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

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(a)

(d)

(b)

(e)

(c)

(f)

Fig. 2. Typical corroded surfaces of the peak-aged AA2024 specimens for: (a) and (d) 0.5 h, (b) and (e) 4 h, (c) and (f) 24 h exposure to EXCO solution.

4.1. Conventional yield stress

Conventional yield stress R p0.2% was calculated based on the nominal cross-section of the specimens and without considering the effective thickness of the specimens. Fig. 3 shows the test results of AA2024 in T3 as well as in PA condition as average values and respective standard deviation derived from three specimens each. It can be noticed that AA2024-T3 exhibits slightly higher degradation of the conventional yield stress R p0.2% than AA2024 in PA con dition, especially for the short corrosion exposure times. For instance, after only 2 h of corrosion exposure the re maining value of R p0.2% for the material in T3 condition is approximately 95 % while the respective value for the material in the PA condition is 97 %. For the higher exposure times, where excessive pitting corrosion is evident on the specimens’ surfaces, the decrease in conventional yield stress R p0.2% seems to be almost the same for both con ditions. Hence, the material exhibits slightly higher corrosion resistance when artificially aged to the PA condition. Still it is not known to the authors the corrosion resistance of the material at other heat treatment conditions, e.g. in under-ageing (UA) or at over-ageing (OA) conditions.