Rolling is known to alter the surface properties of aluminium alloys and to introduce disturbed near-surface microcrystalline layers. The near-surfaces of mostly higher alloyed materials were investigated by various techniques, often combined with a study of their electrochemical behaviour. Cross-sectional transmission electron microscopy (TEM), after ion milling or ultramicrotomy, indicated the presence of disturbed layers characterized by a refined grain structure, rolled-in oxide particles and a fine distribution of intermetallics. Those rolled-in oxide particles reduce the total reflectance of rolled Al alloys. Furthermore, various depth profiling techniques, such as AES, XPS, SIMS and qualitative glow discharge optical emission spectroscopy (GD-OES) have been used to study the in-depth behaviour of specific elements of rolled Al alloys.Here, the surface and near-surface of AlMg0.5 (a commercially pure rolled Al alloy with addition of 0.5 wt.% Mg) after hot and cold rolling, and with and without additional annealing is studied with complementary analytical techniques. Focused ion beam thinning is introduced as a new method for preparing cross-sectional TEM specimens of Al surfaces. Analytical cross-sectional TEM is used to investigate the microstructure and composition. Measuring the total reflectance of progressively etched samples is used as an optical depth profiling method to derive the thickness of disturbed near-surface layers. Quantitative r.f. GD-OES depth profiling is introduced to study the in-depth behaviour of alloying elements, as well as the incorporation of impurity elements within the disturbed layer. The GD-OES depth profiles, total reflectance and cross-sectional TEM analyses are correlated with SEM/energy-dispersive x-ray observations in GD-OES craters.
Rolling is known to alter surface properties of aluminium alloys and to introduce disturbed subsurface layers. These layers are characterised by a refined grain structure, rolled-in oxide particles, a fine distribution of intermetallic particles and various voids and cracks.In previous studies, mostly higher alloyed materials have been investigated. Here, the subsurface of a commercially pure rolled aluminium alloy (99.5% Al) is characterised. Hot and cold rolled sheets, with and without additional annealing are investigated.Measuring total reflectance (TR) of progressively etched samples is used as an optical depth profiling method to derive the thickness of disturbed layers. The in-depth behaviour of alloying, trace and impurity elements in the subsurface regions is studied with quantitative radio frequency glow discharge optical emission spectrometry (r.f.
GDOES). The bottom of glow discharge optical emission spectrometry (GDOES) craters at various depths is investigated with SEM/EDX. Focused ion beam (FIB) thinning isemployed to prepare site-specific cross-sectional TEM specimens. Analytical TEM is used to investigate the thickness, microstructure and composition of the disturbed subsurface.It can be concluded that rolled commercially pure aluminium exhibits disturbed subsurface layers, consisting of a mixture of Al 2 O 3 and metallic aluminium particles, with cracks and voids. These layers are introduced during hot rolling, and reduced in thickness and redistributed over the surface during subsequent cold rolling.
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