PSI - Issue 60

442 M. Suresh Kumar et al. / Procedia Structural Integrity 60 (2024) 433–443 Suresh Kumar et al., / Structural Integrity Procedia 00 (2023) 000 – 000 offered desirable mechanical properties in terms of a trade-off in both static and fatigue loading conditions. Therefore, the optimum creep forming temperature for the alloy is 300°C for 2 hours. 5. Conclusions Creep forming behavior of 5024 H116 alloy is evaluated with a view to understanding the influence of forming temperatures on spring back and mechanical properties. Based on the above study, the following conclusions were drawn: (i) Spring back decreases with increasing temperature and becomes negligible at 300°C (ii) Tensile strength and yield strength were unaffected as a result of creep forming in the entire temperature range between 160-320°C, but the elongation reduced significantly (~15%) in the range of 200-280°C. The reduction in ductility was attributed to the formation of β (Al 3 Mg 2 ) precipitates along the grain boundaries. (iii) The ductility of the material was found to be adversely affected in the case of samples exposed to 200 0 C as compared to 300 0 C, though there was an increase in the fatigue strength from 250 to 290 MPa for 10 6 cycles The increase in fatigue properties for 200 HT sample compared to AR/300 HT is attributed to formation of delaminations as a result of higher amounts of β precipitates along the grain boundaries . However, the presence of grain boundary β precipitates are detrimental to tensile ductility, and hence, adversely affect the structural stability. (iv) The optimum creep forming temperature is 300°C for 2 hours. Creep forming of the alloy in the temperature range of 160-280°C should be avoided in view of the unacceptable reduction in the ductility (% elongation) of the alloy. Acknowledgments The authors thank Dr. S K Bhaumik for helpful discussions and inputs in carrying out this work. The authors also thank Ms Kalavati for her assistance in fractography studies. References Brosi, J.K., Lewandowski, J.J., 2010. Delamination of a sensitized commercial Al – Mg alloy during fatigue crack growth. Scripta Materialia 63(8), 799 - 802. Chen, J.F., Jiang, J.T., Zhen, L., Shao, W.Z., 2014. Stress relaxation behavior of an Al –Zn–Mg– Cu alloy in simulated age - forming process. Journal of Materials Processing Technology 214(4), 775 - 783. Filatov, Y.A., Yelagin, V.I., Zakharov, V.V., 2000. New Al – Mg – Sc alloys. Materials Science and Engineering: A 280(1), 97-101. Gangloff, R.P., Piascik, R.S., Dicus, D.L., Newman Jr, J.C., 1994. Fatigue crack propagation in aerospace aluminum alloys. Journal of aircraft 31(3), 720 - 729. Holman, M.C., 1989. Autoclave age forming large aluminum aircraft panels. Journal of Mechanical Working Technology 20, 477 - 488. Jambu, S., Lenczowski, B., Rauh, R., Juhl, K., 2002. Creep forming of AlMgSc alloys for aeronautic and space applications. International Congress of the Aeronautical Sciences, Toronto, 632.1 – 632.7 Jeshvaghani, R.A., Zohdi, H., Shahverdi, H.R., Bozorg, M., Hadavi, S.M.M., 2012. Influence of multi - step heat treatments in creep age forming of 7075 aluminum alloy: Optimization for springback, strength and exfoliation corrosion. Materials characterization 73, 8 - 15. Kalyanam, S., Beaudoin, A.J., Dodds Jr, R.H., Barlat, F., 2009. Delamination cracking in advanced aluminum – lithium alloys – Experimental and computational studies. Engineering fracture mechanics 76(14), 2174-2191. Kendig, K.L., Miracle, D.B., 2002. Strengthening mechanisms of an Al -Mg- Sc - Zr alloy. Acta Materialia 50(16), 4165 - 4175. Krishnamurthy, S.C., Arseenko, M., Kashiwar, A., Dufour, P., Marchal, Y., Delahaye, J., Idrissi, H., Pardoen, T., Mertens, A., Simar, A., 2023. Controlled precipitation in a new Al -Mg- Sc alloy for enhanced corrosion behavior while maintaining the mechanical performance. Materials Characterization 200, 112886. Kumar, N., Komarasamy, M.,Mishra, R.S., 2014. Plastic deformation behavior of ultrafine - grained Al –Mg– Sc alloy.