Effect of Process Parameters on Microstructures of 7055 Aluminum Alloy in Creep Age Forming

Abstract:

The effects of process parameters on evolution of microstructures of 7055 aluminum alloy in creep age forming were studied and the microstrucures were analyzed using transmission electron microscopy (TEM). Some important results are obtained: with the increasing of ageing time, the size of platelet shaped (known as Guinier-Preston (G-P) zones) precipitates and spherical shaped η' precipitates increased, the number of platelet shaped precipitates increased too, while the number of η' precipitates decreased; the precipitates with almost the same size distributed continuously and uniformly along the grain boundary with quite narrow precipitate free zones (PFZs) at 5 hours of ageing time, when the ageing time increases to 8 hours, the distribution of the precipitates along the grain boundary becomes discontinuous and the PFZs gets wider, while with the further increasing of the ageing time, the precipitates distributed continuously again along the grain boundary and the PFZs become more wider. From comparison of stress-aged alloy to stress-free-aged alloy, it was found that after 20 hours ageing, the precipitates in the stress-aged alloy are slightly coarser and the PFZs are wider, the density of retained η' is lower with the development of η phase.

• Periodical: Applied Mechanics and Materials (Volumes 80-81)
• Pages: 40-45
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.80-81.40
• Online since: July 2011
• Authors: Li Hua Zhan, Yan Guang Li, Ming Hui Huang
• Keywords: Ageing Time, Creep Age Forming, Microstructure, Stress Aging

References

[1] M. Sallah, J. Peddieson, S. Foroudasan, A mathematical model of autoclave age forming, 7th Int. Confer. Comput. Aided Prod. Eng. 28(9) (1991) 211-219.

DOI: 10.1016/0924-0136(91)90220-9

[2] M.C. Holman, Autoclave age forming large aluminium aircraft panels, J. Mech. W. Technol. 20 (1989) 477-488.

DOI: 10.1016/0378-3804(89)90055-7

[3] R. Dif, B. Bes, D. Daniel, Ph. Lassince, H. Ribes, Improving the forming characteristics of aluminium sheets for aerospace applications, Mater. Sci. Forum. 331-337 (2000) 483-488.

DOI: 10.4028/www.scientific.net/msf.331-337.483

[4] K.C. Ho, J. Lin, T.A. Dean, Modelling of springback in creep forming thick aluminum sheets, Int. J. Plast. 20 (2004) 733-751.

DOI: 10.1016/s0749-6419(03)00078-0

[5] P.D. Pitcher, C.M. Styles, Creep age forming of 2024A, 8090 and 7449 alloys, Mater. Sci. Forum. 331-337 (2000) 455-460.

DOI: 10.4028/www.scientific.net/msf.331-337.455

[6] A. Levers, A. Prior, Finite element analysis of shot peening, J. Mater. Process. Technol. 80-81 (1998) 304-308.

DOI: 10.1016/s0924-0136(98)00188-5

[7] W.F. Hosford, S.P. Agrawal, Effect of stress during ageing on the precipitation of θ' in Al-4 wt pct Cu, Metall. Trans. A (Phys. Metallurgy Mater. Sci. ). 6(3) (1975) 487-491.

DOI: 10.1007/bf02658406

[8] B. Skrotzki, G. J. Shiflet, EA. Jr. Starke, On the effect of stress on nucleation and growth of precipitates in an Al-Cu-Mg-Ag alloy, Metall. Trans. A (Phys. Metallurgy Mater. Sci. ). 27A(11) (1996) 3431-3444.

DOI: 10.1007/bf02595436

[9] A.W. Zhu, E. A. Starke Jr, Stress aging of Al-χCu alloys: Experiment, Acta Mater. 49(12) (2001) 2285-2295.

DOI: 10.1016/s1359-6454(01)00119-7

[10] A.W. Zhu, E. A. Starke Jr, Materials aspects of age-forming of Al-χCu alloys, J. Mater. Process. Technol. 117 (2001) 354-358.

[11] D. Bakavos, P. B. Prangnell, B. Bes, et al., Microstructural interaction during stress ageing a 7475 aerospace alloy, Mater. Sci. Forum. 519-521 (2006) 333-338.

DOI: 10.4028/www.scientific.net/msf.519-521.333

[12] D. Bakavos, P. B. Prangnell, B. Bes, F. Eberl, S. Gardiner, Through thickness microstructural gradients in 7475 and 2022 creep-age formed bend coupons, Mater. Sci. Forum. 519-521 (2006) 407-412.

DOI: 10.4028/www.scientific.net/msf.519-521.407

[13] Z. H. Li, B. Q. Xiong, Y. A. Zhang, et al., Microstructural evolution of aluminum alloy 7B04 thick plate by various thermal treatments, Trans. Nonferrous Met. Soc. China. 18 (2008) 40-43.

DOI: 10.1016/s1003-6326(08)60008-4

[14] D. Feng, in Metal Physics(Vol. 3), edited by Sci. Press, Beijing, (1999).

[15] R. Song, Current status and trends in high strength aluminum alloy research, Mater. Rev. 14 (2000) 20-21.

[16] R. Tian, Z. Wang, in Aluminum Alloys and Their Fabrication. Edited by Cent. S. Univ. Technol. Press, Changsha, Hunan，(2000).

[17] K. Shen, Z. Yin, T. Wang, TEM study on microstructure development of single-ageing 7055 aluminum alloys, Trans. Nanjing Univ. Aeronaut. Astronaut. 24 (2007) 265-269.