Metallurgical Structure of A356 Alloy Solidified by Mechanical Stirring

Abstract

The study investigated the effects of mechanical stirring before solidification on the metallurgical structure of hypoeutectic aluminum-silicon A356. A series of stirring trials were conducted in the present study. Emphasis were placed on the morphological changes of the primary phase, which was subjected to different levels of stirring at various values of the rod material and its diameter, insertion temperature and rotation speed. It was found that when the rod was made of the same material as the molten metal, it acted as a nucleation site to generate numerous nucleated primary crystals, which separated from the rod surface continuously into the molten metal with the rotation of the stirring rod, resulting in the refinement and spheroidization of the primary crystals. The ideal semisolid slurry with homogeneous spherical and fine primary crystals could be obtained by optimizing rod insertion temperature, rotation speed and its diameter, which is a key factor in semi-solid forming.