22 0.30 0.01 0.41 0.85
12 89.5 9.5 0.27 0.15 0.16 0.13 0.01 0.05 0.05
2σ 0.2 0.2 0.03 0.02 0.02 0.02 0.01 0.01 0.01
Mean 89.7 8.85 0.20 0.23 0.19 0.07 0.08 0.12 0.48
2σ 0.23 0.22 0.03 0.04 0.04 0.02 0.03 0.03 0.06
As it can be seen in Table 3.8, the matrix concentration is different from the nominal one.
A significant lower amount of Ti, O and Y are measured. Si, Mn, W and C are also detected.
In the Fe-Cr-rich phase, Fe varies from 85.1 to 90.9 at.% and Cr from 7.2 to 11.7 at.%.
Fluctuations of Y, Ti and O elements are also observed from one place to another. As an
example, smaller amounts of Ti, Y and O are measured in box number 5 and 6 located far
from Y-Ti-O rich phases in comparison to boxes 1, 2 and 3 located closer (see Figure 3.9). In
general, the Ti, Y and O concentrations vary from 0.01 to 0.40 at.%, 0.01 to 0.39 at.% and
0.05 to 1.7 at.%, respectively. It must be mentioned that Y and O are almost immiscible in bcc
iron (their equilibrium solubility limits are 0.029 at.% [12] and 0.06 [13] respectively at
102