Effect of mechanical stirring on semi-continuous casting of 7075 aluminum alloy

摘要

order to obtain a superior thixotropic property even in a high strength 7075 aluminum alloy, a billet with a non-dendritic fine-globular structure has been tried to produce by combining a simple mechanical stirring with the verti-cal semi-continuous casting process. The trials were carried out under the various stirring conditions; the position I stirring rotor from the bottom of a mold, the shape of a rotor, the volume of a stirring chamber and the stirring rate. When the temperature within the stirring chamber was nearly constant just below the liquidus temperature and dropped drastically near the liquid-solid interface at the certain stirring conditions, a long sound billet with relatively good surface condition could be produced up to the limitation of the descending capacity of the casting chine. The billet had not only a uniformly fine-grained structure of the average grain size of about 30 #mu#m, but , little macroscopic segregation of the solute elements along the radius in the transverse sections at the various positions along the longitudinal direction of the billet.