Effect of the shear layer on the etching behavior of 6060 aluminum extrusion alloys. (3rd March 2019)

• Record Type: Journal Article
• Authors: Lutz, Alexander; Lapeire, Linsey; Nguyen‐Minh, Tuan; Verbeken, Kim; Terryn, Herman; De Graeve, Iris
• Other Names: Terryn Herman guestEditor.
• Is Part Of: Surface and interface analysis. Volume 51:Number 12(2019)
• Page Start: 1251
• Page End: 1259
• Publication Date: 2019-03-03
• Subjects: aluminum alloys -- EBSD -- extrusion -- preferential grain etching -- shear layer; Surfaces (Physics) -- Periodicals; Surface chemistry -- Periodicals; Thin films -- Periodicals; 541.33
• DOI: 10.1002/sia.6632
• Languages: English
• ISSNs: 0142-2421

Abstract

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.