Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 21    No. 12    December 2011

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Corrosion mechanism associated with
Mg2Si and Si particles in Al−Mg−Si alloys
ZENG Feng-li1 , WEI Zhong-ling2, LI Jin-feng1, LI Chao-xing1, TAN Xing1, ZHANG Zhao3, ZHENG Zi-qiao1

1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Jiaxing Key Laboratory of Light Alloy Technology, Jiaxing 314051, China;
3. Department of Chemistry, Zhejiang University, Hangzhou 310027, China

Abstract:The electrochemical behaviors and coupling behaviors of the Mg2Si and Si phases with α(Al) were investigated, the corrosion morphologies of Al alloys containing Mg2Si and Si particles were observed, and the corrosion mechanism associated with them in Al−Mg−Si alloys was advanced. The results show that Si particle is always cathodic to the alloy base, Mg2Si is anodic to the alloy base and corrosion occurs on its surface at the beginning. However, during its corrosion process, the preferential dissolution of Mg and the enrichment of Si make Mg2Si transform to cathode from anode, leading to the anodic dissolution and corrosion of the alloy base at its adjacent periphery at a later stage. As the mole ratio of Mg to Si in an Al−Mg−Si alloy is less than 1.73, it contains Mg2Si and Si particles simultaneously in the grain boundary area, and corrosion initiates on the Mg2Si surface and the precipitate-free zone (PFZ) at the adjacent periphery of Si particle. As corrosion time is extended, Si particle leads to severe anodic dissolution and corrosion of the PFZ at its adjacent periphery, expedites the polarity transformation between Mg2Si and the PFZ and accelerates the corrosion of PFZ at the adjacent periphery of Mg2Si particle.

 

Key words: Al−Mg−Si alloys; intergranular corrosion; corrosion mechanism; electrochemical behaviors; Mg2Si; Si

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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