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The effects of electromagnetic vibration (EMV) on the refinement and migration of primary silicons in the Al-18 wt pct Si alloy were investigated systematically.It was found that EMV could effectively refine primary silicons.The equivalent diameter of primary silicon first decreases slowly with the current increasing from 1 A to 3 A,but then drops rapidly between 3 A and 10 A,next gradually decreases with increasing current intensity.When the EMV intensity was low,the primary silicons were agglomerated and expelled to the top of a sample,the segregation of silicon grains gradually decreased and the agglomerating phenomena disappeared with the increase of EMV intensity,and the star-like coarse primary silicons turned refined flake or square morphology.The refinement and migration of primary silicons depended on the Lorentz force,gravity and the effective viscous force.