Microstructures of various aluminum dross generated from the aluminum scraps of 1000, 5000 and 6000 series alloys that were recovered individually were observed by an optical microscope, an electron probe microanalyzer (EPMA) and a transmission electron microscope (TEM). Various oxides such as MgO, Fe
3O
4 and SiO
2 in addition to metallic Al, AlN and Al
2O
3 were identified in the dross by X-ray diffraction analysis. Particularly, the formation of MgO and Al
2MgO
4 were marked in the 5000 and 6000 dross since Mg and Si are main additional elements in 5000 and 6000 aluminum alloys. Comparatively large blocks whose size was several tens mm were mainly composed of aluminum. Some inclusions such as Al
6Fe, Al
3Fe and α–Al–Fe–Si and a lot of filmy oxides and porosities were formed in the block. In the case of small particles in 1000 dross whose size was below several mm, Al
2O
3 was formed at the surface and AlN layer was formed in the interior side of Al
2O
3 layer. In 5000 dross, there was MgO or Al
2MgO
4 at the outermost layer of the dross powder.
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