PSI - Issue 10

N. Siskou et al. / Procedia Structural Integrity 10 (2018) 79–84 N. Siskou et al. / Structural Integrity Procedia 00 (2018) 000 – 000

83

5

500

Aluminium alloy 2024-T3, t= 3.20 8 hours artifical ageing at 190° Exposure at EXCO solution

100%

99,65%

97,05%

95,10%

400

100 Conventional yield stress R p0,2% [MPa] 96,77% 94,72% 94,13% 93,45% 100% 200 300

90,90%

0 hours in EXCO 0,5 hours in EXCO 2 hours in EXCO 4 hours in EXCO 24 hours in EXCO

0

peak-ageing

T3

Fig. 3. Experimental results of conventional yield stress R p 0.2% of AA2024 specimens in T3 condition compared against the peak-ageing condition for different corrosion exposure times. 4.2. Elongation at fracture The values of the elongation at fracture A f of the pre-corroded tensile specimens in T3 condition as well as in the PA condition can be seen in Fig.4. An essential A f decrease with increasing exposure time to exfoliation corrosion solution is evident for the material in T3 condition. The remaining percentage of A f is approximately 78 % after only 2 hours corrosion exposure time where no significant surface attack was noticed. Additionally, after the highest cor rosion exposure time, e.g. 24 h in this case, A f was decreased to almost half of the initial value with the remaining value to be approximately equal to 57 %. Regarding PA condition, it can be noticed that it remains almost unaffected by corrosion exposure for the very short exposure times and up to 2 h. Even after 24 h of exposure the remaining per centage of the initial A f value is approximately 79 % while the respective percentage was noticed for the T3 condition after only 2 h corrosion exposure time. Hence, the artificial ageing heat treatment in PA condition seems to impede the corrosion-induced degradation.

25

Aluminium alloy 2024-T3, t = 3.2 mm 8 hours artificial ageing and subsequent Exposure to EXCO solution

100%

20

No EXCO solution 0.5 hr in EXCO solution 2 hr in EXCO solution 4 hr in EXCO solution 24 hr in EXCO solution

89,82%

5 Elongation at fracture A f [%] 76,79% 71,82% 10 15

56,80%

94,05%

100%

89,72%

86,23%

78,93%

0

T3

peak - ageing

Fig. 4. Experimental results of elongation at fracture A f of AA2024 specimens in T3 condition compared against the peak-ageing condition for different corrosion exposure times.