Predicting The Effect of Different Magnetic Fields on The Solute Segregation During Direct-Chill Casting Of Large-Size Magnesium Alloy Slab

Macrosegregation is a common defect that deteriorates the quality of casting slab, which is directly associated with the solute segregation in the two-phase region. To reveal the solute segregation in the molten and solidified region during direct-chill (DC) casting of magnesium alloy slab having the dimensions of 1200 mm (width)×400 mm (thickness), a 3-D coupled model validated by the experimental data was developed and used. The numerical predictions qualitatively revealed the macro flow pattern, solidification characteristic, solute segregation behavior and macrosegregation level under no magnetic field (NMF) and various magnetic fields including harmonic magnetic field (HMF), pulsed magnetic field (PMF) and two forms of out-of-phase pulsed magnetic field (OPMF). It was observed that whether the magnetic field is used or not, the solute deficiency tends to occur in the central part and the solute-enriched area appears near the fillet in the molten and solidified regions, but the segregation level is largely alleviated when the magnetic field is on. The standard deviation of relative segregation on the solidified cross-section under NMF is 38.1%, and decreases in the order from OPMF2 (the current phase in the upper coil is ahead of the lowers), HMF, PMF to OPMF1 (the current phase in the upper coil is ahead of the lowers) whose values are respectively 21.9%, 18.6%, 16.4% and 12.4%, indicating that OPMF1 is a preferable way to reduce the macrosegregation degree