mode and by atomic force microscopy convinced us that the second source of bias should be the most! Mikro 
important in the present case. For example, Figure 5.a shows the AFM image of a polished/etched surface’ phase 
presenting two 0 lamellae in the y matrix. The two depth-of-etching profiles reported in Figure 5.b 
illustrate that the etching is not homogeneous over each of the two phases, but that it is more efficient in . 
the y phase near the 8/y interface. In consequence, the less-reflective (dark) area width can be more than M. Ham 
fourfold wider than the actual size of the lamella. This also explains why the analysis bias appears erratic Lex 
from one sample to another, since it strongly depends on the morphology of the 6 particles: for a given 
actual § phase volume fraction, the more acicular the particles, the larger the estimated volume fraction. 
b hsp 77 Ee reek reneonva area he i bri: 
: Lo Cat oe 
d 100 : bei dene 
Jase 
50, ; - N an 
" position (micron) "8 " Sn 
h 200 . VEXATETTE phase € 
t tess-reflective area zeigen 
P 150 hy 
e EINES N 
d Aa Han 
100 des Her 
50 . . or 
7 position (micron) ram-Iner 
Fig. 5 : a) AFM image of the polished/etched surface of an Inconel 718 sample ; b) depth of-etching gir 
profiles along the AB (up) and CD (down) lines. 3 
Conclusions N Mi 
- we propose to use quantitative analysis of BSEM images to measure Vv(S) with good accuracy. MR S 
- qualitative comparison of samples on the basis of Vv(S) values measured by LM image analysis is very Te ' 
hazardous if the morphology of 5 particles can change from one sample to another (as for instance ©" 
between Fig. 2.a and 2.b). von ZU 
The use of AFM to characterise the topology of the surfaces observed is a powerful approach to 
understand the origin of measurement bias and to improve surface preparation. Finleit 
Acknowledgements en Metall 
Authors are indebted to N. Maloufi from LETAM, Metz, who performed the AFM image acquisition oe 
References Versch 
1. C.T. Sims, N.S. Stoloff, W.C. Hagel, "Superalloys II" d. John Wiley and Sons (1987) wT 
2. M. Sundararaman, P. Mukhopadhyay, S. Banerjee, Metall. Trans. 23A (1992) 2015-2028 ZU Fas 
3. Fullprof version 3.5d oct.98, J. Rodriguez-Carvajal, Laboratoire Léon Brillouin, CEA-CNRS ter, da 
4. Aphelion version 3.0, ADCIS S.A., Caen, FRANCE her 
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