title: Sub-micrometre holotomographic characterisation of the effects of solution heat treatment on an AlMg7.3Si3.5 alloy.
abstract: A strip cast AlMg7.3Si3.5 alloy is investigated by sub-micrometre holotomographic analysis achieving a voxel size of (60 nm)3by cone beam magnification of the focused synchrotron beam using Kirkpatrick-Baez mirrors. The three-dimensional microstructure of the same specimen volume in the as-cast state is compared with that after exposure to 540 °C for 30 min resolving microstructural features down to 180 nm. The three-dimensional analysis of the architecture of the eutectic Mg2Si and the Fe-aluminides reveals how the as-cast microstructure changes during the solution treatment. The alloy in the as-cast condition contains a highly interconnected seaweed-like Mg2Si eutectic. The level of three-dimensional interconnectivity of the Mg2Si eutectic phase decreases by only partial disintegration during the heat treatment correcting the two-dimensional metallographic impression of isolated round particles. Statistical analyses of the particle distribution, sphericity, mean curvatures and Gaussian curvatures describe quantitatively the architectural changes of the Mg2Si phase. This explains the decrease of the high temperature strength of the alloy by the solution treatment tested in hot compression.
authors.affiliation: Institute of Materials Science and Technology, Vienna University of Technology, Karlsplatz 13/308, A-1040 Vienna, Austria ; Eötvös Loránd University, Department of Materials Physics, POB 32, HU-1518 Budapest, Hungary.
authors.forename: D
authors.initials: D
authors.lastname: Tolnai
authors.forename: G
authors.initials: G
authors.lastname: Requena
authors.forename: P
authors.initials: P
authors.lastname: Cloetens
authors.forename: J
authors.initials: J
authors.lastname: Lendvai
authors.forename: H P
authors.initials: HP
authors.lastname: Degischer
keywords: Aluminium alloys; Cast Al–Mg–Si alloys; Coarsening; Mechanical characterisation; Synchrotron tomography