Microstructure and solute distribution of 7075 alloy produced by semi-continuous casting under electromagnetic vibration

The microstructure as well as solute distribution both in microscopic and macroscopic view for 7075 alloy by semi-continuous casting under the electromagnetic vibration were investigated. The results show that there is an optimum frequency range of 10～30 Hz, in which, with the increasing of electromagnetic intensity, the quantity of spheroid-shaped grains increases; the quantity of rosette-shaped grains decreases, the microstructure of the ingot becomes more fine and uniform. At the mean time, alloying elements'solubility increases and the macro-segregation is diminished in a great degree. The electromagnetic vibration makes the grain nuclei in sump increase, temperature and solute distribution of sump become uniform, primary solidified shell and sump height decrease, solute equilibrium partition coefficient increase and solidification temperature interval decrease, the effect of restraining crystal particles growing into dendrite strengthen, which promote alloying elements'solution inside crystal and suppress macro-segregation.