2.4.3. Electron Microscopy

In order to follow the relative redistribution of intermetallic precipitates throughout the matrix at the microscale, scanning electron microscopy (SEM) in backscattered-electron (BSE) imaging mode was carried out. For this purpose, a SUPRA 55 VP SEM (ZEISS, Jena, Germany) equipped with an energy-dispersive X-ray spectroscopy (EDS) analysis and imaging system was used. Samples were mechanically ground and polished down to a finish by employing ethanol lubricant and a 0.05 μm Al2O3 suspension. Detailed evaluation of the evolution of particles at the nano-scale was carried out by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). For this purpose, a JEM 2100F-UHR microscope (JEOL, Tokyo, Japan) equipped with a high-angle annular dark field (HAADF) detector was used. The same microscope is equipped with an EDS facility (Oxford Instruments, Abingdon, UK), which has been used for elemental analyses of the Mg alloys investigated. The specimens for TEM/STEM analyses were prepared by cutting a 3 mm disk out of the slice, and mechanically polishing with polishing paper (up to 2000 grit) and finishing with 1 μm suspension. During polishing only absolute ethanol has been used as a lubricant. Finally, the specimen was ion milled with grazing Ar+ ion beam, by means of a Precision Ion Polishing System (PIPS-II) (GATAN, Pleasanton, CA, USA) operated at 5 kV at the beginning down to 2 kV for the final step.
