Crack Paths 2009

1 %

3.5%NaCl

0 %

1 %

[2.5, 10 Hz]

18%157% % 21%

1 %

10-7

sinusoidal

1 %

Air

3 1 % 2 %1 %1 % 1 Hz

3.5%NaClsinusoidal

Distilled water 5 H z

3.5%NaClsinusoidal 0.1 Hz 1 8 % 83%%

4 %

10-8

2024-T351

∆ K(MPaxm1/2)

S-LR=0.7

2

3

4

5

6

7 8 9 10

Figure 3. Influence of the loading frequency on th FCGRsof the alloy 2024-T351 for a sinusoidal waveform Figure 4. Percentages of flat facets for the

S-L orientation plotted on a da/dN-∆K

graph.

(R=0.7, S-L orientation).

Figure 5. Identification of the flat, large

Figure 6. Morphology of the facets in

and smooth facets in air and saline solution by Keller’s reagent etch pitting (R=0.7, 5 Hz, sinusoidal waveform, 3.5% saline solution. 2024-T351 S-L. R=0.7. 10

Hz. ∆K=4-4.5 MPa√m.Black arrow :

crack propagation direction.

NaCl, ∆K=5.7MPa√m).

Finally it is noteworthy that in the T851 in the S-L orientation temper or the L-T

orientation in the T351 temper the facets are much less numerous, while these

conditions corresponds with a much higher resistance to intergranular stress corrosion

cracking cracking [1], which provides an additional support for the intergranular nature

of these facets and for a relation between the S C Csusceptibility of 2 X X Xaluminum

alloys and a pronounced F C G enhancement in saline solution determined by the

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