Effect of extrusion microstructure on formation of streaking defects on the surface of anodized aluminum extrusions

Zhu, Hanliang, Dahle, Arne K., Zhang, Xinquan and Couper, Malcolm J. (2008). Effect of extrusion microstructure on formation of streaking defects on the surface of anodized aluminum extrusions. In: Proceedings of the 17th Annual International Anodizing Conference. Seventeenth Annual International Anodizing Conference & Exposition, San Francisco, CA, U.S.A., (139-152). 28–30 October 2008.


Author Zhu, Hanliang
Dahle, Arne K.
Zhang, Xinquan
Couper, Malcolm J.
Title of paper Effect of extrusion microstructure on formation of streaking defects on the surface of anodized aluminum extrusions
Conference name Seventeenth Annual International Anodizing Conference & Exposition
Conference location San Francisco, CA, U.S.A.
Conference dates 28–30 October 2008
Convener Aluminum Anodizing Council
Proceedings title Proceedings of the 17th Annual International Anodizing Conference
Place of Publication Wauconda, IL, U.S.A.
Publisher Aluminum Anodizers Council
Publication Year 2008
Sub-type Fully published paper
Open Access Status
Start page 139
End page 152
Total pages 14
Language eng
Formatted Abstract/Summary
Surface appearance is an important characteristic of high quality aluminum components for the automobile and construction industries. Surface defects, such as streaking, are often present on anodized extrusions of 6xxx-series alloys, increasing the fabrication cost of these products. Moreover, streaking often becomes visible only after etching and anodizing treatments, rather than in the as-extruded condition, making it difficult to identify the original causes of these defects.

During anodizing, a transparent oxide layer is formed on the metal surface; this metal/oxide interface is the prevailing surface for reflecting light. Any surface imperfections in the metal/oxide interface will increase the diffused part of the reflected light, ultimately resulting in streak defects. Surface imperfections include etching pits, grain boundary grooves and/or grain etching steps; they are created on the extrusion surface as the result of uneven surface microstructuring during etching. Hence, the severity of surface imperfections depends on the surface microstructure of the extrusion. In this study, the effect of microstructure variants such as intermetallic particles, grain size, grain orientation and precipitation on the formation and severity of surface imperfections, as well as the occurrence of streaking defects, are investigated.
Subjects 091207 Metals and Alloy Materials
0912 Materials Engineering
Keyword Surface defects
Streaking
Surface microstructuring
Extrusion microstructure
Anodizing
Q-Index Code E1
Q-Index Status Provisional Code
Additional Notes Presented during "Focus Session 3: Academic". Source not located.

 
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Created: Thu, 25 Feb 2010, 09:46:02 EST by June Temby on behalf of Faculty Of Engineering, Architecture & Info Tech