Investigation Of Refinement Means For Microstructure Of Hypereutectic Al-Fe Casting Alloys

The influence of cooling rate on the morphology of primary Al3Fe in binary hypereutectic Al-Fe alloys was investigated in this article. Various means such as electric current treatment, thermal rate treatment, addition of the elements of Mg, Mn, RE and spheroidal agent, combination treatment of alloying elements with electric current, and the alternating electric field and alternating magnetic field were adopted to decrease the size of primary Al3Fe.It is shown that the cooling rate plays an important role in determining the morphology of primary Al3Fe. Its morphology changes from the extremely thick plate-like to thick needle-plate like, then to needle-plate like and finally to needle-like shapes with the increase of cooling rate.The electric current treatment changes the morphology of primary iron-rich phase from thick plate-like to flower-like and to needle point-like in Al-Fe casting alloys with the increase of electric current density; the grain-like primary Al3Fe can be obtained if the electric current density is suitable; The similar solidified microstructure may also be obtained after thermal rate treatment. The mechanical property of alloy is improved after molten treatment.Adding Mg promotes the morphology transformation of primary Al3Fe from needle-plate like to branch-like, and to irregular chunk-like and eventually to thin needle-like; Addition of RE propels primary Al3Fe growing to branch-like shape. At the same time, RE induces Al3Fe phase to turn into flower-like; Addition of Mn contributes to the formation of the chunk-like primary Al3Fe; By adding spheroidal agent to the molten with iron-rich phase, the needle-like primary Al3Fe phase could be transformed into irregular flower-like and granule shape.Electric current treatment together with addition of alloying elements can furtherly reduce the size of primary Al3Fe.Solidification under electric field can refine primary Al3Fe. The electric force makes Al3Fe turn into irregular chunk-like and it is distorted and broken under the magnetic field, as a result, primary Al3Fe is refined.