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Microstructure Investigations of Streak Formation in 6063 Aluminum Extrusions by Optical Metallographic Techniques

Published online by Cambridge University Press:  12 March 2013

George Vander Voort ,
Beatriz Suárez-Peña  and
Juan Asensio-Lozano
George Vander Voort
Affiliation:
Struers Inc., 2887 N. Southern Hills Drive, Wadsworth, IL 60083-9293, USA
Beatriz Suárez-Peña
Affiliation:
Materials Science and Metallurgical Engineering Department, The University of Oviedo, Gijón Polytechnic School of Engineering, Viesques University, Gijón, Asturias 33203, Spain
Juan Asensio-Lozano*
Affiliation:
Materials Science and Metallurgical Engineering Department, The University of Oviedo, The School of Mines, Oviedo, Asturias 33004, Spain
*
*Corresponding author. E-mail: [email protected]
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Abstract

The present study investigates the effect of the solidification strategy for AA 6063 alloy on the surface appearance of anodized extrusions. The microstructure of the samples was analyzed using both light optical microscopy and scanning electron microscopy. Results show that if heavy segregation occurs from rapid solidification, coarse Mg2Si particles form, thus reducing the potential for precipitation strengthening by the finer β-Mg2Si developed in the solid state. Differentially-strained regions formed during hot extrusion induce differences in particle size for magnesium silicide (Mg2Si) precipitates. Anodizing generates surface roughness due to Mg2Si particle dissolution and AlFeSi decohesion, which is related to both particle size and deformation. During anodizing, an oxide layer forms on the surface of the extruded products, which can lead to streak formation, usually a subject of rejection due to unacceptable heterogeneous reflectivity.

Keywords

light optical microscopyscanning electron microscopyquantitative metallographic characterization6063 aluminum alloysprecipitationstreak formation
Type
Materials Applications
Information
Microscopy and Microanalysis , Volume 19 , Issue 2 , April 2013 , pp. 276 - 284
Copyright
Copyright © Microscopy Society of America 2013

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