With the help of a self-developed electromagnetic stirring device and alloy melt quenching technology

the effects of stirring parameters on the microstructure of AZ91D Mg alloy during continuously cooling process were investigated at the condition of the electromagnetic frequency of 50Hz.The results reveal that the spheroidal primary α-Mg phase in the semi-solid AZ91D slurry or billet is continuously increased with the stirring frequency increase

and become more round and more homogeneous distribution when the electromagnetic frequency is lower than 50 Hz.The desirable microstructure in semi-solid Mg slurry or billets can be prepared with the electromagnetic frequency up to or over 50 Hz.With the increase of the electromagnetic stirring power

the rosette-like primary α-Mg phase in the semi-solid alloy melt can be intensely subjected to the man-made temperature fluctuation to result in the root remelting effects of the dendritic arm

which forms more and more spheroidal primary α-Mg phase

and the phase become more and more round.Low cooling rate can be beneficial to forming desirable semi-solid microstructure of the Mg alloy by electromagnetic stirring method.