Refining mechanism of pure aluminum under local electromagnetic vibration

Abstract

An electromagnetic vibration (EMV) was generated by simultaneously imposing a strong static magnetic field and an alternative electric current to the metal. Its effects of refining solidification structure of aluminum have been investigated systematically. It is found that the macrostructure can not be refined by solely imposing strong magnetic field or alternative electric current while it is refined under the electromagnetic vibration. The refining period of the structure was examined by changing the imposing period of the electromagnetic vibration. From these experimental results, the refinement behavior in this process is that crystal nuclei dissociated from surface due to surface oscillation and disturbance in the initial stage of the solidification. And owing to the fall of refined grains during electromagnetic vibration, the refined structure was normally gained only at the bottom region of the sample. Finally, a method was proposed to restrain crystal shower by using an upward magnetic force, and a uniform refined structure can be obtained by using this method. © 2009 ISIJ.