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Title: 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

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 oxidemore » layer increased from barrier to outer layer.« less
Authors:
;  [1] ; ;  [2] ;  [2] ;  [1]
  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)
Publication Date:
OSTI Identifier:
22476010
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 99; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
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