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Effect of RRA Treatment on the Microstructure and Fatigue Behavior of 7020 Aluminum Alloy

  • Yong Wang
  • Yunlai Deng
  • Shengdan Liu
  • Zhaojun Shan
  • Jianguo Tang
  • Xinming Zhang
Conference paper

Abstract

The fatigue crack growth (FCG) behavior and fatigue strength of 7020 aluminum alloy in an over aged treatment and two retrogression and re-aging (RRA) treatments were investigated. The microstructures and fractographies were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The result showed that RRA-treated alloys have faster FCG rate than over aged alloy at lower ΔK region due to the dense non-shearable precipitates. And the RRA120 alloy re-aged at 120 °C/24 h has a relatively faster FCG rate than RRA150 alloy re-aged at 150 °C/12 h. RRA-treated alloys have higher fatigue strength than over aged alloy. The fatigue strength corresponding to 107 cycles of over aged, RRA120 and RRA150 conditions are 114, 129 and 118 MPa, respectively. The effect of RRA treatment on the fatigue property is mainly caused by its finer and more dispersed precipitates and narrower precipitate free zone (PFZ).

Keywords

7020 aluminum alloy Retrogression and re-aging (RRA) treatment Microstructure Fatigue crack growth Fatigue strength 

Notes

Acknowledgements

This work is supported by the National Key Research and Development Program of China (2016YFB0300901), the National Science Foundation of China (51474240) and the Key Research and Development Program of Zhongshan (2016A1001).

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Copyright information

© Springer Nature Singapore Pte Ltd. 2018

Authors and Affiliations

  • Yong Wang
    • 1
    • 2
  • Yunlai Deng
    • 1
    • 2
    • 3
  • Shengdan Liu
    • 2
    • 3
  • Zhaojun Shan
    • 2
    • 3
  • Jianguo Tang
    • 1
    • 2
    • 3
  • Xinming Zhang
    • 1
    • 2
    • 3
  1. 1.Light Alloy Research InstituteCentral South UniversityChangshaChina
  2. 2.Key Laboratory of Nonferrous Metal Materials Science and EngineeringMinistry of Education, Central South UniversityChangshaChina
  3. 3.School of Materials Science and EngineeringCentral South UniversityChangshaChina

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