Effects of the simultaneous imposition of electromagnetic and magnetic forces on the solidification structure of pure Al and Al–4.5 wt.%Cu alloy

Effects of the simultaneous imposition of an alternating current and a static magnetic field on the solidification structures of the pure Al and the Al–4.5 wt.%Cu alloy were investigated. The results show that the refined structure was gained by the application of the above complex fields. Owing to the fall of the refined nucleation during the electromagnetic vibration process (i.e. the formation of crystal rains), the refined structure was normally gained only at the bottom region of the sample. A method was proposed to restrain crystal rains by using an upward magnetic force and the results indicated that by using this method, the distribution of the refined grains was changed significantly. It was found that there existed a right magnetic force to make the whole sample refined; as a consequence, the uniformly refined structure was gained. In the case of the completely eliminating crystal rains, the effect of the electromagnetic force on the structure was investigated and result indicated that with the increase of the electromagnetic force density, the size of Al grains decreased and the depth of refinement zone increased. Moreover, the Al–4.5 wt.%Cu alloy was chosen to investigate the influence of the electromagnetic and magnetic forces on the growth of dendrite. It was observed that with the increase of the electromagnetic force density, the columnar dendritic structure changed into equiaxed ones that continued to disintegrate to isolated grains. Similar to the behavior of the pure Al, crystal rains formed during the electromagnetic vibration and could be restrained by using the magnetic force.