J. Mater. Sci. Technol. ›› 2018, Vol. 34 ›› Issue (3): 534-540.DOI: 10.1016/j.jmst.2016.11.008

• Orginal Article • Previous Articles     Next Articles

Effects of Ag Addition on Precipitation and Fatigue Crack Propagation Behavior of a Medium-Strength Al-Zn-Mg Alloy

Lianghua Lin, Zhiyi Liu(), Wenjuan Liu, Yaru Zhou, Tiantian Huang   

  1. 1School of Material Science and Engineering, Central South University, Changsha 410083, China
    2Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China
  • Received:2016-07-14 Revised:2016-10-17 Accepted:2016-11-02 Online:2018-03-20 Published:2018-03-20


Effects of trace addition of Ag on the fatigue crack propagation behavior and microstructure of a medium-strength aged Al-Zn-Mg alloy were investigated in the present work. The results show that a combination of enhanced tensile strength and improved fatigue crack propagation resistance in Al-Zn-Mg alloys is achieved with small addition of Ag. The enhanced strength is attributed to the high density of η′ precipitates within the grains and narrow precipitate free zones in the vicinity of grain boundaries. The main contribution to the improvement of fatigue crack propagation resistance comes from the coarser precipitates within the grains. When subjected to two-step aging, Ag-added alloy shows larger semi-coherent matrix precipitates. These relatively coarser precipitates increase the homogeneity of deformation and therefore improve the fatigue crack propagation resistance. In addition, microstructure analysis indicates that the size and distribution of inclusions as well as the grain structures of Al-Zn-Mg alloys are independent of Ag addition.

Key words: Aluminum alloy, Fatigue crack propagation, Precipitate free zones, Silver