Microstructure of 7N01 Aluminum Alloy Microalloyed with Er and Zr in the Homogenization Process

Abstract:

The microstructure and segregation of 7N01 aluminum alloy microalloyed with Er and Zr before and after homogenization process at 470 °C for 24 h have been investigated using transmission electron microscope (TEM), and scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscope (EDS) and transmission electron detecter (STEM). SEM images and EDS line scan results showed that there were dendritic segregation of Mg and Zn and micron-sized primary phases along dendrites in the as-cast alloy. The primary phases were mainly Al₂Mg₃Zn₃ containing Al, Zn, Mg and Mn. And a small amount of primary phases were the particles containing Al, Zn, Mg, Mn, Cr and Er and the particles containing Al, Zn, Mg, Er, Mn, Fe and Cr. After homogenization at 470°C for 24 h, dendritic segregation of Mg and Zn was eliminated, Al₂Mg₃Zn₃ and the particles containing Al, Zn, Mg and Mn were basically dissolved. The particles containing Al, Zn, Mg, Mn, Cr and Er and the particles containing Al, Zn, Mg, Er, Mn, Fe and Cr remained. Meanwhile, TEM and STEM images showed that a large number of secondary phases appeared after the homogenization, which were mainly distributed in the inter-dendrite area. EDS results showed that the block-shaped and rod-shaped phases with the width of 10-70 nm and length of 100-500 nm were the particles containing Al, Cr and Mn or Al, Mg, Cr and Mn, and the ellipsoid secondary phase with the size of 50-100 nm was MgZn₂.

• Periodical: Materials Science Forum (Volume 993)
• Pages: 123-129
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.993.123
• Online since: May 2020
• Authors: Pei Hao Zhao, Xiao Lan Wu, Kun Yuan Gao*, Yu Sheng Ding, Hui Huang, Sheng Ping Wen, Zuo-Ren Nie
• Keywords: 7N01, Dendritic Segregation, Homogenization, Primary Phase, Secondary Phase

References

[1] L. K. Berg, et al. GP-zones in Al–Zn–Mg alloys and their role in artificial aging. Acta Materialia 49.17 (2001) 3443-3451.

DOI: 10.1016/s1359-6454(01)00251-8

[2] M. Dumont, et al. Characterization of the composition and volume fraction of η' and η precipitates in an Al–Zn–Mg alloy by a combination of atom probe, small-angle X-ray scattering and transmission electron microscopy. Acta Materialia 53.10 (2005) 2881-2892.

DOI: 10.1016/j.actamat.2005.03.004

[3] Jingling Ma, and J. Wen. Corrosion analysis of Al–Zn–In–Mg–Ti–Mn sacrificial anode alloy. Journal of Alloys and Compounds 496.1-2 (2010) 0-115.

DOI: 10.1016/j.jallcom.2010.02.174

[4] Mondal, Chandan, and A. K. Mukhopadhyay. On the nature of T(Al2Mg3Zn3) and S(Al2CuMg) phases present in as-cast and annealed 7055 aluminum alloy. Materials Science & Engineering A (Structural Materials: Properties, Microstructure and Processing) 391.1-2 (2005) 367-376.

DOI: 10.1016/j.msea.2004.09.013

[5] Yu, Xin Xiang, et al. Solidification behavior and elimination of undissolved Al2CuMg phase during homogenization in Ce-modified Al–Zn–Mg–Cu alloy. Rare Metals (2018).

DOI: 10.1007/s12598-018-1172-1

[6] M. Conserva, E. D. Russo, and O. Caloni. Comparison of the influence of chromium and zirconium on the quench sensitivity of Al-Zn-Mg-Cu alloys. Metallurgical Transactions 2.4 (1971) 1227-1232.

DOI: 10.1007/bf02664256

[7] D. S. Thompson, B. S. Subramanya, and S. A. Levy. Quench rate effects in Al-Zn-Mg-Cu alloys. Metallurgical Transactions 2.4 (1971) 1149-1160.

DOI: 10.1007/bf02664247

[8] Seok Park Dong, B. O. Kong, and S. W. Nam. Effect of mn-dispersoid on the low-cycle fatigue life of Al-Zn-mg alloys. Metallurgical & Materials Transactions A 25.7 (1994) 1547-1550.

DOI: 10.1007/bf02665487

[9] S.Y, Park, W.J. Difference in the Hot Compressive Behavior and Processing Maps between the As-cast and Homogenized AI-Zn-Mg-Cu (7075) Alloys. Journal of Materials Science & Technology 32.7 (2016) 660-670.

DOI: 10.1016/j.jmst.2016.04.006

[10] Yun Lai Deng, et al. Microstructural evolution of Al–Zn–Mg–Cu alloy during homogenization. Journal of Materials Science 46.4 (2011) 875-881.

DOI: 10.1007/s10853-010-4828-2

[11] Czurratis, P., et al. The effect of additions of Mn and Cr and the applied solidification technique on the structure of an Al-2.2 at% Zn-1.4 at% Mg alloy. Physica Status Solidi A 108.1 (1988) 171-182.

DOI: 10.1002/pssa.2211080116

[12] Eivani, A. R., et al. Evolution of Grain Boundary Phases during the Homogenization of AA7020 Aluminum Alloy. Metallurgical & Materials Transactions A 40.3 (2009) 717-728.

DOI: 10.1007/s11661-008-9741-9

[13] Kim, K. C., and S. W. Nam. Effects of Mn-dispersoids on the fatigue mechanism in an Al–Zn–Mg alloy. Materials Science & Engineering A (Structural Materials:, Properties, Microstructure and Processing) 244.2 (1998) 257-262.

DOI: 10.1016/s0921-5093(97)00548-0

[14] Li, X. M., and M. J. Starink. Identification and analysis of intermetallic phases in overaged Zr-containing and Cr-containing Al–Zn–Mg–Cu alloys. Journal of Alloys & Compounds 509.2 (2011) 0-476.

DOI: 10.1016/j.jallcom.2010.09.064