Metallurgical characterization of aluminum alloys by Matrix dissolution

Abstract

Aluminum foils produced by cold rolling are able to show defects caused by primary particles that are formed along center line segregation. These particles are formed during casting process where some parameters are critical. In the same way, aluminum extruded parts are also able to show defects caused by intermetallic phases. They were used billets of AA6351 alloy (Al-Mg-Si) produced by “Direct Chill” and also sheets of AA8011 alloy (Al-Fe-Si) produced by “Twin Roll Casting”. Samples were submitted to a chemical etching based on methanol and iodine whose target is corrodes only aluminum matrix. Thus, intermetallic phases were analyzed using optical microscopy and SEM and EDS. Beyond, X-Ray Diffraction analysis were performed as well. On AA8011 alloy, they were identified the phases β-FeSiAl5 and α-Fe2SiAl8 in as-cast samples, that are hazardous to final foil because they do not dissolve during homogenization treatment. On AA6351 alloy, they were identified the phases Mg2Si and α-(Fe, Mn)3Si2Al15. The identification of these phases contributed to process optimization.