Effect of the shear layer on the etching behavior of 6060 aluminum extrusion alloys

Alexander Lutz*, Linsey Lapeire, Tuan Nguyen-Minh, Kim Verbeken, Herman Terryn, Iris De Graeve

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    Abstract

    The occurrence of preferential grain etching (PGE) during alkaline etching of aluminum extrusion alloys from the 6XXX series is often linked to the presence of certain impurity elements such as zinc, causing an undesired etching appearance. In the presented work, an additional culprit in this context is identified, which has not been investigated yet. A clear relation between PGE and the presence of a subsurface shear layer is identified for extruded Al 6060 alloys containing 0.02 and 0.06 wt% Zn. This shear layer can be distinguished from the bulk of the metal by its difference in crystallographic texture as visualized by electron backscatter diffraction (EBSD). For the Zn enriched alloy, the <111>//ND grains are etched away faster than grains with other orientations, resulting in the grainy appearance typical for PGE. Independent of the Zn content in the alloy, once the shear layer is removed and <111>//ND grains are practically absent on the new surface, the depths variations caused by preferential etching disappear. Instead, the surface of the alloy is attacked uniformly by the caustic etch bath.

    Original languageEnglish
    Pages (from-to)1251-1259
    JournalSurface and Interface Analysis
    Volume51
    Issue number12
    DOIs
    Publication statusPublished - 2019

    Bibliographical note

    SPECIAL ISSUE ARTICLE Proceedings 8th Symposium “Aluminium Surface Science and Technology”

    Keywords

    • aluminum alloys
    • EBSD
    • extrusion
    • preferential grain etching
    • shear layer

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