Formation of an aluminum-alloyed coating on AZ91D magnesium alloy in molten salts at lower temperature

被引:53
|
作者
Zhong, C. [1 ]
He, M. F. [1 ]
Liu, L. [1 ]
Chen, Y. J. [1 ]
Shen, B. [1 ]
Wu, Y. T. [1 ]
Deng, Y. D. [1 ]
Hu, W. B. [1 ]
机构
[1] Shanghai Jiao Tong Univ, State Key Lab Met Matrix Composites, Shanghai 200240, Peoples R China
来源
SURFACE & COATINGS TECHNOLOGY | 2010年 / 205卷 / 07期
基金
中国国家自然科学基金;
关键词
Magnesium alloy; Molten salt; Aluminum-alloyed coating; Corrosion resistance; Hardness; IMPROVED CORROSION-RESISTANCE; PURE MAGNESIUM; MG ALLOYS; AL; DEPOSITION; ELECTRODEPOSITION; MICROSTRUCTURE; IMPROVEMENT; PROTECTION; SUBSTRATE;
D O I
10.1016/j.surfcoat.2010.09.034
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
An aluminum-alloyed coating was formed on an AZ91D magnesium alloy in molten salts containing AlCl3 at a lower temperature of 380 degrees C. The microstructure and phase constitution of the alloyed layer were investigated by optical microscopy, scanning electron microscopy, energy dispersive spectrum and X-ray diffraction. The nano-hardness of the coating was studied by nanoindentation associated with scanning probe microscopy. The corrosion resistance of the coated specimen was evaluated in a 3.5 wt.% NaCl solution by electrochemical impedance spectroscopy and cyclic potentiodynamic polarization. The results show that the aluminum-alloyed coating consists of Mg2Al3 and Mg17Al12 intermetallic layers. The formation of the coating is dictated by the negative standard free energy of the reaction: 2AlCl(3) + 3 Mg = 3MgCl(2) + 2Al. This process is associated with a displacement reaction mechanism and diffusion process that takes place during the molten salt treatment. High activity of Al elements in molten salts contributes to the lower temperature formation of the Al-alloyed coating. The alloyed coating markedly improves the hardness as well as the corrosion resistance of the alloy in comparison with the untreated AZ91D magnesium alloy, which is attributed to the formation of the intermetallic compounds. (C) 2010 Elsevier B.V. All rights reserved.
引用
收藏
页码:2412 / 2418
页数:7
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