Sammendrag
Recent experience on characterising the presence and distribution of trace elements in recycled aluminium alloy is described. Two mass spectroscopic techniques, Glow Discharge Mass Spectrometry (GDMS) and Secondary Ion Mass Spectrometry (SIMS) have been applied to the study of commercial 3105 alloys. GDMS gives accurate measurements over a wide range of concentrations for most elements, but has no lateral resolution (~10 mm). Since depth profiling is difficult, GDMS is best suited for bulk analyses. Advanced data processing is required to obtain accurate quantitative results. Secondary Ion Mass Spectrometry (SIMS) can give the same kind of accuracy as GDMS, and has a lateral resolution down to 50 nm for dedicated instruments. The depth resolution can be 1 nm and is mainly limited by atomic mixing caused by the primary ion beam. Three modes are available: Imaging, depth profiling and mass spectra. Obtaining accurate quantitative results requires calibration standards and careful data processing. Scanning Transmission Electron Microscopy (STEM) is an invaluable tool that provides detailed highly localised information and can be applied to surface studies. When good samples having the right geometry can be made, TEM may give high resolution images, element maps and depth profiles, showing the distribution of segregated trace elements.