Abstract:

Size distributions of the secondary phase in different blanks of AA8111 aluminum alloy were studied by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Image J and Nano Measurer. The results show that during the 5 passes of cold-rolling from 7 mm cast-rolled sheet to the finished blanks of 0.24 mm, the secondary phase breaks obviously and the size becomes smaller in the early stage, while with the increase of deformation resistance, the effect of subsequent rolling on the size of the secondary phase is getting smaller and smaller. The rod-shaped and disc-shaped Si elementary phases precipitated out during the homogenization annealing, have a great influence on the secondary phase size distributions and are heritable. The proportion of the secondary phase of greater than 6 μm in the finished blank is 8.9%, and there are some larger secondary phases of about 10 μm. Compared with the finished blanks of AA1235 and AA8079 alloys, it is concluded that the high proportion of the secondary phase size distribution greater than 6 μm in the AA8111 finished blanks is the main reason for the high needle porosity of the finished aluminum foil.

Key words: AA8111 aluminum alloy, finished blanks, secondary phase size, rod-shaped precipitates