Identification and analysis of intermetallic phases in overaged Zr-containing and Cr-containing Al-Zn-Mg-Cu alloys

Li, X.M. and Starink, M.J. (2011) Identification and analysis of intermetallic phases in overaged Zr-containing and Cr-containing Al-Zn-Mg-Cu alloys. Journal of Alloys and Compounds, 509, (12), 471-476. (doi:10.1016/j.jallcom.2010.09.064).


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This paper investigates the effect of alloying elements on the characteristics of intermetallic phases in Zr-containing and Cr-containing 7xxx Al-Zn-Mg-Cu alloys at overaged conditions. Four Al-Zn-Mg-Cu alloy plates with different alloying element contents were studied by optical microscopy based image analysis, differential scanning calorimetry, scanning electron microscopy combined with energy disperse X-ray spectroscopy and transmission electron microscopy. The grain structures, recrystallisation, intermetallic phases and precipitates in the selected alloys have been analysed and the presence of coarse intermetallic phases has been interpreted using established phase diagrams. The different effects of Zr or Cr addition to the alloys have been compared. The experimental results showed that the recrystallised area fraction of Zr-containing alloys is less than that of Cr-containing alloys, being attributable to Zr reducing recrystallisation more effectively than Cr. The detected particles are mainly S phase, Al7Cu2Fe, as well as dispersoids of Al3Zr for Zr-containing alloys and Cr-rich E phase for Cr-containing alloys. These coarse particles, especially the S phase which can not be dissolved during solution treatment, are detrimental to the fracture toughness of the alloys.

Item Type: Article
Additional Information: Acknowledgements The financial support from Southampton University, UK and Alcoa Europe (formerly British Aluminium Plate) is gratefully acknowledged. The experimental alloys were produced at QinetiQ, Farnborough, UK. Mr. J.T. Zhao from Southeast University is thanked for his technical help.
ISSNs: 0925-8388 (print)
1873-4669 (electronic)
Keywords: intermetallic phases, coarse particles, 7xxx, 7075, Al-Zn-Mg-Cu, DSC, toughness, SEM, solution treatment
Subjects: T Technology > TN Mining engineering. Metallurgy
Divisions: University Structure - Pre August 2011 > School of Engineering Sciences > Engineering Materials & Surface Engineering
Faculty of Engineering and the Environment > Engineering Sciences > Engineering Materials Surface Engineering
ePrint ID: 162793
Date Deposited: 27 Aug 2010 13:27
Last Modified: 30 Jan 2015 13:53

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