Effect of microstructure on exfoliation corrosion resistance in an Al-Zn-Mg alloy

Journal Article · Mon Jan 15 04:00:00 EST 2018 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2017.11.029· OSTI ID:22804856

Lu, Xianghan ^[1]; Han, Xiaolei; Du, Zhiwei ^[2]; Wang, Guojun; Lu, Liying; Lei, Jinqin ^[3]; Zhou, Tietao ^[1]

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1. School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)
2. National Analysis and Testing Center for Nonferrous Metals & Electronic Materials, Beijing General Research Institute for Nonferrous Metals, Beijing 100088 (China)
3. Northeast Light Alloy Co., Ltd., Harbin 150060 (China)

Highlights: • A quantitative method was proposed to characterize EXCO resistance. • The EXCO product lead to strain in ND and elongation in RD on nearby grains. • Recrystallized grains are more susceptible to EXCO than fibrous grains. • High fraction of high-angle grain boundaries reduces EXCO resistance. • High coverage ratio of η phases on high-angle grain boundaries reduces EXCO resistance. - Abstract: In this work, the effect of microstructure on exfoliation corrosion (EXCO) resistance in an Al-Zn-Mg alloy were investigated using standard EXCO test, together with detailed microstructural examinations mainly by scanning electron microscopy (SEM) and high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). An EXCO product model was built based on morphologies of EXCO product on longitudinal section and cross section for further measurement and analysis. A quantitative characterization of EXCO resistance by measuring average thickness of EXCO product was conducted, showing average results of 6.94 μm, 10.21 μm and 18.14 μm, which are corresponding to EXCO ratings of P, EA and EB under ASTM G34 standard, respectively. It was concluded that recrystallization, high fraction of high-angle grain boundaries (HAGBs) and high coverage ratio of η phases on HAGBs reduced EXCO resistance.

• OSTI ID: 22804856
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Vol. 135; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM COMPOUNDS
CORROSION RESISTANCE
ELONGATION
MAGNESIUM COMPOUNDS
MICROSTRUCTURE
RECRYSTALLIZATION
SCANNING ELECTRON MICROSCOPY
TERNARY ALLOY SYSTEMS
THICKNESS
TRANSMISSION ELECTRON MICROSCOPY
ZINC COMPOUNDS