Formation of ZrO{sub 2} in coating on Mg–3 wt.%Al–1 wt.%Zn alloy via plasma electrolytic oxidation: Phase and structure of zirconia

Journal Article · Thu Jan 15 00:00:00 EST 2015 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2014.11.014· OSTI ID:22476010

Lee, Kang Min; Kim, Yeon Sung ^[1]; Yang, Hae Woong; Park, Joo Hyun ^[2]

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1. Department of Metallurgy and Materials Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of)
2. School of Materials Science and Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of)

An investigation of the coating structure formed on Mg–3 wt.%Al–1 wt.%Zn alloy sample subjected to plasma electrolytic oxidation was examined by field-emission transmission electron microscopy. The plasma electrolytic oxidation process was conducted in a phosphoric acid electrolyte containing K{sub 2}ZrF{sub 6} for 600 s. Microstructural observations showed that the coating consisting of MgO, MgF{sub 2}, and ZrO{sub 2} phases was divided into three distinctive parts, the barrier, intermediate, and outer layers. Nanocrystalline MgO and MgF{sub 2} compounds were observed mainly in the barrier layer of ~ 1 μm thick near to the substrate. From the intermediate to outer layers, various ZrO{sub 2} polymorphs appeared due to the effects of the plasma arcing temperature on the phase transition of ZrO{sub 2} compounds during the plasma electrolytic oxidation process. In the outer layer, MgO compound grew in the form of a dendrite-like structure surrounded by cubic ZrO{sub 2}. - Highlights: • The barrier layer containing MgO and MgF{sub 2} was observed near to the Mg substrate. • In the intermediate layer, m-, t-, and o-ZrO{sub 2} compounds were additionally detected. • The outer layer contained MgO with the dendrite-like structure surrounded by c-ZrO{sub 2}. • The grain sizes of compounds in oxide layer increased from barrier to outer layer.

• OSTI ID: 22476010
• Journal Information: Materials Characterization, Vol. 99; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM COMPOUNDS
DEPLETION LAYER
DIFFUSION BARRIERS
ELECTROLYTES
GRAIN SIZE
MAGNESIUM COMPOUNDS
MAGNESIUM FLUORIDES
MAGNESIUM OXIDES
NANOSTRUCTURES
OXIDATION
PHASE TRANSFORMATIONS
SUBSTRATES
TERNARY ALLOY SYSTEMS
TRANSMISSION ELECTRON MICROSCOPY
ZINC COMPOUNDS
ZIRCONIUM OXIDES