Observation of As-Cast Microstructure Feature of Al Sheet Used for Can Manufacturing with High Forming Properties

Abstract

As-cast microstructure feature of Al sheet used for pressure can manufacture with high forming properties prepared by different melt-treatment technology was investigated and analyzed with the aids of SEM, EDAX, TEM and selected area electron diffraction(SAED), etc. It is found that oxide inclusions in the Al sheet are mainly γ-Al2O3, and Fe-rich impurity phases in the sheet are mainly Al3Fe,T1 (Al12Fe3Si) or (AlFeSiRE),and the crystal structure of (AlFeSiRE) phase is too complicated to determinate it. The effect of melt-treatment technology on the as-cast microstructure of the sheet is remarkable. When the Al sheet is prepared by no or conventional melt-treatment, there are a number of oxide inclusions, these inclusions distribute non-uniformly and gather together in the larger block form, and their size is about 10-40 μm. Fe-rich impurity phases in the sheet are mainly Al3Fe and T1, and a few of the meta-stable phase Al6Fe exist in Al sheet. These Fe-rich impurity phases appear in the coarse, long needle/flake or skeletal form, and are easy to gather together with oxide inclusions. When the Al sheet is prepared by high-efficient melt-treatment, the number of oxide inclusions is very few obviously, and their size is about or less than 4μm, and their distribution is uniform; Fe-rich impurity phases are mainly (AlFeSiRE), and a small amount of Al3Fe phases also exist in the material. (AlFeSiRE) phases distribute uniformly along grain boundary in tiny group/sphere or short stick form. The phenomenon that Fe-rich phases gather together with oxide inclusions is not discovered in the material.