PSI - Issue 60

M. Suresh Kumar et al. / Procedia Structural Integrity 60 (2024) 433–443 Suresh Kumar et al.,/ Structural Integrity Procedia 00 (2023) 000 – 000

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3.2. Effect of creep forming temperature on static mechanical properties

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Fig. 4. Mechanical properties of the 5024 alloy subjected to simulated exposure to creep forming temperatures in the range 120 to 320 0 C; (a) UTS and YS data and (b) % Elongation Fig.4a shows the effect of exposure to creep forming temperatures on the alloy's ultimate tensile strength (UTS) and yield strength (YS). Results show that the UTS and YS of AR and 120 HT material were nearly the same. Exposure to temperatures in the range of 160-320°C showed a marginal decrease in the strength of the alloy. Although UTS and YS values were relatively less affected (Fig.4a), it is interesting to note that elongation/ductility was reduced significantly due to exposure to temperatures in the range 200 to 280°C (Fig.4b). The reduction in % elongation in the material after exposure to CF temperatures was found to be about 15% as compared to AR condition. However, elongation outside this range, i.e., at 120 and 300°C was relatively less affected. The microstructure of the AR alloy is shown in Fig.5. The alloy essentially consisted of elongated pancake shaped grains of Al-Mg solid solution typical of rolled sheet material (Fig.5a). The average grain size of the alloy measured to be around ~150 μm, ~30 μm and ~15 μm for longitudinal, long -transverse and short transverse directions respectively. Apart from containing nano-sized (~10 nm) secondary Al 3 Sc precipitates, the alloy was observed to have coarse primary Al 3 Sc precipitates in the size range 1-8 µm, and insoluble particles of Al 6 (Fe,Mn) phase in the size range 10- 12μm (Fig.5b). No change in these coarse precipitates’ size and distribution was observed as a result of exposure to CF temperatures.

Fig 5. SEM images showing (a) elongated pan cake shaped microstructure in the AR alloy; (b) primary Al 3 Sc precipitates marked by black arrow, and encircled, and Fe-rich particles (white arrow)