Effect of Microstructure on the Environmentally Induced Cracking Behavior of Al-Zn-Mg-Cu-Zr Aluminum Alloy
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AA7010 is an Al-Zn-Mg-Cu alloy containing Zr, developed as an alternate to traditional AA7075alloy owing to their high strength combined with better fracture toughness. It is necessary to improvethe 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 withmulti-stage working operations, and was coated with 10μm thick Al2O3 ceramic aluminina coatingusing the plasma electrolytic oxidation (PEO) method. The corrosion, stress corrosion cracking (SCC)and nano-mechanical behaviours were examined by means of potentiodynamic polarization, slow strainrate test (SSRT) and nano-indentation tests. The results indicated that the additional thermomechanicaltreatment during the forging process caused a fully recrystallized microstructure, which lead to thepoor 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 thecoating did not provide any improvement in SCC resistance of the alloy. However, the hardness andelastic modulus of the coating were significantly higher than the base alloy.
Abstract
AA7010 is an Al-Zn-Mg-Cu alloy containing Zr, developed as an alternate to traditional AA7075alloy owing to their high strength combined with better fracture toughness. It is necessary to improvethe 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 withmulti-stage working operations, and was coated with 10μm thick Al2O3 ceramic aluminina coatingusing the plasma electrolytic oxidation (PEO) method. The corrosion, stress corrosion cracking (SCC)and nano-mechanical behaviours were examined by means of potentiodynamic polarization, slow strainrate test (SSRT) and nano-indentation tests. The results indicated that the additional thermomechanicaltreatment during the forging process caused a fully recrystallized microstructure, which lead to thepoor 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 thecoating did not provide any improvement in SCC resistance of the alloy. However, the hardness andelastic modulus of the coating were significantly higher than the base alloy.
참고문헌 (14)
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