Effects of low-frequency magnetic field on the solidification behavior of direct chill casting Zn–Sn alloy

The effects of low-frequency magnetic field (LFMF) on the solidification behavior of Zn–Sn alloy were investigated. The application of LFMF refined the macrostructure and microstructure of the billets. The refining effect was stronger with the increasing current intensity. The thickness of the dendritic array region in the direct chill casting (DCC) billet was decreased from 28 to 19 mm with the increasing current intensities to 180A. Similarly, the dendritic spacing at 1/2R (R is the radius) of the billet was reduced from 16.4 to 12.0 μm. LFMF induced forced convection in the melt, enhancing the uniformity of the temperature field, lowering the average melt temperature, and reducing the depth of the liquid sump. The electromagnetic field promoted heterogeneous nucleation and led to a refined and more uniform microstructure. The increase in current intensity also led to a rise in magnetic induction intensity and Lorentz force, with a more pronounced effect in the r ( r is along the radial direction of the billet) direction. The melt velocity and fluctuations increased with the current intensity increasing from 120 to 180A, further reducing the temperature gradients. These results indicate that LFMF significantly refined the macrostructure and microstructure of Zn–Sn alloys, making it a promising technique for large-scale production of high-quality Zn–Sn alloy billets.