Effect Of Electromagnetic Field On The Fe-si Impurity Phases Of Solidified Commercially Pure Aluminum

Commercially pure aluminum has widely usage in various of industries in national economy for its series of excellent characters. To do research on solidification structure of commercially pure aluminum has great meaning because of close relationship between properties and structures. On the other hand, applying electromagnetic fields on solidifying materials, obviously affect structures, is of great importance in making new materials. Therefore, the present observed fundamental phenomenon of commercially pure aluminum solidification structures when electromagnetic fields applied, and electromagnetic mechanism discussed primarily. The present research refers to effects of DC and AC magnetic fields, gradient DC magnetic field, AC electric current, simultaneous magnetic and electric fields on impurity phases distribution, shape, size, components, and impurity intercrystalline contents. Research on those local problems will add theories in EPM and provide sufficient ground for research in future. The present research has conclusions as follows:(1) DC magnetic fields do little changes in grain size, and more character-like or bone-like structures formed. AC magnetic field lead to fan-shaped column grains, and impurities gathered to the center of samples, fined impurity phases formed in the whole sample as well.(2) It is indicated that more a-AlFeSi and lessβ-AlFeSi phase appeared when magnetic field applied, especially in AC magnetic field. Further, more FeAl3 phase formed when AC magnetic field applied. That is, magnetic field can promote formation of a-AlFeSi phase. On the other hand, smaller grain constants gained when magnetic fields applied, that is, increasingly density of Fe and Si in matrix.(3) Gradient DC magnetic field do little effect on grain size for smaller magnetic gradient and rapid cooling rate. Under gradient magnetic field, impurity phases in small pieces, arrayed on the grain boundary, gathered to the Bmax direction.(4) Fined grains gained when AC electric field applied. When AC current comes to 8A, that is, current density of 39.31mA/mm2, with cooling-rate of 20 degree per minute applied, only 1/7 in size of structures out of normal ones, and area fraction decreased 1/3, and impurity phases are of small ball shape, with 2μm in diameter. Fined structures with smaller impurity phases are good for increasing of material plasity. AC electric field can increase density of Fe and Si in intercrystalline, and segregation of Si lighten. In terms of XRD, moreα-AlFeSi phase appeared at the top section of sample, where the electrode positioned. However, phase of Al6Fe less than normal solidified ones and FeAl3 phase disappeared then.(5) Proper electromagnetic references applied would lead to fined structures. Electromagnetic field can increase density of Fe and Si in intercrystalline, and segregation of Si lighten. In I=16A,B=0.34T case, thinner grain boundaries with smaller impurity phases gained; in other cases, electromagnetic field is good for transfer of long acicular shape impurity phases to short bar ones or block like ones. In terms of XRD, phase ofα-AlFeSi decreased or disappeared at the top section of sample, where the electrode positioned. For the middle section, phase ofβ-AlFeSi decreased.