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An ab initio Investigation on the Effects of Impurity in Aluminum Grain Boundary

Published online by Cambridge University Press:  17 March 2011

Guang-Hong Lu ,
Tomoyuki Tamura ,
Masao Kamiko ,
Masanori Kohyama  and
Ryoichi Yamamoto
Guang-Hong Lu
Affiliation:
Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
Tomoyuki Tamura
Affiliation:
Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
Masao Kamiko
Affiliation:
Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
Masanori Kohyama
Affiliation:
Special Division of Green Life Technology, AIST Kansai, 1-8-31 Midorigaoka, Ikedashi, Osaka 563-8577, Japan
Ryoichi Yamamoto
Affiliation:
Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
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Abstract

The electronic structure of AlS9 tilt grain boundary with segregated impurity atoms of Na, Ca, Si and S, respectively, has been investigated by an ab initio pseudopotential method. Na and Ca segregation causes the boundary to expand and the charge density to decrease significantly. There forms several weak bond regions. Si segregation increases the charge density between Si and the neighboring Al atom. There forms a stronger Al-Si bond that is a mixture of covalent and metallic character in the boundary. For S segregation, though there forms the stronger bond between Al and S atom, some Al-S bonds may become weaker than the former Al-Al bonds because of the charge density decrease. It is concluded that the mechanism of Na or Ca-promoted Al grain boundary embrittlement is one kind of ‘decohesion model’, that of Si is ‘bond mobility model’. It can't be decided the embrittlement mechanism by S segregation is classified into ‘bond mobility model’ or ‘decohesion model’.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 699: Symposium R – Electrically Based Microstructural Characterization III , 2001 , R2.4
Copyright
Copyright © Materials Research Society 2002

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