Preparation and Etching Methods for a Light-Optical Microscopy Analysis of Extrusion Seams and Microstructural Contrasting for Aluminum Alloys EN AW-6063 and EN AW-6082

Abstract To begin with, a visualization of the seam location as well as of the microstructure of the entire profile cross-section is necessary in order to evaluate the stability of extrusion processes and the resulting relationships between process, microstructure, and properties of extrusion profiles characterized by an extrusion seam. The investigations aim at determining appropriate preparation and etching methods for a light-optical microscope analysis of the longitudinal as well as the transversal extrusion seam in the alloys EN AW-6063 and EN AW-6082 and – in the best case – a simultaneous microstructural contrasting. For this purpose, different chemical etching techniques have been applied. A reliable uncovering of the seam was possible for both alloys using a HF solution. Etching with Weck's reagent after NaOH pre-etching turned out to be a promising method for microstructural contrasting of the EN AW-6063 alloy. The transversal extrusion seam could not be rendered visible by means of conventional etching methods. In this context, extrusion of both alloys (EN AW-6082 and EN AW-6063) applying the billet-to-billet extrusion method in line with visioplastic analyses allowed for an indirect representation of the extrusion seam.