Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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Effect of Microstructure on the Environmentally Induced Cracking Behavior of Al-Zn-Mg-Cu-Zr Aluminum Alloy

  • Ghosh, Rahul (Materials and Mechanical Entity, Vikram Sarabhai Space Centre) ;
  • Venugopal, A. (Materials and Mechanical Entity, Vikram Sarabhai Space Centre) ;
  • Pradeep, PI (Materials and Mechanical Entity, Vikram Sarabhai Space Centre) ;
  • krishna, L. Rama (International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI)) ;
  • Narayanan, P. Ramesh (Materials and Mechanical Entity, Vikram Sarabhai Space Centre) ;
  • Pant, Bhanu (Materials and Mechanical Entity, Vikram Sarabhai Space Centre) ;
  • Cherian, Roy M (Materials and Mechanical Entity, Vikram Sarabhai Space Centre)
  • Received : 2018.03.28
  • Accepted : 2018.04.25
  • Published : 2018.06.29
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Abstract

AA7010 is an Al-Zn-Mg-Cu alloy containing Zr, developed as an alternate to traditional AA7075 alloy owing to their high strength combined with better fracture toughness. It is necessary to improve the corrosion resistance and surface properties of the alloy by incorporating plasma electrolytic oxidation (PEO) method. AA7010-T7452 aluminum alloy has been processed through the forging route with multi-stage working operations, and was coated with $10{\mu}m$ thick $Al_2O_3$ ceramic aluminina coating using the plasma electrolytic oxidation (PEO) method. The corrosion, stress corrosion cracking (SCC) and nano-mechanical behaviours were examined by means of potentiodynamic polarization, slow strain rate test (SSRT) and nano-indentation tests. The results indicated that the additional thermomechanical treatment during the forging process caused a fully recrystallized microstructure, which lead to the poor environmental cracking resistance of the alloy in 3.5% NaCl solution, despite the overaging treatment. Although the fabricated PEO coating improved general corrosion resistance, the brittle nature of the coating did not provide any improvement in SCC resistance of the alloy. However, the hardness and elastic modulus of the coating were significantly higher than the base alloy.

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