Browsing by Author "Dahle, AK"

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    Effect of extrusion profile on surface microstructure and appearance of aluminum extrusions with different Fe contents
    (Springer, 2013-02-21) Zhu, HL; Wei, T; Couper, MJ; Dahle, AK
    Aluminum alloy extrusions with variations in profiles and Fe-rich particles were produced using different extrusion dies and iron contents. A microstructural examination of the extrusion surface shows that the extrusion profile and iron content have a great effect on the size and number of Fe-rich particles, grain size, texture, and fraction of high-angle grain boundaries due to varying localized plastic deformation and temperature in the extrudate. After etching and anodizing, surface imperfections such as grain boundary grooves that influence the final surface appearance are formed on the extrusion surfaces. The severity of grain boundary grooves is found to be directly linked to the number of Fe-rich particles. Hence, the extrusion profile has a dramatic influence on surface imperfections and the appearance of the final anodized extrusions through its effect on the surface microstructure. © 2013, TMS.
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    Formation of streak defects on anodized aluminum extrusions.
    (Springer, 2010-05) Zhu, HL; Zhang, XQ; Couper, MJ; Dahle, AK
    Streaking is a common surface defect on anodized extrusions of 6xxx series soft alloys. Very often, the defects only become apparent after anodizing, which makes it difficult to identify their root cause. In industry practice, a trial-and-error method has been taken to reduce the intensities of the streak defects, greatly increasing the fabrication cost. This paper describes the formation mechanism of various streak defects on the basis of a literature review and experimental results. This provides a basis for developing effective measures for preventing the formation of these defects for the extrusion industry. © 2010, Springer. The original publication is available at www.springerlink.com