PSI - Issue 68

R.J. Mostert et al. / Procedia Structural Integrity 68 (2025) 351–357 R.J. Mostert et al. / Structural Integrity Procedia 00 (2025) 000–000

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Fig. 4. TDS results for EXCO Exposed [EE], EXCO Exposed and Heat Treated [EE + HT], Heat Treated only [HT] and Baseline [BL] samples.

Fig. 5. (a) Schematic representation of the four distinct fracture zones of the C(T) samples and (b) SEM image of shallow surface cracks in Zone (iv), showing IG cracking (AA2024-T3 sample).

For both the exposed and unexposed K R -samples, the fractographic features of Zone (ii) of the primary fracture surface were found to be similar, with microvoid-coalescence (MVC) dominating, as shown earlier by Pretorius et al. (2024). However, in Zone (iv) no cracking was observed for the baseline (unexposed) samples, while extensive shallow secondary cracking with an intergranular (IG) nature was observed after exposure and straining (Fig. 6).

Fig. 6. SEM images of shallow surface cracks showing intergranular nature on AA 2024-T3 sample.