J. Mater. Sci. Technol. ›› 2021, Vol. 85: 106-117.DOI: 10.1016/j.jmst.2020.12.045

• Research Article • Previous Articles     Next Articles

Investigation on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys with various Zn/Mg ratios

Yan Zoua, Xiaodong Wua,*(), Songbai Tanga, Qianqian Zhua, Hui Songa, Mingxing Guob, Lingfei Caoa,c,**()   

  1. aInternational Joint Laboratory for Light Alloys (Ministry of Education), College of Materials Science and Engineering, Chongqing University, Chongqing, 400044, China
    bState Key Laboratory for Advanced Metals and Materials, University of Science and Technology, Beijing, 100083, China
    cShenyang National Laboratory for Materials Science, Chongqing University, Chongqing, 400044, China
  • Received:2020-09-16 Revised:2020-12-09 Published:2021-09-20 Online:2021-02-01
  • Contact: Xiaodong Wu,Lingfei Cao
  • About author:**International Joint Laboratory for Light Alloys (Ministry of Education), College of Materials Science and Engineering, Chongqing University, Chongqing, 400044, China. caolingfei@cqu.edu.cn (L. Cao).
    *E-mail addresses: xiaodongwu@cqu.edu.cn (X. Wu),

Abstract:

The effects of Zn/Mg ratios on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys aged at 150 °C have been investigated by using tensile tests, optical metallography, scanning electron microscopy, transmission electron microscopy and atom probe tomography analyses. With increasing Zn/Mg ratios, the ageing process is significantly accelerated and the time to peak ageing is reduced. T′ phase predominates in alloys of lower Zn/Mg ratios while η′ phase predominates in alloys with a Zn/Mg ratio over 2.86. Co-existence of T′ phase and η′ phase with a large number density is beneficial to the high strength of alloys. Such precipitates together with narrow precipitate free zones cause a brittle intergranular fracture. A strength model has been established to predict the co-strengthening effect of T′ phase and η′ phase in Al-Zn-Mg-Cu alloys, including the factors of the grain boundary, solid solution and precipitation.

Key words: Al-Zn-Mg-Cu alloys, Zn/Mg ratioMicrostructure, Strength model