Microstructural refinement of DC cast AZ80 Mg billets by low frequency electromagnetic vibration

The effects of variable and stationary magnetic fields applied during DC casting of AZ80 Mg billets were investigated. The experiments were performed both in the absence and in the presence of electromagnetic vibrating force fields, which were induced by the interaction of variable and stationary magnetic fields. The variable and stationary magnetic fields were modulated from 0 to 20,000 A-turns, and the frequency of the variable magnetic field was adjusted in the range of 0–30 Hz. It has been established that electromagnetic vibrations refine the grains in AZ80 billets. Increasing intensities of variable and stationary magnetic fields lead to further grain refinements. The formation of fine crystal grains resulted from the increase in the number of crystal nuclei and the detached dendritic arms in the melt. When the frequency of the variable magnetic field was 30 Hz, microstructures in the billet were greatly refined.